* RFC: Device Namespaces @ 2013-08-22 17:43 Oren Laadan [not found] ` <CAA4jN2aw4zEW=UfKCyqaOvXnbiRb_J9srfCn4OXTFzc6vWBM4A-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> 0 siblings, 1 reply; 63+ messages in thread From: Oren Laadan @ 2013-08-22 17:43 UTC (permalink / raw) To: Linux Containers; +Cc: lxc-devel Hi everyone! We [1] have been working on bringing lightweight virtualization to Linux-based mobile devices like Android (or other Linux-based devices with diverse I/O) and want to share our solution: device namespaces. Imagine you could run several instances of your favorite mobile OS or other distributions in isolated containers, each under the impression of having exclusive access to device drivers; Interact and switch between them within a blink, no flashing, no reboot. Device namespaces are an extension to existing Linux kernel namespaces that brings lightweight virtualization to Linux-based end-user devices, primarily mobile devices. Device namespaces introduce a private and virtual namespace for device drivers to create the illusion for a process group that it interacts exclusively with a set of drivers. Device namespaces also introduce the concepts of an “active” namespace with which a user interacts, vs “non-active” namespaces that run in the background, and the ability to switch between them.[2] We are planning to prepare individual patches to be submitted to the relevant maintainers and mailing lists. In the meantime, we already want to share a set of patches on top of the Android goldfish Kernel 3.4 as well as a user-space demo, so you can see where we are heading and get an overview of the approach and see how it works. We are aware that the patches are not ready for submission in their current state, and we'd highly appreciate any feedback or suggestions which may come to your mind once you have a look [3]. Of particular interest is to elaborate a proper userspace API with respect to existing and future use-cases. To illustrate a simple use-case we also provide a simple userspace demo for Android [4]. I will be presenting "The Case for Linux Device Namespace" [5] at LinuxCon North America 2013 [6]. We will also be attending the Containers Track [7] at LPC 2013 to present the current state of the patches and discuss the best course to proceed. We are looking forward to hear from you! Thanks, Oren. 1: http://www.cellrox.com/ 2: https://github.com/Cellrox/devns-patches/wiki/DeviceNamespace 3: https://github.com/Cellrox/devns-patches 4: https://github.com/Cellrox/devns-demo 5: http://sched.co/1asN1v7 6: http://events.linuxfoundation.org/events/linuxcon-north-america 7: http://www.linuxplumbersconf.org/2013/ocw/events/LPC2013/tracks/153 -- Oren Laadan Cellrox Ltd. ^ permalink raw reply [flat|nested] 63+ messages in thread
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* Re: RFC: Device Namespaces [not found] ` <CAA4jN2aw4zEW=UfKCyqaOvXnbiRb_J9srfCn4OXTFzc6vWBM4A-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> @ 2013-08-22 18:21 ` Serge Hallyn 2013-08-26 10:11 ` Oren Laadan 2013-08-29 19:06 ` RFC: " Andy Lutomirski 1 sibling, 1 reply; 63+ messages in thread From: Serge Hallyn @ 2013-08-22 18:21 UTC (permalink / raw) To: Oren Laadan; +Cc: Linux Containers, lxc-devel Quoting Oren Laadan (orenl@cellrox.com): > Hi everyone! > > We [1] have been working on bringing lightweight virtualization to > Linux-based mobile devices like Android (or other Linux-based devices with > diverse I/O) and want to share our solution: device namespaces. > > Imagine you could run several instances of your favorite mobile OS or other > distributions in isolated containers, each under the impression of having > exclusive access to device drivers; Interact and switch between them within > a blink, no flashing, no reboot. > > Device namespaces are an extension to existing Linux kernel namespaces that > brings lightweight virtualization to Linux-based end-user devices, > primarily mobile devices. > Device namespaces introduce a private and virtual namespace for device > drivers to create the illusion for a process group that it interacts > exclusively with a set of drivers. Device namespaces also introduce the > concepts of an “active” namespace with which a user interacts, vs > “non-active” namespaces that run in the background, and the ability to > switch between them.[2] Note that unless I'm misunderstanding what you're saying here, this is also what net_ns does. A netns can exist with no processes so long as you've bound its /proc/$$/ns/net somewhere. You can then re-enter that ns using ns_attach. I haven't looked closely enough yet to see whether you should be (or are) using the same interface. > We are planning to prepare individual patches to be submitted to the Looking forward to it, and seeing you at the containers track :) > 2: https://github.com/Cellrox/devns-patches/wiki/DeviceNamespace > 3: https://github.com/Cellrox/devns-patches > 4: https://github.com/Cellrox/devns-demo (Have looked over the wiki, will look over the patches as well) -serge _______________________________________________ Containers mailing list Containers@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/containers ^ permalink raw reply [flat|nested] 63+ messages in thread
* Re: RFC: Device Namespaces 2013-08-22 18:21 ` Serge Hallyn @ 2013-08-26 10:11 ` Oren Laadan [not found] ` <CAA4jN2YL7Lfu2+DW-i+MovFxWEhJfT4aBBKREU_vy7JX9TKGHA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> 0 siblings, 1 reply; 63+ messages in thread From: Oren Laadan @ 2013-08-26 10:11 UTC (permalink / raw) Cc: Linux Containers, lxc-devel Hi Serge, On Thu, Aug 22, 2013 at 2:21 PM, Serge Hallyn <serge.hallyn-GeWIH/nMZzLQT0dZR+AlfA@public.gmane.org>wrote: > Quoting Oren Laadan (orenl-3AfRa/s5aFdBDgjK7y7TUQ@public.gmane.org): > > Hi everyone! > > > > We [1] have been working on bringing lightweight virtualization to > > Linux-based mobile devices like Android (or other Linux-based devices > with > > diverse I/O) and want to share our solution: device namespaces. > > > > Imagine you could run several instances of your favorite mobile OS or > other > > distributions in isolated containers, each under the impression of having > > exclusive access to device drivers; Interact and switch between them > within > > a blink, no flashing, no reboot. > > > > Device namespaces are an extension to existing Linux kernel namespaces > that > > brings lightweight virtualization to Linux-based end-user devices, > > primarily mobile devices. > > Device namespaces introduce a private and virtual namespace for device > > drivers to create the illusion for a process group that it interacts > > exclusively with a set of drivers. Device namespaces also introduce the > > concepts of an “active” namespace with which a user interacts, vs > > “non-active” namespaces that run in the background, and the ability to > > switch between them.[2] > > Note that unless I'm misunderstanding what you're saying here, this is > also what net_ns does. A netns can exist with no processes so long as > you've bound its /proc/$$/ns/net somewhere. You can then re-enter that > ns using ns_attach. I haven't looked closely enough yet to see whether > you should be (or are) using the same interface. > > To illustrate the need for device namespaces, consider the use case of running two containers of your favorite OS (say, Android), on a single physical phone. As a user, you either work in one container, or in the other, and you will want to be able to switch between them (just like with apps on mobile devices: you interact with one application at a time, and switch between them). See here for a demo of how it works: http://vimeo.com/60113683 To accomplish this, device namespaces solve two shortcomings of existing namespaces: 1. A namespace for device drivers: each (Android) container needs a private view of all devices. This includes logical drivers, like binder (in Android) but also loop device; and physical devices, like the framebuffer and the touch-screen. In other words, device namespaces virtualize the _major/minor_ and the _state_ of device drivers. With the exception of VFS, network, and PTY (note: all three offer/are virtual devices), device drivers are otherwise not isolated between containers. 2. A namespace for interactive scenarios: a namespace can be "active" - it has access to the hardware, e.g. display and touch-screen. This will be the container with which the user is interacting right now. Otherwise a namespace is "non-active" - it still runs in the background, but can neither alter the display nor receive input from the touch-screen. Switching to another container means a context switch in the relevant drivers, so that they restore the state and now "obey" the other namespace. You can also think about the "active" namespace as foreground, and the "non-active" as background, akin to foreground/background processes in a terminal with job-control. Similar to how a terminal delivers input to the foreground task only but not to the background tasks - this is enforced by the new device namespace. More details on this use-case are in the wiki: https://github.com/Cellrox/devns-patches/wiki/Thinvisor). > We are planning to prepare individual patches to be submitted to the > > Looking forward to it, and seeing you at the containers track :) > Same here! > > > 2: https://github.com/Cellrox/devns-patches/wiki/DeviceNamespace > > 3: https://github.com/Cellrox/devns-patches > > 4: https://github.com/Cellrox/devns-demo > > (Have looked over the wiki, will look over the patches as well) > > -serge > Thanks, Oren. -- Oren Laadan Cellrox Ltd. ^ permalink raw reply [flat|nested] 63+ messages in thread
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* Re: RFC: Device Namespaces [not found] ` <CAA4jN2YL7Lfu2+DW-i+MovFxWEhJfT4aBBKREU_vy7JX9TKGHA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> @ 2013-09-06 17:50 ` Eric W. Biederman [not found] ` <8761udlu0d.fsf-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org> 0 siblings, 1 reply; 63+ messages in thread From: Eric W. Biederman @ 2013-09-06 17:50 UTC (permalink / raw) To: Oren Laadan; +Cc: Linux Containers, lxc-devel Oren Laadan <orenl@cellrox.com> writes: > Hi Serge, > > > On Thu, Aug 22, 2013 at 2:21 PM, Serge Hallyn <serge.hallyn@ubuntu.com>wrote: > >> Quoting Oren Laadan (orenl@cellrox.com): >> > Hi everyone! >> > >> > We [1] have been working on bringing lightweight virtualization to >> > Linux-based mobile devices like Android (or other Linux-based devices >> with >> > diverse I/O) and want to share our solution: device namespaces. >> > >> > Imagine you could run several instances of your favorite mobile OS or >> other >> > distributions in isolated containers, each under the impression of having >> > exclusive access to device drivers; Interact and switch between them >> within >> > a blink, no flashing, no reboot. >> > >> > Device namespaces are an extension to existing Linux kernel namespaces >> that >> > brings lightweight virtualization to Linux-based end-user devices, >> > primarily mobile devices. >> > Device namespaces introduce a private and virtual namespace for device >> > drivers to create the illusion for a process group that it interacts >> > exclusively with a set of drivers. Device namespaces also introduce the >> > concepts of an “active” namespace with which a user interacts, vs >> > “non-active” namespaces that run in the background, and the ability to >> > switch between them.[2] >> >> Note that unless I'm misunderstanding what you're saying here, this is >> also what net_ns does. A netns can exist with no processes so long as >> you've bound its /proc/$$/ns/net somewhere. You can then re-enter that >> ns using ns_attach. I haven't looked closely enough yet to see whether >> you should be (or are) using the same interface. >> >> > To illustrate the need for device namespaces, consider the use case of > running two containers of your favorite OS (say, Android), on a single > physical phone. As a user, you either work in one container, or in the > other, and you will want to be able to switch between them (just like with > apps on mobile devices: you interact with one application at a time, and > switch between them). > > See here for a demo of how it works: http://vimeo.com/60113683 > > To accomplish this, device namespaces solve two shortcomings of existing > namespaces: > > 1. A namespace for device drivers: each (Android) container needs a > private view of all devices. This includes logical drivers, like binder (in > Android) but also loop device; and physical devices, like the framebuffer > and the touch-screen. > > In other words, device namespaces virtualize the _major/minor_ and the > _state_ of device drivers. With the exception of VFS, network, and PTY > (note: all three offer/are virtual devices), device drivers are otherwise > not isolated between containers. > > 2. A namespace for interactive scenarios: a namespace can be "active" - it > has access to the hardware, e.g. display and touch-screen. This will be the > container with which the user is interacting right now. Otherwise a > namespace is "non-active" - it still runs in the background, but can > neither alter the display nor receive input from the touch-screen. > Switching to another container means a context switch in the relevant > drivers, so that they restore the state and now "obey" the other namespace. > > You can also think about the "active" namespace as foreground, and the > "non-active" as background, akin to foreground/background processes in a > terminal with job-control. Similar to how a terminal delivers input to the > foreground task only but not to the background tasks - this is enforced by > the new device namespace. > > More details on this use-case are in the wiki: > https://github.com/Cellrox/devns-patches/wiki/Thinvisor). I think this is going to take some talking, and looking at code. I think you are talking about having wrappers around your devices so you can share. Which is not the quite same problem the rest of us have been thinking of when talking about a device namespace. My first impression is that this is better solved with more appropriate abstractions in userspace or in the kernel. But we can talk at LPC and see what we can hash out. Eric _______________________________________________ Containers mailing list Containers@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/containers ^ permalink raw reply [flat|nested] 63+ messages in thread
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* Re: RFC: Device Namespaces [not found] ` <8761udlu0d.fsf-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org> @ 2013-09-08 12:28 ` Amir Goldstein [not found] ` <CAA2m6vexArJ+6jFbK80Amstk=LK30=XDNHdBHSswP=LgpSP-6A-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> 0 siblings, 1 reply; 63+ messages in thread From: Amir Goldstein @ 2013-09-08 12:28 UTC (permalink / raw) To: Eric W. Biederman; +Cc: Linux Containers, lxc-devel On Fri, Sep 6, 2013 at 7:50 PM, Eric W. Biederman <ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org>wrote: > Oren Laadan <orenl-3AfRa/s5aFdBDgjK7y7TUQ@public.gmane.org> writes: > > > Hi Serge, > > > > > > On Thu, Aug 22, 2013 at 2:21 PM, Serge Hallyn <serge.hallyn-GeWIH/nMZzLQT0dZR+AlfA@public.gmane.org > >wrote: > > > >> Quoting Oren Laadan (orenl-3AfRa/s5aFdBDgjK7y7TUQ@public.gmane.org): > >> > Hi everyone! > >> > > >> > We [1] have been working on bringing lightweight virtualization to > >> > Linux-based mobile devices like Android (or other Linux-based devices > >> with > >> > diverse I/O) and want to share our solution: device namespaces. > >> > > >> > Imagine you could run several instances of your favorite mobile OS or > >> other > >> > distributions in isolated containers, each under the impression of > having > >> > exclusive access to device drivers; Interact and switch between them > >> within > >> > a blink, no flashing, no reboot. > >> > > >> > Device namespaces are an extension to existing Linux kernel namespaces > >> that > >> > brings lightweight virtualization to Linux-based end-user devices, > >> > primarily mobile devices. > >> > Device namespaces introduce a private and virtual namespace for device > >> > drivers to create the illusion for a process group that it interacts > >> > exclusively with a set of drivers. Device namespaces also introduce > the > >> > concepts of an “active” namespace with which a user interacts, vs > >> > “non-active” namespaces that run in the background, and the ability to > >> > switch between them.[2] > >> > >> Note that unless I'm misunderstanding what you're saying here, this is > >> also what net_ns does. A netns can exist with no processes so long as > >> you've bound its /proc/$$/ns/net somewhere. You can then re-enter that > >> ns using ns_attach. I haven't looked closely enough yet to see whether > >> you should be (or are) using the same interface. > >> > >> > > To illustrate the need for device namespaces, consider the use case of > > running two containers of your favorite OS (say, Android), on a single > > physical phone. As a user, you either work in one container, or in the > > other, and you will want to be able to switch between them (just like > with > > apps on mobile devices: you interact with one application at a time, and > > switch between them). > > > > See here for a demo of how it works: http://vimeo.com/60113683 > > > > To accomplish this, device namespaces solve two shortcomings of existing > > namespaces: > > > > 1. A namespace for device drivers: each (Android) container needs a > > private view of all devices. This includes logical drivers, like binder > (in > > Android) but also loop device; and physical devices, like the framebuffer > > and the touch-screen. > > > > In other words, device namespaces virtualize the _major/minor_ and the > > _state_ of device drivers. With the exception of VFS, network, and PTY > > (note: all three offer/are virtual devices), device drivers are otherwise > > not isolated between containers. > > > > 2. A namespace for interactive scenarios: a namespace can be "active" - > it > > has access to the hardware, e.g. display and touch-screen. This will be > the > > container with which the user is interacting right now. Otherwise a > > namespace is "non-active" - it still runs in the background, but can > > neither alter the display nor receive input from the touch-screen. > > Switching to another container means a context switch in the relevant > > drivers, so that they restore the state and now "obey" the other > namespace. > > > > You can also think about the "active" namespace as foreground, and the > > "non-active" as background, akin to foreground/background processes in a > > terminal with job-control. Similar to how a terminal delivers input to > the > > foreground task only but not to the background tasks - this is enforced > by > > the new device namespace. > > > > More details on this use-case are in the wiki: > > https://github.com/Cellrox/devns-patches/wiki/Thinvisor). > > I think this is going to take some talking, and looking at code. > > Hi Eric, If we can get people to take a quick look at the code before LPC that could make the LPC discussions more effective. Even looking at one of the subsystem patches can give a basic idea of the work we have done: https://github.com/Cellrox/linux/commits/devns-goldfish-3.4 I think you are talking about having wrappers around your devices so you > can share. Which is not the quite same problem the rest of us have been > thinking of when talking about a device namespace. > We are interested in all problems related to virtualizated view of devices inside a container, so let our work so far be a starting point to discuss all of them. > > My first impression is that this is better solved with more appropriate > abstractions in userspace or in the kernel. > > But we can talk at LPC and see what we can hash out. > Looking forward to that :-) Amir. > > Eric > _______________________________________________ > Containers mailing list > Containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org > https://lists.linuxfoundation.org/mailman/listinfo/containers > ^ permalink raw reply [flat|nested] 63+ messages in thread
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* Re: RFC: Device Namespaces [not found] ` <CAA2m6vexArJ+6jFbK80Amstk=LK30=XDNHdBHSswP=LgpSP-6A-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> @ 2013-09-09 0:51 ` Eric W. Biederman [not found] ` <871u4yddg4.fsf-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org> 0 siblings, 1 reply; 63+ messages in thread From: Eric W. Biederman @ 2013-09-09 0:51 UTC (permalink / raw) To: Amir Goldstein; +Cc: Linux Containers, lxc-devel Amir Goldstein <amir@cellrox.com> writes: > On Fri, Sep 6, 2013 at 7:50 PM, Eric W. Biederman > <ebiederm@xmission.com> wrote: > > Hi Eric, > > If we can get people to take a quick look at the code before LPC > that could make the LPC discussions more effective. > Even looking at one of the subsystem patches can give a basic > idea of the work we have done: > https://github.com/Cellrox/linux/commits/devns-goldfish-3.4 > > I think you are talking about having wrappers around your devices > so you > can share. Which is not the quite same problem the rest of us > have been > thinking of when talking about a device namespace. > > We are interested in all problems related to virtualizated view of > devices > inside a container, so let our work so far be a starting point to > discuss all of them. > > My first impression is that this is better solved with more > appropriate > abstractions in userspace or in the kernel. As I read your code, you are solving the problem of one opener of a device among a group of openers being able to access a device at a time. Which leads to the question why can't the multiplexing happen in userspace? I think with your design it would not be possible to play a song in one device namespace while doing work in the other. As a security model that isn't wrong but as someone trying to get work done that could be a real pain. The more common concern is to have devices we can use all of the time. There may be a need for a device namespace and multiplexing access to hardware devices makes that clearer. So far nothing has risen to the level of we actually need a device namespace to do X. Especially in an erra of hotplug and dynamic device numbers. It is arguable that you could do your kind of device multiplexing with a fuse device in userspace that implements your desired policy. And policy is where cell situtation seems to fall down because it hard codes one specific policy into the kernel, and a policy most situations don't find useful. Eric _______________________________________________ Containers mailing list Containers@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/containers ^ permalink raw reply [flat|nested] 63+ messages in thread
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* Re: RFC: Device Namespaces [not found] ` <871u4yddg4.fsf-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org> @ 2013-09-10 7:09 ` Amir Goldstein [not found] ` <CAA2m6vc_kWWGDWcdjk26N3YvTqZySLFxPQRjOD9_ypBOka2+GQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> 0 siblings, 1 reply; 63+ messages in thread From: Amir Goldstein @ 2013-09-10 7:09 UTC (permalink / raw) To: Eric W. Biederman; +Cc: Linux Containers, lxc-devel On Mon, Sep 9, 2013 at 2:51 AM, Eric W. Biederman <ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org>wrote: > Amir Goldstein <amir-3AfRa/s5aFdBDgjK7y7TUQ@public.gmane.org> writes: > > > On Fri, Sep 6, 2013 at 7:50 PM, Eric W. Biederman > > <ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org> wrote: > > > > Hi Eric, > > > > If we can get people to take a quick look at the code before LPC > > that could make the LPC discussions more effective. > > Even looking at one of the subsystem patches can give a basic > > idea of the work we have done: > > https://github.com/Cellrox/linux/commits/devns-goldfish-3.4 > > > > I think you are talking about having wrappers around your devices > > so you > > can share. Which is not the quite same problem the rest of us > > have been > > thinking of when talking about a device namespace. > > > > We are interested in all problems related to virtualizated view of > > devices > > inside a container, so let our work so far be a starting point to > > discuss all of them. > > > > My first impression is that this is better solved with more > > appropriate > > abstractions in userspace or in the kernel. > > As I read your code, you are solving the problem of one opener of a > device among a group of openers being able to access a device at a time. > Which leads to the question why can't the multiplexing happen in > userspace? > > I think with your design it would not be possible to play a song in one > device namespace while doing work in the other. As a security model > that isn't wrong but as someone trying to get work done that could be a > real pain. > As a matter of fact, in our multi persona phone, you *can* hear music played from background persona, but you *cannot* see images drawn from background persona. > The more common concern is to have devices we can use all of the time. > > There may be a need for a device namespace and multiplexing access to > hardware devices makes that clearer. So far nothing has risen to the > level of we actually need a device namespace to do X. Especially in an > erra of hotplug and dynamic device numbers. > > It is arguable that you could do your kind of device multiplexing with a > fuse device in userspace that implements your desired policy. > I agree about it being arguable :-) We shall present our arguments on LPC. > > And policy is where cell situtation seems to fall down because it hard > codes one specific policy into the kernel, and a policy most situations > don't find useful. > > It's true that for our product, we have made hardcoded policy decisions in our kernel patches, but that was just as a proof of concept for the technique. We do envision being able to dynamically assign a device to a specific devns (e.g. block,loop) keep a device shared between multi devns (e.g. audio) and in addition to that, being able to multiplex a device between multi devns (e.g. framebuffer) > Eric > ^ permalink raw reply [flat|nested] 63+ messages in thread
