// 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/spdy/chromium/spdy_session.h"

#include <algorithm>
#include <limits>
#include <map>
#include <utility>

#include "base/bind.h"
#include "base/feature_list.h"
#include "base/location.h"
#include "base/logging.h"
#include "base/metrics/histogram_macros.h"
#include "base/metrics/sparse_histogram.h"
#include "base/single_thread_task_runner.h"
#include "base/stl_util.h"
#include "base/strings/string_number_conversions.h"
#include "base/strings/string_split.h"
#include "base/strings/string_util.h"
#include "base/strings/utf_string_conversions.h"
#include "base/threading/thread_task_runner_handle.h"
#include "base/time/time.h"
#include "base/trace_event/trace_event.h"
#include "base/values.h"
#include "crypto/ec_private_key.h"
#include "crypto/ec_signature_creator.h"
#include "net/base/proxy_delegate.h"
#include "net/cert/asn1_util.h"
#include "net/cert/cert_verify_result.h"
#include "net/cert/ct_policy_status.h"
#include "net/http/http_network_session.h"
#include "net/http/http_server_properties.h"
#include "net/http/http_util.h"
#include "net/http/transport_security_state.h"
#include "net/log/net_log.h"
#include "net/log/net_log_capture_mode.h"
#include "net/log/net_log_event_type.h"
#include "net/log/net_log_source_type.h"
#include "net/log/net_log_with_source.h"
#include "net/proxy/proxy_server.h"
#include "net/quic/chromium/quic_http_utils.h"
#include "net/socket/socket.h"
#include "net/socket/ssl_client_socket.h"
#include "net/spdy/chromium/header_coalescer.h"
#include "net/spdy/chromium/spdy_buffer_producer.h"
#include "net/spdy/chromium/spdy_http_utils.h"
#include "net/spdy/chromium/spdy_log_util.h"
#include "net/spdy/chromium/spdy_session_pool.h"
#include "net/spdy/chromium/spdy_stream.h"
#include "net/spdy/core/spdy_frame_builder.h"
#include "net/spdy/core/spdy_protocol.h"
#include "net/spdy/platform/api/spdy_estimate_memory_usage.h"
#include "net/spdy/platform/api/spdy_string_utils.h"
#include "net/ssl/channel_id_service.h"
#include "net/ssl/ssl_cipher_suite_names.h"
#include "net/ssl/ssl_connection_status_flags.h"

namespace net {

namespace {

const int kReadBufferSize = 8 * 1024;
const int kDefaultConnectionAtRiskOfLossSeconds = 10;
const int kHungIntervalSeconds = 10;

// Lifetime of unclaimed pushed stream, in seconds: after this period, a pushed
// stream is cancelled if still not claimed.
const int kPushedStreamLifetimeSeconds = 300;

// Default initial value for HTTP/2 SETTINGS.
const uint32_t kDefaultInitialHeaderTableSize = 4096;
const uint32_t kDefaultInitialEnablePush = 1;
const uint32_t kDefaultInitialInitialWindowSize = 65535;
const uint32_t kDefaultInitialMaxFrameSize = 16384;

// The maximum size of header list that the server is allowed to send.
const uint32_t kSpdyMaxHeaderListSize = 256 * 1024;

// Values of Vary response header on pushed streams.  This is logged to
// Net.PushedStreamVaryResponseHeader, entries must not be changed.
enum PushedStreamVaryResponseHeaderValues {
  // There is no Vary header.
  kNoVaryHeader = 0,
  // The value of Vary is empty.
  kVaryIsEmpty = 1,
  // The value of Vary is "*".
  kVaryIsStar = 2,
  // The value of Vary is "accept-encoding" (case insensitive).
  kVaryIsAcceptEncoding = 3,
  // The value of Vary contains "accept-encoding" (case insensitive) and some
  // other field names as well.
  kVaryHasAcceptEncoding = 4,
  // The value of Vary does not contain "accept-encoding", is not empty, and is
  // not "*".
  kVaryHasNoAcceptEncoding = 5,
  // The number of entries above.
  kNumberOfVaryEntries = 6
};

