On Thu, Nov 06, 2025 at 05:20:05PM +0100, Stefano Garzarella wrote:

On Thu, Oct 23, 2025 at 11:27:45AM -0700, Bobby Eshleman wrote:

quoted

From: Bobby Eshleman <redacted>

Enable network namespace support in the virtio-vsock common transport
layer by declaring namespace pointers in the transmit and receive
paths.

The changes include:
1. Add a 'net' field to virtio_vsock_pkt_info to carry the namespace
  pointer for outgoing packets.
2. Store the namespace and namespace mode in the skb control buffer when
  allocating packets (except for VIRTIO_VSOCK_OP_RST packets which do
  not have an associated socket).
3. Retrieve namespace information from skbs on the receive path for
  lookups using vsock_find_connected_socket_net() and
  vsock_find_bound_socket_net().

This allows users of virtio transport common code
(vhost-vsock/virtio-vsock) to later enable namespace support.

Signed-off-by: Bobby Eshleman <redacted>
---
Changes in v7:
- add comment explaining the !vsk case in virtio_transport_alloc_skb()
---
include/linux/virtio_vsock.h            |  1 +
net/vmw_vsock/virtio_transport_common.c | 21 +++++++++++++++++++--
2 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/include/linux/virtio_vsock.h b/include/linux/virtio_vsock.h
index 29290395054c..f90646f82993 100644
--- a/include/linux/virtio_vsock.h
+++ b/include/linux/virtio_vsock.h

@@ -217,6 +217,7 @@ struct virtio_vsock_pkt_info {

	u32 remote_cid, remote_port;
	struct vsock_sock *vsk;
	struct msghdr *msg;
+	struct net *net;
	u32 pkt_len;
	u16 type;
	u16 op;

diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
index dcc8a1d5851e..b8e52c71920a 100644
--- a/net/vmw_vsock/virtio_transport_common.c
+++ b/net/vmw_vsock/virtio_transport_common.c

@@ -316,6 +316,15 @@ static struct sk_buff *virtio_transport_alloc_skb(struct virtio_vsock_pkt_info *

					 info->flags,
					 zcopy);

+	/*
+	 * If there is no corresponding socket, then we don't have a
+	 * corresponding namespace. This only happens For VIRTIO_VSOCK_OP_RST.
+	 */

So, in virtio_transport_recv_pkt() should we check that `net` is not set?

Should we set it to NULL here?

Sounds good to me.

quoted

+	if (vsk) {
+		virtio_vsock_skb_set_net(skb, info->net);

Ditto here about the net refcnt, can the net disappear?
Should we use get_net() in some way, or the socket will prevent that?

As long as the socket has an outstanding skb it can't be destroyed and
so will have a reference to the net, that is after skb_set_owner_w() and
freeing... so I think this is okay.

But, maybe we could simplify the implied relationship between skb, sk,
and net by removing the VIRTIO_VSOCK_SKB_CB(skb)->net entirely, and only
ever referring to sock_net(skb->sk)? I remember originally having a
reason for adding it to the cb, but my hunch is it that it was probably
some confusion over the !vsk case.

WDYT?

[...]

quoted

	return virtio_transport_send_pkt_info(vsk, &info);

@@ -1578,7 +1593,9 @@ static bool virtio_transport_valid_type(u16 type)

void virtio_transport_recv_pkt(struct virtio_transport *t,
			       struct sk_buff *skb)
{
+	enum vsock_net_mode net_mode = virtio_vsock_skb_net_mode(skb);
	struct virtio_vsock_hdr *hdr = virtio_vsock_hdr(skb);
+	struct net *net = virtio_vsock_skb_net(skb);

Okay, so this is where the skb net is read, so why we touch the virtio-vsock
driver (virtio_transport.c) in the other patch where we changed just
af_vsock.c?

IMO we should move that change here, or in a separate commit.
Or maybe I missed some dependency :-)

100% agree.

Thanks,
Stefano

Thanks!

-Bobby