[PATCH v2] virtio/vsock: fix the transport to work with VMADDR_CID_ANY

[PATCH v2] virtio/vsock: fix the transport to work with VMADDR_CID_ANY

[Wei Wang]

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@intel.com>
---
 net/vmw_vsock/virtio_transport_common.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
index 59ee1be5a6dd..ec2c2afbf0d0 100644
--- a/net/vmw_vsock/virtio_transport_common.c
+++ b/net/vmw_vsock/virtio_transport_common.c
@@ -1299,7 +1299,8 @@ void virtio_transport_recv_pkt(struct virtio_transport *t,
 	space_available = virtio_transport_space_update(sk, pkt);
 
 	/* Update CID in case it has changed after a transport reset event */
-	vsk->local_addr.svm_cid = dst.svm_cid;
+	if (vsk->local_addr.svm_cid != VMADDR_CID_ANY)
+		vsk->local_addr.svm_cid = dst.svm_cid;
 
 	if (space_available)
 		sk->sk_write_space(sk);

base-commit: 5f53fa508db098c9d372423a6dac31c8a5679cdf
-- 
2.25.1

Re: [PATCH v2] virtio/vsock: fix the transport to work with VMADDR_CID_ANY

[Stefano Garzarella]

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@intel.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@vger.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@redhat.com>

RE: [PATCH v2] virtio/vsock: fix the transport to work with VMADDR_CID_ANY

[Wang, Wei W]

Hi Michael,

Do you plan to merge this patch through your tree?
If not, I'll resend to have it applied to the net tree.

Thanks,
Wei

On Friday, November 26, 2021 4:54 PM, Stefano Garzarella wrote:
> 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@intel.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@vger.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@redhat.com>

Re: [PATCH v2] virtio/vsock: fix the transport to work with VMADDR_CID_ANY

[Michael S. Tsirkin]

On Tue, Nov 30, 2021 at 01:34:20AM +0000, Wang, Wei W wrote:
> Hi Michael,
> 
> Do you plan to merge this patch through your tree?
> If not, I'll resend to have it applied to the net tree.
> 
> Thanks,
> Wei


Sure, I'll merge it. Thanks!

> On Friday, November 26, 2021 4:54 PM, Stefano Garzarella wrote:
> > 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@intel.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@vger.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@redhat.com>