// String literals for parsing the Vary header in a pushed response.
const char kVary[] = "vary";
const char kStar[] = "*";
const char kAcceptEncoding[] = "accept-encoding";

enum PushedStreamVaryResponseHeaderValues ParseVaryInPushedResponse(
    const SpdyHeaderBlock& headers) {
  SpdyHeaderBlock::iterator it = headers.find(kVary);
  if (it == headers.end())
    return kNoVaryHeader;
  base::StringPiece value(it->second);
  if (value.empty())
    return kVaryIsEmpty;
  if (value == kStar)
    return kVaryIsStar;
  std::string lowercase_value = ToLowerASCII(value);
  if (lowercase_value == kAcceptEncoding)
    return kVaryIsAcceptEncoding;
  // Both comma and newline delimiters occur in the wild.
  for (const auto& substr :
       SplitString(lowercase_value, ",\n", base::TRIM_WHITESPACE,
                   base::SPLIT_WANT_NONEMPTY)) {
    if (substr == kAcceptEncoding)
      return kVaryHasAcceptEncoding;
  }

  return kVaryHasNoAcceptEncoding;
}

bool IsSpdySettingAtDefaultInitialValue(SpdySettingsIds setting_id,
                                        uint32_t value) {
  switch (setting_id) {
    case SETTINGS_HEADER_TABLE_SIZE:
      return value == kDefaultInitialHeaderTableSize;
    case SETTINGS_ENABLE_PUSH:
      return value == kDefaultInitialEnablePush;
    case SETTINGS_MAX_CONCURRENT_STREAMS:
      // There is no initial limit on the number of concurrent streams.
      return false;
    case SETTINGS_INITIAL_WINDOW_SIZE:
      return value == kDefaultInitialInitialWindowSize;
    case SETTINGS_MAX_FRAME_SIZE:
      return value == kDefaultInitialMaxFrameSize;
    case SETTINGS_MAX_HEADER_LIST_SIZE:
      // There is no initial limit on the size of the header list.
      return false;
    default:
      // Undefined parameters have no initial value.
      return false;
  }
}

std::unique_ptr<base::Value> NetLogSpdyHeadersSentCallback(
    const SpdyHeaderBlock* headers,
    bool fin,
    SpdyStreamId stream_id,
    bool has_priority,
    int weight,
    SpdyStreamId parent_stream_id,
    bool exclusive,
    NetLogSource source_dependency,
    NetLogCaptureMode capture_mode) {
  auto dict = std::make_unique<base::DictionaryValue>();
  dict->Set("headers", ElideSpdyHeaderBlockForNetLog(*headers, capture_mode));
  dict->SetBoolean("fin", fin);
  dict->SetInteger("stream_id", stream_id);
  dict->SetBoolean("has_priority", has_priority);
  if (has_priority) {
    dict->SetInteger("parent_stream_id", parent_stream_id);
    dict->SetInteger("weight", weight);
    dict->SetBoolean("exclusive", exclusive);
  }
  if (source_dependency.IsValid()) {
    source_dependency.AddToEventParameters(dict.get());
  }
  return std::move(dict);
}

std::unique_ptr<base::Value> NetLogSpdyHeadersReceivedCallback(
    const SpdyHeaderBlock* headers,
    bool fin,
    SpdyStreamId stream_id,
    NetLogCaptureMode capture_mode) {
  auto dict = std::make_unique<base::DictionaryValue>();
  dict->Set("headers", ElideSpdyHeaderBlockForNetLog(*headers, capture_mode));
  dict->SetBoolean("fin", fin);
  dict->SetInteger("stream_id", stream_id);
  return std::move(dict);
}

std::unique_ptr<base::Value> NetLogSpdySessionCloseCallback(
    int net_error,
    const SpdyString* description,
    NetLogCaptureMode /* capture_mode */) {
  auto dict = std::make_unique<base::DictionaryValue>();
  dict->SetInteger("net_error", net_error);
  dict->SetString("description", *description);
  return std::move(dict);
}

std::unique_ptr<base::Value> NetLogSpdySessionCallback(
    const HostPortProxyPair* host_pair,
    NetLogCaptureMode /* capture_mode */) {
  auto dict = std::make_unique<base::DictionaryValue>();
  dict->SetString("host", host_pair->first.ToString());
  dict->SetString("proxy", host_pair->second.ToPacString());
  return std::move(dict);
}

