On Thu, Nov 06, 2025 at 06:52:15PM -0800, Bobby Eshleman wrote:
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:
> From: Bobby Eshleman <[email protected]>
>
> 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 <[email protected]>
> ---
> 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.
> + 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?
If vsk == NULL, I'm expecting that also skb->sk is not valid, right?
Indeed we call skb_set_owner_w() only if vsk != NULL in
virtio_transport_alloc_skb().
Maybe we need to change virtio_transport_recv_pkt() where the `net`
should be passed in some way by the caller, so maybe this is the reason
why you needed it in the cb. But also in that case, I think we can get
the `net` in some way and pass it to virtio_transport_recv_pkt() and
avoid the change in the cb:
- vsock_lookpback.c in vsock_loopback_work() we can use vsock->net
- vhost/vsock.c in vhost_vsock_handle_tx_kick(), ditto we can use
vsock->net
- virtio_transport.c we can just pass always the dummy_net
Same fot the net_mode.
Maybe the real problem is in the send_pkt callbacks, where the skb is
used to get the socket, but as you mention, I think in this path
skb_set_owner_w() is already called, so we can get that info from there
in some way.
Not sure, but yeah, if we can remove that, it will be much clear IMO.
Thanks,
Stefano
