net: add sock_set_sndtimeo

Add a helper to directly set the SO_SNDTIMEO_NEW sockopt from kernel
space without going through a fake uaccess.  The interface is
simplified to only pass the seconds value, as that is the only
thing needed at the moment.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

fs/dlm/lowcomms.c

@@ -918,7 +918,6 @@ static void sctp_connect_to_sock(struct connection *con)
 	int result;
 	int addr_len;
 	struct socket *sock;
-	struct __kernel_sock_timeval tv = { .tv_sec = 5, .tv_usec = 0 };
 
 	if (con->nodeid == 0) {
 		log_print("attempt to connect sock 0 foiled");
@@ -970,13 +969,10 @@ static void sctp_connect_to_sock(struct connection *con)
 	 * since O_NONBLOCK argument in connect() function does not work here,
 	 * then, we should restore the default value of this attribute.
 	 */
-	kernel_setsockopt(sock, SOL_SOCKET, SO_SNDTIMEO_NEW, (char *)&tv,
-			  sizeof(tv));
+	sock_set_sndtimeo(sock->sk, 5);
 	result = sock->ops->connect(sock, (struct sockaddr *)&daddr, addr_len,
 				   0);
-	memset(&tv, 0, sizeof(tv));
-	kernel_setsockopt(sock, SOL_SOCKET, SO_SNDTIMEO_NEW, (char *)&tv,
-			  sizeof(tv));
+	sock_set_sndtimeo(sock->sk, 0);
 
 	if (result == -EINPROGRESS)
 		result = 0;

include/net/sock.h

@@ -2691,5 +2691,6 @@ void sock_def_readable(struct sock *sk);
 void sock_no_linger(struct sock *sk);
 void sock_set_priority(struct sock *sk, u32 priority);
 void sock_set_reuseaddr(struct sock *sk);
+void sock_set_sndtimeo(struct sock *sk, s64 secs);
 
 #endif	/* _SOCK_H */

net/core/sock.c

@@ -737,6 +737,17 @@ void sock_set_priority(struct sock *sk, u32 priority)
 }
 EXPORT_SYMBOL(sock_set_priority);
 
+void sock_set_sndtimeo(struct sock *sk, s64 secs)
+{
+	lock_sock(sk);
+	if (secs && secs < MAX_SCHEDULE_TIMEOUT / HZ - 1)
+		sk->sk_sndtimeo = secs * HZ;
+	else
+		sk->sk_sndtimeo = MAX_SCHEDULE_TIMEOUT;
+	release_sock(sk);
+}
+EXPORT_SYMBOL(sock_set_sndtimeo);
+
 /*
  *	This is meant for all protocols to use and covers goings on
  *	at the socket level. Everything here is generic.