net/smc: fix fallback failed while sendmsg with fastopen

[ Upstream commit ce7ca79 ]

Before determining whether the msg has unsupported options, it has been
prematurely terminated by the wrong status check.

For the application, the general usages of MSG_FASTOPEN likes

fd = socket(...)
/* rather than connect */
sendto(fd, data, len, MSG_FASTOPEN)

Hence, We need to check the flag before state check, because the sock
state here is always SMC_INIT when applications tries MSG_FASTOPEN.
Once we found unsupported options, fallback it to TCP.

Fixes: ee9dfbe ("net/smc: handle sockopts forcing fallback")
Signed-off-by: D. Wythe <alibuda@linux.alibaba.com>
Signed-off-by: Simon Horman <simon.horman@corigine.com>

v2 -> v1: Optimize code style
Reviewed-by: Tony Lu <tonylu@linux.alibaba.com>

Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>

net/smc/af_smc.c

@@ -2644,16 +2644,14 @@ static int smc_sendmsg(struct socket *sock, struct msghdr *msg, size_t len)
 {
 	struct sock *sk = sock->sk;
 	struct smc_sock *smc;
-	int rc = -EPIPE;
+	int rc;
 
 	smc = smc_sk(sk);
 	lock_sock(sk);
-	if ((sk->sk_state != SMC_ACTIVE) &&
-	    (sk->sk_state != SMC_APPCLOSEWAIT1) &&
-	    (sk->sk_state != SMC_INIT))
-		goto out;
 
+	/* SMC does not support connect with fastopen */
 	if (msg->msg_flags & MSG_FASTOPEN) {
+		/* not connected yet, fallback */
 		if (sk->sk_state == SMC_INIT && !smc->connect_nonblock) {
 			rc = smc_switch_to_fallback(smc, SMC_CLC_DECL_OPTUNSUPP);
 			if (rc)
@@ -2662,6 +2660,11 @@ static int smc_sendmsg(struct socket *sock, struct msghdr *msg, size_t len)
 			rc = -EINVAL;
 			goto out;
 		}
+	} else if ((sk->sk_state != SMC_ACTIVE) &&
+		   (sk->sk_state != SMC_APPCLOSEWAIT1) &&
+		   (sk->sk_state != SMC_INIT)) {
+		rc = -EPIPE;
+		goto out;
 	}
 
 	if (smc->use_fallback) {