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From: "Michael S. Tsirkin" <mst@redhat.com>
To: Stefano Garzarella <sgarzare@redhat.com>
Cc: David Miller <davem@davemloft.net>,
	netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
	jhansen@vmware.com, jasowang@redhat.com, kvm@vger.kernel.org,
	stefanha@redhat.com, virtualization@lists.linux-foundation.org,
	linux-hyperv@vger.kernel.org, decui@microsoft.com
Subject: Re: [PATCH net-next 1/3] vsock: add network namespace support
Date: Mon, 20 Jan 2020 07:03:20 -0500	[thread overview]
Message-ID: <20200120060601-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <20200120101735.uyh4o64gb4njakw5@steredhat>

On Mon, Jan 20, 2020 at 11:17:35AM +0100, Stefano Garzarella wrote:
> On Mon, Jan 20, 2020 at 10:06:10AM +0100, David Miller wrote:
> > From: Stefano Garzarella <sgarzare@redhat.com>
> > Date: Thu, 16 Jan 2020 18:24:26 +0100
> > 
> > > This patch adds 'netns' module param to enable this new feature
> > > (disabled by default), because it changes vsock's behavior with
> > > network namespaces and could break existing applications.
> > 
> > Sorry, no.
> > 
> > I wonder if you can even design a legitimate, reasonable, use case
> > where these netns changes could break things.
> 
> I forgot to mention the use case.
> I tried the RFC with Kata containers and we found that Kata shim-v1
> doesn't work (Kata shim-v2 works as is) because there are the following
> processes involved:
> - kata-runtime (runs in the init_netns) opens /dev/vhost-vsock and
>   passes it to qemu
> - kata-shim (runs in a container) wants to talk with the guest but the
>   vsock device is assigned to the init_netns and kata-shim runs in a
>   different netns, so the communication is not allowed
> But, as you said, this could be a wrong design, indeed they already
> found a fix, but I was not sure if others could have the same issue.
> 
> In this case, do you think it is acceptable to make this change in
> the vsock's behavior with netns and ask the user to change the design?

David's question is what would be a usecase that's broken
(as opposed to fixed) by enabling this by default.

If it does exist, you need a way for userspace to opt-in,
module parameter isn't that.

> 
> > 
> > I am totally against adding a module parameter for this, it's
> > incredibly confusing for users and will create a test scenerio
> > that is strongly less likely to be covered.
> > 
> 
> Got it, I'll remove the module parameter!
> 
> Thanks,
> Stefano


  reply	other threads:[~2020-01-20 12:03 UTC|newest]

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-16 17:24 [PATCH net-next 0/3] vsock: support network namespace Stefano Garzarella
2020-01-16 17:24 ` Stefano Garzarella
2020-01-16 17:24 ` [PATCH net-next 1/3] vsock: add network namespace support Stefano Garzarella
2020-01-16 17:24   ` Stefano Garzarella
2020-01-20  9:06   ` David Miller
2020-01-20 10:17     ` Stefano Garzarella
2020-01-20 12:03       ` Michael S. Tsirkin [this message]
2020-01-20 13:58         ` Stefano Garzarella
2020-01-20 16:04           ` Michael S. Tsirkin
2020-01-20 16:53             ` Stefano Garzarella
2020-01-20 22:02               ` Michael S. Tsirkin
2020-01-21  9:07                 ` Stefano Garzarella
2020-01-21 11:14                   ` Michael S. Tsirkin
2020-01-21 13:13                     ` Stefano Garzarella
2020-01-21 15:43                     ` Stefan Hajnoczi
2020-01-21 13:59                   ` Stefan Hajnoczi
2020-01-21 14:31                     ` Michael S. Tsirkin
2020-01-21 15:44                       ` Stefan Hajnoczi
2020-01-16 17:24 ` [PATCH net-next 2/3] vsock/virtio_transport_common: handle netns of received packets Stefano Garzarella
2020-01-16 17:24   ` Stefano Garzarella
2020-01-16 17:24 ` [PATCH net-next 3/3] vhost/vsock: use netns of process that opens the vhost-vsock device Stefano Garzarella
2020-01-16 17:24   ` Stefano Garzarella
2020-01-21 15:50 ` [PATCH net-next 0/3] vsock: support network namespace Stefan Hajnoczi
2020-01-22  9:13   ` Stefano Garzarella
2020-04-27 14:25 ` Stefano Garzarella
2020-04-27 14:31   ` Michael S. Tsirkin
2020-04-27 15:21     ` Stefano Garzarella
2020-04-28  8:13   ` Jason Wang
2020-04-28 16:00     ` Stefano Garzarella
2020-04-29  9:21       ` Jason Wang
2020-04-29  9:21         ` Jason Wang

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