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* Re: RFC: Device Namespaces [not found] ` <CAA2m6vc_kWWGDWcdjk26N3YvTqZySLFxPQRjOD9_ypBOka2+GQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> @ 2013-09-25 11:05 ` Janne Karhunen [not found] ` <CAE=NcrbyFFoMn2nfBA_=ZtwD=eGLvqK=L-U9MuGrtJFLZfZppw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> 0 siblings, 1 reply; 63+ messages in thread From: Janne Karhunen @ 2013-09-25 11:05 UTC (permalink / raw) To: Amir Goldstein; +Cc: Linux Containers, Eric W. Biederman, lxc-devel On Tue, Sep 10, 2013 at 10:09 AM, Amir Goldstein <amir-3AfRa/s5aFdBDgjK7y7TUQ@public.gmane.org> wrote: > On Mon, Sep 9, 2013 at 2:51 AM, Eric W. Biederman <ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org>wrote: > >> Amir Goldstein <amir-3AfRa/s5aFdBDgjK7y7TUQ@public.gmane.org> writes: >> >> > On Fri, Sep 6, 2013 at 7:50 PM, Eric W. Biederman >> > <ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org> wrote: >> > >> > Hi Eric, >> > >> > If we can get people to take a quick look at the code before LPC >> > that could make the LPC discussions more effective. Hi, I think we are curious enough to experiment with Erics idea of implementing basic 'device namespace' in userspace (never miss an opportunity to throw away kernel code). Can anyone point out any obvious reason why this would not work if we consider bulk of the work being plain access filtering? That being said, is there a valid reason why binder is part of device namespace here instead of IPC? -- Janne ^ permalink raw reply [flat|nested] 63+ messages in thread
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* Re: RFC: Device Namespaces [not found] ` <CAE=NcrbyFFoMn2nfBA_=ZtwD=eGLvqK=L-U9MuGrtJFLZfZppw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> @ 2013-09-25 20:23 ` Eric W. Biederman [not found] ` <87ioxo4pm5.fsf-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org> 2013-09-25 21:34 ` Eric W. Biederman 1 sibling, 1 reply; 63+ messages in thread From: Eric W. Biederman @ 2013-09-25 20:23 UTC (permalink / raw) To: Janne Karhunen; +Cc: Linux Containers, lxc-devel Janne Karhunen <janne.karhunen-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> writes: > That being said, is there a valid reason why binder is part of device > namespace here instead of IPC? I think the practical issue with binder was simply that binder only allows for a single instance and thus is does not play nicely with containers. Eric ^ permalink raw reply [flat|nested] 63+ messages in thread
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* Re: [lxc-devel] RFC: Device Namespaces [not found] ` <87ioxo4pm5.fsf-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org> @ 2013-09-25 21:17 ` Jeremy Andrus [not found] ` <AD5F7BD2-0166-46BD-AB14-463C0E88BC92-eQaUEPhvms7ENvBUuze7eA@public.gmane.org> 0 siblings, 1 reply; 63+ messages in thread From: Jeremy Andrus @ 2013-09-25 21:17 UTC (permalink / raw) To: Eric W. Biederman; +Cc: Linux Containers, lxc-devel On Sep 25, 2013, at 4:23 PM, Eric W. Biederman <ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org> wrote: > Janne Karhunen <janne.karhunen-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> writes: > >> That being said, is there a valid reason why binder is part of device >> namespace here instead of IPC? > > I think the practical issue with binder was simply that binder only > allows for a single instance and thus is does not play nicely with > containers. It's true that there was a singleton paradigm in binder that had to be overcome, but I agree with Janne. It really belongs in the IPC namespace, and I don't see any technical reason not to move it there. -Jeremy ^ permalink raw reply [flat|nested] 63+ messages in thread
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* Re: [lxc-devel] RFC: Device Namespaces [not found] ` <AD5F7BD2-0166-46BD-AB14-463C0E88BC92-eQaUEPhvms7ENvBUuze7eA@public.gmane.org> @ 2013-09-25 21:47 ` Eric W. Biederman [not found] ` <8738osr2ue.fsf-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org> 0 siblings, 1 reply; 63+ messages in thread From: Eric W. Biederman @ 2013-09-25 21:47 UTC (permalink / raw) To: Jeremy Andrus; +Cc: Linux Containers, lxc-devel Jeremy Andrus <jeremya-eQaUEPhvms7ENvBUuze7eA@public.gmane.org> writes: > On Sep 25, 2013, at 4:23 PM, Eric W. Biederman <ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org> wrote: > >> Janne Karhunen <janne.karhunen-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> writes: >> >>> That being said, is there a valid reason why binder is part of device >>> namespace here instead of IPC? >> >> I think the practical issue with binder was simply that binder only >> allows for a single instance and thus is does not play nicely with >> containers. > > It's true that there was a singleton paradigm in binder that had to be > overcome, but I agree with Janne. It really belongs in the IPC namespace, > and I don't see any technical reason not to move it there. *Blink* I missed the IPC namespace suggestion. The IPC namespace sounds reasonable. Of course binder is still in staging because it has implementation and ABI problems. Little things like a 64bit kernel and a 32bit userspace don't work particularly well. So while fixing those problems it might be possible to fix the single container problem as well. It would be a weird direction for cleanup of binder to come from but I don't see why that wouldn't work. Personally until binder is out of staging it seems reasonable to push for an API that sucks less, or for a more general solution that Androdid could use instead of binder. One of the uses of namespaces is to clean up after problematic kernel design decisions. If we still have the option I would rather fix the problems than clean up after them. Eric ^ permalink raw reply [flat|nested] 63+ messages in thread
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* Re: [lxc-devel] RFC: Device Namespaces [not found] ` <8738osr2ue.fsf-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org> @ 2013-09-29 17:56 ` Amir Goldstein 0 siblings, 0 replies; 63+ messages in thread From: Amir Goldstein @ 2013-09-29 17:56 UTC (permalink / raw) To: Eric W. Biederman; +Cc: Greg Kroah-Hartman, Linux Containers, lxc-devel On Thu, Sep 26, 2013 at 12:47 AM, Eric W. Biederman <ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org>wrote: > Jeremy Andrus <jeremya-eQaUEPhvms7ENvBUuze7eA@public.gmane.org> writes: > > > On Sep 25, 2013, at 4:23 PM, Eric W. Biederman <ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org> > wrote: > > > >> Janne Karhunen <janne.karhunen-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> writes: > >> > >>> That being said, is there a valid reason why binder is part of device > >>> namespace here instead of IPC? > >> > >> I think the practical issue with binder was simply that binder only > >> allows for a single instance and thus is does not play nicely with > >> containers. > > > > It's true that there was a singleton paradigm in binder that had to be > > overcome, but I agree with Janne. It really belongs in the IPC namespace, > > and I don't see any technical reason not to move it there. > > *Blink* I missed the IPC namespace suggestion. > > The IPC namespace sounds reasonable. > Binder rewrite for IPC namespace is in the works (by Oren) We discussed this with Greg and adding namespace support to binder (in staging) seemed reasonable to him as well. > Of course binder is still in staging because it has implementation and > ABI problems. Little things like a 64bit kernel and a 32bit userspace > don't work particularly well. So while fixing those problems it might > be possible to fix the single container problem as well. It would be a > weird direction for cleanup of binder to come from but I don't see why > that wouldn't work. > > Personally until binder is out of staging it seems reasonable to push > for an API that sucks less, or for a more general solution that Androdid > could use instead of binder. > > One of the uses of namespaces is to clean up after problematic kernel > design decisions. If we still have the option I would rather fix the > problems than clean up after them. > > Eric > > _______________________________________________ > Containers mailing list > Containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org > https://lists.linuxfoundation.org/mailman/listinfo/containers > ^ permalink raw reply [flat|nested] 63+ messages in thread
* Device Namespaces [not found] ` <CAE=NcrbyFFoMn2nfBA_=ZtwD=eGLvqK=L-U9MuGrtJFLZfZppw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> 2013-09-25 20:23 ` Eric W. Biederman @ 2013-09-25 21:34 ` Eric W. Biederman [not found] ` <87bo3gshz5.fsf_-_-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org> 1 sibling, 1 reply; 63+ messages in thread From: Eric W. Biederman @ 2013-09-25 21:34 UTC (permalink / raw) To: Linux Containers Cc: Greg Kroah-Hartman, mhw-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8, Kay Sievers, Andy Lutomirski, lxc-devel, Stephane Graber, devel-GEFAQzZX7r8dnm+yROfE0A From conversations at Linux Plumbers Converence it became fairly clear that one if not the roughest edge on containers today is dealing with devices. - Hotplug does not work. - There seems to be no implementation that does a much beyond creating setting up a static set of /dev entries today. - Containers do not see the appropriate uevents for their container. One of the more compelling cases I heard was of someone who was running the a Linux Desktop in container and wanted to just let that container see the devices needed for his desktop, and not everything else. Talking with the OpenVZ folks it appears that preserving device numbers across checkpoint/restart is not currently an issue. However they reuse the same loopback minor number when they can which would hide this issue. So while it is clear we don't need to worry about migrating an application that cares about major/minor numbers of filesystems right now as the set of application that are migrated increases that situation may change. As the case with the network device ifindex has shown it is possible to implement filtering now and later when there is a usecase it is possible to expand filtering to actual namespace local identifiers. Thinking about it for the case of container migration the simplest solution for the rare application that needs something more may be to figure out how to send a kernel hotplug event. Something to think about when we encounter them. So the big issues for a device namespace to solve are filtering which devices a container has access to and being able to dynamically change which devices those are at run time (aka hotplug). After having thought about this for a bit I don't know if a pure userspace solution is sufficient or actually a good idea. - We can manually manage a tmpfs with device nodes in userspace. (But that is deprecated functionality in the mainstream kernel). - We can manually export a subset of sysfs with bind mounts. (But that feels hacky, and is essentially incompatible with hotplug). - We can relay a call of /sbin/hotplug from outside of a container to inside of a container based on policy. (But no one uses /sbin/hotplug anymore). - There is no way to fake netlink uevents for a container to see them. (The best we could do is replace udev everywhere with something that listens on a unix domain socket). - It would be nice to replace the device cgroup with a comprehensive solution that really works. (Among other things the device cgroup does not work in terms of struct device the underlying kernel abstraction for devices). We must manage sysfs entries as well device nodes because: - Seeing more than we should has the real potential to confuse userspace, especially a userspace that replays uevents. - Some device control must happens through writing to sysfs files and if we don't remove all root privileges from a container only by exporting a subset of sysfs to that container can we limit which sysfs nodes can be written to. The current kernel tagged sysfs entry support does not look like a good match for the impelementing device filtering. The common case will be allowing devices like /dev/zero, and /dev/null that live in /sys/devices/virtual and are the devices we are most likely to care about. Those devices need to live in multiple device namespaces so everyone can use them. Perhaps exclusive assignment will be the more common paradigm for device namespaces like it is for network devices in the network namespace but from what little I can of this problem right now I don't think so. I definitely think we should hold off on a kernel level implementation until we really understand the issues and are ready to implement device namespaces correctly. A userspace implementation looks like it can only do about 95% of what is really needed, but at the same time looks like an easy way to experiment until the problem is sufficiently well understood. At the end of the day we need to filter the devices a set of userspace processes can use and be able to change that set of devices dynamically. All of the rest of the infrastructure for that lives in the kernel, and keeping all of the infrastructure in one place where it can be maintained together is likely to be most maintainable. It looks like the code is just complicated enough and the use cases just boring enough that spreading the code to perform container device hotplug and container device filtering between a dozen userspace tools, and a hadful of userspace device managers will not be particularly managable at the end of the day. In summary the situation with device hoptlug and containers sucks today, and we need to do something. Running a linux desktop in a container is a reasonably good example use case. Having one standard common maintainable implementation would be very useful and the most logical place for that would be in the kernel. For now we should focus on simple device filtering and hotplug. Eric ^ permalink raw reply [flat|nested] 63+ messages in thread
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* Re: Device Namespaces [not found] ` <87bo3gshz5.fsf_-_-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org> @ 2013-09-26 5:33 ` Greg Kroah-Hartman [not found] ` <20130926053320.GB3725-U8xfFu+wG4EAvxtiuMwx3w@public.gmane.org> 2013-10-28 23:31 ` Andrey Wagin 1 sibling, 1 reply; 63+ messages in thread From: Greg Kroah-Hartman @ 2013-09-26 5:33 UTC (permalink / raw) To: Eric W. Biederman Cc: Linux Containers, Kay Sievers, Andy Lutomirski, devel-GEFAQzZX7r8dnm+yROfE0A, lxc-devel, mhw-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8, Stephane Graber On Wed, Sep 25, 2013 at 02:34:54PM -0700, Eric W. Biederman wrote: > So the big issues for a device namespace to solve are filtering which > devices a container has access to and being able to dynamically change > which devices those are at run time (aka hotplug). As _all_ devices are hotpluggable now (look, there's no CONFIG_HOTPLUG anymore, because it was redundant), I think you need to really think this through better (pci, memory, cpus, etc.) before you do anything in the kernel. > After having thought about this for a bit I don't know if a pure > userspace solution is sufficient or actually a good idea. > > - We can manually manage a tmpfs with device nodes in userspace. > (But that is deprecated functionality in the mainstream kernel). Yes, but I'm not going to namespace devtmpfs, as that is going to be an impossible task, right? And remember, udev doesn't create device nodes anymore... > - We can manually export a subset of sysfs with bind mounts. > (But that feels hacky, and is essentially incompatible with hotplug). True. > - We can relay a call of /sbin/hotplug from outside of a container > to inside of a container based on policy. > (But no one uses /sbin/hotplug anymore). That's right, they should be listening to libudev events, so why can't your daemon shuffle them off to the proper container, all in userspace? > - There is no way to fake netlink uevents for a container to see them. > (The best we could do is replace udev everywhere with something that > listens on a unix domain socket). You shouldn't need to do this. > - It would be nice to replace the device cgroup with a comprehensive > solution that really works. (Among other things the device cgroup > does not work in terms of struct device the underlying kernel > abstraction for devices). I didn't even know there was a device cgroup. Which means that if there is one, odds are it's useless. > We must manage sysfs entries as well device nodes because: > - Seeing more than we should has the real potential to confuse > userspace, especially a userspace that replays uevents. You should never replay uevents. If you don't do that, why can't you see all of sysfs? > - Some device control must happens through writing to sysfs files and > if we don't remove all root privileges from a container only by > exporting a subset of sysfs to that container can we limit which > sysfs nodes can be written to. But you have the issue of controlling devices in a "shared" way, which isn't going to be usable for almost all devices. > The current kernel tagged sysfs entry support does not look like a good > match for the impelementing device filtering. The common case will > be allowing devices like /dev/zero, and /dev/null that live in > /sys/devices/virtual and are the devices we are most likely to care > about. Those devices need to live in multiple device namespaces so > everyone can use them. Perhaps exclusive assignment will be the more > common paradigm for device namespaces like it is for network devices in > the network namespace but from what little I can of this problem right now I > don't think so. > > I definitely think we should hold off on a kernel level implementation > until we really understand the issues and are ready to implement device > namespaces correctly. I agree, especially as I don't think this will ever work. > A userspace implementation looks like it can only do about 95% of what > is really needed, but at the same time looks like an easy way to > experiment until the problem is sufficiently well understood. 95% is probably way better than what you have today, and will fit the needs of almost everyone today, so why not do it? I'd argue that those last 5% either are custom solutions that never get merged, or candidates for true virtulization. > In summary the situation with device hoptlug and containers sucks today, > and we need to do something. Running a linux desktop in a container is > a reasonably good example use case. No it isn't. I'd argue that this is a horrible use case, one that you shouldn't do. Why not just use multi-head machines like people do who really want to do this, relying on user separation? That's a workable solution that is quite common and works very well today. > Having one standard common maintainable implementation would be very > useful and the most logical place for that would be in the kernel. > For now we should focus on simple device filtering and hotplug. Just listen for libudev stuff, don't try to filter them, or ever "replay" them, that way lies madness, and lots of nasty race conditions that is guaranteed to break things. good luck, greg k-h ^ permalink raw reply [flat|nested] 63+ messages in thread
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* Re: Device Namespaces [not found] ` <20130926053320.GB3725-U8xfFu+wG4EAvxtiuMwx3w@public.gmane.org> @ 2013-09-26 8:25 ` Janne Karhunen [not found] ` <CAE=NcrbPXGWU8FUgwchXyL5HjXf+4AKbgUWGe1ZO=Xcq=iV-Lg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> 2013-10-01 6:19 ` Janne Karhunen 1 sibling, 1 reply; 63+ messages in thread From: Janne Karhunen @ 2013-09-26 8:25 UTC (permalink / raw) To: Greg Kroah-Hartman Cc: Linux Containers, Kay Sievers, Andy Lutomirski, devel-GEFAQzZX7r8dnm+yROfE0A, Eric W. Biederman, lxc-devel, mhw-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8, Stephane Graber On Thu, Sep 26, 2013 at 8:33 AM, Greg Kroah-Hartman <gregkh-hQyY1W1yCW8ekmWlsbkhG0B+6BGkLq7r@public.gmane.org> wrote: >> In summary the situation with device hoptlug and containers sucks today, >> and we need to do something. Running a linux desktop in a container is >> a reasonably good example use case. > > No it isn't. I'd argue that this is a horrible use case, one that you > shouldn't do. Why not just use multi-head machines like people do who > really want to do this, relying on user separation? That's a workable > solution that is quite common and works very well today. I suppose so, but now you take the assumption that there is no need for running multiple Linux variants on the same host (say Ubuntu and Android side by side). Is this something you would not like to see done? -- Janne ^ permalink raw reply [flat|nested] 63+ messages in thread
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* Re: Device Namespaces [not found] ` <CAE=NcrbPXGWU8FUgwchXyL5HjXf+4AKbgUWGe1ZO=Xcq=iV-Lg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> @ 2013-09-26 13:56 ` Greg Kroah-Hartman [not found] ` <20130926135604.GA16624-U8xfFu+wG4EAvxtiuMwx3w@public.gmane.org> 0 siblings, 1 reply; 63+ messages in thread From: Greg Kroah-Hartman @ 2013-09-26 13:56 UTC (permalink / raw) To: Janne Karhunen Cc: Linux Containers, Kay Sievers, Andy Lutomirski, devel-GEFAQzZX7r8dnm+yROfE0A, Eric W. Biederman, lxc-devel, mhw-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8, Stephane Graber On Thu, Sep 26, 2013 at 11:25:56AM +0300, Janne Karhunen wrote: > On Thu, Sep 26, 2013 at 8:33 AM, Greg Kroah-Hartman > <gregkh-hQyY1W1yCW8ekmWlsbkhG0B+6BGkLq7r@public.gmane.org> wrote: > > >> In summary the situation with device hoptlug and containers sucks today, > >> and we need to do something. Running a linux desktop in a container is > >> a reasonably good example use case. > > > > No it isn't. I'd argue that this is a horrible use case, one that you > > shouldn't do. Why not just use multi-head machines like people do who > > really want to do this, relying on user separation? That's a workable > > solution that is quite common and works very well today. > > I suppose so, but now you take the assumption that there is no > need for running multiple Linux variants on the same host (say > Ubuntu and Android side by side). Is this something you would > not like to see done? You can do that today without any need for device namespaces, so why is this an issue here? greg k-h ^ permalink raw reply [flat|nested] 63+ messages in thread
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* Re: Device Namespaces [not found] ` <20130926135604.GA16624-U8xfFu+wG4EAvxtiuMwx3w@public.gmane.org> @ 2013-09-26 17:01 ` Janne Karhunen [not found] ` <CAE=NcrY3xC1AF_GV2b1KsF7AwYZTuGBuKLS5yBUWoWcmKU4YBg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> 0 siblings, 1 reply; 63+ messages in thread From: Janne Karhunen @ 2013-09-26 17:01 UTC (permalink / raw) To: Greg Kroah-Hartman Cc: Linux Containers, Kay Sievers, Andy Lutomirski, devel, Eric W. Biederman, lxc-devel, mhw, Stephane Graber On Thu, Sep 26, 2013 at 4:56 PM, Greg Kroah-Hartman <gregkh-hQyY1W1yCW8ekmWlsbkhG0B+6BGkLq7r@public.gmane.org> wrote: >> I suppose so, but now you take the assumption that there is no >> need for running multiple Linux variants on the same host (say >> Ubuntu and Android side by side). Is this something you would >> not like to see done? > > You can do that today without any need for device namespaces, so why is > this an issue here? I think you misunderstood me. I wasn't so much advocating on the device namespace part, just the issue at hand (device access filtering based on which ns happens to be 'active'). We are already trying to do this in userspace, let's see how that goes. That being said, our wish would be to support any combination of OS's and frankly, I'd be slightly annoyed to tell the customer that they can't do two Androids or we magically run out of bits. -- Janne ^ permalink raw reply [flat|nested] 63+ messages in thread
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* Re: Device Namespaces [not found] ` <CAE=NcrY3xC1AF_GV2b1KsF7AwYZTuGBuKLS5yBUWoWcmKU4YBg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> @ 2013-09-26 17:07 ` Greg Kroah-Hartman [not found] ` <20130926170757.GA9345-U8xfFu+wG4EAvxtiuMwx3w@public.gmane.org> 0 siblings, 1 reply; 63+ messages in thread From: Greg Kroah-Hartman @ 2013-09-26 17:07 UTC (permalink / raw) To: Janne Karhunen Cc: Linux Containers, Kay Sievers, Andy Lutomirski, devel, Eric W. Biederman, lxc-devel, mhw, Stephane Graber On Thu, Sep 26, 2013 at 08:01:31PM +0300, Janne Karhunen wrote: > That being said, our wish would be to support any combination of > OS's and frankly, I'd be slightly annoyed to tell the customer that > they can't do two Androids or we magically run out of bits. If you want to support "any" combination of operating systems, then use a hypervisor, that's what they are there for :) ^ permalink raw reply [flat|nested] 63+ messages in thread
