SUNRPC: Set the TCP_SYNCNT to match the socket timeout

Set the TCP SYN count so that we abort the connection attempt at around
the expected timeout value.
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

net/sunrpc/xprtsock.c

@@ -2230,9 +2230,13 @@ static void xs_tcp_set_socket_timeouts(struct rpc_xprt *xprt,
 		struct socket *sock)
 {
 	struct sock_xprt *transport = container_of(xprt, struct sock_xprt, xprt);
+	struct net *net = sock_net(sock->sk);
+	unsigned long connect_timeout;
+	unsigned long syn_retries;
 	unsigned int keepidle;
 	unsigned int keepcnt;
 	unsigned int timeo;
+	unsigned long t;
 
 	spin_lock(&xprt->transport_lock);
 	keepidle = DIV_ROUND_UP(xprt->timeout->to_initval, HZ);
@@ -2250,6 +2254,16 @@ static void xs_tcp_set_socket_timeouts(struct rpc_xprt *xprt,
 
 	/* TCP user timeout (see RFC5482) */
 	tcp_sock_set_user_timeout(sock->sk, timeo);
+
+	/* Connect timeout */
+	connect_timeout = max_t(unsigned long,
+				DIV_ROUND_UP(xprt->connect_timeout, HZ), 1);
+	syn_retries = max_t(unsigned long,
+			    READ_ONCE(net->ipv4.sysctl_tcp_syn_retries), 1);
+	for (t = 0; t <= syn_retries && (1UL << t) < connect_timeout; t++)
+		;
+	if (t <= syn_retries)
+		tcp_sock_set_syncnt(sock->sk, t - 1);
 }
 
 static void xs_tcp_set_connect_timeout(struct rpc_xprt *xprt,