ipv4: add ip_sock_set_recverr

Add a helper to directly set the IP_RECVERR sockopt from kernel space
without going through a fake uaccess.

Signed-off-by: Christoph Hellwig <[e-mail]>
Reviewed-by: David Howells <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

include/net/ip.h

···
 }
 
 void ip_sock_set_freebind(struct sock *sk);
+void ip_sock_set_recverr(struct sock *sk);
 void ip_sock_set_tos(struct sock *sk, int val);
 
 #endif	/* _IP_H */

net/ipv4/ip_sockglue.c

···
 }
 EXPORT_SYMBOL(ip_sock_set_freebind);
 
+void ip_sock_set_recverr(struct sock *sk)
+{
+	lock_sock(sk);
+	inet_sk(sk)->recverr = true;
+	release_sock(sk);
+}
+EXPORT_SYMBOL(ip_sock_set_recverr);
+
 /*
  *	Socket option code for IP. This is the end of the line after any
  *	TCP,UDP etc options on an IP socket.

net/rxrpc/local_object.c

···
 		/* Fall through */
 	case AF_INET:
 		/* we want to receive ICMP errors */
-		opt = 1;
-		ret = kernel_setsockopt(local->socket, SOL_IP, IP_RECVERR,
-					(char *) &opt, sizeof(opt));
-		if (ret < 0) {
-			_debug("setsockopt failed");
-			goto error;
-		}
+		ip_sock_set_recverr(local->socket->sk);
 
 		/* we want to set the don't fragment bit */
 		opt = IP_PMTUDISC_DO;