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* Re: Device Namespaces [not found] ` <20130926170757.GA9345-U8xfFu+wG4EAvxtiuMwx3w@public.gmane.org> @ 2013-09-26 17:56 ` Janne Karhunen 2013-09-30 15:37 ` James Bottomley 1 sibling, 0 replies; 63+ messages in thread From: Janne Karhunen @ 2013-09-26 17:56 UTC (permalink / raw) To: Greg Kroah-Hartman Cc: Linux Containers, Kay Sievers, Andy Lutomirski, devel, Eric W. Biederman, lxc-devel, mhw, Stephane Graber On Thu, Sep 26, 2013 at 8:07 PM, Greg Kroah-Hartman <gregkh-hQyY1W1yCW8ekmWlsbkhG0B+6BGkLq7r@public.gmane.org> wrote: >> That being said, our wish would be to support any combination of >> OS's and frankly, I'd be slightly annoyed to tell the customer that >> they can't do two Androids or we magically run out of bits. > > If you want to support "any" combination of operating systems, then use > a hypervisor, that's what they are there for :) Only relevant mobile OS's are of interest ;) -- Janne ^ permalink raw reply [flat|nested] 63+ messages in thread
* Re: Device Namespaces [not found] ` <20130926170757.GA9345-U8xfFu+wG4EAvxtiuMwx3w@public.gmane.org> 2013-09-26 17:56 ` Janne Karhunen @ 2013-09-30 15:37 ` James Bottomley [not found] ` <1380555439.2161.5.camel-sFMDBYUN5F8GjUHQrlYNx2Wm91YjaHnnhRte9Li2A+AAvxtiuMwx3w@public.gmane.org> 1 sibling, 1 reply; 63+ messages in thread From: James Bottomley @ 2013-09-30 15:37 UTC (permalink / raw) To: Greg Kroah-Hartman Cc: Linux Containers, Kay Sievers, Stephane Graber, Andy Lutomirski, Eric W. Biederman, lxc-devel, mhw, devel On Thu, 2013-09-26 at 10:07 -0700, Greg Kroah-Hartman wrote: > On Thu, Sep 26, 2013 at 08:01:31PM +0300, Janne Karhunen wrote: > > That being said, our wish would be to support any combination of > > OS's and frankly, I'd be slightly annoyed to tell the customer that > > they can't do two Androids or we magically run out of bits. > > If you want to support "any" combination of operating systems, then use > a hypervisor, that's what they are there for :) No that's not quite the right way to think about it: The correct statement is only use a hypervisor if you need different kernels. With Windows, it happens to be true that you need a different kernel for each different OS version. However; with Linux, thanks to strong ABI backwards compatibility, you mostly don't. The way OpenVZ works today is that it installs a modified kernel which can then bring up every Linux OS in a separate container. Our use case is the hosters that give you root login to a virtual private server and allow you to upgrade it on your own. The reason for using a container rather than a hypervisor is the old density and elasticity one: 3x the density (i.e. 1/3 the overhead cost to the hoster) and the boot only needs to start at init, not bring up of virtual hardware and booting a second kernel. James ^ permalink raw reply [flat|nested] 63+ messages in thread
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* Re: Device Namespaces [not found] ` <1380555439.2161.5.camel-sFMDBYUN5F8GjUHQrlYNx2Wm91YjaHnnhRte9Li2A+AAvxtiuMwx3w@public.gmane.org> @ 2013-09-30 16:11 ` Greg Kroah-Hartman [not found] ` <20130930161117.GA26459-U8xfFu+wG4EAvxtiuMwx3w@public.gmane.org> 0 siblings, 1 reply; 63+ messages in thread From: Greg Kroah-Hartman @ 2013-09-30 16:11 UTC (permalink / raw) To: James Bottomley Cc: Linux Containers, Kay Sievers, Stephane Graber, Andy Lutomirski, Eric W. Biederman, lxc-devel, mhw, devel On Mon, Sep 30, 2013 at 08:37:19AM -0700, James Bottomley wrote: > On Thu, 2013-09-26 at 10:07 -0700, Greg Kroah-Hartman wrote: > > On Thu, Sep 26, 2013 at 08:01:31PM +0300, Janne Karhunen wrote: > > > That being said, our wish would be to support any combination of > > > OS's and frankly, I'd be slightly annoyed to tell the customer that > > > they can't do two Androids or we magically run out of bits. > > > > If you want to support "any" combination of operating systems, then use > > a hypervisor, that's what they are there for :) > > No that's not quite the right way to think about it: The correct > statement is only use a hypervisor if you need different kernels. With > Windows, it happens to be true that you need a different kernel for each > different OS version. However; with Linux, thanks to strong ABI > backwards compatibility, you mostly don't. The way OpenVZ works today > is that it installs a modified kernel which can then bring up every > Linux OS in a separate container. Our use case is the hosters that give > you root login to a virtual private server and allow you to upgrade it > on your own. The reason for using a container rather than a hypervisor > is the old density and elasticity one: 3x the density (i.e. 1/3 the > overhead cost to the hoster) and the boot only needs to start at init, > not bring up of virtual hardware and booting a second kernel. I understand that some people really like the idea of using OpenVZ for various things like this, but to claim that because of it we need to hack up the driver core in the kernel into unimaginable pieces is not necessarily something that I'll agree with. But all of this is just words, I have yet to see any patches for any of this, so I'll just wait until that happens before worrying about it... thanks, greg k-h ^ permalink raw reply [flat|nested] 63+ messages in thread
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* Re: Device Namespaces [not found] ` <20130930161117.GA26459-U8xfFu+wG4EAvxtiuMwx3w@public.gmane.org> @ 2013-09-30 16:33 ` James Bottomley 0 siblings, 0 replies; 63+ messages in thread From: James Bottomley @ 2013-09-30 16:33 UTC (permalink / raw) To: Greg Kroah-Hartman Cc: Linux Containers, Kay Sievers, Stephane Graber, Andy Lutomirski, Eric W. Biederman, lxc-devel, mhw, devel On Mon, 2013-09-30 at 09:11 -0700, Greg Kroah-Hartman wrote: > On Mon, Sep 30, 2013 at 08:37:19AM -0700, James Bottomley wrote: > > On Thu, 2013-09-26 at 10:07 -0700, Greg Kroah-Hartman wrote: > > > On Thu, Sep 26, 2013 at 08:01:31PM +0300, Janne Karhunen wrote: > > > > That being said, our wish would be to support any combination of > > > > OS's and frankly, I'd be slightly annoyed to tell the customer that > > > > they can't do two Androids or we magically run out of bits. > > > > > > If you want to support "any" combination of operating systems, then use > > > a hypervisor, that's what they are there for :) > > > > No that's not quite the right way to think about it: The correct > > statement is only use a hypervisor if you need different kernels. With > > Windows, it happens to be true that you need a different kernel for each > > different OS version. However; with Linux, thanks to strong ABI > > backwards compatibility, you mostly don't. The way OpenVZ works today > > is that it installs a modified kernel which can then bring up every > > Linux OS in a separate container. Our use case is the hosters that give > > you root login to a virtual private server and allow you to upgrade it > > on your own. The reason for using a container rather than a hypervisor > > is the old density and elasticity one: 3x the density (i.e. 1/3 the > > overhead cost to the hoster) and the boot only needs to start at init, > > not bring up of virtual hardware and booting a second kernel. > > I understand that some people really like the idea of using OpenVZ for > various things like this, but to claim that because of it we need to > hack up the driver core in the kernel into unimaginable pieces is not > necessarily something that I'll agree with. I don't believe I claimed that. In fact, from 3.9 we can already bring up an OpenVZ containerised system running different versions of Linux that you can give someone root access to with no kernel modifications whatsoever. The user space solution currently works for us because we're handing out server VPSs, so the device configuration is fixed as we init the container. However, we do have use cases for dynamic instead of static device configurations, which is why we're participating in the debate. > But all of this is just words, I have yet to see any patches for any of > this, so I'll just wait until that happens before worrying about it... Well, that's because we're still debating what the best approach is. If you want a historical parallel: the comments you make above (hack up the ... kernel into unimaginable pieces) is an almost exact mirror of the comments that were made rejecting the in-kernel Checkpoint/Restore patches at the 2010 Kernel Summit ... yet we have it fully functional today in a form that proved acceptable. James ^ permalink raw reply [flat|nested] 63+ messages in thread
* Re: Device Namespaces [not found] ` <20130926053320.GB3725-U8xfFu+wG4EAvxtiuMwx3w@public.gmane.org> 2013-09-26 8:25 ` Janne Karhunen @ 2013-10-01 6:19 ` Janne Karhunen [not found] ` <CAE=NcrYV2RiMV7PcwEjFGFRBrz9XdZGs86Wau2a+6xpYN2aEHA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> 1 sibling, 1 reply; 63+ messages in thread From: Janne Karhunen @ 2013-10-01 6:19 UTC (permalink / raw) To: Greg Kroah-Hartman Cc: Linux Containers, Kay Sievers, Andy Lutomirski, devel, Eric W. Biederman, lxc-devel, mhw, Stephane Graber On Thu, Sep 26, 2013 at 8:33 AM, Greg Kroah-Hartman <gregkh-hQyY1W1yCW8ekmWlsbkhG0B+6BGkLq7r@public.gmane.org> wrote: >> - We can relay a call of /sbin/hotplug from outside of a container >> to inside of a container based on policy. >> (But no one uses /sbin/hotplug anymore). > > That's right, they should be listening to libudev events, so why can't > your daemon shuffle them off to the proper container, all in userspace? Which reminds me, one potential reason being.. http://lists.linuxfoundation.org/pipermail/containers/2013-May/032591.html -- Janne ^ permalink raw reply [flat|nested] 63+ messages in thread
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* Re: Device Namespaces [not found] ` <CAE=NcrYV2RiMV7PcwEjFGFRBrz9XdZGs86Wau2a+6xpYN2aEHA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> @ 2013-10-01 17:27 ` Andy Lutomirski [not found] ` <CALCETrWWoHzuJcnfEUY+cFpOgT5gnG8U1cVbCW0_8V7Z_v6DJw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> 2013-10-01 17:33 ` Greg Kroah-Hartman 1 sibling, 1 reply; 63+ messages in thread From: Andy Lutomirski @ 2013-10-01 17:27 UTC (permalink / raw) To: Janne Karhunen Cc: Greg Kroah-Hartman, Linux Containers, Kay Sievers, Stephane Graber, Eric W. Biederman, lxc-devel, mhw, devel On Tue, Oct 1, 2013 at 7:19 AM, Janne Karhunen <janne.karhunen-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote: > On Thu, Sep 26, 2013 at 8:33 AM, Greg Kroah-Hartman > <gregkh-hQyY1W1yCW8ekmWlsbkhG0B+6BGkLq7r@public.gmane.org> wrote: > >>> - We can relay a call of /sbin/hotplug from outside of a container >>> to inside of a container based on policy. >>> (But no one uses /sbin/hotplug anymore). >> >> That's right, they should be listening to libudev events, so why can't >> your daemon shuffle them off to the proper container, all in userspace? > > Which reminds me, one potential reason being.. > http://lists.linuxfoundation.org/pipermail/containers/2013-May/032591.html > Can't the daemon live outside the container and shuffle stuff in? IOW, there seems to be little point in containerizing things if you're just going to punch a privilege hole in the namespace. FWIW, I think that the capability evolution rules are crap, but changing them is a can of worms, and enough people seem to thing the status quo is acceptable that this is unlikely to ever get fixed. --Andy ^ permalink raw reply [flat|nested] 63+ messages in thread
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* Re: Device Namespaces [not found] ` <CALCETrWWoHzuJcnfEUY+cFpOgT5gnG8U1cVbCW0_8V7Z_v6DJw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> @ 2013-10-01 17:53 ` Serge E. Hallyn [not found] ` <20131001175345.GA4145-7LNsyQBKDXoIagZqoN9o3w@public.gmane.org> 2013-10-01 18:36 ` Janne Karhunen 1 sibling, 1 reply; 63+ messages in thread From: Serge E. Hallyn @ 2013-10-01 17:53 UTC (permalink / raw) To: Andy Lutomirski Cc: Kay Sievers, Linux Containers, lxc-devel, Stephane Graber, Eric W. Biederman, Greg Kroah-Hartman, mhw, devel Quoting Andy Lutomirski (luto-kltTT9wpgjJwATOyAt5JVQ@public.gmane.org): > On Tue, Oct 1, 2013 at 7:19 AM, Janne Karhunen <janne.karhunen-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote: > > On Thu, Sep 26, 2013 at 8:33 AM, Greg Kroah-Hartman > > <gregkh-hQyY1W1yCW8ekmWlsbkhG0B+6BGkLq7r@public.gmane.org> wrote: > > > >>> - We can relay a call of /sbin/hotplug from outside of a container > >>> to inside of a container based on policy. > >>> (But no one uses /sbin/hotplug anymore). > >> > >> That's right, they should be listening to libudev events, so why can't > >> your daemon shuffle them off to the proper container, all in userspace? > > > > Which reminds me, one potential reason being.. > > http://lists.linuxfoundation.org/pipermail/containers/2013-May/032591.html > > > > Can't the daemon live outside the container and shuffle stuff in? That's exactly what Michael Warfield is suggesting, fwiw. -serge ^ permalink raw reply [flat|nested] 63+ messages in thread
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* Re: Device Namespaces [not found] ` <20131001175345.GA4145-7LNsyQBKDXoIagZqoN9o3w@public.gmane.org> @ 2013-10-01 19:51 ` Eric W. Biederman [not found] ` <87had0wz07.fsf-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org> 0 siblings, 1 reply; 63+ messages in thread From: Eric W. Biederman @ 2013-10-01 19:51 UTC (permalink / raw) To: Serge E. Hallyn Cc: Kay Sievers, Linux Containers, lxc-devel, Andy Lutomirski, devel, Greg Kroah-Hartman, mhw, Stephane Graber "Serge E. Hallyn" <serge-A9i7LUbDfNHQT0dZR+AlfA@public.gmane.org> writes: > Quoting Andy Lutomirski (luto-kltTT9wpgjJwATOyAt5JVQ@public.gmane.org): >> On Tue, Oct 1, 2013 at 7:19 AM, Janne Karhunen <janne.karhunen-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote: >> > On Thu, Sep 26, 2013 at 8:33 AM, Greg Kroah-Hartman >> > <gregkh-hQyY1W1yCW8ekmWlsbkhG0B+6BGkLq7r@public.gmane.org> wrote: >> > >> >>> - We can relay a call of /sbin/hotplug from outside of a container >> >>> to inside of a container based on policy. >> >>> (But no one uses /sbin/hotplug anymore). >> >> >> >> That's right, they should be listening to libudev events, so why can't >> >> your daemon shuffle them off to the proper container, all in userspace? >> > >> > Which reminds me, one potential reason being.. >> > http://lists.linuxfoundation.org/pipermail/containers/2013-May/032591.html >> > >> >> Can't the daemon live outside the container and shuffle stuff in? > > That's exactly what Michael Warfield is suggesting, fwiw. Michael Warfields example of dynamically assigning serial ports to containers is a pretty good test case. Serial ports are extremely well known kernel objects who evolution effectively stopped long ago. When we need it we have ptys to virtual serial ports when we need it, but in general unprivileged users are safe to directly use a serial port device. Glossing over the details. The general problem is some policy exists outside of the container that deciedes if an when a container gets a serial port and stuffs it in. The expectation is that system containers will then run the udev rules and send the libuevent event. To make that all work without kernel modifications requires placing a faux-udev in the container, that listens for a device assignment from outside the container and then does exactly what udev would have done. The problems with this that I see are: - udev is a moving target making it hard to build a faux-udev that will work everywhere. - On distro's running systemd and udev integration is sufficiently tight that I am not certain a faux-udev is possible or will continue to be possible. - There are two other widely deployed solutions for managing hotplug devices besides udev. So given these difficulties I do not believe that the evolution of linux device management is done, and that patches to udev, the kernel or both will be needed. While it would be good for testing and understanding the problem I don't think a faux-udev will be a long term maintainable solution. I also understand the point that we aren't talking patches yet and just discussing ideas. Right now it is my hope that if we talk this out we can figure out a general direction that has a hope of working. From where I am standing faking uevents instead of replacing udev/mdev/whatever looks simpler and more maintainable. Eric ^ permalink raw reply [flat|nested] 63+ messages in thread
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* Re: Device Namespaces [not found] ` <87had0wz07.fsf-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org> @ 2013-10-01 20:46 ` Serge Hallyn 2013-10-01 22:59 ` [lxc-devel] " Michael H. Warfield 2013-10-02 22:55 ` Eric W. Biederman 2013-10-01 20:57 ` Greg Kroah-Hartman 2013-10-01 22:19 ` Michael H. Warfield 2 siblings, 2 replies; 63+ messages in thread From: Serge Hallyn @ 2013-10-01 20:46 UTC (permalink / raw) To: Eric W. Biederman Cc: Greg Kroah-Hartman, Linux Containers, Kay Sievers, Stephane Graber, Andy Lutomirski, lxc-devel, mhw, devel Quoting Eric W. Biederman (ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org): > "Serge E. Hallyn" <serge-A9i7LUbDfNHQT0dZR+AlfA@public.gmane.org> writes: > > > Quoting Andy Lutomirski (luto-kltTT9wpgjJwATOyAt5JVQ@public.gmane.org): > >> On Tue, Oct 1, 2013 at 7:19 AM, Janne Karhunen <janne.karhunen-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote: > >> > On Thu, Sep 26, 2013 at 8:33 AM, Greg Kroah-Hartman > >> > <gregkh-hQyY1W1yCW8ekmWlsbkhG0B+6BGkLq7r@public.gmane.org> wrote: > >> > > >> >>> - We can relay a call of /sbin/hotplug from outside of a container > >> >>> to inside of a container based on policy. > >> >>> (But no one uses /sbin/hotplug anymore). > >> >> > >> >> That's right, they should be listening to libudev events, so why can't > >> >> your daemon shuffle them off to the proper container, all in userspace? > >> > > >> > Which reminds me, one potential reason being.. > >> > http://lists.linuxfoundation.org/pipermail/containers/2013-May/032591.html > >> > > >> > >> Can't the daemon live outside the container and shuffle stuff in? > > > > That's exactly what Michael Warfield is suggesting, fwiw. > > Michael Warfields example of dynamically assigning serial ports to > containers is a pretty good test case. Serial ports are extremely well > known kernel objects who evolution effectively stopped long ago. When > we need it we have ptys to virtual serial ports when we need it, but in > general unprivileged users are safe to directly use a serial port > device. > > Glossing over the details. The general problem is some policy exists > outside of the container that deciedes if an when a container gets a > serial port and stuffs it in. > > The expectation is that system containers will then run the udev > rules and send the libuevent event. I thought the suggestion was that udev on the host would be given container-specific rules, saying "plop this device into /dev/container1/" (with /dev/container1 being bind-mounted to $container1_rootfs/dev). -serge ^ permalink raw reply [flat|nested] 63+ messages in thread
* Re: [lxc-devel] Device Namespaces 2013-10-01 20:46 ` Serge Hallyn @ 2013-10-01 22:59 ` Michael H. Warfield 2013-10-02 22:55 ` Eric W. Biederman 1 sibling, 0 replies; 63+ messages in thread From: Michael H. Warfield @ 2013-10-01 22:59 UTC (permalink / raw) To: Serge Hallyn Cc: Greg Kroah-Hartman, Michael H.Warfield, Kay Sievers, Andy Lutomirski, Eric W. Biederman, lxc-devel, Linux Containers, devel [-- Attachment #1.1: Type: text/plain, Size: 4401 bytes --] On Tue, 2013-10-01 at 15:46 -0500, Serge Hallyn wrote: > Quoting Eric W. Biederman (ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org): > > "Serge E. Hallyn" <serge-A9i7LUbDfNHQT0dZR+AlfA@public.gmane.org> writes: > > > > > Quoting Andy Lutomirski (luto-kltTT9wpgjJwATOyAt5JVQ@public.gmane.org): > > >> On Tue, Oct 1, 2013 at 7:19 AM, Janne Karhunen <janne.karhunen@gmail.com> wrote: > > >> > On Thu, Sep 26, 2013 at 8:33 AM, Greg Kroah-Hartman > > >> > <gregkh-hQyY1W1yCW8ekmWlsbkhG0B+6BGkLq7r@public.gmane.org> wrote: > > >> > > > >> >>> - We can relay a call of /sbin/hotplug from outside of a container > > >> >>> to inside of a container based on policy. > > >> >>> (But no one uses /sbin/hotplug anymore). > > >> >> > > >> >> That's right, they should be listening to libudev events, so why can't > > >> >> your daemon shuffle them off to the proper container, all in userspace? > > >> > > > >> > Which reminds me, one potential reason being.. > > >> > http://lists.linuxfoundation.org/pipermail/containers/2013-May/032591.html > > >> > > > >> > > >> Can't the daemon live outside the container and shuffle stuff in? > > > > > > That's exactly what Michael Warfield is suggesting, fwiw. > > > > Michael Warfields example of dynamically assigning serial ports to > > containers is a pretty good test case. Serial ports are extremely well > > known kernel objects who evolution effectively stopped long ago. When > > we need it we have ptys to virtual serial ports when we need it, but in > > general unprivileged users are safe to directly use a serial port > > device. > > > > Glossing over the details. The general problem is some policy exists > > outside of the container that deciedes if an when a container gets a > > serial port and stuffs it in. > > > > The expectation is that system containers will then run the udev > > rules and send the libuevent event. > I thought the suggestion was that udev on the host would be given > container-specific rules, saying "plop this device into /dev/container1/" > (with /dev/container1 being bind-mounted to $container1_rootfs/dev). I think that the "given container-specific rules, saying..." thing was on my chart of options as the one with the big cloudy shaped object in the lower right corner labeled "and then a miracle occurs". The basic part is the mapping from /dev into /dev/lxc/container. That should be doable based on the rules in the host and a basic udev trigger along with a simple mapping configuration. The "given container-specific" part becomes a morass if it gets complicated enough. What I was envisioning was a very simple system of container specific {match} and {map} objects. If a name or symlink passed to the daemon from a udev trigger matched a match, then the name and symlinks and additional maps would be mapped into the appropriate container subdirectory. That works real well if the container and host udev rules are congruent. The tough part is the "container-specific" rules which was the part I specifically mentioned that I had no clue how to make happen. That's a non-trivial task if the container is allowed to make arbitrary udev rule changes based on what they are allowed to receive from the host (and how do we trigger the changes in the host when a change is made in the container). It's easily doable where the container rules are congruent with the host rules. Where they are orthogonal gets much more complicated. But... All that being said, I will take the congruent solution as a starting point (and that will not be an 80% solution - it will be more like a 95% solution) and we can argue about the corner cases and deltas after that. Doable, yes, for some value of doable. I like what Greg was saying about using libudev but I'm totally in the dark as to how to effectively hook that or if it would even work in the container. That one is not in my realm. > -serge Regards, Mike -- Michael H. Warfield (AI4NB) | Desk: (404) 236-2807 Senior Researcher - X-Force | Cell: (678) 463-0932 IBM Security Services | mhw-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org mhw-UGBql2FAF+1Wk0Htik3J/w@public.gmane.org 6303 Barfield Road | http://www.iss.net/ Atlanta, Georgia 30328 | http://www.wittsend.com/mhw/ | PGP Key: 0x674627FF [-- Attachment #1.2: This is a digitally signed message part --] [-- Type: application/pgp-signature, Size: 482 bytes --] [-- Attachment #2: Type: text/plain, Size: 205 bytes --] _______________________________________________ Containers mailing list Containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org https://lists.linuxfoundation.org/mailman/listinfo/containers ^ permalink raw reply [flat|nested] 63+ messages in thread
