[RFC PATCH v6 06/22] af_vsock: implement send logic for SEQPACKET

[Arseny Krasnov <arseny.krasnov@kaspersky.com>]

This adds some logic to current stream enqueue function for SEQPACKET
support:
1) Use transport's seqpacket enqueue callback.
2) Return value from enqueue function is whole record length or error
   for SOCK_SEQPACKET.

Signed-off-by: Arseny Krasnov <arseny.krasnov@kaspersky.com>
---
 include/net/af_vsock.h   |  2 ++
 net/vmw_vsock/af_vsock.c | 22 ++++++++++++++++------
 2 files changed, 18 insertions(+), 6 deletions(-)

diff --git a/include/net/af_vsock.h b/include/net/af_vsock.h
index a8c4039e40cf..aed306292ab3 100644
--- a/include/net/af_vsock.h
+++ b/include/net/af_vsock.h
@@ -139,6 +139,8 @@ struct vsock_transport {
 	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);
+	int (*seqpacket_enqueue)(struct vsock_sock *vsk, struct msghdr *msg,
+				 int flags, size_t len);
 
 	/* Notification. */
 	int (*notify_poll_in)(struct vsock_sock *, size_t, bool *);
diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
index 5bf64a3e678a..a031f165494d 100644
--- a/net/vmw_vsock/af_vsock.c
+++ b/net/vmw_vsock/af_vsock.c
@@ -1830,9 +1830,14 @@ static int vsock_connectible_sendmsg(struct socket *sock, struct msghdr *msg,
 		 * responsibility to check how many bytes we were able to send.
 		 */
 
-		written = transport->stream_enqueue(
-				vsk, msg,
-				len - total_written);
+		if (sk->sk_type == SOCK_SEQPACKET) {
+			written = transport->seqpacket_enqueue(vsk,
+						msg, msg->msg_flags,
+						len - total_written);
+		} else {
+			written = transport->stream_enqueue(vsk,
+					msg, len - total_written);
+		}
 		if (written < 0) {
 			err = -ENOMEM;
 			goto out_err;
@@ -1844,12 +1849,17 @@ static int vsock_connectible_sendmsg(struct socket *sock, struct msghdr *msg,
 				vsk, written, &send_data);
 		if (err < 0)
 			goto out_err;
-
 	}
 
 out_err:
-	if (total_written > 0)
-		err = total_written;
+	if (total_written > 0) {
+		/* Return number of written bytes only if:
+		 * 1) SOCK_STREAM socket.
+		 * 2) SOCK_SEQPACKET socket when whole buffer is sent.
+		 */
+		if (sk->sk_type == SOCK_STREAM || total_written == len)
+			err = total_written;
+	}
 out:
 	release_sock(sk);
 	return err;
-- 
2.25.1