net/smc: sync err code when tcp connection was refused

In the current implementation, when TCP initiates a connection
to an unavailable [ip,port], ECONNREFUSED will be stored in the
TCP socket, but SMC will not. However, some apps (like curl) use
getsockopt(,,SO_ERROR,,) to get the error information, which makes
them miss the error message and behave strangely.

Fixes: 50717a37 ("net/smc: nonblocking connect rework")
Signed-off-by: Nliuyacan <liuyacan@corp.netease.com>
Reviewed-by: NTony Lu <tonylu@linux.alibaba.com>
Acked-by: NKarsten Graul <kgraul@linux.ibm.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/smc/af_smc.c

@@ -1475,6 +1475,8 @@ static void smc_connect_work(struct work_struct *work)
 		smc->sk.sk_state = SMC_CLOSED;
 		if (rc == -EPIPE || rc == -EAGAIN)
 			smc->sk.sk_err = EPIPE;
+		else if (rc == -ECONNREFUSED)
+			smc->sk.sk_err = ECONNREFUSED;
 		else if (signal_pending(current))
 			smc->sk.sk_err = -sock_intr_errno(timeo);
 		sock_put(&smc->sk); /* passive closing */