* Re: Device Namespaces 2013-10-01 20:46 ` Serge Hallyn 2013-10-01 22:59 ` [lxc-devel] " Michael H. Warfield @ 2013-10-02 22:55 ` Eric W. Biederman 1 sibling, 0 replies; 63+ messages in thread From: Eric W. Biederman @ 2013-10-02 22:55 UTC (permalink / raw) To: Serge Hallyn Cc: Greg Kroah-Hartman, Linux Containers, Kay Sievers, Stephane Graber, Andy Lutomirski, lxc-devel, mhw, devel Serge Hallyn <serge.hallyn-GeWIH/nMZzLQT0dZR+AlfA@public.gmane.org> writes: >> Glossing over the details. The general problem is some policy exists >> outside of the container that deciedes if an when a container gets a >> serial port and stuffs it in. >> >> The expectation is that system containers will then run the udev >> rules and send the libuevent event. > > I thought the suggestion was that udev on the host would be given > container-specific rules, saying "plop this device into /dev/container1/" > (with /dev/container1 being bind-mounted to $container1_rootfs/dev). That is what I was trying to describe. We still need something that lets the software in the container know it needs to do something. I may be blind but right now short of replacing the internal udev, or modifying the kernel I don't see a solution for letting software in a container know there is a new device it can use. Once we get the notification issue sorted out I think we have enough to bring up a full desktop environment in a container and be able to say we don't need anything else from devices unless someone discovers that checkpoint/restart actually needs minor numbers to be preserved. Eric ^ permalink raw reply [flat|nested] 63+ messages in thread
* Re: Device Namespaces [not found] ` <87had0wz07.fsf-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org> 2013-10-01 20:46 ` Serge Hallyn @ 2013-10-01 20:57 ` Greg Kroah-Hartman [not found] ` <20131001205718.GA17036-U8xfFu+wG4EAvxtiuMwx3w@public.gmane.org> 2013-10-01 22:19 ` Michael H. Warfield 2 siblings, 1 reply; 63+ messages in thread From: Greg Kroah-Hartman @ 2013-10-01 20:57 UTC (permalink / raw) To: Eric W. Biederman Cc: Linux Containers, Kay Sievers, Andy Lutomirski, devel, lxc-devel, mhw, Stephane Graber On Tue, Oct 01, 2013 at 12:51:36PM -0700, Eric W. Biederman wrote: > "Serge E. Hallyn" <serge-A9i7LUbDfNHQT0dZR+AlfA@public.gmane.org> writes: > > > Quoting Andy Lutomirski (luto-kltTT9wpgjJwATOyAt5JVQ@public.gmane.org): > >> On Tue, Oct 1, 2013 at 7:19 AM, Janne Karhunen <janne.karhunen-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote: > >> > On Thu, Sep 26, 2013 at 8:33 AM, Greg Kroah-Hartman > >> > <gregkh-hQyY1W1yCW8ekmWlsbkhG0B+6BGkLq7r@public.gmane.org> wrote: > >> > > >> >>> - We can relay a call of /sbin/hotplug from outside of a container > >> >>> to inside of a container based on policy. > >> >>> (But no one uses /sbin/hotplug anymore). > >> >> > >> >> That's right, they should be listening to libudev events, so why can't > >> >> your daemon shuffle them off to the proper container, all in userspace? > >> > > >> > Which reminds me, one potential reason being.. > >> > http://lists.linuxfoundation.org/pipermail/containers/2013-May/032591.html > >> > > >> > >> Can't the daemon live outside the container and shuffle stuff in? > > > > That's exactly what Michael Warfield is suggesting, fwiw. > > Michael Warfields example of dynamically assigning serial ports to > containers is a pretty good test case. Serial ports are extremely well > known kernel objects who evolution effectively stopped long ago. When > we need it we have ptys to virtual serial ports when we need it, but in > general unprivileged users are safe to directly use a serial port > device. > > Glossing over the details. The general problem is some policy exists > outside of the container that deciedes if an when a container gets a > serial port and stuffs it in. > > The expectation is that system containers will then run the udev > rules and send the libuevent event. > > To make that all work without kernel modifications requires placing > a faux-udev in the container, that listens for a device assignment from > outside the container and then does exactly what udev would have done. > > The problems with this that I see are: > > - udev is a moving target making it hard to build a faux-udev that will > work everywhere. How is udev a moving target? Use libudev and all should be fine, that's an ABI you can rely on, right? Or, if you don't like/want udev, use mdev in your container. Or something else, what does this have to do with the kernel? > - On distro's running systemd and udev integration is sufficiently tight > that I am not certain a faux-udev is possible or will continue to be > possible. That's not a kernel issue, that's a "ouch, this is hard, let's give up" issue. Or perhaps it is a "maybe I shouldn't even be trying to do this" type issue... :) > - There are two other widely deployed solutions for managing hotplug > devices besides udev. I know of mdev, what's the other one? The hacked-up shell script that Android uses? Or something else? > So given these difficulties I do not believe that the evolution of linux > device management is done, and that patches to udev, the kernel or both > will be needed. While it would be good for testing and understanding > the problem I don't think a faux-udev will be a long term maintainable > solution. You are saying that for some reason you feel helpless with the way userspace is going, so we have to change the kernel. That's horrible, and is not going to be a reason I accept to change the kernel, sorry. > I also understand the point that we aren't talking patches yet and just > discussing ideas. Right now it is my hope that if we talk this out we > can figure out a general direction that has a hope of working. > > From where I am standing faking uevents instead of replacing > udev/mdev/whatever looks simpler and more maintainable. Have you really looked into this? Numerous people, who understand this code path and userspace issues, have said it is not a good idea at all. But hey, what do I know... I still have yet to see a reason why you can't use libudev today for something like this. Anyway, I'm done discussing this as it's pointless this early, I'm going to refrain for any more pithy comments until someone posts some code, as this is just wasting people's time at the moment. greg k-h ^ permalink raw reply [flat|nested] 63+ messages in thread
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* Re: Device Namespaces [not found] ` <20131001205718.GA17036-U8xfFu+wG4EAvxtiuMwx3w@public.gmane.org> @ 2013-10-02 22:45 ` Eric W. Biederman 0 siblings, 0 replies; 63+ messages in thread From: Eric W. Biederman @ 2013-10-02 22:45 UTC (permalink / raw) To: Greg Kroah-Hartman Cc: Linux Containers, Kay Sievers, Andy Lutomirski, devel, lxc-devel, mhw, Stephane Graber I think libudev is a solution to a completely different problem. It is possible I am blind but I just don't see how libudev even attempts to solve the problem. The desire is to plop a distro install into a subdirectory. Fire up a container around it, and let the distro's userspace do it's thing to manage hotplug events. devtmpfs can be faked fairly easily. I don't know about sysfs. Sending events that say you have hotplugged is the largest practical problem. On the minimal side I think the patch below is enough to let us fake up uevents for the container and make things work. I have heard the words faking uevents and is a bad thing. But I have not heard a reason or seen any attempt at explanation. My guess is that we are simply talking about different problems. I would like to see someone wire up all of the userspace bits and see how well hotplug can be made to work before I walk down the path represented by this patch but it seems reasonable. But I do have anecdotal reports from someone who walked a similar path that this is enough to bring up a full desktop system in a container. Eric diff --git a/include/linux/netlink.h b/include/linux/netlink.h index 7a6c396a263b..46d05783da82 100644 --- a/include/linux/netlink.h +++ b/include/linux/netlink.h @@ -38,6 +38,7 @@ extern void netlink_table_ungrab(void); #define NL_CFG_F_NONROOT_RECV (1 << 0) #define NL_CFG_F_NONROOT_SEND (1 << 1) +#define NL_CFG_F_IMPERSONATE_KERN (1 << 2) /* optional Netlink kernel configuration parameters */ struct netlink_kernel_cfg { diff --git a/lib/kobject_uevent.c b/lib/kobject_uevent.c index 52e5abbc41db..f75e34397df8 100644 --- a/lib/kobject_uevent.c +++ b/lib/kobject_uevent.c @@ -375,9 +375,12 @@ static int uevent_net_init(struct net *net) struct uevent_sock *ue_sk; struct netlink_kernel_cfg cfg = { .groups = 1, - .flags = NL_CFG_F_NONROOT_RECV, + .flags = NL_CFG_F_NONROOT_RECV | NL_CFG_F_IMPERSONATE_KERN, }; + if (net->user_ns != &init_user_ns) + return 0; + ue_sk = kzalloc(sizeof(*ue_sk), GFP_KERNEL); if (!ue_sk) return -ENOMEM; @@ -399,6 +402,9 @@ static void uevent_net_exit(struct net *net) { struct uevent_sock *ue_sk; + if (net->user_ns != &init_user_ns) + return; + mutex_lock(&uevent_sock_mutex); list_for_each_entry(ue_sk, &uevent_sock_list, list) { if (sock_net(ue_sk->sk) == net) diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c index 0c61b59175dc..71863cc465eb 100644 --- a/net/netlink/af_netlink.c +++ b/net/netlink/af_netlink.c @@ -1252,7 +1252,7 @@ static int netlink_release(struct socket *sock) skb_queue_purge(&sk->sk_write_queue); - if (nlk->portid) { + if (sk_hashed(sk)) { struct netlink_notify n = { .net = sock_net(sk), .protocol = sk->sk_protocol, @@ -1409,11 +1409,21 @@ static int netlink_bind(struct socket *sock, struct sockaddr *addr, return err; } - if (nlk->portid) { + if (sk_hashed(sk)) { if (nladdr->nl_pid != nlk->portid) return -EINVAL; } else { - err = nladdr->nl_pid ? + bool autobind = nladdr->nl_pid == 0; + if (nladdr->nl_pid == 0 && (nladdr->nl_pad == 0xffff)) { + if (!(nl_table[sk->sk_protocol].flags & NL_CFG_F_IMPERSONATE_KERN)) + return -EPERM; + if (net->user_ns == &init_user_ns) + return -EPERM; + if (!ns_capable(net->user_ns, CAP_NET_ADMIN)) + return -EPERM; + autobind = false; + } + err = !autobind ? netlink_insert(sk, net, nladdr->nl_pid) : netlink_autobind(sock); if (err) @@ -1467,7 +1477,7 @@ static int netlink_connect(struct socket *sock, struct sockaddr *addr, if (nladdr->nl_groups && !netlink_capable(sock, NL_CFG_F_NONROOT_SEND)) return -EPERM; - if (!nlk->portid) + if (!sk_hashed(sk)) err = netlink_autobind(sock); if (err == 0) { @@ -2228,7 +2238,7 @@ static int netlink_sendmsg(struct kiocb *kiocb, struct socket *sock, dst_group = nlk->dst_group; } - if (!nlk->portid) { + if (!sk_hashed(sk)) { err = netlink_autobind(sock); if (err) goto out; ^ permalink raw reply related [flat|nested] 63+ messages in thread
* Re: Device Namespaces [not found] ` <87had0wz07.fsf-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org> 2013-10-01 20:46 ` Serge Hallyn 2013-10-01 20:57 ` Greg Kroah-Hartman @ 2013-10-01 22:19 ` Michael H. Warfield 2 siblings, 0 replies; 63+ messages in thread From: Michael H. Warfield @ 2013-10-01 22:19 UTC (permalink / raw) To: Eric W. Biederman Cc: Kay Sievers, Linux Containers, lxc-devel, Andy Lutomirski, Greg Kroah-Hartman, Stephane Graber, devel [-- Attachment #1.1: Type: text/plain, Size: 5040 bytes --] On Tue, 2013-10-01 at 12:51 -0700, Eric W. Biederman wrote: > "Serge E. Hallyn" <serge-A9i7LUbDfNHQT0dZR+AlfA@public.gmane.org> writes: > > > Quoting Andy Lutomirski (luto-kltTT9wpgjJwATOyAt5JVQ@public.gmane.org): > >> On Tue, Oct 1, 2013 at 7:19 AM, Janne Karhunen <janne.karhunen@gmail.com> wrote: > >> > On Thu, Sep 26, 2013 at 8:33 AM, Greg Kroah-Hartman > >> > <gregkh-hQyY1W1yCW8ekmWlsbkhG0B+6BGkLq7r@public.gmane.org> wrote: > >> > > >> >>> - We can relay a call of /sbin/hotplug from outside of a container > >> >>> to inside of a container based on policy. > >> >>> (But no one uses /sbin/hotplug anymore). > >> >> > >> >> That's right, they should be listening to libudev events, so why can't > >> >> your daemon shuffle them off to the proper container, all in userspace? > >> > > >> > Which reminds me, one potential reason being.. > >> > http://lists.linuxfoundation.org/pipermail/containers/2013-May/032591.html > >> > > >> > >> Can't the daemon live outside the container and shuffle stuff in? > > > > That's exactly what Michael Warfield is suggesting, fwiw. > Michael Warfields example of dynamically assigning serial ports to > containers is a pretty good test case. Serial ports are extremely well > known kernel objects who evolution effectively stopped long ago. When > we need it we have ptys to virtual serial ports when we need it, but in > general unprivileged users are safe to directly use a serial port > device. > Glossing over the details. The general problem is some policy exists > outside of the container that deciedes if an when a container gets a > serial port and stuffs it in. Actually, I don't necessarily see that as a problem as much as a necessity. If a container can decide when it gets a serial port or other device, I would think that would constitute a security issue and container isolation violation. Restricting what container can have access to what has to be determined in the host and, once you've drunk that koolaid, you might as well stuff it in somewhere. Policy has to be in the host or you will never get the security corner cases right. Ultimately, it is the host which is in charge of the hardware and is managing the containers (it can start them up, shut them down, or manage them) so, at its base level, is is the responsibility of the host to manage those devices between the containers. That being said, there is the additional issue of, what does the container do when we hand it a device and how do we let it know. That's now classically the issue of udev and formerly hotplug and their predecessors... > The expectation is that system containers will then run the udev > rules and send the libuevent event. Which makes sense. Something along the line of a socket into the container to send selected events from the user space daemon in the host would make some sense there. > To make that all work without kernel modifications requires placing > a faux-udev in the container, that listens for a device assignment from > outside the container and then does exactly what udev would have done. > The problems with this that I see are: > - udev is a moving target making it hard to build a faux-udev that will > work everywhere. Well, it is an it isn't. Yeah the rules have been changing (I'm getting tired of the "deprecated" rule warnings) but I've seen worse, much worse. > - On distro's running systemd and udev integration is sufficiently tight > that I am not certain a faux-udev is possible or will continue to be > possible. Actually, I think that's a non-issue. IIRC, systemd (now) discontinues its udev operation when it detects it's in a container. That was at the heart of the entire Fedora 15/16 in a container meltdown with the broken versions of systemd trying to run udev in the container. What do we do in place of it? I don't know. > - There are two other widely deployed solutions for managing hotplug > devices besides udev. > So given these difficulties I do not believe that the evolution of linux > device management is done, and that patches to udev, the kernel or both > will be needed. While it would be good for testing and understanding > the problem I don't think a faux-udev will be a long term maintainable > solution. > I also understand the point that we aren't talking patches yet and just > discussing ideas. Right now it is my hope that if we talk this out we > can figure out a general direction that has a hope of working. > From where I am standing faking uevents instead of replacing > udev/mdev/whatever looks simpler and more maintainable. > Eric Mike -- Michael H. Warfield (AI4NB) | (770) 985-6132 | mhw-BetbSzk+GohWk0Htik3J/w@public.gmane.org /\/\|=mhw=|\/\/ | (678) 463-0932 | http://www.wittsend.com/mhw/ NIC whois: MHW9 | An optimist believes we live in the best of all PGP Key: 0x674627FF | possible worlds. A pessimist is sure of it! [-- Attachment #1.2: This is a digitally signed message part --] [-- Type: application/pgp-signature, Size: 482 bytes --] [-- Attachment #2: Type: text/plain, Size: 205 bytes --] _______________________________________________ Containers mailing list Containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org https://lists.linuxfoundation.org/mailman/listinfo/containers ^ permalink raw reply [flat|nested] 63+ messages in thread
* Re: Device Namespaces [not found] ` <CALCETrWWoHzuJcnfEUY+cFpOgT5gnG8U1cVbCW0_8V7Z_v6DJw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> 2013-10-01 17:53 ` Serge E. Hallyn @ 2013-10-01 18:36 ` Janne Karhunen 1 sibling, 0 replies; 63+ messages in thread From: Janne Karhunen @ 2013-10-01 18:36 UTC (permalink / raw) To: Andy Lutomirski Cc: Greg Kroah-Hartman, Linux Containers, Kay Sievers, Stephane Graber, Eric W. Biederman, lxc-devel, mhw, devel On Tue, Oct 1, 2013 at 8:27 PM, Andy Lutomirski <luto-kltTT9wpgjJwATOyAt5JVQ@public.gmane.org> wrote: >> http://lists.linuxfoundation.org/pipermail/containers/2013-May/032591.html > > Can't the daemon live outside the container and shuffle stuff in? > IOW, there seems to be little point in containerizing things if you're > just going to punch a privilege hole in the namespace. Yeah. I will try to experiment just how much can be 'stuffed in' without effective caps. It certainly would be better this way. > FWIW, I think that the capability evolution rules are crap, but > changing them is a can of worms, and enough people seem to thing the > status quo is acceptable that this is unlikely to ever get fixed. I have noted (Casey almost tried to strangle me during the last security summit for even daring to talk about it). -- Janne ^ permalink raw reply [flat|nested] 63+ messages in thread
* Re: Device Namespaces [not found] ` <CAE=NcrYV2RiMV7PcwEjFGFRBrz9XdZGs86Wau2a+6xpYN2aEHA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> 2013-10-01 17:27 ` Andy Lutomirski @ 2013-10-01 17:33 ` Greg Kroah-Hartman [not found] ` <20131001173342.GA19267-U8xfFu+wG4EAvxtiuMwx3w@public.gmane.org> 1 sibling, 1 reply; 63+ messages in thread From: Greg Kroah-Hartman @ 2013-10-01 17:33 UTC (permalink / raw) To: Janne Karhunen Cc: Linux Containers, Kay Sievers, Andy Lutomirski, devel, Eric W. Biederman, lxc-devel, mhw, Stephane Graber On Tue, Oct 01, 2013 at 09:19:58AM +0300, Janne Karhunen wrote: > On Thu, Sep 26, 2013 at 8:33 AM, Greg Kroah-Hartman > <gregkh-hQyY1W1yCW8ekmWlsbkhG0B+6BGkLq7r@public.gmane.org> wrote: > > >> - We can relay a call of /sbin/hotplug from outside of a container > >> to inside of a container based on policy. > >> (But no one uses /sbin/hotplug anymore). > > > > That's right, they should be listening to libudev events, so why can't > > your daemon shuffle them off to the proper container, all in userspace? > > Which reminds me, one potential reason being.. > http://lists.linuxfoundation.org/pipermail/containers/2013-May/032591.html I really wish I had never seen that patch, and I am glad it was rejected. ^ permalink raw reply [flat|nested] 63+ messages in thread
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* Re: Device Namespaces [not found] ` <20131001173342.GA19267-U8xfFu+wG4EAvxtiuMwx3w@public.gmane.org> @ 2013-10-01 18:23 ` Janne Karhunen 0 siblings, 0 replies; 63+ messages in thread From: Janne Karhunen @ 2013-10-01 18:23 UTC (permalink / raw) To: Greg Kroah-Hartman Cc: Linux Containers, Kay Sievers, Andy Lutomirski, devel, Eric W. Biederman, lxc-devel, mhw, Stephane Graber On Tue, Oct 1, 2013 at 8:33 PM, Greg Kroah-Hartman <gregkh-hQyY1W1yCW8ekmWlsbkhG0B+6BGkLq7r@public.gmane.org> wrote: >> > That's right, they should be listening to libudev events, so why can't >> > your daemon shuffle them off to the proper container, all in userspace? >> >> Which reminds me, one potential reason being.. >> http://lists.linuxfoundation.org/pipermail/containers/2013-May/032591.html > > I really wish I had never seen that patch, and I am glad it was > rejected. Thanks, I agree. Just wanted to point out the reason and bring up the discussion. -- Janne ^ permalink raw reply [flat|nested] 63+ messages in thread
* Re: Device Namespaces [not found] ` <87bo3gshz5.fsf_-_-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org> 2013-09-26 5:33 ` Greg Kroah-Hartman @ 2013-10-28 23:31 ` Andrey Wagin 1 sibling, 0 replies; 63+ messages in thread From: Andrey Wagin @ 2013-10-28 23:31 UTC (permalink / raw) To: Eric W. Biederman Cc: Greg Kroah-Hartman, Linux Containers, Kay Sievers, Andy Lutomirski, devel-GEFAQzZX7r8dnm+yROfE0A, lxc-devel, mhw-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8, Stephane Graber 2013/9/26 Eric W. Biederman <ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org> > > > From conversations at Linux Plumbers Converence it became fairly clear > that one if not the roughest edge on containers today is dealing with > devices. > > - Hotplug does not work. > - There seems to be no implementation that does a much beyond creating > setting up a static set of /dev entries today. > - Containers do not see the appropriate uevents for their container. > > One of the more compelling cases I heard was of someone who was running > the a Linux Desktop in container and wanted to just let that container > see the devices needed for his desktop, and not everything else. I had experience of implementing this functionality in OpenVZ kernel. I had requirements to not modify user-space tools, so that implementations looks as dirty hack, but even hotplug of devices are workin there. .... > > So the big issues for a device namespace to solve are filtering which > devices a container has access to and being able to dynamically change > which devices those are at run time (aka hotplug). > > After having thought about this for a bit I don't know if a pure > userspace solution is sufficient or actually a good idea. I would prefer to think a bit more about userspace solution. We can try to expand udev functionality. > > - We can manually manage a tmpfs with device nodes in userspace. > (But that is deprecated functionality in the mainstream kernel). > - We can manually export a subset of sysfs with bind mounts. > (But that feels hacky, and is essentially incompatible with hotplug). > - We can relay a call of /sbin/hotplug from outside of a container > to inside of a container based on policy. > (But no one uses /sbin/hotplug anymore). > - There is no way to fake netlink uevents for a container to see them. > (The best we could do is replace udev everywhere with something that > listens on a unix domain socket). or we can teach udev to listens on a unix domain socket. The host udev listens netlink. When it gets an event about a new device, it decides for which containers it must be avaliable, does all required actions and sends events in containers. Probably the protocol of notifications must be unified for all udev-like services. > > - It would be nice to replace the device cgroup with a comprehensive > solution that really works. (Among other things the device cgroup > does not work in terms of struct device the underlying kernel > abstraction for devices). > > We must manage sysfs entries as well device nodes because: > - Seeing more than we should has the real potential to confuse > userspace, especially a userspace that replays uevents. > - Some device control must happens through writing to sysfs files and > if we don't remove all root privileges from a container only by > exporting a subset of sysfs to that container can we limit which > sysfs nodes can be written to. Sorry if a following idea will sound crazy. Can we use fuse filesystems for filtering sysfs and devtmpfs? When a CT mounts sysfs, it will mount fuse-sysfs, which is implemented by userspace program on host system. * This way allows to emulate the behavior of uevent files in containers, if we will use unix sockets between udev services. * Probably a userspace daemon will be more flexible and customizable than something in kernel Do we have a use case when a perfomance of sysfs is critical? Thanks, Andrey ^ permalink raw reply [flat|nested] 63+ messages in thread
* Re: RFC: Device Namespaces [not found] ` <CAA4jN2aw4zEW=UfKCyqaOvXnbiRb_J9srfCn4OXTFzc6vWBM4A-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> 2013-08-22 18:21 ` Serge Hallyn @ 2013-08-29 19:06 ` Andy Lutomirski [not found] ` <521F9BBE.2070505-kltTT9wpgjJwATOyAt5JVQ@public.gmane.org> 1 sibling, 1 reply; 63+ messages in thread From: Andy Lutomirski @ 2013-08-29 19:06 UTC (permalink / raw) To: Oren Laadan Cc: containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA, lxc-devel On 08/22/2013 10:43 AM, Oren Laadan wrote: > Hi everyone! > > We [1] have been working on bringing lightweight virtualization to > Linux-based mobile devices like Android (or other Linux-based devices with > diverse I/O) and want to share our solution: device namespaces. Have you looked at systemd-logind? It seems to do something similar. ^ permalink raw reply [flat|nested] 63+ messages in thread
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* Re: [lxc-devel] RFC: Device Namespaces [not found] ` <521F9BBE.2070505-kltTT9wpgjJwATOyAt5JVQ@public.gmane.org> @ 2013-09-03 19:35 ` Stéphane Graber 0 siblings, 0 replies; 63+ messages in thread From: Stéphane Graber @ 2013-09-03 19:35 UTC (permalink / raw) To: Andy Lutomirski Cc: containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA, lxc-devel [-- Attachment #1.1: Type: text/plain, Size: 1006 bytes --] On Thu, Aug 29, 2013 at 12:06:38PM -0700, Andy Lutomirski wrote: > On 08/22/2013 10:43 AM, Oren Laadan wrote: > > Hi everyone! > > > > We [1] have been working on bringing lightweight virtualization to > > Linux-based mobile devices like Android (or other Linux-based devices with > > diverse I/O) and want to share our solution: device namespaces. > > Have you looked at systemd-logind? It seems to do something similar. logind can be used to know the list of existing user sessions and which have console access, it also creates and to some extent manages cgroups but it doesn't do anything that the device namespace would at the kernel level. The main benefit from having a device namespace in the kernel would be to only get the uevents and device access for devices that are either owned or shared with the container. Being able to have fake devices replace some of the standard ones would also be nice to have. -- Stéphane Graber Ubuntu developer http://www.ubuntu.com [-- Attachment #1.2: Digital signature --] [-- Type: application/pgp-signature, Size: 836 bytes --] [-- Attachment #2: Type: text/plain, Size: 205 bytes --] _______________________________________________ Containers mailing list Containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org https://lists.linuxfoundation.org/mailman/listinfo/containers ^ permalink raw reply [flat|nested] 63+ messages in thread
