Re: [PATCH net-next v1 2/3] virtio_transport_common: Set sibling VMs flag on the receive path

[Stefano Garzarella]

On Tue, Dec 01, 2020 at 05:25:04PM +0200, Andra Paraschiv wrote:
> The vsock flag can be set during the connect() setup logic, when
> initializing the vsock address data structure variable. Then the vsock
> transport is assigned, also considering this flag.
>
> The vsock transport is also assigned on the (listen) receive path. The
> flag needs to be set considering the use case.
>
> Set the vsock flag of the remote address to the one targeted for sibling
> VMs communication if the following conditions are met:
>
> * The source CID of the packet is higher than VMADDR_CID_HOST.
> * The destination CID of the packet is higher than VMADDR_CID_HOST.
>
> Signed-off-by: Andra Paraschiv <andraprs@xxxxxxxxxx>
> ---
> net/vmw_vsock/virtio_transport_common.c | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
> index 5956939eebb78..871c84e0916b1 100644
> --- a/net/vmw_vsock/virtio_transport_common.c
> +++ b/net/vmw_vsock/virtio_transport_common.c
> @@ -1062,6 +1062,14 @@ virtio_transport_recv_listen(struct sock *sk, struct virtio_vsock_pkt *pkt,
> 	vsock_addr_init(&vchild->remote_addr, le64_to_cpu(pkt->hdr.src_cid),
> 			le32_to_cpu(pkt->hdr.src_port));

Maybe is better to create an helper function that other transports can 
use for the same purpose or we can put this code in the 
vsock_assign_transport() and set this flag only when the 'psk' argument 
is not NULL (this is the case when it's called by the transports when we 
receive a new connection request and 'psk' is the listener socket).

The second way should allow us to support all the transports without 
touching them.

> +	/* If the packet is coming with the source and destination CIDs higher
> +	 * than VMADDR_CID_HOST, then a vsock channel should be established for
> +	 * sibling VMs communication.
> +	 */
> +	if (vchild->local_addr.svm_cid > VMADDR_CID_HOST &&
> +	    vchild->remote_addr.svm_cid > VMADDR_CID_HOST)
> +		vchild->remote_addr.svm_flag = VMADDR_FLAG_SIBLING_VMS_COMMUNICATION;

svm_flag is always initialized to 0 in vsock_addr_init(), so this 
assignment is the first one and it's okay, but to avoid future issues 
I'd use |= here to set the flag.

Thanks,
Stefano

> +
> 	ret = vsock_assign_transport(vchild, vsk);
> 	/* Transport assigned (looking at remote_addr) must be the same
> 	 * where we received the request.
> -- 2.20.1 (Apple Git-117)
>
>
>
>
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