Initial implementation of Chrome-Freshness header.

net/http/http_cache_transaction.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/http/http_cache_transaction.h"
 
 #include "build/build_config.h"
 
 #if defined(OS_POSIX)
 #include <unistd.h>
 #endif
 
 #include <algorithm>
 #include <string>
 
 #include "base/bind.h"
 #include "base/compiler_specific.h"
+#include "base/format_macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/metrics/field_trial.h"
 #include "base/metrics/histogram.h"
 #include "base/metrics/sparse_histogram.h"
 #include "base/rand_util.h"
 #include "base/strings/string_number_conversions.h"
+#include "base/strings/string_piece.h"
 #include "base/strings/string_util.h"
+#include "base/strings/stringprintf.h"
 #include "base/time/time.h"
 #include "net/base/completion_callback.h"
 #include "net/base/io_buffer.h"
 #include "net/base/load_flags.h"
 #include "net/base/load_timing_info.h"
 #include "net/base/net_errors.h"
 #include "net/base/net_log.h"
 #include "net/base/upload_data_stream.h"
 #include "net/cert/cert_status_flags.h"
 #include "net/disk_cache/disk_cache.h"
 #include "net/http/disk_based_cert_cache.h"
 #include "net/http/http_network_session.h"
 #include "net/http/http_request_info.h"
 #include "net/http/http_response_headers.h"
 #include "net/http/http_transaction.h"
 #include "net/http/http_util.h"
 #include "net/http/partial_data.h"
 #include "net/ssl/ssl_cert_request_info.h"
 #include "net/ssl/ssl_config_service.h"
 
 using base::Time;
 using base::TimeDelta;
 using base::TimeTicks;
 
 namespace {
 
+// TODO(ricea): Move this to HttpResponseHeaders once it is standardised.
+static const char kFreshnessHeader[] = "Chromium-Resource-Freshness";
+
 // Stores data relevant to the statistics of writing and reading entire
 // certificate chains using DiskBasedCertCache. |num_pending_ops| is the number
 // of certificates in the chain that have pending operations in the
 // DiskBasedCertCache. |start_time| is the time that the read and write
 // commands began being issued to the DiskBasedCertCache.
 // TODO(brandonsalmon): Remove this when it is no longer necessary to
 // collect data.
 class SharedChainData : public base::RefCounted<SharedChainData> {
  public:
   SharedChainData(int num_ops, TimeTicks start)
@@ skipping 2189 matching lines @@
   if (!partial_.get()) {
     // Need to customize the request, so this forces us to allocate :(
     custom_request_.reset(new HttpRequestInfo(*request_));
     request_ = custom_request_.get();
   }
   DCHECK(custom_request_.get());
 
   bool use_if_range = partial_.get() && !partial_->IsCurrentRangeCached() &&
                       !invalid_range_;
 
+  if (!use_if_range) {
+    // stale-while-revalidate is not useful when we only have a partial response
+    // cached, so don't set the header in that case.
+    TimeDelta stale_while_revalidate;
+    if (response_.headers->GetStaleWhileRevalidateValue(
+            &stale_while_revalidate) &&
+        stale_while_revalidate > TimeDelta()) {
+      TimeDelta max_age =
+          response_.headers->GetFreshnessLifetime(response_.response_time);
+      TimeDelta current_age = response_.headers->GetCurrentAge(
+          response_.request_time, response_.response_time, Time::Now());
+
+      custom_request_->extra_headers.SetHeader(
+          kFreshnessHeader,
+          base::StringPrintf("max-age=%" PRId64
+                             ",stale-while-revalidate=%" PRId64 ",age=%" PRId64,
+                             max_age.InSeconds(),
+                             stale_while_revalidate.InSeconds(),
+                             current_age.InSeconds()));
+    }
+  }
+
   if (!etag_value.empty()) {
     if (use_if_range) {
       // We don't want to switch to WRITE mode if we don't have this block of a
       // byte-range request because we may have other parts cached.
       custom_request_->extra_headers.SetHeader(
           HttpRequestHeaders::kIfRange, etag_value);
     } else {
       custom_request_->extra_headers.SetHeader(
           HttpRequestHeaders::kIfNoneMatch, etag_value);
     }
@@ skipping 476 matching lines @@
     default:
       NOTREACHED();
   }
 }
 
 void HttpCache::Transaction::OnIOComplete(int result) {
   DoLoop(result);
 }
 
 }  // namespace net