std::unique_ptr<base::Value> NetLogSpdyInitializedCallback(
    NetLogSource source,
    NetLogCaptureMode /* capture_mode */) {
  auto dict = std::make_unique<base::DictionaryValue>();
  if (source.IsValid()) {
    source.AddToEventParameters(dict.get());
  }
  dict->SetString("protocol", NextProtoToString(kProtoHTTP2));
  return std::move(dict);
}

std::unique_ptr<base::Value> NetLogSpdySendSettingsCallback(
    const SettingsMap* settings,
    NetLogCaptureMode /* capture_mode */) {
  auto dict = std::make_unique<base::DictionaryValue>();
  auto settings_list = std::make_unique<base::ListValue>();
  for (SettingsMap::const_iterator it = settings->begin();
       it != settings->end(); ++it) {
    const SpdySettingsIds id = it->first;
    const uint32_t value = it->second;
    const char* settings_string;
    SettingsIdToString(id, &settings_string);
    settings_list->AppendString(
        SpdyStringPrintf("[id:%u (%s) value:%u]", id, settings_string, value));
  }
  dict->Set("settings", std::move(settings_list));
  return std::move(dict);
}

std::unique_ptr<base::Value> NetLogSpdyRecvSettingCallback(
    SpdySettingsIds id,
    uint32_t value,
    NetLogCaptureMode /* capture_mode */) {
  auto dict = std::make_unique<base::DictionaryValue>();
  const char* settings_string;
  SettingsIdToString(id, &settings_string);
  dict->SetString("id", SpdyStringPrintf("%u (%s)", id, settings_string));
  dict->SetInteger("value", value);
  return std::move(dict);
}

std::unique_ptr<base::Value> NetLogSpdyWindowUpdateFrameCallback(
    SpdyStreamId stream_id,
    uint32_t delta,
    NetLogCaptureMode /* capture_mode */) {
  auto dict = std::make_unique<base::DictionaryValue>();
  dict->SetInteger("stream_id", static_cast<int>(stream_id));
  dict->SetInteger("delta", delta);
  return std::move(dict);
}

std::unique_ptr<base::Value> NetLogSpdySessionWindowUpdateCallback(
    int32_t delta,
    int32_t window_size,
    NetLogCaptureMode /* capture_mode */) {
  auto dict = std::make_unique<base::DictionaryValue>();
  dict->SetInteger("delta", delta);
  dict->SetInteger("window_size", window_size);
  return std::move(dict);
}

std::unique_ptr<base::Value> NetLogSpdyDataCallback(
    SpdyStreamId stream_id,
    int size,
    bool fin,
    NetLogCaptureMode /* capture_mode */) {
  auto dict = std::make_unique<base::DictionaryValue>();
  dict->SetInteger("stream_id", static_cast<int>(stream_id));
  dict->SetInteger("size", size);
  dict->SetBoolean("fin", fin);
  return std::move(dict);
}

std::unique_ptr<base::Value> NetLogSpdyRecvRstStreamCallback(
    SpdyStreamId stream_id,
    SpdyErrorCode error_code,
    NetLogCaptureMode /* capture_mode */) {
  auto dict = std::make_unique<base::DictionaryValue>();
  dict->SetInteger("stream_id", static_cast<int>(stream_id));
  dict->SetString(
      "error_code",
      SpdyStringPrintf("%u (%s)", error_code, ErrorCodeToString(error_code)));
  return std::move(dict);
}

std::unique_ptr<base::Value> NetLogSpdySendRstStreamCallback(
    SpdyStreamId stream_id,
    SpdyErrorCode error_code,
    const SpdyString* description,
    NetLogCaptureMode /* capture_mode */) {
  auto dict = std::make_unique<base::DictionaryValue>();
  dict->SetInteger("stream_id", static_cast<int>(stream_id));
  dict->SetString(
      "error_code",
      SpdyStringPrintf("%u (%s)", error_code, ErrorCodeToString(error_code)));
  dict->SetString("description", *description);
  return std::move(dict);
}

std::unique_ptr<base::Value> NetLogSpdyPingCallback(
    SpdyPingId unique_id,
    bool is_ack,
    const char* type,
    NetLogCaptureMode /* capture_mode */) {
  auto dict = std::make_unique<base::DictionaryValue>();
  dict->SetInteger("unique_id", static_cast<int>(unique_id));
  dict->SetString("type", type);
  dict->SetBoolean("is_ack", is_ack);
  return std::move(dict);
}

