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. 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. > > > 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. Best, Bobby