* Re: Device Namespaces @ 2013-09-29 19:28 Amir Goldstein [not found] ` <CAA2m6veny-7_ONMA973Wu36U4kz4gAuw0dpodkb8+GZDv6VNBQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> 0 siblings, 1 reply; 63+ messages in thread From: Amir Goldstein @ 2013-09-29 19:28 UTC (permalink / raw) To: Greg Kroah-Hartman Cc: Linux Containers, Kay Sievers, Andy Lutomirski, devel-GEFAQzZX7r8dnm+yROfE0A, Eric W. Biederman, lxc-devel, mhw-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8, Stephane Graber On Thu, Sep 26, 2013 at 8:33 AM, Greg Kroah-Hartman < gregkh-hQyY1W1yCW8ekmWlsbkhG0B+6BGkLq7r@public.gmane.org> wrote: > On Wed, Sep 25, 2013 at 02:34:54PM -0700, Eric W. Biederman wrote: > > So the big issues for a device namespace to solve are filtering which > > devices a container has access to and being able to dynamically change > > which devices those are at run time (aka hotplug). > > As _all_ devices are hotpluggable now (look, there's no CONFIG_HOTPLUG > anymore, because it was redundant), I think you need to really think > this through better (pci, memory, cpus, etc.) before you do anything in > the kernel. > > > After having thought about this for a bit I don't know if a pure > > userspace solution is sufficient or actually a good idea. > > > > - We can manually manage a tmpfs with device nodes in userspace. > > (But that is deprecated functionality in the mainstream kernel). > > Yes, but I'm not going to namespace devtmpfs, as that is going to be an > impossible task, right? > That sounds like a challenge ;-) Seriously, as Serge correctly noted, it would not be that different from devpts if you start from an empty devtmpfs and populate it with devices that are "added in the context of that namespace". The semantics in which devices are "added in the context of a namespace" is the missing piece of the puzzle. What we really like to see is a setns() style API that can be used to add a device in the context of a namespace in either a "shared" or "private" mode. This kind of API is a required building block for us to write device drivers that are namespace aware in a way that userspace will have enough flexibility for dynamic configuration. We are trying to come up with a proposal for that sort of API. When we have something decent, we shall post it. > And remember, udev doesn't create device nodes anymore... > > > - We can manually export a subset of sysfs with bind mounts. > > (But that feels hacky, and is essentially incompatible with hotplug). > > True. > > > - We can relay a call of /sbin/hotplug from outside of a container > > to inside of a container based on policy. > > (But no one uses /sbin/hotplug anymore). > > That's right, they should be listening to libudev events, so why can't > your daemon shuffle them off to the proper container, all in userspace? > > > - There is no way to fake netlink uevents for a container to see them. > > (The best we could do is replace udev everywhere with something that > > listens on a unix domain socket). > > You shouldn't need to do this. > > > - It would be nice to replace the device cgroup with a comprehensive > > solution that really works. (Among other things the device cgroup > > does not work in terms of struct device the underlying kernel > > abstraction for devices). > > I didn't even know there was a device cgroup. > > Which means that if there is one, odds are it's useless. > > > We must manage sysfs entries as well device nodes because: > > - Seeing more than we should has the real potential to confuse > > userspace, especially a userspace that replays uevents. > > You should never replay uevents. If you don't do that, why can't you > see all of sysfs? > > > - Some device control must happens through writing to sysfs files and > > if we don't remove all root privileges from a container only by > > exporting a subset of sysfs to that container can we limit which > > sysfs nodes can be written to. > > But you have the issue of controlling devices in a "shared" way, which > isn't going to be usable for almost all devices. > > > The current kernel tagged sysfs entry support does not look like a good > > match for the impelementing device filtering. The common case will > > be allowing devices like /dev/zero, and /dev/null that live in > > /sys/devices/virtual and are the devices we are most likely to care > > about. Those devices need to live in multiple device namespaces so > > everyone can use them. Perhaps exclusive assignment will be the more > > common paradigm for device namespaces like it is for network devices in > > the network namespace but from what little I can of this problem right > now I > > don't think so. > > > > I definitely think we should hold off on a kernel level implementation > > until we really understand the issues and are ready to implement device > > namespaces correctly. > > I agree, especially as I don't think this will ever work. > > > A userspace implementation looks like it can only do about 95% of what > > is really needed, but at the same time looks like an easy way to > > experiment until the problem is sufficiently well understood. > > 95% is probably way better than what you have today, and will fit the > needs of almost everyone today, so why not do it? > > I'd argue that those last 5% either are custom solutions that never get > merged, or candidates for true virtulization. > > > In summary the situation with device hoptlug and containers sucks today, > > and we need to do something. Running a linux desktop in a container is > > a reasonably good example use case. > > No it isn't. I'd argue that this is a horrible use case, one that you > shouldn't do. Why not just use multi-head machines like people do who > really want to do this, relying on user separation? That's a workable > solution that is quite common and works very well today. > > > Having one standard common maintainable implementation would be very > > useful and the most logical place for that would be in the kernel. > > For now we should focus on simple device filtering and hotplug. > > Just listen for libudev stuff, don't try to filter them, or ever > "replay" them, that way lies madness, and lots of nasty race conditions > that is guaranteed to break things. > > good luck, > > greg k-h > ^ permalink raw reply [flat|nested] 63+ messages in thread
[parent not found: <CAA2m6veny-7_ONMA973Wu36U4kz4gAuw0dpodkb8+GZDv6VNBQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>]
* Re: Device Namespaces [not found] ` <CAA2m6veny-7_ONMA973Wu36U4kz4gAuw0dpodkb8+GZDv6VNBQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> @ 2013-09-29 20:06 ` Greg Kroah-Hartman [not found] ` <20130929200620.GA31304-U8xfFu+wG4EAvxtiuMwx3w@public.gmane.org> 2013-10-03 0:44 ` Eric W. Biederman 1 sibling, 1 reply; 63+ messages in thread From: Greg Kroah-Hartman @ 2013-09-29 20:06 UTC (permalink / raw) To: Amir Goldstein Cc: Linux Containers, Kay Sievers, Andy Lutomirski, devel-GEFAQzZX7r8dnm+yROfE0A, Eric W. Biederman, lxc-devel, mhw-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8, Stephane Graber On Sun, Sep 29, 2013 at 10:28:55PM +0300, Amir Goldstein wrote: > > > > On Thu, Sep 26, 2013 at 8:33 AM, Greg Kroah-Hartman <gregkh@linuxfoundation.org > > wrote: > > On Wed, Sep 25, 2013 at 02:34:54PM -0700, Eric W. Biederman wrote: > > So the big issues for a device namespace to solve are filtering which > > devices a container has access to and being able to dynamically change > > which devices those are at run time (aka hotplug). > > As _all_ devices are hotpluggable now (look, there's no CONFIG_HOTPLUG > anymore, because it was redundant), I think you need to really think > this through better (pci, memory, cpus, etc.) before you do anything in > the kernel. > > > After having thought about this for a bit I don't know if a pure > > userspace solution is sufficient or actually a good idea. > > > > - We can manually manage a tmpfs with device nodes in userspace. > > (But that is deprecated functionality in the mainstream kernel). > > Yes, but I'm not going to namespace devtmpfs, as that is going to be an > impossible task, right? > > > That sounds like a challenge ;-) > Seriously, as Serge correctly noted, it would not be that different from devpts > if you start from an empty devtmpfs and populate it with devices that are > "added in the context of that namespace". The semantics in which > devices are "added in the context of a namespace" is the missing piece > of the puzzle. And the fact that these devices are almost all created before userspace starts up, is a non-trivial "piece of the puzzle" :) Good luck, greg k-h ^ permalink raw reply [flat|nested] 63+ messages in thread
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* Re: Device Namespaces [not found] ` <20130929200620.GA31304-U8xfFu+wG4EAvxtiuMwx3w@public.gmane.org> @ 2013-09-30 15:36 ` Michael H. Warfield 0 siblings, 0 replies; 63+ messages in thread From: Michael H. Warfield @ 2013-09-30 15:36 UTC (permalink / raw) To: Greg Kroah-Hartman Cc: Linux Containers, Kay Sievers, Andy Lutomirski, Eric W. Biederman, lxc-devel, Stephane Graber, devel-GEFAQzZX7r8dnm+yROfE0A [-- Attachment #1.1: Type: text/plain, Size: 10741 bytes --] On Sun, 2013-09-29 at 13:06 -0700, Greg Kroah-Hartman wrote: > On Sun, Sep 29, 2013 at 10:28:55PM +0300, Amir Goldstein wrote: > > > > > > > > On Thu, Sep 26, 2013 at 8:33 AM, Greg Kroah-Hartman <gregkh@linuxfoundation.org > > > wrote: > > > > On Wed, Sep 25, 2013 at 02:34:54PM -0700, Eric W. Biederman wrote: > > > So the big issues for a device namespace to solve are filtering which > > > devices a container has access to and being able to dynamically change > > > which devices those are at run time (aka hotplug). > > > > As _all_ devices are hotpluggable now (look, there's no CONFIG_HOTPLUG > > anymore, because it was redundant), I think you need to really think > > this through better (pci, memory, cpus, etc.) before you do anything in > > the kernel. > > > > > After having thought about this for a bit I don't know if a pure > > > userspace solution is sufficient or actually a good idea. > > > > > > - We can manually manage a tmpfs with device nodes in userspace. > > > (But that is deprecated functionality in the mainstream kernel). > > > > Yes, but I'm not going to namespace devtmpfs, as that is going to be an > > impossible task, right? > > > > > > That sounds like a challenge ;-) > > Seriously, as Serge correctly noted, it would not be that different from devpts > > if you start from an empty devtmpfs and populate it with devices that are > > "added in the context of that namespace". The semantics in which > > devices are "added in the context of a namespace" is the missing piece > > of the puzzle. > And the fact that these devices are almost all created before userspace > starts up, is a non-trivial "piece of the puzzle" :) That's putting it mildly. As I said in the Containers session at Linux Plumbers, I agree with you (wrt device namespaces), but we do have (a) problem(s) to solve. The more I've thought on this, the more I agree with you and that there's got to be a better way. I'm not going to address the Android use case issues here which Janne raised (which are very valid), since I've got other fish to fry and I haven't even begun to look at the complexities of Android in an LXC container on a non-android host, much less Android on Android or other on Android. This may have some applicability to the Android case, I just haven't thought it through yet. Anything on a common kernel should work and standard distributions seem to be no problem now, but Android is a rather unique beast, to say the least. I will disagree with you on one point, though, from that session. When I mentioned both persistent and dynamic devices, you said they were mutually exclusive. It may be a difference in semantics or terminology but I would beg to differ there, so I'll explain that too... In my "worst case, real world, right now" scenario of the USB sharing device and multiple USB serial adapters for serial consoles, I have several different issues that are illustrative of several problems I'm trying to overcome. With this sharing device, you get a "/dev/usbshare" HID device on all the connected hosts which do NOT have the USB bus that's being shared. The device that has control of the bus does NOT see the /dev/usbshare device but does see all the USB devices (the serial port adapters - /dev/ttyUSB* - in this case) which are connected to it. So, when you switch the sharing from system A to system B, all the shared serial devices disappear from A and the /dev/usbshare device appears, while the usbshare device disappears from system B and all the usb serial devices appear together. Either system may (and do) have other static usb serial devices attached so the numbering and order of /dev/ttyUSB* may vary and can even change depending if a host had been booted with the usb bus shared to it or not. Ok... That's the "dynamic" devices I was referring to. They come and go and may have differing names under differing circumstances. Very real world dynamic. Now... For consistency, I have udev rules that map those serial devices to other names, based on their device USB serial numbers. That naming convention remains persistent on that system as the devices come and go and remains consistent between the systems with those rules. So that's my "dynamic" with "persistent" devices. I have persistent names on dynamic devices. Perhaps I could have chosen my terminology better but, that's what I was arguing for in that Plumbers session when I used those terms. Now, for the complications... If I wish to (and I most certainly do) divvy up these serial devices between containers, I have several things which need to be managed. The /dev/usbshare device needs to be mapped to ALL containers which may wish to request the shared bus (plus the host). It's generally only a very momentary device access and collisions would be extremely rare and non-harmful in any case (two containers both wanting the bus on the same host - shrug...). It's actually far less confusing and difficult than merely the collisions and contention between systems, and that's been easily managable, given the rarity of cross serial console access (the real world use case). The /dev/ttyUSB* devices need to be mapped to their specific containers with or without removing them from the host and possibly allowing for multiple containers. Device access is easily managed by the device driver for multiple access (EBUSY) and not a problem. This could be more complicated if, for example, we were talking about USB drives, loop devices, or other devices which multiple access, but that's another layer of complication. The "persistent" udev symlinks also need to be mapped to the containers. I think I can do this equally well in the host as the real devices... > Good luck, I'm scratching on an idea that started forming just after that session. I told Serge that "I think I can do it and it will (should) suck less." Basically, it exploits some of the properties of devtmpfs to accomplish some of our goals. You're right about the user space problem. Something needs to manage the devices in a coherent manner as devices come and go and as containers come and go in asynchronous manner. In my mind, the only place for that is in the host. "Non trivial" is a jaw dropping understatement and I can see where you feel it would be impossible to manage in applying namespaces to devtmpfs. That leaves the user space in the host. I can see where it would be intractable in the kernel. I may get beat mercilessly for suggesting this but, just as with cgroups, if we create a subdirectory in devtmpfs for subsystem (LXC) and container, we can then bind mount that subtree off of devtmpfs to the container and then the host can map and manipulate the device subtree into the container (even if the container is denied mknod capability). That leaves the host to manage all the devices, which actually makes a LOT of sense (to me) since it should be responsible for the devices and the overall kernel operations. That would be no different than needing to configure device passthroughs for KVM / VirtualBox / VMware hypervisors. Example... In the host I would have something like this... /dev/lxc/ romulus remus gemini janus And then bind mount each of those subdirectories to /var/lib/lxc/${Container}/rootfs/dev directory. Then map the devices from the host /dev to the container /dev with mknod in the host and relative symlinks. That also (I think) helps me deal with some of the (mis)behavior of systemd where it contains unconfigurable behavior (mounting devtmpfs) controlled by "magic cookies" (/dev mounted on another major/minor from / to disable it mounting devtmpfs). I initially recoiled in horror of the thought of overloading the devtmpfs subtree with container based subdirectories, devices, and symlinks but the idea grew on me that this might be better than what we're dealing with now of mounting tmpfs on the /dev mount point in all theses containers and then having to populate them just to prevent systemd from creating collisions with devtmpfs and the resulting violation of the container isolation. It DOES still leave the problem of dealing with udev rules in the container and subsidiary device syslinks in the container which may not correspond to the rules in the host. That's still problem in my mind (but already present and miniscule to what we would be solving). I could pattern match everything coming out of udev in a trigger and map devices and symlinks into the new subtree in the host but I have no way to manage propagating the rules in the container down into the processor in the host or a way to trigger those udev rules in the containers. Suggestions there might be nice (as well as the cat calls). I'm not sure I have it clear in my head yet how I would deal with bringing up a container and then mapping all the required existing devices over to it. That's your user space problem in a nutshell. That's easy to handle with udev as things come and go but, when the user space comes after and udev isn't processing triggers, how do I handle the mappings. That's also non-trivial in my mind. Device creation would seem to be pretty trivial. Device removal, not so much. If I create another node on devtmpfs and that major/minor gets removed, will it also get removed? I also have to remove the symlinks. The removal process just feels more complicated in my mind. Greg, I think you are absolutely right, this needs to be managed in user space and not in kernel space and we do have the tools to do it. I think I can do some of it in a way that will suck less compared to how we're (LXC is) doing it now. I'm just not so sure how comprehensive the solution will be or how well it will work. I've still got several other takeaways from that session to put a bow on before really testing this idea further. I really have not fully fleshed this idea out and it's going to take me some time. There may also me some other corner cases I haven't considered. And then there's Android. Sigh... And maybe I'm just totally off base and crazy. Wouldn't be the first time, won't be the last time. > greg k-h Regards, Mike -- Michael H. Warfield (AI4NB) | (770) 985-6132 | mhw-BetbSzk+GohWk0Htik3J/w@public.gmane.org /\/\|=mhw=|\/\/ | (678) 463-0932 | http://www.wittsend.com/mhw/ NIC whois: MHW9 | An optimist believes we live in the best of all PGP Key: 0x674627FF | possible worlds. A pessimist is sure of it! [-- Attachment #1.2: This is a digitally signed message part --] [-- Type: application/pgp-signature, Size: 482 bytes --] [-- Attachment #2: Type: text/plain, Size: 205 bytes --] _______________________________________________ Containers mailing list Containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org https://lists.linuxfoundation.org/mailman/listinfo/containers ^ permalink raw reply [flat|nested] 63+ messages in thread
* Re: Device Namespaces [not found] ` <CAA2m6veny-7_ONMA973Wu36U4kz4gAuw0dpodkb8+GZDv6VNBQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> 2013-09-29 20:06 ` Greg Kroah-Hartman @ 2013-10-03 0:44 ` Eric W. Biederman [not found] ` <87a9iri3ot.fsf-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org> 1 sibling, 1 reply; 63+ messages in thread From: Eric W. Biederman @ 2013-10-03 0:44 UTC (permalink / raw) To: Amir Goldstein Cc: Greg Kroah-Hartman, Linux Containers, Kay Sievers, Andy Lutomirski, devel-GEFAQzZX7r8dnm+yROfE0A, lxc-devel, mhw-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8, Stephane Graber Amir Goldstein <amir-3AfRa/s5aFdBDgjK7y7TUQ@public.gmane.org> writes: > What we really like to see is a setns() style API that can be used to > add a device in the context of a namespace in either a "shared" or > "private" mode. I think you mean an "ip link set dev FOO netns XXX" style API. Right now one of the best suggestions on the table is: mkdir -p /dev/container/X ln /dev/zero /dev/container/X/zero ln /dev/null /dev/container/X/null ... With /dev/container/X mounted on /dev for container X. Which seems to cover putting a device in a namespace, while allowing things to still be reasonably managed. There are a few other variations on that scheme but nothing that says we must have kernel support or to create any kind of kernel context beyond which directory the device nodes live in. > This kind of API is a required building block for us to write device > drivers that are namespace aware in a way that userspace will have > enough flexibility for dynamic configuration. > > We are trying to come up with a proposal for that sort of API. When > we have something decent, we shall post it. I really think what you need to write are special drivers that facilitate your use case. For the networking stack we wound up adding veth pairs, and macvlan devices, to handle the common sharing modes. Outside of your sharing situation I am not seeing any need or any advantage of creating devices that are modified to be sharable and I am seeing a lot of disadvantages to implementing things that way. The biggest is that you seem to working independent of the subsystem maintainers of those devices which is generally a poor idea. Unprivileged creation of device nodes we can handle if it can be shown that it is safe to create device nodes. As I understand your problem you are trying to multiplex a device by building a device with a built in stop light. Where one opener can write and the other openers are stopped/dropped. That sounds very similar to macvlan, or ethernet bridging. From the patches you have floated I suspect it would be very simple to build and just need a little bit of glue. Eric ^ permalink raw reply [flat|nested] 63+ messages in thread
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* Re: Device Namespaces [not found] ` <87a9iri3ot.fsf-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org> @ 2013-10-03 0:59 ` Eric W. Biederman 2013-10-03 8:58 ` Amir Goldstein 1 sibling, 0 replies; 63+ messages in thread From: Eric W. Biederman @ 2013-10-03 0:59 UTC (permalink / raw) To: Amir Goldstein Cc: Greg Kroah-Hartman, Linux Containers, Kay Sievers, Andy Lutomirski, devel-GEFAQzZX7r8dnm+yROfE0A, lxc-devel, mhw-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8, Stephane Graber ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org (Eric W. Biederman) writes: >> This kind of API is a required building block for us to write device >> drivers that are namespace aware in a way that userspace will have >> enough flexibility for dynamic configuration. >> >> We are trying to come up with a proposal for that sort of API. When >> we have something decent, we shall post it. > > I really think what you need to write are special drivers that > facilitate your use case. Even more practically if you can write special drivers it removes a level of policy from the kernel, and allows those special drivers to use at other times for other occassions. Eric ^ permalink raw reply [flat|nested] 63+ messages in thread
