ipv6: add ip6_sock_set_v6only

Add a helper to directly set the IPV6_V6ONLY 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/ipv6.h

@@ -1177,4 +1177,15 @@ int ipv6_sock_mc_join_ssm(struct sock *sk, int ifindex,
 			  const struct in6_addr *addr, unsigned int mode);
 int ipv6_sock_mc_drop(struct sock *sk, int ifindex,
 		      const struct in6_addr *addr);
+
+static inline int ip6_sock_set_v6only(struct sock *sk)
+{
+	if (inet_sk(sk)->inet_num)
+		return -EINVAL;
+	lock_sock(sk);
+	sk->sk_ipv6only = true;
+	release_sock(sk);
+	return 0;
+}
+
 #endif /* _NET_IPV6_H */

net/ipv6/ip6_udp_tunnel.c

@@ -25,10 +25,7 @@ int udp_sock_create6(struct net *net, struct udp_port_cfg *cfg,
 		goto error;
 
 	if (cfg->ipv6_v6only) {
-		int val = 1;
-
-		err = kernel_setsockopt(sock, IPPROTO_IPV6, IPV6_V6ONLY,
-					(char *) &val, sizeof(val));
+		err = ip6_sock_set_v6only(sock->sk);
 		if (err < 0)
 			goto error;
 	}

net/sunrpc/svcsock.c

@@ -1328,7 +1328,6 @@ static struct svc_xprt *svc_create_socket(struct svc_serv *serv,
 	struct sockaddr *newsin = (struct sockaddr *)&addr;
 	int		newlen;
 	int		family;
-	int		val;
 	RPC_IFDEBUG(char buf[RPC_MAX_ADDRBUFLEN]);
 
 	dprintk("svc: svc_create_socket(%s, %d, %s)\n",
@@ -1364,11 +1363,8 @@ static struct svc_xprt *svc_create_socket(struct svc_serv *serv,
 	 * getting requests from IPv4 remotes.  Those should
 	 * be shunted to a PF_INET listener via rpcbind.
 	 */
-	val = 1;
 	if (family == PF_INET6)
-		kernel_setsockopt(sock, SOL_IPV6, IPV6_V6ONLY,
-					(char *)&val, sizeof(val));
-
+		ip6_sock_set_v6only(sock->sk);
 	if (type == SOCK_STREAM)
 		sock->sk->sk_reuse = SK_CAN_REUSE; /* allow address reuse */
 	error = kernel_bind(sock, sin, len);