net: add sock_set_reuseport

Add a helper to directly set the SO_REUSEPORT sockopt from kernel space
without going through a fake uaccess.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/sock.h

@@ -2695,6 +2695,7 @@ void sock_set_keepalive(struct sock *sk);
 void sock_set_priority(struct sock *sk, u32 priority);
 void sock_set_rcvbuf(struct sock *sk, int val);
 void sock_set_reuseaddr(struct sock *sk);
+void sock_set_reuseport(struct sock *sk);
 void sock_set_sndtimeo(struct sock *sk, s64 secs);
 
 #endif	/* _SOCK_H */

net/core/sock.c

@@ -729,6 +729,14 @@ void sock_set_reuseaddr(struct sock *sk)
 }
 EXPORT_SYMBOL(sock_set_reuseaddr);
 
+void sock_set_reuseport(struct sock *sk)
+{
+	lock_sock(sk);
+	sk->sk_reuseport = true;
+	release_sock(sk);
+}
+EXPORT_SYMBOL(sock_set_reuseport);
+
 void sock_no_linger(struct sock *sk)
 {
 	lock_sock(sk);

net/sunrpc/xprtsock.c

@@ -1594,21 +1594,6 @@ static int xs_get_random_port(void)
 	return rand + min;
 }
 
-/**
- * xs_set_reuseaddr_port - set the socket's port and address reuse options
- * @sock: socket
- *
- * Note that this function has to be called on all sockets that share the
- * same port, and it must be called before binding.
- */
-static void xs_sock_set_reuseport(struct socket *sock)
-{
-	int opt = 1;
-
-	kernel_setsockopt(sock, SOL_SOCKET, SO_REUSEPORT,
-			(char *)&opt, sizeof(opt));
-}
-
 static unsigned short xs_sock_getport(struct socket *sock)
 {
 	struct sockaddr_storage buf;
@@ -1801,7 +1786,7 @@ static struct socket *xs_create_sock(struct rpc_xprt *xprt,
 	xs_reclassify_socket(family, sock);
 
 	if (reuseport)
-		xs_sock_set_reuseport(sock);
+		sock_set_reuseport(sock->sk);
 
 	err = xs_bind(transport, sock);
 	if (err) {