Resolve RFC 6761 localhost names to loopback

net/dns/host_resolver_impl.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_impl.h"
 
 #if defined(OS_WIN)
 #include <Winsock2.h>
 #elif defined(OS_POSIX)
 #include <netdb.h>
@@ skipping 1979 matching lines @@
   if (ServeFromCache(key, info, &net_error, addresses)) {
     source_net_log.AddEvent(NetLog::TYPE_HOST_RESOLVER_IMPL_CACHE_HIT);
     return net_error;
   }
   // TODO(szym): Do not do this if nsswitch.conf instructs not to.
   // http://crbug.com/117655
   if (ServeFromHosts(key, info, addresses)) {
     source_net_log.AddEvent(NetLog::TYPE_HOST_RESOLVER_IMPL_HOSTS_HIT);
     return OK;
   }
+
+  // Per RFC 6761 section 6.3, resolve localhost to loopback without
+  // sending it out on the network.
+  if (IsLocalhost(base::StringToLowerASCII(key.hostname))) {

[Ryan Sleevi, 2015/06/11 00:34:03]

BUG: Should IsLocalhost be doing the case conversions? Probably

[estark, 2015/06/11 02:35:32]

Done.

+    addresses->clear();
+    IPAddressNumber ip_address;
+    ParseIPLiteralToNumber("127.0.0.1", &ip_address);

[Ryan Sleevi, 2015/06/11 00:34:03]

BUG 1: This isn't correct for localhost6 (which should be ::1)
BUG 2: This isn't respecting |info.address_family()| or |key.address_family|
BUG 3: Parsing is slow for a constant! boo-urns!

const unsigned char kLocalhostIPv4 = { 127, 0, 0, 1};
addresses->push_back(IPEndpoint(IPAddressNumber(kLocalhostIPv4, kLocalhostIPv4 +
arraysize(kLocalhostIPv4)), info.port()));

[for example]

[estark, 2015/06/11 02:35:32]

Done by factoring out the hostname check of IsLocalhost() into
IsLocalhostHostname() with an output parameter that indicates if it was a IPv6-y
name. (Feels kinda gross... open to other ideas.)
Done. Wasn't sure what to do with ADDRESS_FAMILY_UNSPECIFIED, so I returned
both, but no idea if that's correct or not?
Done. Third Simpsons reference today that I've had to look up. :(

+    addresses->push_back(IPEndPoint(ip_address, info.port()));
+    return OK;
+  }
+
   return ERR_DNS_CACHE_MISS;
 }
 
 int HostResolverImpl::ResolveFromCache(const RequestInfo& info,
                                        AddressList* addresses,
                                        const BoundNetLog& source_net_log) {
   DCHECK(CalledOnValidThread());
   DCHECK(addresses);
 
   // Update the net log and notify registered observers.
@@ skipping 192 matching lines @@
         effective_address_family = ADDRESS_FAMILY_IPV4;
         effective_flags |= HOST_RESOLVER_DEFAULT_FAMILY_SET_DUE_TO_NO_IPV6;
       }
     }
   }
 
   std::string hostname = info.hostname();
   // Redirect .localhost queries to "localhost." to make sure that they
   // are never sent out on the network, per RFC 6761.
   if (IsLocalhostTLD(info.hostname()))
     hostname = kLocalhost;

[mmenke, 2015/06/11 00:36:51]

Peppering this file with multiple localhost checks seems weird.  IsLocalhost
also calls IsLocalhostTLD.  Do we need logic here and the new code, too?

[estark, 2015/06/11 02:35:32]

Ah, that's nice, we don't need both. Removed.

 
   return Key(hostname, effective_address_family, effective_flags);
 }
 
 bool HostResolverImpl::IsIPv6Reachable(const BoundNetLog& net_log) {
   base::TimeTicks now = base::TimeTicks::Now();
   bool cached = true;
   if ((now - last_ipv6_probe_time_).InMilliseconds() > kIPv6ProbePeriodMs) {
     IPAddressNumber address(kIPv6ProbeAddress,
                             kIPv6ProbeAddress + arraysize(kIPv6ProbeAddress));
@@ skipping 189 matching lines @@
     dns_client_->SetConfig(dns_config);
     num_dns_failures_ = 0;
     if (dns_client_->GetConfig())
       UMA_HISTOGRAM_BOOLEAN("AsyncDNS.DnsClientEnabled", true);
   }
 
   AbortDnsTasks();
 }
 
 }  // namespace net