std::unique_ptr<base::Value> NetLogSpdyRecvGoAwayCallback(
    SpdyStreamId last_stream_id,
    int active_streams,
    int unclaimed_streams,
    SpdyErrorCode error_code,
    SpdyStringPiece debug_data,
    NetLogCaptureMode capture_mode) {
  auto dict = std::make_unique<base::DictionaryValue>();
  dict->SetInteger("last_accepted_stream_id", static_cast<int>(last_stream_id));
  dict->SetInteger("active_streams", active_streams);
  dict->SetInteger("unclaimed_streams", unclaimed_streams);
  dict->SetString(
      "error_code",
      SpdyStringPrintf("%u (%s)", error_code, ErrorCodeToString(error_code)));
  dict->SetString("debug_data",
                  ElideGoAwayDebugDataForNetLog(capture_mode, debug_data));
  return std::move(dict);
}

std::unique_ptr<base::Value> NetLogSpdyPushPromiseReceivedCallback(
    const SpdyHeaderBlock* headers,
    SpdyStreamId stream_id,
    SpdyStreamId promised_stream_id,
    NetLogCaptureMode capture_mode) {
  auto dict = std::make_unique<base::DictionaryValue>();
  dict->Set("headers", ElideSpdyHeaderBlockForNetLog(*headers, capture_mode));
  dict->SetInteger("id", stream_id);
  dict->SetInteger("promised_stream_id", promised_stream_id);
  return std::move(dict);
}

std::unique_ptr<base::Value> NetLogSpdyAdoptedPushStreamCallback(
    SpdyStreamId stream_id,
    const GURL* url,
    NetLogCaptureMode capture_mode) {
  auto dict = std::make_unique<base::DictionaryValue>();
  dict->SetInteger("stream_id", stream_id);
  dict->SetString("url", url->spec());
  return std::move(dict);
}

std::unique_ptr<base::Value> NetLogSpdySessionStalledCallback(
    size_t num_active_streams,
    size_t num_created_streams,
    size_t num_pushed_streams,
    size_t max_concurrent_streams,
    const SpdyString& url,
    NetLogCaptureMode capture_mode) {
  auto dict = std::make_unique<base::DictionaryValue>();
  dict->SetInteger("num_active_streams", num_active_streams);
  dict->SetInteger("num_created_streams", num_created_streams);
  dict->SetInteger("num_pushed_streams", num_pushed_streams);
  dict->SetInteger("max_concurrent_streams", max_concurrent_streams);
  dict->SetString("url", url);
  return std::move(dict);
}

std::unique_ptr<base::Value> NetLogSpdyPriorityCallback(
    SpdyStreamId stream_id,
    SpdyStreamId parent_stream_id,
    int weight,
    bool exclusive,
    NetLogCaptureMode capture_mode) {
  auto dict = std::make_unique<base::DictionaryValue>();
  dict->SetInteger("stream_id", stream_id);
  dict->SetInteger("parent_stream_id", parent_stream_id);
  dict->SetInteger("weight", weight);
  dict->SetBoolean("exclusive", exclusive);
  return std::move(dict);
}

// Helper function to return the total size of an array of objects
// with .size() member functions.
template <typename T, size_t N>
size_t GetTotalSize(const T (&arr)[N]) {
  size_t total_size = 0;
  for (size_t i = 0; i < N; ++i) {
    total_size += arr[i].size();
  }
  return total_size;
}

// Helper class for std:find_if on STL container containing
// SpdyStreamRequest weak pointers.
class RequestEquals {
 public:
  explicit RequestEquals(const base::WeakPtr<SpdyStreamRequest>& request)
      : request_(request) {}

  bool operator()(const base::WeakPtr<SpdyStreamRequest>& request) const {
    return request_.get() == request.get();
  }

 private:
  const base::WeakPtr<SpdyStreamRequest> request_;
};

// The maximum number of concurrent streams we will ever create.  Even if
// the server permits more, we will never exceed this limit.
const size_t kMaxConcurrentStreamLimit = 256;

class SpdyServerPushHelper : public ServerPushDelegate::ServerPushHelper {
 public:
  explicit SpdyServerPushHelper(base::WeakPtr<SpdySession> session,
                                const GURL& url)
      : session_(session), request_url_(url) {}

  void Cancel() override {
    if (session_)
      session_->CancelPush(request_url_);
  }

  const GURL& GetURL() const override { return request_url_; }

 private:
  base::WeakPtr<SpdySession> session_;
  const GURL request_url_;
};

