netdev - Re: [PATCH 2/4] VSOCK DRIVER: support communication using additional guest cid

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Date:   Mon, 2 Aug 2021 16:13:41 -0400
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     fuguancheng <fuguancheng@...edance.com>
Cc:     jasowang@...hat.com, stefanha@...hat.com, sgarzare@...hat.com,
        davem@...emloft.net, kuba@...nel.org, arseny.krasnov@...persky.com,
        andraprs@...zon.com, colin.king@...onical.com, kvm@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/4] VSOCK DRIVER: support communication using additional
 guest cid

On Mon, Aug 02, 2021 at 08:07:18PM +0800, fuguancheng wrote:
> Changes in this patch are made to allow the guest communicate
> with the host using the additional cids specified when
> creating the guest.
> 
> In original settings, the packet sent with the additional CIDS will
> be rejected when received by the host, the newly added function
> vhost_vsock_contain_cid will fix this error.
> 
> Now that we have multiple CIDS, the VMADDR_CID_ANY now behaves like
> this:
> 1. The client will use the first available cid specified in the cids
> array if VMADDR_CID_ANY is used.
> 2. The host will still use the original default CID.
> 3. If a guest server binds to VMADDR_CID_ANY, then the server can
> choose to connect to any of the available CIDs for this guest.
> 
> Signed-off-by: fuguancheng <fuguancheng@...edance.com>
> ---
>  drivers/vhost/vsock.c                   | 14 +++++++++++++-
>  net/vmw_vsock/af_vsock.c                |  2 +-
>  net/vmw_vsock/virtio_transport_common.c |  5 ++++-
>  3 files changed, 18 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
> index f66c87de91b8..013f8ebf8189 100644
> --- a/drivers/vhost/vsock.c
> +++ b/drivers/vhost/vsock.c
> @@ -74,6 +74,18 @@ struct vhost_vsock {
>  	bool seqpacket_allow;
>  };
>  
> +static bool
> +vhost_vsock_contain_cid(struct vhost_vsock *vsock, u32 cid)
> +{
> +	u32 index;
> +
> +	for (index = 0; index < vsock->num_cid; index++) {
> +		if (cid == vsock->cids[index])
> +			return true;
> +	}
> +	return false;
> +}
> +
>  static u32 vhost_transport_get_local_cid(void)
>  {
>  	return VHOST_VSOCK_DEFAULT_HOST_CID;

Doing this linear scan on data path is not going to scale
well with lots of CIDs.

> @@ -584,7 +596,7 @@ static void vhost_vsock_handle_tx_kick(struct vhost_work *work)
>  
>  		/* Only accept correctly addressed packets */
>  		if (vsock->num_cid > 0 &&
> -		    (pkt->hdr.src_cid) == vsock->cids[0] &&
> +			vhost_vsock_contain_cid(vsock, pkt->hdr.src_cid) &&
>  		    le64_to_cpu(pkt->hdr.dst_cid) == vhost_transport_get_local_cid())
>  			virtio_transport_recv_pkt(&vhost_transport, pkt);
>  		else
> diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
> index 4e1fbe74013f..c22ae7101e55 100644
> --- a/net/vmw_vsock/af_vsock.c
> +++ b/net/vmw_vsock/af_vsock.c
> @@ -251,7 +251,7 @@ static struct sock *__vsock_find_connected_socket(struct sockaddr_vm *src,
>  	list_for_each_entry(vsk, vsock_connected_sockets(src, dst),
>  			    connected_table) {
>  		if (vsock_addr_equals_addr(src, &vsk->remote_addr) &&
> -		    dst->svm_port == vsk->local_addr.svm_port) {
> +		    vsock_addr_equals_addr(&vsk->local_addr, dst)) {
>  			return sk_vsock(vsk);
>  		}
>  	}
> diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
> index 169ba8b72a63..cb45e2f801f1 100644
> --- a/net/vmw_vsock/virtio_transport_common.c
> +++ b/net/vmw_vsock/virtio_transport_common.c
> @@ -197,7 +197,10 @@ static int virtio_transport_send_pkt_info(struct vsock_sock *vsk,
>  	if (unlikely(!t_ops))
>  		return -EFAULT;
>  
> -	src_cid = t_ops->transport.get_local_cid();
> +	if (vsk->local_addr.svm_cid != VMADDR_CID_ANY)
> +		src_cid = vsk->local_addr.svm_cid;
> +	else
> +		src_cid = t_ops->transport.get_local_cid();
>  	src_port = vsk->local_addr.svm_port;
>  	if (!info->remote_cid) {
>  		dst_cid	= vsk->remote_addr.svm_cid;
> -- 
> 2.11.0
> 
>