[RFC PATCH v5 04/19] af_vsock: implement SEQPACKET receive loop

@@ -135,6 +135,11 @@ struct vsock_transport {
 	bool (*stream_is_active)(struct vsock_sock *);
 	bool (*stream_allow)(u32 cid, u32 port);
 
+	/* SEQ_PACKET. */
+	size_t (*seqpacket_seq_get_len)(struct vsock_sock *vsk);
+	int (*seqpacket_dequeue)(struct vsock_sock *vsk, struct msghdr *msg,
+				     int flags, bool *msg_ready);
+
 	/* Notification. */
 	int (*notify_poll_in)(struct vsock_sock *, size_t, bool *);
 	int (*notify_poll_out)(struct vsock_sock *, size_t, bool *);

@@ -1972,6 +1972,98 @@ static int __vsock_stream_recvmsg(struct sock *sk, struct msghdr *msg,
 	return err;
 }
 
+static int __vsock_seqpacket_recvmsg(struct sock *sk, struct msghdr *msg,
+				     size_t len, int flags)
+{
+	const struct vsock_transport *transport;
+	const struct iovec *orig_iov;
+	unsigned long orig_nr_segs;
+	bool msg_ready;
+	struct vsock_sock *vsk;
+	size_t record_len;
+	long timeout;
+	int err = 0;
+	DEFINE_WAIT(wait);
+
+	vsk = vsock_sk(sk);
+	transport = vsk->transport;
+
+	timeout = sock_rcvtimeo(sk, flags & MSG_DONTWAIT);
+	orig_nr_segs = msg->msg_iter.nr_segs;
+	orig_iov = msg->msg_iter.iov;
+	msg_ready = false;
+	record_len = 0;
+
+	while (1) {
+		err = vsock_wait_data(sk, &wait, timeout, NULL, 0);
+
+		if (err <= 0) {
+			/* In case of any loop break(timeout, signal
+			 * interrupt or shutdown), we report user that
+			 * nothing was copied.
+			 */
+			err = 0;
+			break;
+		}
+
+		if (record_len == 0) {
+			record_len =
+				transport->seqpacket_seq_get_len(vsk);
+
+			if (record_len == 0)
+				continue;
+		}
+
+		err = transport->seqpacket_dequeue(vsk, msg,
+					flags, &msg_ready);
+
+		if (err < 0) {
+			if (err == -EAGAIN) {
+				iov_iter_init(&msg->msg_iter, READ,
+					      orig_iov, orig_nr_segs,
+					      len);
+				/* Clear 'MSG_EOR' here, because dequeue
+				 * callback above set it again if it was
+				 * set by sender. This 'MSG_EOR' is from
+				 * dropped record.
+				 */
+				msg->msg_flags &= ~MSG_EOR;
+				record_len = 0;
+				continue;
+			}
+
+			err = -ENOMEM;
+			break;
+		}
+
+		if (msg_ready)
+			break;
+	}
+
+	if (sk->sk_err)
+		err = -sk->sk_err;
+	else if (sk->sk_shutdown & RCV_SHUTDOWN)
+		err = 0;
+
+	if (msg_ready) {
+		/* User sets MSG_TRUNC, so return real length of
+		 * packet.
+		 */
+		if (flags & MSG_TRUNC)
+			err = record_len;
+		else
+			err = len - msg->msg_iter.count;
+
+		/* Always set MSG_TRUNC if real length of packet is
+		 * bigger than user's buffer.
+		 */
+		if (record_len > len)
+			msg->msg_flags |= MSG_TRUNC;
+	}
+
+	return err;
+}
+
 static int
 vsock_connectible_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
 			  int flags)

@@ -2027,7 +2119,10 @@ vsock_connectible_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
 		goto out;
 	}
 
-	err = __vsock_stream_recvmsg(sk, msg, len, flags);
+	if (sk->sk_type == SOCK_STREAM)
+		err = __vsock_stream_recvmsg(sk, msg, len, flags);
+	else
+		err = __vsock_seqpacket_recvmsg(sk, msg, len, flags);
 
 out:
 	release_sock(sk);