* Re: Device Namespaces [not found] ` <87a9iri3ot.fsf-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org> 2013-10-03 0:59 ` Eric W. Biederman @ 2013-10-03 8:58 ` Amir Goldstein [not found] ` <CAA2m6vc3OFmS9VwiTavRzPqhn+qoe6vDCO2sitXpEQ8a1JVyfg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> 1 sibling, 1 reply; 63+ messages in thread From: Amir Goldstein @ 2013-10-03 8:58 UTC (permalink / raw) To: Eric W. Biederman Cc: Greg Kroah-Hartman, Linux Containers, Kay Sievers, Andy Lutomirski, devel-GEFAQzZX7r8dnm+yROfE0A, lxc-devel, mhw-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8, Stephane Graber On Thu, Oct 3, 2013 at 3:44 AM, Eric W. Biederman <ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org>wrote: > Amir Goldstein <amir-3AfRa/s5aFdBDgjK7y7TUQ@public.gmane.org> writes: > > > What we really like to see is a setns() style API that can be used to > > add a device in the context of a namespace in either a "shared" or > > "private" mode. > > I think you mean an "ip link set dev FOO netns XXX" style API. > correct. > > Right now one of the best suggestions on the table is: > > mkdir -p /dev/container/X > ln /dev/zero /dev/container/X/zero > ln /dev/null /dev/container/X/null > ... > > With /dev/container/X mounted on /dev for container X. > > Which seems to cover putting a device in a namespace, while allowing > things to still be reasonably managed. > > There are a few other variations on that scheme but nothing that says we > must have kernel support or to create any kind of kernel context beyond > which directory the device nodes live in. > > > This kind of API is a required building block for us to write device > > drivers that are namespace aware in a way that userspace will have > > enough flexibility for dynamic configuration. > > > > We are trying to come up with a proposal for that sort of API. When > > we have something decent, we shall post it. > > I really think what you need to write are special drivers that > facilitate your use case. > > For the networking stack we wound up adding veth pairs, and macvlan > devices, to handle the common sharing modes. > > Outside of your sharing situation I am not seeing any need or any > advantage of creating devices that are modified to be sharable and I am > seeing a lot of disadvantages to implementing things that way. The > biggest is that you seem to working independent of the subsystem > maintainers of those devices which is generally a poor idea. > > Unprivileged creation of device nodes we can handle if it can be shown > that it is safe to create device nodes. > > As I understand your problem you are trying to multiplex a device by > building a device with a built in stop light. Where one opener can > write and the other openers are stopped/dropped. That sounds very > similar to macvlan, or ethernet bridging. From the patches you have > floated I suspect it would be very simple to build and just need a > little bit of glue. > Excellent! let's focus the discussion on a new device driver we want to write which is namespace aware. let's call this device driver valarm-dev. Similarly to Android's alarm-dev, valarm-dev can be used to request RTC wakeup calls from user space and get/set RTC values, but with valarm-dev, every container may use different values for current time. As you can see in our patch set, we already have a version of alarm-dev that maintains its state inside a context, instead of in global variable, so it is capable of providing different context per namespace. And now for the 1M$ question: per *which* namespace do we attribute the current realtime clock time? To UTS namespace (because T historically stands for Time)? To device namespace? Even if device namespace would exist, we do not want to tie the policy decision of "separate time" to a very wide definition of "separate devices". So what we want to create, is an API for device driver writers, that will enable to write a namespace aware device and allow userspace to configure when the namespace aware device context is unshared. We would like to share with you our very initial thoughts about how this will be implemented: - Extend register_pernet_subsys/device(ops) API to register_perns_subsys/device(nstype, ops) API - Extend pernet_operations to perns_operations that include optional migrate() and/or unshare() ops - Let valarm-dev register_peruser_subsys/device(&alarm_userns_ops) - Implement a new syscall (or netlink command if it makes more sense) setdevns(int dev_fd, int ns_fd, int nstype, int flags) - Unlike the netlink set netns case, this API is not used solely to *move* a device to a different namespace, but also to *unshare* a device context between namespaces, for those devices that resigtered unshare() ops. This is our missing piece of the puzzle. After that, whether we make changes to existing drivers (e.g. evdev) or write new virtualized drivers (e.g. vevdev) is a technicality. We care not which way to go, whichever way seems more maintainable. What do you think of this master plan? P.S. Please try to refrain from addressing the validity of the use case of alarm-dev in particular, as we do not wish to get engage "Android sucks" wars. We simply want to present the case for improving the namespace infrastructure to cater the needs of device driver writers that wish to tailor their drivers for containers based products. Cheers, Amir. > > Eric > ^ permalink raw reply [flat|nested] 63+ messages in thread
[parent not found: <CAA2m6vc3OFmS9VwiTavRzPqhn+qoe6vDCO2sitXpEQ8a1JVyfg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>]
* Re: Device Namespaces [not found] ` <CAA2m6vc3OFmS9VwiTavRzPqhn+qoe6vDCO2sitXpEQ8a1JVyfg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> @ 2013-10-03 9:17 ` Eric W. Biederman 0 siblings, 0 replies; 63+ messages in thread From: Eric W. Biederman @ 2013-10-03 9:17 UTC (permalink / raw) To: Amir Goldstein Cc: Greg Kroah-Hartman, Linux Containers, Kay Sievers, Andy Lutomirski, devel-GEFAQzZX7r8dnm+yROfE0A, lxc-devel, mhw-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8, Stephane Graber Amir Goldstein <amir@cellrox.com> writes: > Excellent! let's focus the discussion on a new device driver we want > to write > which is namespace aware. let's call this device driver valarm-dev. > Similarly to Android's alarm-dev, valarm-dev can be used to request > RTC wakeup calls > from user space and get/set RTC values, but with valarm-dev, every > container > may use different values for current time. > > As you can see in our patch set, we already have a version of > alarm-dev that maintains > its state inside a context, instead of in global variable, so it is > capable of providing > different context per namespace. > > And now for the 1M$ question: per *which* namespace do we attribute > the current realtime clock time? To none of them. Just use a different minor per instance, then you don't have a hard question to answer. > To UTS namespace (because T historically stands for Time)? To device > namespace? > Even if device namespace would exist, we do not want to tie the policy > decision of "separate time" > to a very wide definition of "separate devices". > > So what we want to create, is an API for device driver writers, that > will enable to write a namespace > aware device and allow userspace to configure when the namespace aware > device context is unshared. > We would like to share with you our very initial thoughts about how > this will be implemented: > - Extend register_pernet_subsys/device(ops) API > to register_perns_subsys/device(nstype, ops) API > - Extend pernet_operations to perns_operations that include optional > migrate() and/or unshare() ops > - Let valarm-dev register_peruser_subsys/device(&alarm_userns_ops) For the network subsystem that makes sense. But it doesn't make sense for devices. It is just an unneeded extra complication. > - Implement a new syscall (or netlink command if it makes more sense) > setdevns(int dev_fd, int ns_fd, int nstype, int flags) ioctl? master device? How do people communicate with raw devices these days? > - Unlike the netlink set netns case, this API is not used solely to > *move* a device to a different namespace, > but also to *unshare* a device context between namespaces, for those > devices that resigtered unshare() ops. I really think this all makes most sense a driver a virtual driver at a time. > This is our missing piece of the puzzle. > After that, whether we make changes to existing drivers (e.g. evdev) > or write new virtualized drivers (e.g. vevdev) > is a technicality. We care not which way to go, whichever way seems > more maintainable. > > What do you think of this master plan? I think by making your devices behavior depend on which namespace they are in you are making the drivers unnecesarily fragile, and unnecessarily unusable. I think the code will be simpler/cleaner/better if you don't need to have context outside of your drivers. > P.S. Please try to refrain from addressing the validity of the use > case of alarm-dev in particular, > as we do not wish to get engage "Android sucks" wars. > We simply want to present the case for improving the namespace > infrastructure to cater the needs > of device driver writers that wish to tailor their drivers for > containers based products. I think this is a driver interface problem, not a namespace problem. None of the similar drivers that exist in the network namespace change their behavior depending on which namespace they are in. The two practical choices I see are. 1) Use a bunch of minors for your driver. 2) Act roughly like /dev/pts and use different mounts of the filesystem to create new instances. I think different minors is probably easier, but we have two successfull models I am aware of so I have mentioned both. Eric _______________________________________________ Containers mailing list Containers@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/containers ^ permalink raw reply [flat|nested] 63+ messages in thread
* device namespaces @ 2021-06-08 9:38 Enrico Weigelt, metux IT consult 2021-06-08 12:30 ` Christian Brauner 0 siblings, 1 reply; 63+ messages in thread From: Enrico Weigelt, metux IT consult @ 2021-06-08 9:38 UTC (permalink / raw) To: containers, linux-kernel Hello folks, I'm going to implement device namespaces, where containers can get an entirely different view of the devices in the machine (usually just a specific subset, but possibly additional virtual devices). For start I'd like to add a simple mapping of dev maj/min (leaving aside sysfs, udev, etc). An important requirement for me is that the parent ns can choose to delegate devices from those it full access too (child namespaces can do the same to their childs), and the assignment can change (for simplicity ignoring the case of removing devices that are already opened by some process - haven't decided yet whether they should be forcefully closed or whether keeping them open is a valid use case). The big question for me now is how exactly to do the table maintenance from userland. We already have entries in /proc/<pid>/ns/*. I'm thinking about using them as command channel, like this: * new child namespaces are created with empty mapping * mapping manipulation is done by just writing commands to the ns file * access is only granted if the writing process itself is in the parent's device ns and has CAP_SYS_ADMIN (or maybe their could be some admin user for the ns ? or the 'root' of the corresponding user_ns ?) * if the caller has some restrictions on some particular device, these are automatically added (eg. if you're restricted to readonly, you can't give rw to the child ns). Is this a good way to go ? Or what would be a better one ? --mtx -- --- Hinweis: unverschlüsselte E-Mails können leicht abgehört und manipuliert werden ! Für eine vertrauliche Kommunikation senden Sie bitte ihren GPG/PGP-Schlüssel zu. --- Enrico Weigelt, metux IT consult Free software and Linux embedded engineering info@metux.net -- +49-151-27565287 ^ permalink raw reply [flat|nested] 63+ messages in thread
* Re: device namespaces 2021-06-08 9:38 device namespaces Enrico Weigelt, metux IT consult @ 2021-06-08 12:30 ` Christian Brauner 2021-06-08 12:41 ` Greg Kroah-Hartman 0 siblings, 1 reply; 63+ messages in thread From: Christian Brauner @ 2021-06-08 12:30 UTC (permalink / raw) To: Enrico Weigelt, metux IT consult, Greg Kroah-Hartman Cc: containers, linux-kernel On Tue, Jun 08, 2021 at 11:38:16AM +0200, Enrico Weigelt, metux IT consult wrote: > Hello folks, > > > I'm going to implement device namespaces, where containers can get an > entirely different view of the devices in the machine (usually just a > specific subset, but possibly additional virtual devices). > > For start I'd like to add a simple mapping of dev maj/min (leaving aside > sysfs, udev, etc). An important requirement for me is that the parent ns > can choose to delegate devices from those it full access too (child > namespaces can do the same to their childs), and the assignment can > change (for simplicity ignoring the case of removing devices that are > already opened by some process - haven't decided yet whether they should > be forcefully closed or whether keeping them open is a valid use case). > > The big question for me now is how exactly to do the table maintenance > from userland. We already have entries in /proc/<pid>/ns/*. I'm thinking > about using them as command channel, like this: > > * new child namespaces are created with empty mapping > * mapping manipulation is done by just writing commands to the ns file > * access is only granted if the writing process itself is in the > parent's device ns and has CAP_SYS_ADMIN (or maybe their could be some > admin user for the ns ? or the 'root' of the corresponding user_ns ?) > * if the caller has some restrictions on some particular device, these > are automatically added (eg. if you're restricted to readonly, you > can't give rw to the child ns). > > Is this a good way to go ? Or what would be a better one ? Ccing Greg. Without adressing specific problems, I should warn you that this idea is not new and the plan is unlikely to go anywhere. Especially not without support from Greg. Also note that I have done work to make it possible to do sufficient device management in containers. There's a longer series associated with this but the gist is 692ec06d7c92 ("netns: send uevent messages") where you can forward uevents to containers. I spoke about this at Plumbers in 2018 or so too. For example, LXD makes use of this. When you hotplug a device into a container LXD will forward the generated uevents to the container making it possible for the container to manage those devices. That's fully under control of userspace and means we don't need to burden the kernel with this. ^ permalink raw reply [flat|nested] 63+ messages in thread
* Re: device namespaces 2021-06-08 12:30 ` Christian Brauner @ 2021-06-08 12:41 ` Greg Kroah-Hartman 2021-06-08 14:10 ` Hannes Reinecke 0 siblings, 1 reply; 63+ messages in thread From: Greg Kroah-Hartman @ 2021-06-08 12:41 UTC (permalink / raw) To: Enrico Weigelt, metux IT consult Cc: Christian Brauner, containers, linux-kernel On Tue, Jun 08, 2021 at 02:30:50PM +0200, Christian Brauner wrote: > On Tue, Jun 08, 2021 at 11:38:16AM +0200, Enrico Weigelt, metux IT consult wrote: > > Hello folks, > > > > > > I'm going to implement device namespaces, where containers can get an > > entirely different view of the devices in the machine (usually just a > > specific subset, but possibly additional virtual devices). > > > > For start I'd like to add a simple mapping of dev maj/min (leaving aside > > sysfs, udev, etc). An important requirement for me is that the parent ns > > can choose to delegate devices from those it full access too (child > > namespaces can do the same to their childs), and the assignment can > > change (for simplicity ignoring the case of removing devices that are > > already opened by some process - haven't decided yet whether they should > > be forcefully closed or whether keeping them open is a valid use case). > > > > The big question for me now is how exactly to do the table maintenance > > from userland. We already have entries in /proc/<pid>/ns/*. I'm thinking > > about using them as command channel, like this: > > > > * new child namespaces are created with empty mapping > > * mapping manipulation is done by just writing commands to the ns file > > * access is only granted if the writing process itself is in the > > parent's device ns and has CAP_SYS_ADMIN (or maybe their could be some > > admin user for the ns ? or the 'root' of the corresponding user_ns ?) > > * if the caller has some restrictions on some particular device, these > > are automatically added (eg. if you're restricted to readonly, you > > can't give rw to the child ns). > > > > Is this a good way to go ? Or what would be a better one ? > > Ccing Greg. Without adressing specific problems, I should warn you that > this idea is not new and the plan is unlikely to go anywhere. Especially > not without support from Greg. Hah, yeah, this is a non-starter. Enrico, what real problem are you trying to solve by doing this? And have you tried anything with this yet? We almost never talk about "proposals" without seeing real code as it's pointless to discuss things when you haven't even proven that it can work. So let's see code before even talking about this... And as Christian points out, you can do this today without any kernel changes, so to think you need to modify the kernel means that you haven't even tried this at all? greg k-h ^ permalink raw reply [flat|nested] 63+ messages in thread
* Re: device namespaces 2021-06-08 12:41 ` Greg Kroah-Hartman @ 2021-06-08 14:10 ` Hannes Reinecke 2021-06-08 14:29 ` Christian Brauner 0 siblings, 1 reply; 63+ messages in thread From: Hannes Reinecke @ 2021-06-08 14:10 UTC (permalink / raw) To: gregkh; +Cc: christian.brauner, containers, linux-kernel, lkml On Tue, Jun 08, 2021 Greg-KH wrote: > On Tue, Jun 08, 2021 at 02:30:50PM +0200, Christian Brauner wrote: >> On Tue, Jun 08, 2021 at 11:38:16AM +0200, Enrico Weigelt, >> metux IT consult wrote: >>> Hello folks, >>> >>> >>> I'm going to implement device namespaces, where containers can get >>> an entirely different view of the devices in the machine (usually >>> just a specific subset, but possibly additional virtual devices). >>> [ .. ] >>> Is this a good way to go ? Or what would be a better one ? >> >> Ccing Greg. Without adressing specific problems, I should warn you >> that this idea is not new and the plan is unlikely to go anywhere. >> Especially not without support from Greg. > > Hah, yeah, this is a non-starter. > > Enrico, what real problem are you trying to solve by doing this? And > have you tried anything with this yet? We almost never talk about > "proposals" without seeing real code as it's pointless to discuss > things when you haven't even proven that it can work. > > So let's see code before even talking about this... > > And as Christian points out, you can do this today without any kernel > changes, so to think you need to modify the kernel means that you > haven't even tried this at all? > Curious, I had been looking into this, too. And I have to side with Greg and Christian that your proposal should already be possible today (cf device groups, which curiously has a near-identical interface to what you proposed). Also, I think that a generic 'device namespace' is too broad a scope; some subsystems like net already inherited namespace support, and it turns out to be not exactly trivial to implement. What I'm looking at, though, is to implement 'block' namespaces, to restrict access to _new_ block devices to any give namespace. Case in point: if a container creates a ramdisk it's questionable whether other containers should even see it. iSCSI devices are a similar case; when starting iSCSI devices from containers their use should be restricted to that container. And that's not only the device node in /dev, but would also entail sysfs access, which from my understanding is not modified with the current code. uevent redirection would help here, but from what I've seen it's only for net devices; feels a bit awkward to have a network namespace to get uevents for block devices, but then I'll have to test. And, of course, that also doesn't change the sysfs layout. Cheers, Hannes -- Dr. Hannes Reinecke Kernel Storage Architect hare@suse.de +49 911 74053 688 SUSE Software Solutions Germany GmbH, Maxfeldstr. 5, 90409 Nürnberg HRB 36809 (AG Nürnberg), GF: Felix Imendörffer ^ permalink raw reply [flat|nested] 63+ messages in thread
* Re: device namespaces 2021-06-08 14:10 ` Hannes Reinecke @ 2021-06-08 14:29 ` Christian Brauner 2021-06-08 15:54 ` Hannes Reinecke 0 siblings, 1 reply; 63+ messages in thread From: Christian Brauner @ 2021-06-08 14:29 UTC (permalink / raw) To: Hannes Reinecke; +Cc: gregkh, containers, linux-kernel, lkml On Tue, Jun 08, 2021 at 04:10:08PM +0200, Hannes Reinecke wrote: > On Tue, Jun 08, 2021 Greg-KH wrote: > > On Tue, Jun 08, 2021 at 02:30:50PM +0200, Christian Brauner wrote: > >> On Tue, Jun 08, 2021 at 11:38:16AM +0200, Enrico Weigelt, > >> metux IT consult wrote: > >>> Hello folks, > >>> > >>> > >>> I'm going to implement device namespaces, where containers can get > >>> an entirely different view of the devices in the machine (usually > >>> just a specific subset, but possibly additional virtual devices). > >>> > [ .. ] > >>> Is this a good way to go ? Or what would be a better one ? > >> > >> Ccing Greg. Without adressing specific problems, I should warn you > >> that this idea is not new and the plan is unlikely to go anywhere. > >> Especially not without support from Greg. > > > > Hah, yeah, this is a non-starter. > > > > Enrico, what real problem are you trying to solve by doing this? And > > have you tried anything with this yet? We almost never talk about > > "proposals" without seeing real code as it's pointless to discuss > > things when you haven't even proven that it can work. > > > > So let's see code before even talking about this... > > > > And as Christian points out, you can do this today without any kernel > > changes, so to think you need to modify the kernel means that you > > haven't even tried this at all? > > > Curious, I had been looking into this, too. > And I have to side with Greg and Christian that your proposal should > already be possible today (cf device groups, which curiously has a > near-identical interface to what you proposed). > Also, I think that a generic 'device namespace' is too broad a scope; > some subsystems like net already inherited namespace support, and it > turns out to be not exactly trivial to implement. > > What I'm looking at, though, is to implement 'block' namespaces, to > restrict access to _new_ block devices to any give namespace. > Case in point: if a container creates a ramdisk it's questionable > whether other containers should even see it. iSCSI devices are a similar > case; when starting iSCSI devices from containers their use should be > restricted to that container. > And that's not only the device node in /dev, but would also entail sysfs > access, which from my understanding is not modified with the current code. Hey Hannes. :) It isn't and we likely shouldn't. You'd likely need to get into the business of namespacing devtmpfs one way or the other which Seth Forshee and I once did. But that's really not needed anymore imho. Device management, i.e. creating device nodes should be the job of a container manager. We already do that for example (Hotplugging devices ranging from net devices, to disks, to GPUs.) and it works great. To make this really clean you will likely have to significanly rework sysfs too and I don't think that churn is worth it and introduces a layer of complexity I find outright nakable. And ignoring sysfs or hacking around it is also not an option I find tasteful. > > uevent redirection would help here, but from what I've seen it's only > for net devices; feels a bit awkward to have a network namespace to get > uevents for block devices, but then I'll have to test. Just to move everyone on the same page. This is not specific to network devices actually. You are right though that network devices are correctly namespaced. Specifically you only get uevents in the network namespace that network device is moved into. The sysfs permissions for network devices were correct if you created that network device in the network namespace but they were wrong when you moved a network device between network namespaces (with different owning user namespaces). That lead to all kinds of weird issues. I fixed that a while back. Uevent messages (and therefore injection of uevents) are not tied to network devices. They are tied to network namespaces simply because the transport layer is Netlink but that's about it. ^ permalink raw reply [flat|nested] 63+ messages in thread
