Resolve RFC 6761 localhost names to loopback

net/dns/host_resolver_impl.cc

Index: net/dns/host_resolver_impl.cc
diff --git a/net/dns/host_resolver_impl.cc b/net/dns/host_resolver_impl.cc
index 970ec1f457ade5ba90b1b2ac6224f57e782c0271..7d00256d132b08b4b0f2e518be4ce6438156a6c3 100644
--- a/net/dns/host_resolver_impl.cc
+++ b/net/dns/host_resolver_impl.cc
@@ -1997,6 +1997,17 @@ int HostResolverImpl::ResolveHelper(const Key& key,
     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;
 }