HTTP Cache Age calculation mechanism changed with RFC 7234

net/http/http_response_headers.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.
 
 // The rules for header parsing were borrowed from Firefox:
 // http://lxr.mozilla.org/seamonkey/source/netwerk/protocol/http/src/nsHttpResponseHead.cpp
 // The rules for parsing content-types were also borrowed from Firefox:
 // http://lxr.mozilla.org/mozilla/source/netwerk/base/src/nsURLHelper.cpp#834
 
 #include "net/http/http_response_headers.h"
@@ skipping 1110 matching lines @@
 //    *              response
 //    * now
 //    *      is the current (local) time
 //    */
 //   apparent_age = max(0, response_time - date_value);
 //   corrected_received_age = max(apparent_age, age_value);
 //   response_delay = response_time - request_time;
 //   corrected_initial_age = corrected_received_age + response_delay;
 //   resident_time = now - response_time;
 //   current_age   = corrected_initial_age + resident_time;
 //

[mmenke, 2017/01/19 16:11:18]

I assume this comment needs to be updated, too (And the RFC reference is
certainly wrong now)

[billyjay, 2017/01/20 19:23:26]

Done.

 TimeDelta HttpResponseHeaders::GetCurrentAge(const Time& request_time,
                                              const Time& response_time,
                                              const Time& current_time) const {
   // If there is no Date header, then assume that the server response was
   // generated at the time when we received the response.
   Time date_value;
   if (!GetDateValue(&date_value))
     date_value = response_time;
 
   // If there is no Age header, then assume age is zero.  GetAgeValue does not
   // modify its out param if the value does not exist.
   TimeDelta age_value;
   GetAgeValue(&age_value);
 
   TimeDelta apparent_age = std::max(TimeDelta(), response_time - date_value);
-  TimeDelta corrected_received_age = std::max(apparent_age, age_value);
   TimeDelta response_delay = response_time - request_time;
-  TimeDelta corrected_initial_age = corrected_received_age + response_delay;
+  TimeDelta corrected_age_value = age_value + response_delay;
+  TimeDelta corrected_initial_age = std::max(apparent_age, corrected_age_value);

[mmenke, 2017/01/19 16:11:18]

We should have a test for the changed behavior.

[billyjay, 2017/01/20 19:23:26]

Done.

   TimeDelta resident_time = current_time - response_time;
   TimeDelta current_age = corrected_initial_age + resident_time;
 
   return current_age;
 }
 
 bool HttpResponseHeaders::GetMaxAgeValue(TimeDelta* result) const {
   return GetCacheControlDirective("max-age", result);
 }
 
@@ skipping 308 matching lines @@
   return true;
 }
 
 bool HttpResponseHeaders::IsChunkEncoded() const {
   // Ignore spurious chunked responses from HTTP/1.0 servers and proxies.
   return GetHttpVersion() >= HttpVersion(1, 1) &&
       HasHeaderValue("Transfer-Encoding", "chunked");
 }
 
 }  // namespace net