From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: [PATCH net-next 1/3] vsock: add network namespace support Date: Mon, 20 Jan 2020 11:04:00 -0500 Message-ID: <20200120110319-mutt-send-email-mst@kernel.org> References: <20200116172428.311437-1-sgarzare@redhat.com> <20200116172428.311437-2-sgarzare@redhat.com> <20200120.100610.546818167633238909.davem@davemloft.net> <20200120101735.uyh4o64gb4njakw5@steredhat> <20200120060601-mutt-send-email-mst@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: Sender: kvm-owner@vger.kernel.org To: Stefano Garzarella Cc: David Miller , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Jorgen Hansen , Jason Wang , kvm , Stefan Hajnoczi , virtualization@lists.linux-foundation.org, linux-hyperv@vger.kernel.org, Dexuan Cui List-Id: virtualization@lists.linuxfoundation.org On Mon, Jan 20, 2020 at 02:58:01PM +0100, Stefano Garzarella wrote: > On Mon, Jan 20, 2020 at 1:03 PM Michael S. Tsirkin wrote: > > 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 > > > > 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. > > Yes, I got that. Thanks for clarifying. > I just reported a broken example that can be fixed with a different > design (due to the fact that before this series, vsock devices were > accessible to all netns). > > > > > If it does exist, you need a way for userspace to opt-in, > > module parameter isn't that. > > Okay, but I honestly can't find a case that can't be solved. > So I don't know whether to add an option (ioctl, sysfs ?) or wait for > a real case to come up. > > I'll try to see better if there's any particular case where we need > to disable netns in vsock. > > Thanks, > Stefano Me neither. so what did you have in mind when you wrote: "could break existing applications"?