netdev - Re: [RFC PATCH v6 13/22] virtio/vsock: add SEQPACKET receive logic

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Date:   Mon, 15 Mar 2021 12:15:35 +0100
From:   Stefano Garzarella <sgarzare@...hat.com>
To:     Arseny Krasnov <arseny.krasnov@...persky.com>
Cc:     Stefan Hajnoczi <stefanha@...hat.com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Jorgen Hansen <jhansen@...are.com>,
        Norbert Slusarek <nslusarek@....net>,
        Colin Ian King <colin.king@...onical.com>,
        Andra Paraschiv <andraprs@...zon.com>, kvm@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, stsp2@...dex.ru, oxffffaa@...il.com
Subject: Re: [RFC PATCH v6 13/22] virtio/vsock: add SEQPACKET receive logic

On Sun, Mar 07, 2021 at 09:02:50PM +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@...persky.com>
>---
> net/vmw_vsock/virtio_transport_common.c | 63 +++++++++++++++++--------
> 1 file changed, 44 insertions(+), 19 deletions(-)
>
>diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
>index 6fc78fec41c0..9d86375935ce 100644
>--- a/net/vmw_vsock/virtio_transport_common.c
>+++ b/net/vmw_vsock/virtio_transport_common.c
>@@ -165,6 +165,14 @@ void virtio_transport_deliver_tap_pkt(struct virtio_vsock_pkt *pkt)
> }
> EXPORT_SYMBOL_GPL(virtio_transport_deliver_tap_pkt);
>
>+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;
>+}
>+
> /* This function can only be used on connecting/connected sockets,
>  * since a socket assigned to a transport is required.
>  *
>@@ -1062,25 +1070,27 @@ virtio_transport_recv_enqueue(struct vsock_sock *vsk,
> 		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;
>+	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;
>+			}
> 		}
> 	}
>
>@@ -1100,9 +1110,13 @@ virtio_transport_recv_connected(struct sock *sk,
> 	int err = 0;
>
> 	switch (le16_to_cpu(pkt->hdr.op)) {
>+	case VIRTIO_VSOCK_OP_SEQ_BEGIN:
>+	case VIRTIO_VSOCK_OP_SEQ_END:
> 	case VIRTIO_VSOCK_OP_RW:
> 		virtio_transport_recv_enqueue(vsk, pkt);
>-		sk->sk_data_ready(sk);
>+
>+		if (le16_to_cpu(pkt->hdr.op) != VIRTIO_VSOCK_OP_SEQ_BEGIN)
>+			sk->sk_data_ready(sk);
> 		return err;
> 	case VIRTIO_VSOCK_OP_CREDIT_UPDATE:
> 		sk->sk_write_space(sk);
>@@ -1245,6 +1259,12 @@ 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.
>  */
>@@ -1270,7 +1290,7 @@ 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;
> 	}
>@@ -1287,6 +1307,11 @@ 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);

We must release the refcnt acquired by vsock_find_connected_socket() or 
vsock_find_bound_socket(), so we need to add:

                 sock_put(sk);


>+		goto free_pkt;
>+	}
>+
> 	vsk = vsock_sk(sk);
>
> 	lock_sock(sk);
>-- 
>2.25.1
>