[PATCH v2 0/3] vsock: add namespace support to vhost-vsock

[Bobby Eshleman <bobbyeshleman@gmail.com>]

Picking up Stefano's v1 [1], this series adds netns support to
vhost-vsock. Unlike v1, this series does not address guest-to-host (g2h)
namespaces, defering that for future implementation and discussion.

Any vsock created with /dev/vhost-vsock is a global vsock, accessible
from any namespace. Any vsock created with /dev/vhost-vsock-netns is a
"scoped" vsock, accessible only to sockets in its namespace. If a global
vsock or scoped vsock share the same CID, the scoped vsock takes
precedence.

If a socket in a namespace connects with a global vsock, the CID becomes
unavailable to any VMM in that namespace when creating new vsocks. If
disconnected, the CID becomes available again.

Testing

QEMU with /dev/vhost-vsock-netns support:
	https://github.com/beshleman/qemu/tree/vsock-netns

Test: Scoped vsocks isolated by namespace

  host# ip netns add ns1
  host# ip netns add ns2
  host# ip netns exec ns1 \
				  qemu-system-x86_64 \
					  -m 8G -smp 4 -cpu host -enable-kvm \
					  -serial mon:stdio \
					  -drive if=virtio,file=${IMAGE1} \
					  -device vhost-vsock-pci,netns=on,guest-cid=15
  host# ip netns exec ns2 \
				  qemu-system-x86_64 \
					  -m 8G -smp 4 -cpu host -enable-kvm \
					  -serial mon:stdio \
					  -drive if=virtio,file=${IMAGE2} \
					  -device vhost-vsock-pci,netns=on,guest-cid=15

  host# socat - VSOCK-CONNECT:15:1234
  2025/03/10 17:09:40 socat[255741] E connect(5, AF=40 cid:15 port:1234, 16): No such device

  host# echo foobar1 | sudo ip netns exec ns1 socat - VSOCK-CONNECT:15:1234
  host# echo foobar2 | sudo ip netns exec ns2 socat - VSOCK-CONNECT:15:1234

  vm1# socat - VSOCK-LISTEN:1234
  foobar1
  vm2# socat - VSOCK-LISTEN:1234
  foobar2

Test: Global vsocks accessible to any namespace

  host# qemu-system-x86_64 \
	  -m 8G -smp 4 -cpu host -enable-kvm \
	  -serial mon:stdio \
	  -drive if=virtio,file=${IMAGE2} \
	  -device vhost-vsock-pci,guest-cid=15,netns=off

  host# echo foobar | sudo ip netns exec ns1 socat - VSOCK-CONNECT:15:1234

  vm# socat - VSOCK-LISTEN:1234
  foobar

Test: Connecting to global vsock makes CID unavailble to namespace

  host# qemu-system-x86_64 \
	  -m 8G -smp 4 -cpu host -enable-kvm \
	  -serial mon:stdio \
	  -drive if=virtio,file=${IMAGE2} \
	  -device vhost-vsock-pci,guest-cid=15,netns=off

  vm# socat - VSOCK-LISTEN:1234

  host# sudo ip netns exec ns1 socat - VSOCK-CONNECT:15:1234
  host# ip netns exec ns1 \
				  qemu-system-x86_64 \
					  -m 8G -smp 4 -cpu host -enable-kvm \
					  -serial mon:stdio \
					  -drive if=virtio,file=${IMAGE1} \
					  -device vhost-vsock-pci,netns=on,guest-cid=15

  qemu-system-x86_64: -device vhost-vsock-pci,netns=on,guest-cid=15: vhost-vsock: unable to set guest cid: Address already in use

Signed-off-by: Bobby Eshleman <bobbyeshleman@gmail.com>
---
Changes in v2:
- only support vhost-vsock namespaces
- all g2h namespaces retain old behavior, only common API changes
  impacted by vhost-vsock changes
- add /dev/vhost-vsock-netns for "opt-in"
- leave /dev/vhost-vsock to old behavior
- removed netns module param
- Link to v1: https://lore.kernel.org/r/20200116172428.311437-1-sgarzare@redhat.com

Changes in v1:
- added 'netns' module param to vsock.ko to enable the
  network namespace support (disabled by default)
- added 'vsock_net_eq()' to check the "net" assigned to a socket
  only when 'netns' support is enabled
- Link to RFC: https://patchwork.ozlabs.org/cover/1202235/

---
Stefano Garzarella (3):
      vsock: add network namespace support
      vsock/virtio_transport_common: handle netns of received packets
      vhost/vsock: use netns of process that opens the vhost-vsock-netns device

 drivers/vhost/vsock.c                   | 96 +++++++++++++++++++++++++++------
 include/linux/miscdevice.h              |  1 +
 include/linux/virtio_vsock.h            |  2 +
 include/net/af_vsock.h                  | 10 ++--
 net/vmw_vsock/af_vsock.c                | 85 +++++++++++++++++++++++------
 net/vmw_vsock/hyperv_transport.c        |  2 +-
 net/vmw_vsock/virtio_transport.c        |  5 +-
 net/vmw_vsock/virtio_transport_common.c | 14 ++++-
 net/vmw_vsock/vmci_transport.c          |  4 +-
 net/vmw_vsock/vsock_loopback.c          |  4 +-
 10 files changed, 180 insertions(+), 43 deletions(-)
---
base-commit: 0ea09cbf8350b70ad44d67a1dcb379008a356034
change-id: 20250312-vsock-netns-45da9424f726

Best regards,
-- 
Bobby Eshleman <bobbyeshleman@gmail.com>