Fix host lookup on linux, to skip IPv6 if there are no global IPv6 addresses.

runtime/bin/socket_linux.cc

Index: runtime/bin/socket_linux.cc
diff --git a/runtime/bin/socket_linux.cc b/runtime/bin/socket_linux.cc
index 08d8fe1e840220f907c7a36e7ae995bdb5f754e3..693e5c3333b2253998508b886b08bc2b8ce8655f 100644
--- a/runtime/bin/socket_linux.cc
+++ b/runtime/bin/socket_linux.cc
@@ -239,16 +239,22 @@ AddressList<SocketAddress>* Socket::LookupAddress(const char* host,
   memset(&hints, 0, sizeof(hints));
   hints.ai_family = SocketAddress::FromType(type);
   hints.ai_socktype = SOCK_STREAM;
-  hints.ai_flags = 0;
+  hints.ai_flags = (AI_V4MAPPED | AI_ADDRCONFIG);
   hints.ai_protocol = IPPROTO_TCP;
   struct addrinfo* info = NULL;
   int status = getaddrinfo(host, 0, &hints, &info);
   if (status != 0) {
-    ASSERT(*os_error == NULL);
-    *os_error = new OSError(status,
-                            gai_strerror(status),
-                            OSError::kGetAddressInfo);
-    return NULL;
+    // We failed, try without AI_ADDRCONFIG. This can happen when looking up
+    // e.g. '::1', when there are no global IPv6 addresses.
+    hints.ai_flags = AI_V4MAPPED;
+    status = getaddrinfo(host, 0, &hints, &info);
+    if (status != 0) {
+      ASSERT(*os_error == NULL);
+      *os_error = new OSError(status,
+                              gai_strerror(status),
+                              OSError::kGetAddressInfo);
+      return NULL;
+    }
   }
   intptr_t count = 0;
   for (struct addrinfo* c = info; c != NULL; c = c->ai_next) {