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

runtime/bin/socket_linux.cc

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
 #if defined(TARGET_OS_LINUX)
 
 #include <errno.h>  // NOLINT
 #include <stdio.h>  // NOLINT
 #include <stdlib.h>  // NOLINT
@@ skipping 221 matching lines @@
 
 
 AddressList<SocketAddress>* Socket::LookupAddress(const char* host,
                                                   int type,
                                                   OSError** os_error) {
   // Perform a name lookup for a host name.
   struct addrinfo hints;
   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) {
     if (c->ai_family == AF_INET || c->ai_family == AF_INET6) count++;
   }
   intptr_t i = 0;
   AddressList<SocketAddress>* addresses = new AddressList<SocketAddress>(count);
   for (struct addrinfo* c = info; c != NULL; c = c->ai_next) {
     if (c->ai_family == AF_INET || c->ai_family == AF_INET6) {
       addresses->SetAt(i, new SocketAddress(c->ai_addr));
@@ skipping 356 matching lines @@
   mreq.gr_interface = interfaceIndex;
   memmove(&mreq.gr_group, &addr->ss, SocketAddress::GetAddrLength(addr));
   return TEMP_FAILURE_RETRY_BLOCK_SIGNALS(setsockopt(
       fd, proto, MCAST_LEAVE_GROUP, &mreq, sizeof(mreq))) == 0;
 }
 
 }  // namespace bin
 }  // namespace dart
 
 #endif  // defined(TARGET_OS_LINUX)