[TIPC]: Allow stream receive to read from multiple TIPC messages

This patch allows a stream socket to receive data from multiple
TIPC messages in its receive queue, without requiring the use of
the MSG_WAITALL flag.

Acknowledgements to Florian Westphal <fw-tipc@strlen.de> for
identifying this issue and suggesting how to correct it.
Signed-off-by: Allan Stephens <allan.stephens@windriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/tipc/socket.c

@@ -1065,7 +1065,9 @@ restart:
 	/* Loop around if more data is required */
 
 	if ((sz_copied < buf_len)    /* didn't get all requested data */
-	    && (flags & MSG_WAITALL) /* ... and need to wait for more */
+	    && (!skb_queue_empty(&sock->sk->sk_receive_queue) ||
+		(flags & MSG_WAITALL))
+				     /* ... and more is ready or required */
 	    && (!(flags & MSG_PEEK)) /* ... and aren't just peeking at data */
 	    && (!err)                /* ... and haven't reached a FIN */
 	    )