tipc: add SO_RCVLOWAT support to stream socket receive path

Add support for the SO_RCVLOWAT socket option to TIPC's stream socket
type.
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Allan Stephens <allan.stephens@windriver.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/tipc/socket.c

@@ -1026,9 +1026,8 @@ static int recv_stream(struct kiocb *iocb, struct socket *sock,
 	struct sk_buff *buf;
 	struct tipc_msg *msg;
 	unsigned int sz;
-	int sz_to_copy;
+	int sz_to_copy, target, needed;
 	int sz_copied = 0;
-	int needed;
 	char __user *crs = m->msg_iov->iov_base;
 	unsigned char *buf_crs;
 	u32 err;
@@ -1050,6 +1049,8 @@ static int recv_stream(struct kiocb *iocb, struct socket *sock,
 		goto exit;
 	}
 
+	target = sock_rcvlowat(sk, flags & MSG_WAITALL, buf_len);
+
 restart:
 
 	/* Look for a message in receive queue; wait if necessary */
@@ -1138,7 +1139,7 @@ static int recv_stream(struct kiocb *iocb, struct socket *sock,
 
 	if ((sz_copied < buf_len) &&	/* didn't get all requested data */
 	    (!skb_queue_empty(&sk->sk_receive_queue) ||
-	     (flags & MSG_WAITALL)) &&	/* and more is ready or required */
+	    (sz_copied < target)) &&	/* and more is ready or required */
 	    (!(flags & MSG_PEEK)) &&	/* and aren't just peeking at data */
 	    (!err))			/* and haven't reached a FIN */
 		goto restart;