Re: [RFC PATCH v3 09/13] virtio/vsock: add SEQPACKET receive logic

[Stefano Garzarella <sgarzare@redhat.com>]

On Mon, Jan 25, 2021 at 02:14:41PM +0300, Arseny Krasnov wrote:
>This modifies current receive logic for SEQPACKET support:
>1) Inserts 'SEQ_BEGIN' packet to socket's rx queue.
>2) Inserts 'RW' packet to socket's rx queue, but without merging with
>   buffer of last packet in queue.
>3) Performs check for packet and socket types on receive(if mismatch,
>   then reset connection).
>
>Signed-off-by: Arseny Krasnov <arseny.krasnov@kaspersky.com>
>---
> net/vmw_vsock/virtio_transport_common.c | 79 ++++++++++++++++++-------
> 1 file changed, 58 insertions(+), 21 deletions(-)
>
>diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
>index dcce35d7b462..90f9feef9d8f 100644
>--- a/net/vmw_vsock/virtio_transport_common.c
>+++ b/net/vmw_vsock/virtio_transport_common.c
>@@ -397,6 +397,14 @@ virtio_transport_stream_do_dequeue(struct vsock_sock *vsk,
> 	return err;
> }
>
>+static u16 virtio_transport_get_type(struct sock *sk)
>+{
>+	if (sk->sk_type == SOCK_STREAM)
>+		return VIRTIO_VSOCK_TYPE_STREAM;
>+	else
>+		return VIRTIO_VSOCK_TYPE_SEQPACKET;
>+}
>+
> static inline void virtio_transport_del_n_free_pkt(struct virtio_vsock_pkt *pkt)
> {
> 	list_del(&pkt->list);
>@@ -1050,39 +1058,49 @@ virtio_transport_recv_enqueue(struct vsock_sock *vsk,
> 			      struct virtio_vsock_pkt *pkt)
> {
> 	struct virtio_vsock_sock *vvs = vsk->trans;
>-	bool can_enqueue, free_pkt = false;
>+	bool free_pkt = false;
>
> 	pkt->len = le32_to_cpu(pkt->hdr.len);
> 	pkt->off = 0;
>
> 	spin_lock_bh(&vvs->rx_lock);
>
>-	can_enqueue = virtio_transport_inc_rx_pkt(vvs, pkt);
>-	if (!can_enqueue) {
>+	if (!virtio_transport_inc_rx_pkt(vvs, pkt)) {

This is an unnecessary change, it should go in another patch.

> 		free_pkt = true;
> 		goto out;
> 	}
>
>-	/* Try to copy small packets into the buffer of last packet queued,
>-	 * to avoid wasting memory queueing the entire buffer with a small
>-	 * payload.
>-	 */
>-	if (pkt->len <= GOOD_COPY_LEN && !list_empty(&vvs->rx_queue)) {
>-		struct virtio_vsock_pkt *last_pkt;
>+	switch (le16_to_cpu(pkt->hdr.type)) {
>+	case VIRTIO_VSOCK_TYPE_STREAM: {

We already checked the 'type' in virtio_transport_recv_pkt(), so there 
is no need to this switch, I think you can simply add

        if (le16_to_cpu(pkt->hdr.type) == VIRTIO_VSOCK_TYPE_STREAM) {

>+		/* Try to copy small packets into the buffer of last packet queued,
>+		 * to avoid wasting memory queueing the entire buffer with a small
>+		 * payload.
>+		 */
>+		if (pkt->len <= GOOD_COPY_LEN && !list_empty(&vvs->rx_queue)) {
>+			struct virtio_vsock_pkt *last_pkt;
>
>-		last_pkt = list_last_entry(&vvs->rx_queue,
>-					   struct virtio_vsock_pkt, list);
>+			last_pkt = list_last_entry(&vvs->rx_queue,
>+						   struct virtio_vsock_pkt, list);
>
>-		/* If there is space in the last packet queued, we copy the
>-		 * new packet in its buffer.
>-		 */
>-		if (pkt->len <= last_pkt->buf_len - last_pkt->len) {
>-			memcpy(last_pkt->buf + last_pkt->len, pkt->buf,
>-			       pkt->len);
>-			last_pkt->len += pkt->len;
>-			free_pkt = true;
>-			goto out;
>+			/* If there is space in the last packet queued, we copy the
>+			 * new packet in its buffer.
>+			 */
>+			if (pkt->len <= last_pkt->buf_len - last_pkt->len) {
>+				memcpy(last_pkt->buf + last_pkt->len, pkt->buf,
>+				       pkt->len);
>+				last_pkt->len += pkt->len;
>+				free_pkt = true;
>+				goto out;
>+			}
> 		}
>+
>+		break;
>+	}
>+	case VIRTIO_VSOCK_TYPE_SEQPACKET: {
>+		break;
>+	}
>+	default:
>+		goto out;
> 	}
>
> 	list_add_tail(&pkt->list, &vvs->rx_queue);
>@@ -1101,6 +1119,14 @@ virtio_transport_recv_connected(struct sock *sk,
> 	int err = 0;
>
> 	switch (le16_to_cpu(pkt->hdr.op)) {
>+	case VIRTIO_VSOCK_OP_SEQ_BEGIN: {
>+		struct virtio_vsock_sock *vvs = vsk->trans;
>+
>+		spin_lock_bh(&vvs->rx_lock);
>+		list_add_tail(&pkt->list, &vvs->rx_queue);
>+		spin_unlock_bh(&vvs->rx_lock);
>+		return err;
>+	}

Are there any problems if we use virtio_transport_recv_enqueue() in this 
case?

> 	case VIRTIO_VSOCK_OP_RW:
> 		virtio_transport_recv_enqueue(vsk, pkt);
> 		sk->sk_data_ready(sk);
>@@ -1247,6 +1273,12 @@ virtio_transport_recv_listen(struct sock *sk, struct virtio_vsock_pkt *pkt,
> 	return 0;
> }
>
>+static bool virtio_transport_valid_type(u16 type)
>+{
>+	return (type == VIRTIO_VSOCK_TYPE_STREAM) ||
>+	       (type == VIRTIO_VSOCK_TYPE_SEQPACKET);
>+}
>+
> /* We are under the virtio-vsock's vsock->rx_lock or vhost-vsock's vq->mutex
>  * lock.
>  */
>@@ -1272,7 +1304,7 @@ void virtio_transport_recv_pkt(struct virtio_transport *t,
> 					le32_to_cpu(pkt->hdr.buf_alloc),
> 					le32_to_cpu(pkt->hdr.fwd_cnt));
>
>-	if (le16_to_cpu(pkt->hdr.type) != VIRTIO_VSOCK_TYPE_STREAM) {
>+	if (!virtio_transport_valid_type(le16_to_cpu(pkt->hdr.type))) {
> 		(void)virtio_transport_reset_no_sock(t, pkt);
> 		goto free_pkt;
> 	}
>@@ -1289,6 +1321,11 @@ void virtio_transport_recv_pkt(struct virtio_transport *t,
> 		}
> 	}
>
>+	if (virtio_transport_get_type(sk) != le16_to_cpu(pkt->hdr.type)) {
>+		(void)virtio_transport_reset_no_sock(t, pkt);
>+		goto free_pkt;
>+	}
>+
> 	vsk = vsock_sk(sk);
>
> 	space_available = virtio_transport_space_update(sk, pkt);
>-- 
>2.25.1
>

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