* Re: device namespaces 2021-06-08 14:29 ` Christian Brauner @ 2021-06-08 15:54 ` Hannes Reinecke 2021-06-08 17:16 ` Eric W. Biederman 0 siblings, 1 reply; 63+ messages in thread From: Hannes Reinecke @ 2021-06-08 15:54 UTC (permalink / raw) To: Christian Brauner; +Cc: gregkh, containers, linux-kernel, lkml On 6/8/21 4:29 PM, Christian Brauner wrote: > On Tue, Jun 08, 2021 at 04:10:08PM +0200, Hannes Reinecke wrote: >> On Tue, Jun 08, 2021 Greg-KH wrote: >>> On Tue, Jun 08, 2021 at 02:30:50PM +0200, Christian Brauner wrote: >>>> On Tue, Jun 08, 2021 at 11:38:16AM +0200, Enrico Weigelt, >>>> metux IT consult wrote: >>>>> Hello folks, >>>>> >>>>> >>>>> I'm going to implement device namespaces, where containers can get >>>>> an entirely different view of the devices in the machine (usually >>>>> just a specific subset, but possibly additional virtual devices). >>>>> >> [ .. ] >>>>> Is this a good way to go ? Or what would be a better one ? >>>> >>>> Ccing Greg. Without adressing specific problems, I should warn you >>>> that this idea is not new and the plan is unlikely to go anywhere. >>>> Especially not without support from Greg. >>> >>> Hah, yeah, this is a non-starter. >>> >>> Enrico, what real problem are you trying to solve by doing this? And >>> have you tried anything with this yet? We almost never talk about >>> "proposals" without seeing real code as it's pointless to discuss >>> things when you haven't even proven that it can work. >>> >>> So let's see code before even talking about this... >>> >>> And as Christian points out, you can do this today without any kernel >>> changes, so to think you need to modify the kernel means that you >>> haven't even tried this at all? >>> >> Curious, I had been looking into this, too. >> And I have to side with Greg and Christian that your proposal should >> already be possible today (cf device groups, which curiously has a >> near-identical interface to what you proposed). >> Also, I think that a generic 'device namespace' is too broad a scope; >> some subsystems like net already inherited namespace support, and it >> turns out to be not exactly trivial to implement. >> >> What I'm looking at, though, is to implement 'block' namespaces, to >> restrict access to _new_ block devices to any give namespace. >> Case in point: if a container creates a ramdisk it's questionable >> whether other containers should even see it. iSCSI devices are a similar >> case; when starting iSCSI devices from containers their use should be >> restricted to that container. >> And that's not only the device node in /dev, but would also entail sysfs >> access, which from my understanding is not modified with the current code. > > Hey Hannes. :) > > It isn't and we likely shouldn't. You'd likely need to get into the > business of namespacing devtmpfs one way or the other which Seth Forshee > and I once did. But that's really not needed anymore imho. Device > management, i.e. creating device nodes should be the job of a container > manager. We already do that for example (Hotplugging devices ranging > from net devices, to disks, to GPUs.) and it works great. > Right; clearly you can do that within the container. But my main grudge here is not the container but rather the system _hosting_ the container. That is typically using devtmpfs and hence will see _all_ devices, even those belonging to the container. This is causing grief to no end if eg the host system starts activating LVM on devices which are passed to the qemu instance running within a container ... > To make this really clean you will likely have to significantly rework > sysfs too and I don't think that churn is worth it and introduces a > layer of complexity I find outright nakable. And ignoring sysfs or > hacking around it is also not an option I find tasteful. > Network namespaces already have the bits and pieces to modify sysfs, so we should be able to leverage that for block, too. And I think by restricting it to 'block' devices we should be to keep the required sysfs modifications in a manageable level. >> >> uevent redirection would help here, but from what I've seen it's only >> for net devices; feels a bit awkward to have a network namespace to get >> uevents for block devices, but then I'll have to test. > > Just to move everyone on the same page. This is not specific to network > devices actually. > > You are right though that network devices are correctly namespaced. > Specifically you only get uevents in the network namespace that network > device is moved into. The sysfs permissions for network devices were > correct if you created that network device in the network namespace but > they were wrong when you moved a network device between network > namespaces (with different owning user namespaces). That lead to all > kinds of weird issues. I fixed that a while back. > Granted, modifying sysfs layout is not something for the faint-hearted, and one really has to look closely to ensure you end up with a consistent layout afterwards. But let's see how things go; might well be that it turns out to be too complex to consider. Can't tell yet. Cheers, Hannes -- Dr. Hannes Reinecke Kernel Storage Architect hare@suse.de +49 911 74053 688 SUSE Software Solutions Germany GmbH, Maxfeldstr. 5, 90409 Nürnberg HRB 36809 (AG Nürnberg), GF: Felix Imendörffer ^ permalink raw reply [flat|nested] 63+ messages in thread
* Re: device namespaces 2021-06-08 15:54 ` Hannes Reinecke @ 2021-06-08 17:16 ` Eric W. Biederman 2021-06-09 6:38 ` Christian Brauner 0 siblings, 1 reply; 63+ messages in thread From: Eric W. Biederman @ 2021-06-08 17:16 UTC (permalink / raw) To: Hannes Reinecke; +Cc: Christian Brauner, gregkh, containers, linux-kernel, lkml Hannes Reinecke <hare@suse.de> writes: > On 6/8/21 4:29 PM, Christian Brauner wrote: >> On Tue, Jun 08, 2021 at 04:10:08PM +0200, Hannes Reinecke wrote: >>> On Tue, Jun 08, 2021 Greg-KH wrote: >>>> On Tue, Jun 08, 2021 at 02:30:50PM +0200, Christian Brauner wrote: >>>>> On Tue, Jun 08, 2021 at 11:38:16AM +0200, Enrico Weigelt, >>>>> metux IT consult wrote: >>>>>> Hello folks, >>>>>> >>>>>> >>>>>> I'm going to implement device namespaces, where containers can get >>>>>> an entirely different view of the devices in the machine (usually >>>>>> just a specific subset, but possibly additional virtual devices). >>>>>> >>> [ .. ] >>>>>> Is this a good way to go ? Or what would be a better one ? >>>>> >>>>> Ccing Greg. Without adressing specific problems, I should warn you >>>>> that this idea is not new and the plan is unlikely to go anywhere. >>>>> Especially not without support from Greg. >>>> >>>> Hah, yeah, this is a non-starter. >>>> >>>> Enrico, what real problem are you trying to solve by doing this? And >>>> have you tried anything with this yet? We almost never talk about >>>> "proposals" without seeing real code as it's pointless to discuss >>>> things when you haven't even proven that it can work. >>>> >>>> So let's see code before even talking about this... >>>> >>>> And as Christian points out, you can do this today without any kernel >>>> changes, so to think you need to modify the kernel means that you >>>> haven't even tried this at all? >>>> >>> Curious, I had been looking into this, too. >>> And I have to side with Greg and Christian that your proposal should >>> already be possible today (cf device groups, which curiously has a >>> near-identical interface to what you proposed). >>> Also, I think that a generic 'device namespace' is too broad a scope; >>> some subsystems like net already inherited namespace support, and it >>> turns out to be not exactly trivial to implement. >>> >>> What I'm looking at, though, is to implement 'block' namespaces, to >>> restrict access to _new_ block devices to any give namespace. >>> Case in point: if a container creates a ramdisk it's questionable >>> whether other containers should even see it. iSCSI devices are a similar >>> case; when starting iSCSI devices from containers their use should be >>> restricted to that container. >>> And that's not only the device node in /dev, but would also entail sysfs >>> access, which from my understanding is not modified with the current code. >> >> Hey Hannes. :) >> >> It isn't and we likely shouldn't. You'd likely need to get into the >> business of namespacing devtmpfs one way or the other which Seth Forshee >> and I once did. But that's really not needed anymore imho. Device >> management, i.e. creating device nodes should be the job of a container >> manager. We already do that for example (Hotplugging devices ranging >> from net devices, to disks, to GPUs.) and it works great. >> > Right; clearly you can do that within the container. > But my main grudge here is not the container but rather the system > _hosting_ the container. > That is typically using devtmpfs and hence will see _all_ devices, even > those belonging to the container. > This is causing grief to no end if eg the host system starts activating > LVM on devices which are passed to the qemu instance running within a > container ... > >> To make this really clean you will likely have to significantly rework >> sysfs too and I don't think that churn is worth it and introduces a >> layer of complexity I find outright nakable. And ignoring sysfs or >> hacking around it is also not an option I find tasteful. >> > Network namespaces already have the bits and pieces to modify sysfs, so > we should be able to leverage that for block, too. > And I think by restricting it to 'block' devices we should be to keep > the required sysfs modifications in a manageable level. > >>> >>> uevent redirection would help here, but from what I've seen it's only >>> for net devices; feels a bit awkward to have a network namespace to get >>> uevents for block devices, but then I'll have to test. >> >> Just to move everyone on the same page. This is not specific to network >> devices actually. >> >> You are right though that network devices are correctly namespaced. >> Specifically you only get uevents in the network namespace that network >> device is moved into. The sysfs permissions for network devices were >> correct if you created that network device in the network namespace but >> they were wrong when you moved a network device between network >> namespaces (with different owning user namespaces). That lead to all >> kinds of weird issues. I fixed that a while back. >> > Granted, modifying sysfs layout is not something for the faint-hearted, > and one really has to look closely to ensure you end up with a > consistent layout afterwards. > > But let's see how things go; might well be that it turns out to be too > complex to consider. Can't tell yet. I would suggest aiming for something like devptsfs without the complication of /dev/ptmx. That is a pseudo filesystem that has a control node and virtual block devices that were created using that control node. That is the cleanest solution I know and is not strictly limited to use with containers so it can also gain greater traction. The interaction with devtmpfs should be simply having devtmpfs create a mount point for that filesystem. This could be a new cleaner api for things like loopback devices. However the limitation for block devices that I am aware of is that we don't currently have any filesystems in the kernel that are written robustly enough that we can be expected to be secure when mounted on top of an evil block device. Some of the network filesystems are built to withstand evil network packets, and possibly evil servers. So with care we can probably allow for unprivileged mounts there. Eric ^ permalink raw reply [flat|nested] 63+ messages in thread
* Re: device namespaces 2021-06-08 17:16 ` Eric W. Biederman @ 2021-06-09 6:38 ` Christian Brauner 2021-06-09 7:02 ` Hannes Reinecke 0 siblings, 1 reply; 63+ messages in thread From: Christian Brauner @ 2021-06-09 6:38 UTC (permalink / raw) To: Eric W. Biederman; +Cc: Hannes Reinecke, gregkh, containers, linux-kernel, lkml On Tue, Jun 08, 2021 at 12:16:43PM -0500, Eric W. Biederman wrote: > Hannes Reinecke <hare@suse.de> writes: > > > On 6/8/21 4:29 PM, Christian Brauner wrote: > >> On Tue, Jun 08, 2021 at 04:10:08PM +0200, Hannes Reinecke wrote: > >>> On Tue, Jun 08, 2021 Greg-KH wrote: > >>>> On Tue, Jun 08, 2021 at 02:30:50PM +0200, Christian Brauner wrote: > >>>>> On Tue, Jun 08, 2021 at 11:38:16AM +0200, Enrico Weigelt, > >>>>> metux IT consult wrote: > >>>>>> Hello folks, > >>>>>> > >>>>>> > >>>>>> I'm going to implement device namespaces, where containers can get > >>>>>> an entirely different view of the devices in the machine (usually > >>>>>> just a specific subset, but possibly additional virtual devices). > >>>>>> > >>> [ .. ] > >>>>>> Is this a good way to go ? Or what would be a better one ? > >>>>> > >>>>> Ccing Greg. Without adressing specific problems, I should warn you > >>>>> that this idea is not new and the plan is unlikely to go anywhere. > >>>>> Especially not without support from Greg. > >>>> > >>>> Hah, yeah, this is a non-starter. > >>>> > >>>> Enrico, what real problem are you trying to solve by doing this? And > >>>> have you tried anything with this yet? We almost never talk about > >>>> "proposals" without seeing real code as it's pointless to discuss > >>>> things when you haven't even proven that it can work. > >>>> > >>>> So let's see code before even talking about this... > >>>> > >>>> And as Christian points out, you can do this today without any kernel > >>>> changes, so to think you need to modify the kernel means that you > >>>> haven't even tried this at all? > >>>> > >>> Curious, I had been looking into this, too. > >>> And I have to side with Greg and Christian that your proposal should > >>> already be possible today (cf device groups, which curiously has a > >>> near-identical interface to what you proposed). > >>> Also, I think that a generic 'device namespace' is too broad a scope; > >>> some subsystems like net already inherited namespace support, and it > >>> turns out to be not exactly trivial to implement. > >>> > >>> What I'm looking at, though, is to implement 'block' namespaces, to > >>> restrict access to _new_ block devices to any give namespace. > >>> Case in point: if a container creates a ramdisk it's questionable > >>> whether other containers should even see it. iSCSI devices are a similar > >>> case; when starting iSCSI devices from containers their use should be > >>> restricted to that container. > >>> And that's not only the device node in /dev, but would also entail sysfs > >>> access, which from my understanding is not modified with the current code. > >> > >> Hey Hannes. :) > >> > >> It isn't and we likely shouldn't. You'd likely need to get into the > >> business of namespacing devtmpfs one way or the other which Seth Forshee > >> and I once did. But that's really not needed anymore imho. Device > >> management, i.e. creating device nodes should be the job of a container > >> manager. We already do that for example (Hotplugging devices ranging > >> from net devices, to disks, to GPUs.) and it works great. > >> > > Right; clearly you can do that within the container. > > But my main grudge here is not the container but rather the system > > _hosting_ the container. > > That is typically using devtmpfs and hence will see _all_ devices, even > > those belonging to the container. > > This is causing grief to no end if eg the host system starts activating > > LVM on devices which are passed to the qemu instance running within a > > container ... > > > >> To make this really clean you will likely have to significantly rework > >> sysfs too and I don't think that churn is worth it and introduces a > >> layer of complexity I find outright nakable. And ignoring sysfs or > >> hacking around it is also not an option I find tasteful. > >> > > Network namespaces already have the bits and pieces to modify sysfs, so > > we should be able to leverage that for block, too. > > And I think by restricting it to 'block' devices we should be to keep > > the required sysfs modifications in a manageable level. > > > >>> > >>> uevent redirection would help here, but from what I've seen it's only > >>> for net devices; feels a bit awkward to have a network namespace to get > >>> uevents for block devices, but then I'll have to test. > >> > >> Just to move everyone on the same page. This is not specific to network > >> devices actually. > >> > >> You are right though that network devices are correctly namespaced. > >> Specifically you only get uevents in the network namespace that network > >> device is moved into. The sysfs permissions for network devices were > >> correct if you created that network device in the network namespace but > >> they were wrong when you moved a network device between network > >> namespaces (with different owning user namespaces). That lead to all > >> kinds of weird issues. I fixed that a while back. > >> > > Granted, modifying sysfs layout is not something for the faint-hearted, > > and one really has to look closely to ensure you end up with a > > consistent layout afterwards. > > > > But let's see how things go; might well be that it turns out to be too > > complex to consider. Can't tell yet. > > I would suggest aiming for something like devptsfs without the > complication of /dev/ptmx. > > That is a pseudo filesystem that has a control node and virtual block > devices that were created using that control node. Also see android/binder/binderfs.c > > That is the cleanest solution I know and is not strictly limited to use > with containers so it can also gain greater traction. The interaction > with devtmpfs should be simply having devtmpfs create a mount point for > that filesystem. > > This could be a new cleaner api for things like loopback devices. I sent a patchset that implemented this last year. ^ permalink raw reply [flat|nested] 63+ messages in thread
* Re: device namespaces 2021-06-09 6:38 ` Christian Brauner @ 2021-06-09 7:02 ` Hannes Reinecke 2021-06-09 7:21 ` Christian Brauner 0 siblings, 1 reply; 63+ messages in thread From: Hannes Reinecke @ 2021-06-09 7:02 UTC (permalink / raw) To: Christian Brauner, Eric W. Biederman Cc: gregkh, containers, linux-kernel, lkml On 6/9/21 8:38 AM, Christian Brauner wrote: > On Tue, Jun 08, 2021 at 12:16:43PM -0500, Eric W. Biederman wrote: >> Hannes Reinecke <hare@suse.de> writes: >> >>> On 6/8/21 4:29 PM, Christian Brauner wrote: >>>> On Tue, Jun 08, 2021 at 04:10:08PM +0200, Hannes Reinecke wrote: [ .. ] >>> Granted, modifying sysfs layout is not something for the faint-hearted, >>> and one really has to look closely to ensure you end up with a >>> consistent layout afterwards. >>> >>> But let's see how things go; might well be that it turns out to be too >>> complex to consider. Can't tell yet. >> >> I would suggest aiming for something like devptsfs without the >> complication of /dev/ptmx. >> >> That is a pseudo filesystem that has a control node and virtual block >> devices that were created using that control node. > > Also see android/binder/binderfs.c > Ah. Will have a look. >> >> That is the cleanest solution I know and is not strictly limited to use >> with containers so it can also gain greater traction. The interaction >> with devtmpfs should be simply having devtmpfs create a mount point for >> that filesystem. >> >> This could be a new cleaner api for things like loopback devices. > > I sent a patchset that implemented this last year. > Do you have a pointer/commit hash for this? Cheers, Hannes -- Dr. Hannes Reinecke Kernel Storage Architect hare@suse.de +49 911 74053 688 SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg HRB 36809 (AG Nürnberg), Geschäftsführer: Felix Imendörffer ^ permalink raw reply [flat|nested] 63+ messages in thread
* Re: device namespaces 2021-06-09 7:02 ` Hannes Reinecke @ 2021-06-09 7:21 ` Christian Brauner 2021-06-09 7:54 ` Hannes Reinecke 0 siblings, 1 reply; 63+ messages in thread From: Christian Brauner @ 2021-06-09 7:21 UTC (permalink / raw) To: Hannes Reinecke; +Cc: Eric W. Biederman, gregkh, containers, linux-kernel, lkml On Wed, Jun 09, 2021 at 09:02:36AM +0200, Hannes Reinecke wrote: > On 6/9/21 8:38 AM, Christian Brauner wrote: > > On Tue, Jun 08, 2021 at 12:16:43PM -0500, Eric W. Biederman wrote: > > > Hannes Reinecke <hare@suse.de> writes: > > > > > > > On 6/8/21 4:29 PM, Christian Brauner wrote: > > > > > On Tue, Jun 08, 2021 at 04:10:08PM +0200, Hannes Reinecke wrote: > [ .. ] > > > > Granted, modifying sysfs layout is not something for the faint-hearted, > > > > and one really has to look closely to ensure you end up with a > > > > consistent layout afterwards. > > > > > > > > But let's see how things go; might well be that it turns out to be too > > > > complex to consider. Can't tell yet. > > > > > > I would suggest aiming for something like devptsfs without the > > > complication of /dev/ptmx. > > > > > > That is a pseudo filesystem that has a control node and virtual block > > > devices that were created using that control node. > > > > Also see android/binder/binderfs.c > > > Ah. Will have a look. I implemented this a few years back and I think it should've made it onto Android by default now. So that approach does indeed work well, it seems: https://chromium.googlesource.com/aosp/platform/system/core/+/master/rootdir/init.rc#257 This should be easier to follow than the devpts case because you don't need to wade through the {t,p}ty layer. > > > > > > > That is the cleanest solution I know and is not strictly limited to use > > > with containers so it can also gain greater traction. The interaction > > > with devtmpfs should be simply having devtmpfs create a mount point for > > > that filesystem. > > > > > > This could be a new cleaner api for things like loopback devices. > > > > I sent a patchset that implemented this last year. > > > Do you have a pointer/commit hash for this? Yes, sure: https://lore.kernel.org/linux-block/20200424162052.441452-1-christian.brauner@ubuntu.com/ You can also just pull my branch. I think it's still based on v5.7 or sm: https://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux.git/log/?h=loopfs I'm happy to collaborate on this too. Christian ^ permalink raw reply [flat|nested] 63+ messages in thread
* Re: device namespaces 2021-06-09 7:21 ` Christian Brauner @ 2021-06-09 7:54 ` Hannes Reinecke 2021-06-09 8:09 ` Christian Brauner 0 siblings, 1 reply; 63+ messages in thread From: Hannes Reinecke @ 2021-06-09 7:54 UTC (permalink / raw) To: Christian Brauner Cc: Eric W. Biederman, gregkh, containers, linux-kernel, lkml On 6/9/21 9:21 AM, Christian Brauner wrote: > On Wed, Jun 09, 2021 at 09:02:36AM +0200, Hannes Reinecke wrote: >> On 6/9/21 8:38 AM, Christian Brauner wrote: >>> On Tue, Jun 08, 2021 at 12:16:43PM -0500, Eric W. Biederman wrote: >>>> Hannes Reinecke <hare@suse.de> writes: >>>> >>>>> On 6/8/21 4:29 PM, Christian Brauner wrote: >>>>>> On Tue, Jun 08, 2021 at 04:10:08PM +0200, Hannes Reinecke wrote: >> [ .. ] >>>>> Granted, modifying sysfs layout is not something for the faint-hearted, >>>>> and one really has to look closely to ensure you end up with a >>>>> consistent layout afterwards. >>>>> >>>>> But let's see how things go; might well be that it turns out to be too >>>>> complex to consider. Can't tell yet. >>>> >>>> I would suggest aiming for something like devptsfs without the >>>> complication of /dev/ptmx. >>>> >>>> That is a pseudo filesystem that has a control node and virtual block >>>> devices that were created using that control node. >>> >>> Also see android/binder/binderfs.c >>> >> Ah. Will have a look. > > I implemented this a few years back and I think it should've made it > onto Android by default now. So that approach does indeed work well, it > seems: > https://chromium.googlesource.com/aosp/platform/system/core/+/master/rootdir/init.rc#257 > > This should be easier to follow than the devpts case because you don't > need to wade through the {t,p}ty layer. > >> >>>> >>>> That is the cleanest solution I know and is not strictly limited to use >>>> with containers so it can also gain greater traction. The interaction >>>> with devtmpfs should be simply having devtmpfs create a mount point for >>>> that filesystem. >>>> >>>> This could be a new cleaner api for things like loopback devices. >>> >>> I sent a patchset that implemented this last year. >>> >> Do you have a pointer/commit hash for this? > > Yes, sure: > https://lore.kernel.org/linux-block/20200424162052.441452-1-christian.brauner@ubuntu.com/ > > You can also just pull my branch. I think it's still based on v5.7 or sm: > https://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux.git/log/?h=loopfs > > I'm happy to collaborate on this too. > How _very_ curious. 'kernfs: handle multiple namespace tags' and 'loop: preserve sysfs backwards compability' are essentially the same patches I did for my block namespaces prototyp; I named it 'KOBJ_NS_TYPE_BLK', not 'KOBJ_NS_TYPE_USER', though :-) Guess we really should cooperate. Speaking of which: why did you name it 'user' namespace? There already is a generic 'user_namespace' in include/linux/user_namespace.h, serving as a container for all namespaces; as such it probably should include this 'user' namespace, leading to quite some confusion. Or did I misunderstood something here? Cheers, Hannes -- Dr. Hannes Reinecke Kernel Storage Architect hare@suse.de +49 911 74053 688 SUSE Software Solutions Germany GmbH, Maxfeldstr. 5, 90409 Nürnberg HRB 36809 (AG Nürnberg), GF: Felix Imendörffer ^ permalink raw reply [flat|nested] 63+ messages in thread