}  // namespace

SpdyProtocolErrorDetails MapFramerErrorToProtocolError(
    Http2DecoderAdapter::SpdyFramerError err) {
  switch (err) {
    case Http2DecoderAdapter::SPDY_NO_ERROR:
      return SPDY_ERROR_NO_ERROR;
    case Http2DecoderAdapter::SPDY_INVALID_STREAM_ID:
      return SPDY_ERROR_INVALID_STREAM_ID;
    case Http2DecoderAdapter::SPDY_INVALID_CONTROL_FRAME:
      return SPDY_ERROR_INVALID_CONTROL_FRAME;
    case Http2DecoderAdapter::SPDY_CONTROL_PAYLOAD_TOO_LARGE:
      return SPDY_ERROR_CONTROL_PAYLOAD_TOO_LARGE;
    case Http2DecoderAdapter::SPDY_ZLIB_INIT_FAILURE:
      return SPDY_ERROR_ZLIB_INIT_FAILURE;
    case Http2DecoderAdapter::SPDY_UNSUPPORTED_VERSION:
      return SPDY_ERROR_UNSUPPORTED_VERSION;
    case Http2DecoderAdapter::SPDY_DECOMPRESS_FAILURE:
      return SPDY_ERROR_DECOMPRESS_FAILURE;
    case Http2DecoderAdapter::SPDY_COMPRESS_FAILURE:
      return SPDY_ERROR_COMPRESS_FAILURE;
    case Http2DecoderAdapter::SPDY_GOAWAY_FRAME_CORRUPT:
      return SPDY_ERROR_GOAWAY_FRAME_CORRUPT;
    case Http2DecoderAdapter::SPDY_RST_STREAM_FRAME_CORRUPT:
      return SPDY_ERROR_RST_STREAM_FRAME_CORRUPT;
    case Http2DecoderAdapter::SPDY_INVALID_PADDING:
      return SPDY_ERROR_INVALID_PADDING;
    case Http2DecoderAdapter::SPDY_INVALID_DATA_FRAME_FLAGS:
      return SPDY_ERROR_INVALID_DATA_FRAME_FLAGS;
    case Http2DecoderAdapter::SPDY_INVALID_CONTROL_FRAME_FLAGS:
      return SPDY_ERROR_INVALID_CONTROL_FRAME_FLAGS;
    case Http2DecoderAdapter::SPDY_UNEXPECTED_FRAME:
      return SPDY_ERROR_UNEXPECTED_FRAME;
    case Http2DecoderAdapter::SPDY_INTERNAL_FRAMER_ERROR:
      return SPDY_ERROR_INTERNAL_FRAMER_ERROR;
    case Http2DecoderAdapter::SPDY_INVALID_CONTROL_FRAME_SIZE:
      return SPDY_ERROR_INVALID_CONTROL_FRAME_SIZE;
    case Http2DecoderAdapter::SPDY_OVERSIZED_PAYLOAD:
      return SPDY_ERROR_OVERSIZED_PAYLOAD;
    case Http2DecoderAdapter::LAST_ERROR:
      NOTREACHED();
  }
  NOTREACHED();
  return static_cast<SpdyProtocolErrorDetails>(-1);
}

