Add an opt-out header for HTTP throttling. Never throttle for localhost.

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 f3b01271910f21a755fe0494fdf5b0eccb646dd6..d1f870da232fcd4f6a6a0a3c189761fc6f1af73a 100644
--- a/net/base/net_util.cc
+++ b/net/base/net_util.cc
@@ -1,4 +1,4 @@
-// Copyright (c) 2010 The Chromium Authors. All rights reserved.
+// Copyright (c) 2011 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.
 
@@ -2111,4 +2111,36 @@ int GetPortFromSockaddr(const struct sockaddr* address, socklen_t address_len) {
   return ntohs(*port_field);
 }
 
+bool IsLocalhost(const std::string& host) {
+  if (host == "localhost")

[wtc, 2011/03/23 00:06:58]

We should also check for "localhost.localdomain",
"localhost6", and "localhost6.localdomain6".

[Jói, 2011/03/23 23:38:24]

Thanks, I was unaware of these.

+    return true;
+
+  IPAddressNumber ip_number;
+  if (ParseIPLiteralToNumber(host, &ip_number)) {
+    size_t size = ip_number.size();
+    if (size == 4) {

[wtc, 2011/03/23 00:06:58]

Nit: we usually use a switch statement for this kind of
if-else-if statement.

[Jói, 2011/03/23 23:38:24]

Done.

+      IPAddressNumber localhost_prefix;
+      localhost_prefix.push_back(127);
+      for (int i = 0; i < 3; ++i) {
+        localhost_prefix.push_back(0);
+      }
+      return IPNumberMatchesPrefix(ip_number, localhost_prefix, 8);
+    } else if (size == 16) {
+      if (!ip_number[15] == 1)

[wtc, 2011/03/23 00:06:58]

BUG: this should be
  ip_number[15] != 1

(You should add the test case "::2" to the unit test.)

But, can you use the IN6_IS_ADDR_LOOPBACK macro?
This file already uses that macro.

[Jói, 2011/03/23 23:38:24]

Thanks, fixed that and added the test case.

I could use IN6_IS_ADDR_LOOPBACK but it would involve rearranging the bytes into
an IN6_ADDR (8 words instead of the 16 bytes of our IPAddressNumber) because a
straight cast would not be endian-safe (I'm not sure we target any big-endian
architectures right now, but with some of the mobile platforms we might?).

Let me know if you still prefer that I use the macro.

+        return false;
+
+      for (int i = 0; i < 15; ++i) {
+        if (ip_number[i] != 0)
+          return false;
+      }
+
+      return true;
+    } else {
+      NOTREACHED();
+    }
+  }
+
+  return false;
+}
+
 }  // namespace net