Always treat .localhost as loopback

net/base/net_util.cc

Index: net/base/net_util.cc
diff --git a/net/base/net_util.cc b/net/base/net_util.cc
index 3b49dffb5c20d889003a09755276ddaa8e41542d..a16d9e7116bd45f70d19bcf114b803e870de63a3 100644
--- a/net/base/net_util.cc
+++ b/net/base/net_util.cc
@@ -144,6 +144,9 @@ static const int kAllowedFtpPorts[] = {
   22,   // ssh
 };
 
+static const char kLocalhostTLD[] = ".localhost";
+static const int kLocalhostTLDLength = strlen(kLocalhostTLD);
+
 bool IPNumberPrefixCheck(const IPAddressNumber& ip_number,
                          const unsigned char* ip_prefix,
                          size_t prefix_length_in_bits) {
@@ -984,7 +987,8 @@ bool IsLocalhost(const std::string& host) {
   if (host == "localhost" ||
       host == "localhost.localdomain" ||
       host == "localhost6" ||
-      host == "localhost6.localdomain6")
+      host == "localhost6.localdomain6" ||
+      IsLocalhostTLD(host))
     return true;
 
   IPAddressNumber ip_number;
@@ -1014,6 +1018,14 @@ bool IsLocalhost(const std::string& host) {
   return false;
 }
 
+bool IsLocalhostTLD(const std::string& host) {

[Ryan Sleevi, 2015/02/19 22:24:56]

I guess it depends on the rules for |host| here, but it's valid to have a
trailing dot in DNS to indicate end-label

that is

"localhost.localhost." is valid and equivalent to "localhost.localhost" (the .
traditionally signals to OS libraries that have suffix search orders not to
execute them)

This is probably a bug that we don't handle these on line 987-991, but it really
depends on the API contract we want. I'm pretty sure these functions will
receive . suffices as inputs, so we should probably handle them.

[estark, 2015/02/20 01:55:19]

Gotcha. Done in this function, and filed another bug for lines 987-991:
crbug.com/460331

+  int host_length = host.length();

[Ryan Sleevi, 2015/02/19 22:24:56]

s/int/size_t/ - right numeric for the job

[estark, 2015/02/20 01:55:19]

Done.

+  if (host_length < kLocalhostTLDLength)
+    return false;
+  return host.compare(host_length - kLocalhostTLDLength, std::string::npos,
+                      kLocalhostTLD) == 0;
+}
+
 NetworkInterface::NetworkInterface()
     : type(NetworkChangeNotifier::CONNECTION_UNKNOWN), prefix_length(0) {
 }