RDMA/addr: Fix build breakage when IPv6 is disabled

Commit 38617c64 ("RDMA/addr: Add support for translating IPv6
addresses") broke the build when CONFIG_IPV6=n, because the ib_addr
module unconditionally attempted to call ipv6_chk_addr() and other
IPv6 functions that are not defined when IPv6 is disabled. Fix this
by only building IPv6 support if CONFIG_IPV6 is turned on, and
add a Kconfig dependency to prevent the ib_addr code from being built
in when IPv6 is built modular.

Signed-off-by: Roland Dreier <[e-mail]>

drivers/infiniband/Kconfig

···
 config INFINIBAND_ADDR_TRANS
 	bool
 	depends on INET
+	depends on !(INFINIBAND = y && IPV6 = m)
 	default y
 
 source "drivers/infiniband/hw/mthca/Kconfig"

drivers/infiniband/core/addr.c

···
 		ret = rdma_copy_addr(dev_addr, dev, NULL);
 		dev_put(dev);
 		break;
+
+#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
 	case AF_INET6:
 		for_each_netdev(&init_net, dev) {
 			if (ipv6_chk_addr(&init_net,
···
 			}
 		}
 		break;
-	default:
-		break;
+#endif
 	}
 	return ret;
 }
···
 {
 	struct rtable *rt;
 	struct flowi fl;
-	struct dst_entry *dst;
 
 	memset(&fl, 0, sizeof fl);
-	if (dst_in->sa_family == AF_INET)  {
+
+	switch (dst_in->sa_family) {
+	case AF_INET:
 		fl.nl_u.ip4_u.daddr =
 			((struct sockaddr_in *) dst_in)->sin_addr.s_addr;
 
···
 
 		neigh_event_send(rt->u.dst.neighbour, NULL);
 		ip_rt_put(rt);
+		break;
 
-	} else {
+#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
+	case AF_INET6:
+	{
+		struct dst_entry *dst;
+
 		fl.nl_u.ip6_u.daddr =
 			((struct sockaddr_in6 *) dst_in)->sin6_addr;
 
···
 
 		neigh_event_send(dst->neighbour, NULL);
 		dst_release(dst);
+		break;
+	}
+#endif
 	}
 }
 
···
 	return ret;
 }
 
+#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
 static int addr6_resolve_remote(struct sockaddr_in6 *src_in,
 			       struct sockaddr_in6 *dst_in,
 			       struct rdma_dev_addr *addr)
···
 	dst_release(dst);
 	return ret;
 }
+#else
+static int addr6_resolve_remote(struct sockaddr_in6 *src_in,
+			       struct sockaddr_in6 *dst_in,
+			       struct rdma_dev_addr *addr)
+{
+	return -EADDRNOTAVAIL;
+}
+#endif
 
 static int addr_resolve_remote(struct sockaddr *src_in,
 				struct sockaddr *dst_in,
···
 	struct net_device *dev;
 	int ret;
 
-	if (dst_in->sa_family == AF_INET) {
+	switch (dst_in->sa_family) {
+	case AF_INET:
+	{
 		__be32 src_ip = ((struct sockaddr_in *) src_in)->sin_addr.s_addr;
 		__be32 dst_ip = ((struct sockaddr_in *) dst_in)->sin_addr.s_addr;
 
···
 				memcpy(addr->dst_dev_addr, dev->dev_addr, MAX_ADDR_LEN);
 		}
 		dev_put(dev);
-	} else {
+		break;
+	}
+
+#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
+	case AF_INET6:
+	{
 		struct in6_addr *a;
 
 		for_each_netdev(&init_net, dev)
···
 			if (!ret)
 				memcpy(addr->dst_dev_addr, dev->dev_addr, MAX_ADDR_LEN);
 		}
+		break;
+	}
+#endif
+
+	default:
+		ret = -EADDRNOTAVAIL;
+		break;
 	}
 
 	return ret;