linux-kernel - Re: [PATCH v2] virtio/vsock: fix the transport to work with VMADDR_CID

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Date:   Fri, 26 Nov 2021 09:53:41 +0100
From:   Stefano Garzarella <sgarzare@...hat.com>
To:     Wei Wang <wei.w.wang@...el.com>
Cc:     mst@...hat.com, stefanha@...hat.com, davem@...emloft.net,
        linux-kernel@...r.kernel.org,
        virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH v2] virtio/vsock: fix the transport to work with
 VMADDR_CID_ANY

On Thu, Nov 25, 2021 at 08:18:23PM -0500, Wei Wang wrote:
>The VMADDR_CID_ANY flag used by a socket means that the socket isn't bound
>to any specific CID. For example, a host vsock server may want to be bound
>with VMADDR_CID_ANY, so that a guest vsock client can connect to the host
>server with CID=VMADDR_CID_HOST (i.e. 2), and meanwhile, a host vsock
>client can connect to the same local server with CID=VMADDR_CID_LOCAL
>(i.e. 1).
>
>The current implementation sets the destination socket's svm_cid to a
>fixed CID value after the first client's connection, which isn't an
>expected operation. For example, if the guest client first connects to the
>host server, the server's svm_cid gets set to VMADDR_CID_HOST, then other
>host clients won't be able to connect to the server anymore.
>
>Reproduce steps:
>1. Run the host server:
>   socat VSOCK-LISTEN:1234,fork -
>2. Run a guest client to connect to the host server:
>   socat - VSOCK-CONNECT:2:1234
>3. Run a host client to connect to the host server:
>   socat - VSOCK-CONNECT:1:1234
>
>Without this patch, step 3. above fails to connect, and socat complains
>"socat[1720] E connect(5, AF=40 cid:1 port:1234, 16): Connection
>reset by peer".
>With this patch, the above works well.
>
>Fixes: c0cfa2d8a788 ("vsock: add multi-transports support")
>Signed-off-by: Wei Wang <wei.w.wang@...el.com>
>---
> net/vmw_vsock/virtio_transport_common.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)

Usually fixes for net/vmw_vsock/* are applied through the net tree 
(netdev@...r.kernel.org) that seems not CCed. Please use 
./scripts/get_maintainer.pl next time.

Maybe this one can be queued by Michael, let's wait a bit, otherwise 
please resend CCing netdev and using "net" tag.

Anyway the patch LGTM:

Reviewed-by: Stefano Garzarella <sgarzare@...hat.com>