[Linux] Enable connecting to localhost when offline.

net/base/host_resolver_proc.cc

 // Copyright (c) 2010 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "net/base/host_resolver_proc.h"
 
 #include "build/build_config.h"
 
 #if defined(OS_POSIX) && !defined(OS_MACOSX)
 #include <resolv.h>
@@ skipping 198 matching lines @@
   //   The IPv4 or IPv6 loopback address is not considered a valid global
   //   address.
   // See http://crbug.com/5234.
   //
   // OpenBSD does not support it, either.
   hints.ai_flags = 0;
 #else
   hints.ai_flags = AI_ADDRCONFIG;
 #endif
 
+  // On Linux AI_ADDRCONFIG doesn't consider loopback addreses, even if only
+  // loopback addresses are configured. So don't use it when there are only
+  // loopback addresses.
+  if (host_resolver_flags & HOST_RESOLVER_LOOPBACK_ONLY)
+    hints.ai_flags &= ~AI_ADDRCONFIG;
+
   if (host_resolver_flags & HOST_RESOLVER_CANONNAME)
     hints.ai_flags |= AI_CANONNAME;
 
   // Restrict result set to only this socket type to avoid duplicates.
   hints.ai_socktype = SOCK_STREAM;
 
   int err = getaddrinfo(host.c_str(), NULL, &hints, &ai);
 #if defined(OS_POSIX) && !defined(OS_MACOSX) && !defined(OS_OPENBSD)
   net::DnsReloadTimer* dns_timer = Singleton<net::DnsReloadTimer>::get();
   // If we fail, re-initialise the resolver just in case there have been any
@@ skipping 14 matching lines @@
 #endif
     }
     return ERR_NAME_NOT_RESOLVED;
   }
 
   addrlist->Adopt(ai);
   return OK;
 }
 
 }  // namespace net