Always treat .localhost as loopback

net/dns/host_resolver_proc.cc

 // Copyright (c) 2012 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/dns/host_resolver_proc.h"
 
 #include "build/build_config.h"
 
 #include "base/logging.h"
 #include "base/sys_byteorder.h"
 #include "net/base/address_list.h"
 #include "net/base/dns_reloader.h"
 #include "net/base/net_errors.h"
+#include "net/base/net_util.h"
 #include "net/base/sys_addrinfo.h"
 
 #if defined(OS_OPENBSD)
 #define AI_ADDRCONFIG 0
 #endif
 
 namespace net {
 
 namespace {
 
@@ skipping 158 matching lines @@
   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;
 
 #if defined(OS_POSIX) && !defined(OS_MACOSX) && !defined(OS_OPENBSD) && \
     !defined(OS_ANDROID)
   DnsReloaderMaybeReload();
 #endif
-  int err = getaddrinfo(host.c_str(), NULL, &hints, &ai);
+
+  // Redirect .localhost queries to localhost to make sure that they are
+  // never sent out on the network, per RFC 6761.
+  int err = getaddrinfo(IsLocalhostTLD(host) ? "localhost" : host.c_str(), NULL,
+                        &hints, &ai);
   bool should_retry = false;
   // If the lookup was restricted (either by address family, or address
   // detection), and the results where all localhost of a single family,
   // maybe we should retry.  There were several bugs related to these
   // issues, for example http://crbug.com/42058 and http://crbug.com/49024
   if ((hints.ai_family != AF_UNSPEC || hints.ai_flags & AI_ADDRCONFIG) &&
       err == 0 && IsAllLocalhostOfOneFamily(ai)) {
     if (host_resolver_flags & HOST_RESOLVER_DEFAULT_FAMILY_SET_DUE_TO_NO_IPV6) {
       hints.ai_family = AF_UNSPEC;
       should_retry = true;
@@ skipping 55 matching lines @@
   return SystemHostResolverCall(hostname,
                                 address_family,
                                 host_resolver_flags,
                                 addr_list,
                                 os_error);
 }
 
 SystemHostResolverProc::~SystemHostResolverProc() {}
 
 }  // namespace net