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// Copyright 2014 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/spdy/hpack_huffman_aggregator.h"
#include "base/metrics/bucket_ranges.h"
#include "base/metrics/field_trial.h"
#include "base/metrics/histogram.h"
#include "base/metrics/sample_vector.h"
#include "base/stl_util.h"
#include "base/strings/string_number_conversions.h"
#include "base/strings/string_util.h"
#include "net/base/load_flags.h"
#include "net/http/http_request_headers.h"
#include "net/http/http_request_info.h"
#include "net/http/http_response_headers.h"
#include "net/spdy/hpack_encoder.h"
#include "net/spdy/spdy_http_utils.h"
namespace net {
namespace {
const char kHistogramName[] = "Net.SpdyHpackEncodedCharacterFrequency";
const size_t kTotalCountsPublishThreshold = 50000;
// Each encoder uses the default dynamic table size of 4096 total bytes.
const size_t kMaxEncoders = 20;
} // namespace
HpackHuffmanAggregator::HpackHuffmanAggregator()
: counts_(256, 0),
total_counts_(0),
max_encoders_(kMaxEncoders) {
}
HpackHuffmanAggregator::~HpackHuffmanAggregator() {
STLDeleteContainerPairSecondPointers(encoders_.begin(), encoders_.end());
encoders_.clear();
}
void HpackHuffmanAggregator::AggregateTransactionCharacterCounts(
const HttpRequestInfo& request,
const HttpRequestHeaders& request_headers,
const ProxyServer& proxy,
const HttpResponseHeaders& response_headers) {
if (IsCrossOrigin(request)) {
return;
}
HostPortPair endpoint = HostPortPair(request.url.HostNoBrackets(),
request.url.EffectiveIntPort());
HpackEncoder* encoder = ObtainEncoder(
SpdySessionKey(endpoint, proxy, request.privacy_mode));
// Convert and encode the request and response header sets.
{
SpdyHeaderBlock headers;
CreateSpdyHeadersFromHttpRequest(
request, request_headers, SPDY4, false, &headers);
std::string tmp_out;
encoder->EncodeHeaderSet(headers, &tmp_out);
}
{
SpdyHeaderBlock headers;
CreateSpdyHeadersFromHttpResponse(response_headers, &headers);
std::string tmp_out;
encoder->EncodeHeaderSet(headers, &tmp_out);
}
if (total_counts_ >= kTotalCountsPublishThreshold) {
PublishCounts();
}
}
// static
bool HpackHuffmanAggregator::UseAggregator() {
const std::string group_name =
base::FieldTrialList::FindFullName("HpackHuffmanAggregator");
if (group_name == "Enabled") {
return true;
}
return false;
}
// static
void HpackHuffmanAggregator::CreateSpdyHeadersFromHttpResponse(
const HttpResponseHeaders& headers,
SpdyHeaderBlock* headers_out) {
// Lower-case header names, and coalesce multiple values delimited by \0.
// Also add the fixed status header.
std::string name, value;
void* it = NULL;
while (headers.EnumerateHeaderLines(&it, &name, &value)) {
base::StringToLowerASCII(&name);
if (headers_out->find(name) == headers_out->end()) {
(*headers_out)[name] = value;
} else {
(*headers_out)[name] += std::string(1, '\0') + value;
}
}
(*headers_out)[":status"] = base::IntToString(headers.response_code());
}
// static
bool HpackHuffmanAggregator::IsCrossOrigin(const HttpRequestInfo& request) {
// Require that the request is top-level, or that it shares
// an origin with its referer.
HostPortPair endpoint = HostPortPair(request.url.HostNoBrackets(),
request.url.EffectiveIntPort());
if ((request.load_flags & LOAD_MAIN_FRAME) == 0) {
std::string referer_str;
if (!request.extra_headers.GetHeader(HttpRequestHeaders::kReferer,
&referer_str)) {
// Require a referer.
return true;
}
GURL referer(referer_str);
HostPortPair referer_endpoint = HostPortPair(referer.HostNoBrackets(),
referer.EffectiveIntPort());
if (!endpoint.Equals(referer_endpoint)) {
// Cross-origin request.
return true;
}
}
return false;
}
HpackEncoder* HpackHuffmanAggregator::ObtainEncoder(const SpdySessionKey& key) {
for (OriginEncoders::iterator it = encoders_.begin();
it != encoders_.end(); ++it) {
if (key.Equals(it->first)) {
// Move to head of list and return.
OriginEncoder origin_encoder = *it;
encoders_.erase(it);
encoders_.push_front(origin_encoder);
return origin_encoder.second;
}
}
// Not found. Create a new encoder, evicting one if needed.
encoders_.push_front(std::make_pair(
key, new HpackEncoder(ObtainHpackHuffmanTable())));
if (encoders_.size() > max_encoders_) {
delete encoders_.back().second;
encoders_.pop_back();
}
encoders_.front().second->SetCharCountsStorage(&counts_, &total_counts_);
return encoders_.front().second;
}
void HpackHuffmanAggregator::PublishCounts() {
// base::Histogram requires that values be 1-indexed.
const size_t kRangeMin = 1;
const size_t kRangeMax = counts_.size() + 1;
const size_t kBucketCount = kRangeMax + 1;
base::BucketRanges ranges(kBucketCount + 1);
for (size_t i = 0; i != ranges.size(); ++i) {
ranges.set_range(i, i);
}
ranges.ResetChecksum();
// Copy |counts_| into a SampleVector.
base::SampleVector samples(&ranges);
for (size_t i = 0; i != counts_.size(); ++i) {
samples.Accumulate(i + 1, counts_[i]);
}
STATIC_HISTOGRAM_POINTER_BLOCK(
kHistogramName,
AddSamples(samples),
base::LinearHistogram::FactoryGet(
kHistogramName, kRangeMin, kRangeMax, kBucketCount,
base::HistogramBase::kUmaTargetedHistogramFlag));
// Clear counts.
counts_.assign(counts_.size(), 0);
total_counts_ = 0;
}
} // namespace net
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