tipc: set sk_err correctly when connection fails

Should a connect fail, if the publication/server is unavailable or
due to some other error, a positive value will be returned and errno
is never set. If the application code checks for an explicit zero
return from connect (success) or a negative return (failure), it
will not catch the error and subsequent send() calls will fail as
shown from the strace snippet below.

socket(0x1e /* PF_??? */, SOCK_SEQPACKET, 0) = 3
connect(3, {sa_family=0x1e /* AF_??? */, sa_data="\2\1\322\4\0\0\322\4\0\0\0\0\0\0"}, 16) = 111
sendto(3, "test", 4, 0, NULL, 0)        = -1 EPIPE (Broken pipe)

The reason for this behaviour is that TIPC wrongly inverts error
codes set in sk_err.
Signed-off-by: NErik Hugne <erik.hugne@ericsson.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/tipc/socket.c

@@ -1257,7 +1257,7 @@ static u32 filter_connect(struct tipc_sock *tsock, struct sk_buff **buf)
 		/* Accept only ACK or NACK message */
 		if (unlikely(msg_errcode(msg))) {
 			sock->state = SS_DISCONNECTING;
-			sk->sk_err = -ECONNREFUSED;
+			sk->sk_err = ECONNREFUSED;
 			retval = TIPC_OK;
 			break;
 		}
@@ -1268,7 +1268,7 @@ static u32 filter_connect(struct tipc_sock *tsock, struct sk_buff **buf)
 		res = auto_connect(sock, msg);
 		if (res) {
 			sock->state = SS_DISCONNECTING;
-			sk->sk_err = res;
+			sk->sk_err = -res;
 			retval = TIPC_OK;
 			break;
 		}