net/9p: add vsock transport

Add vsock as a transport option for 9P client connections. This
allows mounting 9P filesystems over VM sockets without requiring TCP/IP
networking or additional userspace tools, which can be useful with
hypervisors other than Qemu/KVM, for example Hyper-V/WSL which is used
by podman machine on Windows[1][2].

The implementation extends trans_fd.c with vsock support, reusing the
existing socket infrastructure. A new p9_fd_create_vsock() function
handles vsock connection setup by parsing the CID from the mount source,
creating an AF_VSOCK socket, and connecting to the specified endpoint.
All other transport operations (close, request, cancel) use the shared
fd transport implementation.

The privport mount option is not currently implemented for vsock and
returns -EOPNOTSUPP if specified.

Add CONFIG_NET_9P_VSOCK option that conditionally compiles vsock support
into 9pnet_fd.ko. This follows the pattern where socket-based transports
(TCP, Unix, vsock) share trans_fd.c, while specialized hardware transports
(virtio, xen, rdma) have dedicated files.

Usage:
  mount -t 9p -o trans=vsock[,port=<port>] <CID> /mnt/point

Link: https://github.com/podman-container-tools/podman/blob/main/cmd/podman/machine/server9p.go [1]
Link: https://github.com/podman-container-tools/podman/blob/main/cmd/podman/machine/client9p.go [2]
Signed-off-by: Matus Skvarla <skvarlamatus@gmail.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Acked-by: Stefano Garzarella <sgarzare@redhat.com>
Message-ID: <20260709161741.15138-1-skvarlamatus@gmail.com>
Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>

0 files changed, 0 insertions, 0 deletions