Re: [PATCH nfs-utils v3 00/14] add NFS over AF_VSOCK support

["Daniel P. Berrange" <berrange@redhat.com>]

On Fri, Sep 22, 2017 at 08:00:11AM -0400, Chuck Lever wrote:
> 
> > On Sep 22, 2017, at 7:55 AM, Daniel P. Berrange <berrange@redhat.com> wrote:
> > 
> > On Fri, Sep 22, 2017 at 07:43:39AM -0400, Chuck Lever wrote:
> >> 
> >>> On Sep 22, 2017, at 5:55 AM, Steven Whitehouse <swhiteho@redhat.com> wrote:
> >>> 
> >>> Hi,
> >>> 
> >>> 
> >>> On 21/09/17 18:00, Stefan Hajnoczi wrote:
> >>>> On Tue, Sep 19, 2017 at 01:24:52PM -0400, J. Bruce Fields wrote:
> >>>>> On Tue, Sep 19, 2017 at 05:44:27PM +0100, Daniel P. Berrange wrote:
> >>>>>> On Tue, Sep 19, 2017 at 11:48:10AM -0400, Chuck Lever wrote:
> >>>>>>>> On Sep 19, 2017, at 11:10 AM, Daniel P. Berrange <berrange@redhat.com> wrote:
> >>>>>>>> VSOCK requires no guest configuration, it won't be broken accidentally
> >>>>>>>> by NetworkManager (or equivalent), it won't be mistakenly blocked by
> >>>>>>>> guest admin/OS adding "deny all" default firewall policy. Similar
> >>>>>>>> applies on the host side, and since there's separation from IP networking,
> >>>>>>>> there is no possibility of the guest ever getting a channel out to the
> >>>>>>>> LAN, even if the host is mis-configurated.
> >>>>>>> We don't seem to have configuration fragility problems with other
> >>>>>>> deployments that scale horizontally.
> >>>>>>> 
> >>>>>>> IMO you should focus on making IP reliable rather than trying to
> >>>>>>> move familiar IP-based services to other network fabrics.
> >>>>>> I don't see that ever happening, except in a scenario where a single
> >>>>>> org is in tight control of the whole stack (host & guest), which is
> >>>>>> not the case for cloud in general - only some on-site clouds.
> >>>>> Can you elaborate?
> >>>>> 
> >>>>> I think we're having trouble understanding why you can't just say "don't
> >>>>> do that" to someone whose guest configuration is interfering with the
> >>>>> network interface they need for NFS.
> >>>> Dan can add more information on the OpenStack use case, but your
> >>>> question is equally relevant to the other use case I mentioned - easy
> >>>> file sharing between host and guest.
> >>>> 
> >>>> Management tools like virt-manager (https://virt-manager.org/) should
> >>>> support a "share directory with VM" feature.  The user chooses a
> >>>> directory on the host, a mount point inside the guest, and then clicks
> >>>> OK.  The directory should appear inside the guest.
> >>>> 
> >>>> VMware, VirtualBox, etc have had file sharing for a long time.  It's a
> >>>> standard feature.
> >>>> 
> >>>> Here is how to implement it using AF_VSOCK:
> >>>> 1. Check presence of virtio-vsock device in VM or hotplug it.
> >>>> 2. Export directory from host NFS server (nfs-ganesha, nfsd, etc).
> >>>> 3. Send qemu-guest-agent command to (optionally) add /etc/fstab entry
> >>>>   and then mount.
> >>>> 
> >>>> The user does not need to take any action inside the guest.
> >>>> Non-technical users can share files without even knowing what NFS is.
> >>>> 
> >>>> There are too many scenarios where guest administrator action is
> >>>> required with NFS over TCP/IP.  We can't tell them "don't do that"
> >>>> because it makes this feature unreliable.
> >>>> 
> >>>> Today we ask users to set up NFS or CIFS themselves.  In many cases that
> >>>> is inconvenient and an easy file sharing feature would be much better.
> >>>> 
> >>>> Stefan
> >>>> 
> >>> 
> >>> I don't think we should give up on making NFS easy to use with TCP/IP in such situations. With IPv6 we could have (for example) a device with a well known link-local address at the host end, and an automatically allocated link-local address at the guest end. In other words the same as VSOCK, but with IPv6 rather than VSOCK addresses. At that point the remainder of the NFS config steps would be identical to those you've outlined with VSOCK above.
> >>> 
> >>> Creating a (virtual) network device which is restricted to host/guest communication and automatically configures itself should be a lot less work than adding a whole new protocol to NFS I think. It could also be used for many other use cases too, as well as giving the choice between NFS and CIFS. So it is much more flexible, and should be quicker to implement too,
> >> 
> >> I agree. IMO mechanisms already exist to handle a self-configuring
> >> NFS mount. Use IPv6 link-local and the automounter and an entry in
> >> /etc/hosts. Done, and no-one even had to type "mount".
> >> 
> >> If firewall configuration is a chronic problem, let's address that.
> > 
> > This just isn't practical in the general case. Even on a single Linux OS
> > distro there are multiple ways to manage firewalls (Fedora as a static
> > init script, or firewalld, and many users invent their own personal way
> > of doing it). There are countless other OS, many closed source with 3rd
> > party firewall products in use. And then there are the firewall policies
> > defined by organization's IT departments that mandate particular ways of
> > doing things with layers of approval to go through to get changes made.
> > 
> > IOW, while improving firewall configuraiton is a worthy goal, it isn't
> > a substitute for host<->guest file system sharing over a non-network
> > based transport. 
> 
> OK, but how do you expect to get support for NFS/VSOCK into all
> these 3rd party environments?

Assuming it is accepted as a feature in NFS server, support in Linux would
flow into the distros as the vendors either updated to newer version, or
backport the feature. There would need to be support written for other
commonly used OS (which basically means Windows) too over time, which
would probablybe made available via the existing KVM Windows guest
support ISO (which provides paravirt devices for disk, net, balloon,
etc, etc). 

Regards,
Daniel
-- 
|: https://berrange.com      -o-    https://www.flickr.com/photos/dberrange :|
|: https://libvirt.org         -o-            https://fstop138.berrange.com :|
|: https://entangle-photo.org    -o-    https://www.instagram.com/dberrange :|