SUNRPC: Set the TCP user timeout option on client sockets

Use the TCP_USER_TIMEOUT socket option to advertise to the server
how long we will keep the connection open if there is unacknowledged
data. See RFC5482.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

net/sunrpc/xprtsock.c

@@ -2117,6 +2117,7 @@ static int xs_tcp_finish_connecting(struct rpc_xprt *xprt, struct socket *sock)
 		unsigned int keepidle = xprt->timeout->to_initval / HZ;
 		unsigned int keepcnt = xprt->timeout->to_retries + 1;
 		unsigned int opt_on = 1;
+		unsigned int timeo;
 
 		/* TCP Keepalive options */
 		kernel_setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE,
@@ -2128,6 +2129,12 @@ static int xs_tcp_finish_connecting(struct rpc_xprt *xprt, struct socket *sock)
 		kernel_setsockopt(sock, SOL_TCP, TCP_KEEPCNT,
 				(char *)&keepcnt, sizeof(keepcnt));
 
+		/* TCP user timeout (see RFC5482) */
+		timeo = jiffies_to_msecs(xprt->timeout->to_initval) *
+			(xprt->timeout->to_retries + 1);
+		kernel_setsockopt(sock, SOL_TCP, TCP_USER_TIMEOUT,
+				(char *)&timeo, sizeof(timeo));
+
 		write_lock_bh(&sk->sk_callback_lock);
 
 		xs_save_old_callbacks(transport, sk);