[RFC PATCH v2 05/13] af_vsock: implement send logic for SOCK_SEQPACKET

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

This adds some logic to current stream enqueue function for SEQPACKET
support:
1) Send record begin marker with length of record.
2) Return value from enqueue function is wholevrecord length or error for
   SOCK_SEQPACKET.

Signed-off-by: Arseny Krasnov <arseny.krasnov@kaspersky.com>
---
 include/net/af_vsock.h   |  1 +
 net/vmw_vsock/af_vsock.c | 32 ++++++++++++++++++++++++++++----
 2 files changed, 29 insertions(+), 4 deletions(-)

diff --git a/include/net/af_vsock.h b/include/net/af_vsock.h
index 46073842d489..ec6bf4600ef8 100644
--- a/include/net/af_vsock.h
+++ b/include/net/af_vsock.h
@@ -136,6 +136,7 @@ struct vsock_transport {
 	bool (*stream_allow)(u32 cid, u32 port);
 
 	/* SEQ_PACKET. */
+	bool (*seqpacket_seq_send_len)(struct vsock_sock *, size_t len);
 	size_t (*seqpacket_seq_get_len)(struct vsock_sock *);
 	ssize_t (*seqpacket_dequeue)(struct vsock_sock *, struct msghdr *,
 				     size_t len, int flags);
diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
index 5bf887190881..4a7cdf7756c0 100644
--- a/net/vmw_vsock/af_vsock.c
+++ b/net/vmw_vsock/af_vsock.c
@@ -1683,8 +1683,8 @@ static int vsock_stream_getsockopt(struct socket *sock,
 	return 0;
 }
 
-static int vsock_stream_sendmsg(struct socket *sock, struct msghdr *msg,
-				size_t len)
+static int vsock_connectible_sendmsg(struct socket *sock, struct msghdr *msg,
+				     size_t len)
 {
 	struct sock *sk;
 	struct vsock_sock *vsk;
@@ -1737,6 +1737,12 @@ static int vsock_stream_sendmsg(struct socket *sock, struct msghdr *msg,
 	if (err < 0)
 		goto out;
 
+	if (sk->sk_type == SOCK_SEQPACKET) {
+		err = transport->seqpacket_seq_send_len(vsk, len);
+		if (err < 0)
+			goto out;
+	}
+
 	while (total_written < len) {
 		ssize_t written;
 
@@ -1815,13 +1821,31 @@ static int vsock_stream_sendmsg(struct socket *sock, struct msghdr *msg,
 	}
 
 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;
 }
 
+static int vsock_stream_sendmsg(struct socket *sock, struct msghdr *msg,
+				size_t len)
+{
+	return vsock_connectible_sendmsg(sock, msg, len);
+}
+
+static int vsock_seqpacket_sendmsg(struct socket *sock, struct msghdr *msg,
+				   size_t len)
+{
+	return vsock_connectible_sendmsg(sock, msg, len);
+}
+
 static int vsock_wait_data(struct sock *sk, struct wait_queue_entry *wait,
 			   long timeout,
 			   struct vsock_transport_recv_notify_data *recv_data,
-- 
2.25.1