net: fix build errors if ipv6 is disabled

CONFIG_IPV6=n is still a valid choice ;)

It appears we can remove dead code.

Reported-by: Wu Fengguang <[e-mail]>
Signed-off-by: Eric Dumazet <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

include/net/ip6_checksum.h

···
 	}
 }
 
+#if IS_ENABLED(CONFIG_IPV6)
 static inline void tcp_v6_send_check(struct sock *sk, struct sk_buff *skb)
 {
 	struct ipv6_pinfo *np = inet6_sk(sk);
 
 	__tcp_v6_send_check(skb, &np->saddr, &sk->sk_v6_daddr);
 }
+#endif
 
 int udp6_csum_init(struct sk_buff *skb, struct udphdr *uh, int proto);
 #endif

net/ipv4/ping.c

···
 		 (int)sk->sk_bound_dev_if);
 
 	err = 0;
-	if ((sk->sk_family == AF_INET && isk->inet_rcv_saddr) ||
-	    (sk->sk_family == AF_INET6 &&
-	     !ipv6_addr_any(&sk->sk_v6_rcv_saddr)))
+	if (sk->sk_family == AF_INET && isk->inet_rcv_saddr)
 		sk->sk_userlocks |= SOCK_BINDADDR_LOCK;
+#if IS_ENABLED(CONFIG_IPV6)
+	if (sk->sk_family == AF_INET6 && !ipv6_addr_any(&sk->sk_v6_rcv_saddr))
+		sk->sk_userlocks |= SOCK_BINDADDR_LOCK;
+#endif
 
 	if (snum)
 		sk->sk_userlocks |= SOCK_BINDPORT_LOCK;

net/ipv4/tcp_metrics.c

···
 		addr.addr.a4 = tw->tw_daddr;
 		hash = (__force unsigned int) addr.addr.a4;
 		break;
+#if IS_ENABLED(CONFIG_IPV6)
 	case AF_INET6:
 		*(struct in6_addr *)addr.addr.a6 = tw->tw_v6_daddr;
 		hash = ipv6_addr_hash(&tw->tw_v6_daddr);
 		break;
+#endif
 	default:
 		return NULL;
 	}
···
 		addr.addr.a4 = inet_sk(sk)->inet_daddr;
 		hash = (__force unsigned int) addr.addr.a4;
 		break;
+#if IS_ENABLED(CONFIG_IPV6)
 	case AF_INET6:
 		*(struct in6_addr *)addr.addr.a6 = sk->sk_v6_daddr;
 		hash = ipv6_addr_hash(&sk->sk_v6_daddr);
 		break;
+#endif
 	default:
 		return NULL;
 	}

net/sunrpc/svcsock.c

···
 				&inet_sk(sk)->inet_rcv_saddr,
 				inet_sk(sk)->inet_num);
 		break;
+#if IS_ENABLED(CONFIG_IPV6)
 	case PF_INET6:
 		len = snprintf(buf, remaining, "ipv6 %s %pI6 %d\n",
 				proto_name,
 				&sk->sk_v6_rcv_saddr,
 				inet_sk(sk)->inet_num);
 		break;
+#endif
 	default:
 		len = snprintf(buf, remaining, "*unknown-%d*\n",
 				sk->sk_family);

security/lsm_audit.c

···
 						"faddr", "fport");
 				break;
 			}
+#if IS_ENABLED(CONFIG_IPV6)
 			case AF_INET6: {
 				struct inet_sock *inet = inet_sk(sk);
 
···
 						"faddr", "fport");
 				break;
 			}
+#endif
 			case AF_UNIX:
 				u = unix_sk(sk);
 				if (u->path.dentry) {