* Re: device namespaces 2021-06-09 7:54 ` Hannes Reinecke @ 2021-06-09 8:09 ` Christian Brauner 2021-06-11 18:14 ` Eric W. Biederman 0 siblings, 1 reply; 63+ messages in thread From: Christian Brauner @ 2021-06-09 8:09 UTC (permalink / raw) To: Hannes Reinecke; +Cc: Eric W. Biederman, gregkh, containers, linux-kernel, lkml On Wed, Jun 09, 2021 at 09:54:05AM +0200, Hannes Reinecke wrote: > On 6/9/21 9:21 AM, Christian Brauner wrote: > > On Wed, Jun 09, 2021 at 09:02:36AM +0200, Hannes Reinecke wrote: > >> On 6/9/21 8:38 AM, Christian Brauner wrote: > >>> On Tue, Jun 08, 2021 at 12:16:43PM -0500, Eric W. Biederman wrote: > >>>> Hannes Reinecke <hare@suse.de> writes: > >>>> > >>>>> On 6/8/21 4:29 PM, Christian Brauner wrote: > >>>>>> On Tue, Jun 08, 2021 at 04:10:08PM +0200, Hannes Reinecke wrote: > >> [ .. ] > >>>>> Granted, modifying sysfs layout is not something for the faint-hearted, > >>>>> and one really has to look closely to ensure you end up with a > >>>>> consistent layout afterwards. > >>>>> > >>>>> But let's see how things go; might well be that it turns out to be too > >>>>> complex to consider. Can't tell yet. > >>>> > >>>> I would suggest aiming for something like devptsfs without the > >>>> complication of /dev/ptmx. > >>>> > >>>> That is a pseudo filesystem that has a control node and virtual block > >>>> devices that were created using that control node. > >>> > >>> Also see android/binder/binderfs.c > >>> > >> Ah. Will have a look. > > > > I implemented this a few years back and I think it should've made it > > onto Android by default now. So that approach does indeed work well, it > > seems: > > https://chromium.googlesource.com/aosp/platform/system/core/+/master/rootdir/init.rc#257 > > > > This should be easier to follow than the devpts case because you don't > > need to wade through the {t,p}ty layer. > > > >> > >>>> > >>>> That is the cleanest solution I know and is not strictly limited to use > >>>> with containers so it can also gain greater traction. The interaction > >>>> with devtmpfs should be simply having devtmpfs create a mount point for > >>>> that filesystem. > >>>> > >>>> This could be a new cleaner api for things like loopback devices. > >>> > >>> I sent a patchset that implemented this last year. > >>> > >> Do you have a pointer/commit hash for this? > > > > Yes, sure: > > https://lore.kernel.org/linux-block/20200424162052.441452-1-christian.brauner@ubuntu.com/ > > > > You can also just pull my branch. I think it's still based on v5.7 or sm: > > https://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux.git/log/?h=loopfs > > > > I'm happy to collaborate on this too. > > > How _very_ curious. 'kernfs: handle multiple namespace tags' and 'loop: > preserve sysfs backwards compability' are essentially the same patches I > did for my block namespaces prototyp; I named it 'KOBJ_NS_TYPE_BLK', not > 'KOBJ_NS_TYPE_USER', though :-) > > Guess we really should cooperate. > > Speaking of which: why did you name it 'user' namespace? > There already is a generic 'user_namespace' in > include/linux/user_namespace.h, serving as a container for all > namespaces; as such it probably should include this 'user' namespace, > leading to quite some confusion. > > Or did I misunderstood something here? Ah yes, you misunderstand. The KOBJ_NS_TYPE_* tags are namespace tags. So KOBJ_NS_TYPE_NET is a network namespace tag. So KOBJ_NS_TYPE_USER is a user namespace tag not a completely new namespace. The idea very roughly being that devices such as loop devices are ultimately filtered by user namespace which is taken from the s_user_ns the loopfs instance is mounted in. We should compare notes. Christian ^ permalink raw reply [flat|nested] 63+ messages in thread
* Re: device namespaces 2021-06-09 8:09 ` Christian Brauner @ 2021-06-11 18:14 ` Eric W. Biederman 2021-06-14 7:49 ` Enrico Weigelt, metux IT consult 0 siblings, 1 reply; 63+ messages in thread From: Eric W. Biederman @ 2021-06-11 18:14 UTC (permalink / raw) To: Christian Brauner; +Cc: Hannes Reinecke, gregkh, containers, linux-kernel, lkml Christian Brauner <christian.brauner@ubuntu.com> writes: > On Wed, Jun 09, 2021 at 09:54:05AM +0200, Hannes Reinecke wrote: >> On 6/9/21 9:21 AM, Christian Brauner wrote: >> > On Wed, Jun 09, 2021 at 09:02:36AM +0200, Hannes Reinecke wrote: >> >> On 6/9/21 8:38 AM, Christian Brauner wrote: >> >>> On Tue, Jun 08, 2021 at 12:16:43PM -0500, Eric W. Biederman wrote: >> >>>> Hannes Reinecke <hare@suse.de> writes: >> >>>> >> >>>>> On 6/8/21 4:29 PM, Christian Brauner wrote: >> >>>>>> On Tue, Jun 08, 2021 at 04:10:08PM +0200, Hannes Reinecke wrote: >> >> [ .. ] >> >>>>> Granted, modifying sysfs layout is not something for the faint-hearted, >> >>>>> and one really has to look closely to ensure you end up with a >> >>>>> consistent layout afterwards. >> >>>>> >> >>>>> But let's see how things go; might well be that it turns out to be too >> >>>>> complex to consider. Can't tell yet. >> >>>> >> >>>> I would suggest aiming for something like devptsfs without the >> >>>> complication of /dev/ptmx. >> >>>> >> >>>> That is a pseudo filesystem that has a control node and virtual block >> >>>> devices that were created using that control node. >> >>> >> >>> Also see android/binder/binderfs.c >> >>> >> >> Ah. Will have a look. >> > >> > I implemented this a few years back and I think it should've made it >> > onto Android by default now. So that approach does indeed work well, it >> > seems: >> > https://chromium.googlesource.com/aosp/platform/system/core/+/master/rootdir/init.rc#257 >> > >> > This should be easier to follow than the devpts case because you don't >> > need to wade through the {t,p}ty layer. >> > >> >> >> >>>> >> >>>> That is the cleanest solution I know and is not strictly limited to use >> >>>> with containers so it can also gain greater traction. The interaction >> >>>> with devtmpfs should be simply having devtmpfs create a mount point for >> >>>> that filesystem. >> >>>> >> >>>> This could be a new cleaner api for things like loopback devices. >> >>> >> >>> I sent a patchset that implemented this last year. >> >>> >> >> Do you have a pointer/commit hash for this? >> > >> > Yes, sure: >> > https://lore.kernel.org/linux-block/20200424162052.441452-1-christian.brauner@ubuntu.com/ >> > >> > You can also just pull my branch. I think it's still based on v5.7 or sm: >> > https://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux.git/log/?h=loopfs >> > >> > I'm happy to collaborate on this too. >> > >> How _very_ curious. 'kernfs: handle multiple namespace tags' and 'loop: >> preserve sysfs backwards compability' are essentially the same patches I >> did for my block namespaces prototyp; I named it 'KOBJ_NS_TYPE_BLK', not >> 'KOBJ_NS_TYPE_USER', though :-) >> >> Guess we really should cooperate. >> >> Speaking of which: why did you name it 'user' namespace? >> There already is a generic 'user_namespace' in >> include/linux/user_namespace.h, serving as a container for all >> namespaces; as such it probably should include this 'user' namespace, >> leading to quite some confusion. >> >> Or did I misunderstood something here? > > Ah yes, you misunderstand. The KOBJ_NS_TYPE_* tags are namespace tags. > So KOBJ_NS_TYPE_NET is a network namespace tag. So KOBJ_NS_TYPE_USER is > a user namespace tag not a completely new namespace. The idea very > roughly being that devices such as loop devices are ultimately filtered > by user namespace which is taken from the s_user_ns the loopfs instance > is mounted in. We should compare notes. There are two easy possibilities. - All of the devices on the filesystem show up in sysfs with unique major minor numbers. - None of the devices on the filesystem show up in sysfs. (Which I believe is what devpts does). I favor none of the virtual devices showing up in sysfs. Maybe existing userspace needs the devices in sysfs, but if the solution is simply to skip sysfs for virtual devices that is much simpler. Eric ^ permalink raw reply [flat|nested] 63+ messages in thread
* Re: device namespaces 2021-06-11 18:14 ` Eric W. Biederman @ 2021-06-14 7:49 ` Enrico Weigelt, metux IT consult 2021-06-14 8:22 ` Greg KH 2021-06-14 17:36 ` Eric W. Biederman 0 siblings, 2 replies; 63+ messages in thread From: Enrico Weigelt, metux IT consult @ 2021-06-14 7:49 UTC (permalink / raw) To: Eric W. Biederman, Christian Brauner Cc: Hannes Reinecke, gregkh, containers, linux-kernel On 11.06.21 20:14, Eric W. Biederman wrote: Hi, > I favor none of the virtual devices showing up in sysfs. Maybe existing > userspace needs the devices in sysfs, but if the solution is simply to > skip sysfs for virtual devices that is much simpler. Sorry for being a little bit confused, but by virtual devices you mean things like pty's or all the other stuff we already see under /sys/device/virtual ? I'm yet unsure what the better way is. If we're just talking about pty's specifically, I maybe could live with threating them like "special sort of pipes", but I guess that would require some extra magic. If I'm not mistaken, the whole sysfs stuff is automatically handled device classes and bus'es - seems that tty's are also class devs. How would you skip the virtual devices from sysfs ? Adding some filter into sysfs that looks at the device class (or some flag within it) ? --mtx -- --- Hinweis: unverschlüsselte E-Mails können leicht abgehört und manipuliert werden ! Für eine vertrauliche Kommunikation senden Sie bitte ihren GPG/PGP-Schlüssel zu. --- Enrico Weigelt, metux IT consult Free software and Linux embedded engineering info@metux.net -- +49-151-27565287 ^ permalink raw reply [flat|nested] 63+ messages in thread
* Re: device namespaces 2021-06-14 7:49 ` Enrico Weigelt, metux IT consult @ 2021-06-14 8:22 ` Greg KH 2021-06-14 17:36 ` Eric W. Biederman 1 sibling, 0 replies; 63+ messages in thread From: Greg KH @ 2021-06-14 8:22 UTC (permalink / raw) To: Enrico Weigelt, metux IT consult Cc: Eric W. Biederman, Christian Brauner, Hannes Reinecke, containers, linux-kernel On Mon, Jun 14, 2021 at 09:49:22AM +0200, Enrico Weigelt, metux IT consult wrote: > On 11.06.21 20:14, Eric W. Biederman wrote: > > Hi, > > > I favor none of the virtual devices showing up in sysfs. Maybe existing > > userspace needs the devices in sysfs, but if the solution is simply to > > skip sysfs for virtual devices that is much simpler. > > Sorry for being a little bit confused, but by virtual devices you mean > things like pty's or all the other stuff we already see under > /sys/device/virtual ? > > I'm yet unsure what the better way is. If we're just talking about pty's > specifically, I maybe could live with threating them like "special sort > of pipes", but I guess that would require some extra magic. > > If I'm not mistaken, the whole sysfs stuff is automatically handled > device classes and bus'es - seems that tty's are also class devs. > > How would you skip the virtual devices from sysfs ? Adding some filter > into sysfs that looks at the device class (or some flag within it) ? Wait, step back. What _EXACTLY_ are you wanting to do here? If you have not looked at how sysfs handles devices today, that leads me to believe that you do not have a real model in place. Again, spend some time and write some code please before continuing this thread. We don't like to talk about vague things when you do not even have an idea of what you want. good luck! greg k-h ^ permalink raw reply [flat|nested] 63+ messages in thread
* Re: device namespaces 2021-06-14 7:49 ` Enrico Weigelt, metux IT consult 2021-06-14 8:22 ` Greg KH @ 2021-06-14 17:36 ` Eric W. Biederman 2021-06-15 11:24 ` Enrico Weigelt, metux IT consult 1 sibling, 1 reply; 63+ messages in thread From: Eric W. Biederman @ 2021-06-14 17:36 UTC (permalink / raw) To: Enrico Weigelt, metux IT consult Cc: Christian Brauner, Hannes Reinecke, gregkh, containers, linux-kernel "Enrico Weigelt, metux IT consult" <lkml@metux.net> writes: > On 11.06.21 20:14, Eric W. Biederman wrote: > > Hi, > >> I favor none of the virtual devices showing up in sysfs. Maybe existing >> userspace needs the devices in sysfs, but if the solution is simply to >> skip sysfs for virtual devices that is much simpler. > > Sorry for being a little bit confused, but by virtual devices you mean > things like pty's or all the other stuff we already see under > /sys/device/virtual ? By virtual devices I mean all devices that are not physical pieces of hardware. For block devices I mean devices such as loopback devices that are created on demand. Ramdisks that start this conversation could also be considered virtual devices. > How would you skip the virtual devices from sysfs ? Adding some filter > into sysfs that looks at the device class (or some flag within it) ? I would just not run the code to create sysfs entries when the virtual devices are created. If you have virtual devices showing up in their own filesystem they don't even need major or minor numbers. You can just have files that accept ioctls like device nodes. In principle it is possible to skip a lot of the historical infrastructure. If the infrastructure is not needed it is worth skipping. I haven't dug into the block layer recently enough to say what is needed or not. I think there are some thing such as stat on a mounted filesystem that need a major and minor numbers. Which probably means you have to use major and minor numbers. By virtue of using common infrastructure that implies showing up in sysfs and devtmpfs. Things would be limited just by not mounting devtmpfs in a container. It is worth checking how much of the common infrastructure you need when you start creating virtual devices. The only reason the network devices need changes to sysfs is to allow different network devices with the same name to show up in different network namespaces. If you can fundamentally avoid the problem of devices with the same name needing to show up in sysfs and devtmpfs by using filesystems then sysfs and devtmpfs needs no changes. Hotplug is sufficiently widespread now that it should be possible to avoid the hard problem of having duplicate names for block devices, one way or another. Thus talking of changing sysfs seems completely unnecessary. Eric ^ permalink raw reply [flat|nested] 63+ messages in thread
* Re: device namespaces 2021-06-14 17:36 ` Eric W. Biederman @ 2021-06-15 11:24 ` Enrico Weigelt, metux IT consult 2021-06-15 11:33 ` Greg KH 0 siblings, 1 reply; 63+ messages in thread From: Enrico Weigelt, metux IT consult @ 2021-06-15 11:24 UTC (permalink / raw) To: Eric W. Biederman Cc: Christian Brauner, Hannes Reinecke, gregkh, containers, linux-kernel On 14.06.21 19:36, Eric W. Biederman wrote: > By virtual devices I mean all devices that are not physical pieces > of hardware. For block devices I mean devices such as loopback > devices that are created on demand. Ramdisks that start this > conversation could also be considered virtual devices. Ok. Do you also count partitions in here ? IMHO we've got another category to look up: devices that (can) create more (sub)devices. Examples coming into my head are loopdev, ptmx, partitions, etc. The big problem here: fist we'd need to be clear on the actual semantics in namespaced context, for example: * what happens when you talk to /dev/loop0 and create a new loopdev inside a container - shall it be ever visible on the host ? * what if you want to create an loopdev on some file thats only visible to the host, but that loopdev shall appear inside a container ? ("virtual disk" scenario) >> How would you skip the virtual devices from sysfs ? Adding some filter >> into sysfs that looks at the device class (or some flag within it) ? > > I would just not run the code to create sysfs entries when the virtual > devices are created. Oh, that would most likely make userland unhappy. Besides, that won't be so trivial due to the way sysfs works. Because sysfs more or less just presents kobj's. Each kobj may have attributes, a parent, and a list of childs. A device is n kobj, and it needs to be registered into the device hierarchy to work at all. Sysfs itself doesn't really know whether something is a virtual device (or a device at all) - it just calls some functions from kobject_type for things like reading/writing attributes, etc. But I don't see anything where kobject_type's can implement their own iterators. As things are right now, not registering a device in sysfs means not registering it at all. By the way: i'm just wondering whether it would make sense to give kobject_type it's own iteration and lookup functions. Unless I'm fully mistaken, that could help solving several other problems, e.g. device renaming (currently *very* tricky and only works to some extend for network devices). IMHO, we could then eg. fetch the device names (/sys/devices/...) directly from the struct device instead of the kset (perhaps a simple list instead of kset would also do here), and also create the symlinks (e.g. /sys/class/.../) on the fly. Once that's done, renaming a device should become rather simple. At that point, adding multiple views or certain parts of sysfs (e.g. the devices hierarchy) could perhaps be done by implementing special iterators take take the view criteria into account. @Greg: what's your take on that iterator idea ? > If you have virtual devices showing up in their own filesystem they > don't even need major or minor numbers. You can just have files > that accept ioctls like device nodes. In principle it is > possible to skip a lot of the historical infrastructure. If the > infrastructure is not needed it is worth skipping. Ah, I see where you're going. You wanna completely drop these virtual devices and replace them by a synthentic fs that *looks* like it contains devices ? Well, theoretically it should be possible, since fs' may handle opening device nodes completely own, instead of calling generic code (is there any that actually does ?). BUT: in that case we have to really make sure that processes inside the container cannot ever open any device node outside that special fs. > I haven't dug into the block layer recently enough to say what is needed > or not. I think there are some thing such as stat on a mounted > filesystem that need a major and minor numbers. Which probably means > you have to use major and minor numbers. By virtue of using common > infrastructure that implies showing up in sysfs and devtmpfs. Things > would be limited just by not mounting devtmpfs in a container. Note that this approach also needs to support things like dynamically creating new device nodes (inside the container), udev, ... otherwise you'd need very special handling in userland again (lxc folks would become very unhappy ;-)) > It is worth checking how much of the common infrastructure you need when > you start creating virtual devices. s/virtual devices/synthetic filesystems/; You approach goes much into the Plan9 direction (which in generally I'd love to see). But whatever we gonna do here needs to remain compatible with what existing userland expects - we've got a lot of Unix tradition to keep here. OR: we had to declare that (once inside the devns) we throw it all alway and it create something entirely new that's more like an Plan9 subsystem than an Linux container. Also interesting, but not what i've started this discussion for. > The only reason the network devices need changes to sysfs is to allow > different network devices with the same name to show up in different > network namespaces. > > If you can fundamentally avoid the problem of devices with the same > name needing to show up in sysfs and devtmpfs by using filesystems > then sysfs and devtmpfs needs no changes. Well, that's only for the sysfs part. Network devices still need to be namespaced in other places (socket, etc) - what's already done by netns. But yes, it sounds nice if we had entirely different namespaces for network device names (e.g. any of the hosts network devices could appear simply as "eth0" inside a container, if you want to) --mtx -- --- Hinweis: unverschlüsselte E-Mails können leicht abgehört und manipuliert werden ! Für eine vertrauliche Kommunikation senden Sie bitte ihren GPG/PGP-Schlüssel zu. --- Enrico Weigelt, metux IT consult Free software and Linux embedded engineering info@metux.net -- +49-151-27565287 ^ permalink raw reply [flat|nested] 63+ messages in thread
* Re: device namespaces 2021-06-15 11:24 ` Enrico Weigelt, metux IT consult @ 2021-06-15 11:33 ` Greg KH 0 siblings, 0 replies; 63+ messages in thread From: Greg KH @ 2021-06-15 11:33 UTC (permalink / raw) To: Enrico Weigelt, metux IT consult Cc: Eric W. Biederman, Christian Brauner, Hannes Reinecke, containers, linux-kernel On Tue, Jun 15, 2021 at 01:24:24PM +0200, Enrico Weigelt, metux IT consult wrote: > @Greg: what's your take on that iterator idea ? I want you to stop talking about ideas, and try to implement them before this conversation wastes anyone else's time and energy. There is a good reason we do not do this type of "let's discuss things!" in the kernel community, and that is because almost none of it matters without working code. So please, let's see some patches that implement your ideas and then we can discuss them. Until then, consider this thread ignored from me. greg k-h ^ permalink raw reply [flat|nested] 63+ messages in thread
end of thread, other threads:[~2021-06-15 11:33 UTC | newest] Thread overview: 63+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2013-08-22 17:43 RFC: Device Namespaces Oren Laadan [not found] ` <CAA4jN2aw4zEW=UfKCyqaOvXnbiRb_J9srfCn4OXTFzc6vWBM4A-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> 2013-08-22 18:21 ` Serge Hallyn 2013-08-26 10:11 ` Oren Laadan [not found] ` <CAA4jN2YL7Lfu2+DW-i+MovFxWEhJfT4aBBKREU_vy7JX9TKGHA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> 2013-09-06 17:50 ` Eric W. Biederman [not found] ` <8761udlu0d.fsf-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org> 2013-09-08 12:28 ` Amir Goldstein [not found] ` <CAA2m6vexArJ+6jFbK80Amstk=LK30=XDNHdBHSswP=LgpSP-6A-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> 2013-09-09 0:51 ` Eric W. Biederman [not found] ` <871u4yddg4.fsf-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org> 2013-09-10 7:09 ` Amir Goldstein [not found] ` <CAA2m6vc_kWWGDWcdjk26N3YvTqZySLFxPQRjOD9_ypBOka2+GQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> 2013-09-25 11:05 ` Janne Karhunen [not found] ` <CAE=NcrbyFFoMn2nfBA_=ZtwD=eGLvqK=L-U9MuGrtJFLZfZppw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> 2013-09-25 20:23 ` Eric W. Biederman [not found] ` <87ioxo4pm5.fsf-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org> 2013-09-25 21:17 ` [lxc-devel] " Jeremy Andrus [not found] ` <AD5F7BD2-0166-46BD-AB14-463C0E88BC92-eQaUEPhvms7ENvBUuze7eA@public.gmane.org> 2013-09-25 21:47 ` Eric W. Biederman [not found] ` <8738osr2ue.fsf-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org> 2013-09-29 17:56 ` Amir Goldstein 2013-09-25 21:34 ` Eric W. Biederman [not found] ` <87bo3gshz5.fsf_-_-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org> 2013-09-26 5:33 ` Greg Kroah-Hartman [not found] ` <20130926053320.GB3725-U8xfFu+wG4EAvxtiuMwx3w@public.gmane.org> 2013-09-26 8:25 ` Janne Karhunen [not found] ` <CAE=NcrbPXGWU8FUgwchXyL5HjXf+4AKbgUWGe1ZO=Xcq=iV-Lg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> 2013-09-26 13:56 ` Greg Kroah-Hartman [not found] ` <20130926135604.GA16624-U8xfFu+wG4EAvxtiuMwx3w@public.gmane.org> 2013-09-26 17:01 ` Janne Karhunen [not found] ` <CAE=NcrY3xC1AF_GV2b1KsF7AwYZTuGBuKLS5yBUWoWcmKU4YBg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> 2013-09-26 17:07 ` Greg Kroah-Hartman [not found] ` <20130926170757.GA9345-U8xfFu+wG4EAvxtiuMwx3w@public.gmane.org> 2013-09-26 17:56 ` Janne Karhunen 2013-09-30 15:37 ` James Bottomley [not found] ` <1380555439.2161.5.camel-sFMDBYUN5F8GjUHQrlYNx2Wm91YjaHnnhRte9Li2A+AAvxtiuMwx3w@public.gmane.org> 2013-09-30 16:11 ` Greg Kroah-Hartman [not found] ` <20130930161117.GA26459-U8xfFu+wG4EAvxtiuMwx3w@public.gmane.org> 2013-09-30 16:33 ` James Bottomley 2013-10-01 6:19 ` Janne Karhunen [not found] ` <CAE=NcrYV2RiMV7PcwEjFGFRBrz9XdZGs86Wau2a+6xpYN2aEHA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> 2013-10-01 17:27 ` Andy Lutomirski [not found] ` <CALCETrWWoHzuJcnfEUY+cFpOgT5gnG8U1cVbCW0_8V7Z_v6DJw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> 2013-10-01 17:53 ` Serge E. Hallyn [not found] ` <20131001175345.GA4145-7LNsyQBKDXoIagZqoN9o3w@public.gmane.org> 2013-10-01 19:51 ` Eric W. Biederman [not found] ` <87had0wz07.fsf-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org> 2013-10-01 20:46 ` Serge Hallyn 2013-10-01 22:59 ` [lxc-devel] " Michael H. Warfield 2013-10-02 22:55 ` Eric W. Biederman 2013-10-01 20:57 ` Greg Kroah-Hartman [not found] ` <20131001205718.GA17036-U8xfFu+wG4EAvxtiuMwx3w@public.gmane.org> 2013-10-02 22:45 ` Eric W. Biederman 2013-10-01 22:19 ` Michael H. Warfield 2013-10-01 18:36 ` Janne Karhunen 2013-10-01 17:33 ` Greg Kroah-Hartman [not found] ` <20131001173342.GA19267-U8xfFu+wG4EAvxtiuMwx3w@public.gmane.org> 2013-10-01 18:23 ` Janne Karhunen 2013-10-28 23:31 ` Andrey Wagin 2013-08-29 19:06 ` RFC: " Andy Lutomirski [not found] ` <521F9BBE.2070505-kltTT9wpgjJwATOyAt5JVQ@public.gmane.org> 2013-09-03 19:35 ` [lxc-devel] " Stéphane Graber 2013-09-29 19:28 Amir Goldstein [not found] ` <CAA2m6veny-7_ONMA973Wu36U4kz4gAuw0dpodkb8+GZDv6VNBQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> 2013-09-29 20:06 ` Greg Kroah-Hartman [not found] ` <20130929200620.GA31304-U8xfFu+wG4EAvxtiuMwx3w@public.gmane.org> 2013-09-30 15:36 ` Michael H. Warfield 2013-10-03 0:44 ` Eric W. Biederman [not found] ` <87a9iri3ot.fsf-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org> 2013-10-03 0:59 ` Eric W. Biederman 2013-10-03 8:58 ` Amir Goldstein [not found] ` <CAA2m6vc3OFmS9VwiTavRzPqhn+qoe6vDCO2sitXpEQ8a1JVyfg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> 2013-10-03 9:17 ` Eric W. Biederman 2021-06-08 9:38 device namespaces Enrico Weigelt, metux IT consult 2021-06-08 12:30 ` Christian Brauner 2021-06-08 12:41 ` Greg Kroah-Hartman 2021-06-08 14:10 ` Hannes Reinecke 2021-06-08 14:29 ` Christian Brauner 2021-06-08 15:54 ` Hannes Reinecke 2021-06-08 17:16 ` Eric W. Biederman 2021-06-09 6:38 ` Christian Brauner 2021-06-09 7:02 ` Hannes Reinecke 2021-06-09 7:21 ` Christian Brauner 2021-06-09 7:54 ` Hannes Reinecke 2021-06-09 8:09 ` Christian Brauner 2021-06-11 18:14 ` Eric W. Biederman 2021-06-14 7:49 ` Enrico Weigelt, metux IT consult 2021-06-14 8:22 ` Greg KH 2021-06-14 17:36 ` Eric W. Biederman 2021-06-15 11:24 ` Enrico Weigelt, metux IT consult 2021-06-15 11:33 ` Greg KH
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