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[79.53.30.11]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-49e7d69f3c0sm57509095e9.6.2026.09.15.03.16.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 15 Sep 2026 03:16:51 -0700 (PDT) Date: Tue, 15 Sep 2026 12:16:47 +0200 From: Stefano Garzarella To: Bobby Eshleman Cc: "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Jonathan Corbet , Shuah Khan , Stefan Hajnoczi , "Michael S. Tsirkin" , Jason Wang , Xuan Zhuo , Eugenio =?utf-8?B?UMOpcmV6?= , Shuah Khan , Randy Dunlap , virtualization@lists.linux.dev, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, kvm@vger.kernel.org, linux-kselftest@vger.kernel.org, sargun@sargun.me, jlinbox@meta.com, Bobby Eshleman Subject: Re: [PATCH net-next 0/6] vsock: assign the guest vsock device to a network namespace Message-ID: References: <20260902-vsock-guest-ns-v1-0-9995383e9a8b@meta.com> Precedence: bulk X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: wmpJ2TaDvf0Z3iYRN0ZeFfT1Cu7elzYt615-SY9p5nQ_1789467413 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline On Fri, Sep 04, 2026 at 10:30:28AM -0700, Bobby Eshleman wrote: >On Fri, Sep 04, 2026 at 10:55:17AM +0200, Stefano Garzarella wrote: >> On Wed, Sep 02, 2026 at 04:00:46PM -0700, Bobby Eshleman wrote: >> > vsock network namespaces let a host put each VM in a namespace of its >> > own. A guest has no equivalent yet. It has a single G2H device that >> > cannot be assigned to a network namespace. >> >> Thanks for this, I'll do a proper review next week, in the mean time some >> comments below: >> >> > >> > This series lets a guest move that device into a network namespace. A >> > new ioctl on /dev/vsock, IOCTL_VM_SOCKETS_ASSIGN_G2H_NETNS, assigns the >> > device to the namespace of the calling process. The namespace's existing >> >> Why an ioctl? >> >> I'm asking because I'd like to know if you've already considered any >> alternatives (sysfs, netlink, etc.) >> >> How do you think the ioctl should be used? Should we provide an userspace >> tool, or extending some existing tools? >> >> Thanks, >> Stefano > >Really only because /dev/vsock exists and the prior series used it. Yeah, I vaguely remember that we may have discussed switching to netlink in that thread, but I can't find it. > >Considering netlink, it might be the better option because there is a >lot of prior art solving problems we might have in the future. For >example, I was thinking about when users suddenly lose access to vsock, >with just the current assign ioctl there is no way for apps or users to >figure out why this happened. We can have an ioctl() setter for user, >but in netdev world users can actually get a notification via netlink as >to which namespace the device went to and what its ifindex is there (see >__dev_change_net_namespace() for the RTM_DELLINK and RTM_NEWLINK >messages). There is probably more, but that's the case that comes to >mind. netlink seems like the right way to go, do you think it'll be a real pain to implement? > >> >> > ns_mode then decides who may use it: a "global" namespace shares the >> > device with every other global namespace, and a "local" namespace keeps >> > the host connection to itself. The device starts out in the initial >> > namespace, so until the ioctl is issued nothing has moved and no mode >> > has changed. There is no explicit unassign as assigning the device back >> > to the initial namespace is equivalent. >> > >> > The ioctl requires CAP_NET_ADMIN in the initial user namespace. >> > >> > Connections that can no longer reach the device after a move are reset, >> > so that a namespace which has lost access cannot keep using a socket it >> > opened while it still had access. Following netdevs, the device returns >> > to the initial namespace when the namespace it was moved to is deleted. >> > >> > Transports opt in through a new netns_assign_allow callback. Only >> > virtio-vsock implements it here. >> >> Why? (Not asking to support all the others, asking to explain the reason or >> ask helps from others to extend it) >> >> Thanks, >> Stefano > >Sure, can add a note here about extending it. I just didn't want to >implement code without having an environment allowing me to test it. It's fine, I'm not asking you to do it ;-) Sorry again for the delay, I hope to review this series today/tomorrow. Thanks, Stefano