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

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Date:   Tue, 1 Dec 2020 17:22:13 +0100
From:   Stefano Garzarella <sgarzare@...hat.com>
To:     Andra Paraschiv <andraprs@...zon.com>
Cc:     netdev <netdev@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        "David S . Miller" <davem@...emloft.net>,
        David Duncan <davdunc@...zon.com>,
        Dexuan Cui <decui@...rosoft.com>,
        Alexander Graf <graf@...zon.de>,
        Jorgen Hansen <jhansen@...are.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Stefan Hajnoczi <stefanha@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>
Subject: Re: [PATCH net-next v1 2/3] virtio_transport_common: Set sibling VMs
 flag on the receive path

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@...zon.com>
>---
> 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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