Fast-fail WPAD detection.

net/base/address_family.h

 // 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.
 
 #ifndef NET_BASE_ADDRESS_FAMILY_H_
 #define NET_BASE_ADDRESS_FAMILY_H_
 
 namespace net {
 
 // Enum wrapper around the address family types supported by host resolver
 // procedures.
 enum AddressFamily {
   ADDRESS_FAMILY_UNSPECIFIED,   // AF_UNSPEC
   ADDRESS_FAMILY_IPV4,          // AF_INET
   ADDRESS_FAMILY_IPV6,          // AF_INET6
 };
 
 // HostResolverFlags is a bitflag enum used by host resolver procedures to
 // determine the value of addrinfo.ai_flags and work around getaddrinfo
 // peculiarities.
 enum {
   HOST_RESOLVER_CANONNAME = 1 << 0,  // AI_CANONNAME
   // Hint to the resolver proc that only loopback addresses are configured.
   HOST_RESOLVER_LOOPBACK_ONLY = 1 << 1,
   // Indicate the address family was set because no IPv6 support was detected.
   HOST_RESOLVER_DEFAULT_FAMILY_SET_DUE_TO_NO_IPV6 = 1 << 2,
+  // The resolver should only invoke getaddrinfo, not DnsClient.
+  HOST_RESOLVER_SYSTEM_ONLY = 1 << 3
 };
 typedef int HostResolverFlags;
 
 }  // namespace net
 
 #endif  // NET_BASE_ADDRESS_FAMILY_H_