Error MapFramerErrorToNetError(Http2DecoderAdapter::SpdyFramerError err) {
  switch (err) {
    case Http2DecoderAdapter::SPDY_NO_ERROR:
      return OK;
    case Http2DecoderAdapter::SPDY_INVALID_CONTROL_FRAME:
      return ERR_SPDY_PROTOCOL_ERROR;
    case Http2DecoderAdapter::SPDY_CONTROL_PAYLOAD_TOO_LARGE:
      return ERR_SPDY_FRAME_SIZE_ERROR;
    case Http2DecoderAdapter::SPDY_ZLIB_INIT_FAILURE:
      return ERR_SPDY_COMPRESSION_ERROR;
    case Http2DecoderAdapter::SPDY_UNSUPPORTED_VERSION:
      return ERR_SPDY_PROTOCOL_ERROR;
    case Http2DecoderAdapter::SPDY_DECOMPRESS_FAILURE:
      return ERR_SPDY_COMPRESSION_ERROR;
    case Http2DecoderAdapter::SPDY_COMPRESS_FAILURE:
      return ERR_SPDY_COMPRESSION_ERROR;
    case Http2DecoderAdapter::SPDY_GOAWAY_FRAME_CORRUPT:
      return ERR_SPDY_PROTOCOL_ERROR;
    case Http2DecoderAdapter::SPDY_RST_STREAM_FRAME_CORRUPT:
      return ERR_SPDY_PROTOCOL_ERROR;
    case Http2DecoderAdapter::SPDY_INVALID_PADDING:
      return ERR_SPDY_PROTOCOL_ERROR;
    case Http2DecoderAdapter::SPDY_INVALID_DATA_FRAME_FLAGS:
      return ERR_SPDY_PROTOCOL_ERROR;
    case Http2DecoderAdapter::SPDY_INVALID_CONTROL_FRAME_FLAGS:
      return ERR_SPDY_PROTOCOL_ERROR;
    case Http2DecoderAdapter::SPDY_UNEXPECTED_FRAME:
      return ERR_SPDY_PROTOCOL_ERROR;
    case Http2DecoderAdapter::SPDY_INTERNAL_FRAMER_ERROR:
      return ERR_SPDY_PROTOCOL_ERROR;
    case Http2DecoderAdapter::SPDY_INVALID_CONTROL_FRAME_SIZE:
      return ERR_SPDY_FRAME_SIZE_ERROR;
    case Http2DecoderAdapter::SPDY_INVALID_STREAM_ID:
      return ERR_SPDY_PROTOCOL_ERROR;
    case Http2DecoderAdapter::SPDY_OVERSIZED_PAYLOAD:
      return ERR_SPDY_FRAME_SIZE_ERROR;
    case Http2DecoderAdapter::LAST_ERROR:
      NOTREACHED();
  }
  NOTREACHED();
  return ERR_SPDY_PROTOCOL_ERROR;
}

SpdyProtocolErrorDetails MapRstStreamStatusToProtocolError(
    SpdyErrorCode error_code) {
  switch (error_code) {
    case ERROR_CODE_NO_ERROR:
      return STATUS_CODE_NO_ERROR;
    case ERROR_CODE_PROTOCOL_ERROR:
      return STATUS_CODE_PROTOCOL_ERROR;
    case ERROR_CODE_INTERNAL_ERROR:
      return STATUS_CODE_INTERNAL_ERROR;
    case ERROR_CODE_FLOW_CONTROL_ERROR:
      return STATUS_CODE_FLOW_CONTROL_ERROR;
    case ERROR_CODE_SETTINGS_TIMEOUT:
      return STATUS_CODE_SETTINGS_TIMEOUT;
    case ERROR_CODE_STREAM_CLOSED:
      return STATUS_CODE_STREAM_CLOSED;
    case ERROR_CODE_FRAME_SIZE_ERROR:
      return STATUS_CODE_FRAME_SIZE_ERROR;
    case ERROR_CODE_REFUSED_STREAM:
      return STATUS_CODE_REFUSED_STREAM;
    case ERROR_CODE_CANCEL:
      return STATUS_CODE_CANCEL;
    case ERROR_CODE_COMPRESSION_ERROR:
      return STATUS_CODE_COMPRESSION_ERROR;
    case ERROR_CODE_CONNECT_ERROR:
      return STATUS_CODE_CONNECT_ERROR;
    case ERROR_CODE_ENHANCE_YOUR_CALM:
      return STATUS_CODE_ENHANCE_YOUR_CALM;
    case ERROR_CODE_INADEQUATE_SECURITY:
      return STATUS_CODE_INADEQUATE_SECURITY;
    case ERROR_CODE_HTTP_1_1_REQUIRED:
      return STATUS_CODE_HTTP_1_1_REQUIRED;
  }
  NOTREACHED();
  return static_cast<SpdyProtocolErrorDetails>(-1);
}

SpdyErrorCode MapNetErrorToGoAwayStatus(Error err) {
  switch (err) {
    case OK:
      return ERROR_CODE_NO_ERROR;
    case ERR_SPDY_PROTOCOL_ERROR:
      return ERROR_CODE_PROTOCOL_ERROR;
    case ERR_SPDY_FLOW_CONTROL_ERROR:
      return ERROR_CODE_FLOW_CONTROL_ERROR;
    case ERR_SPDY_FRAME_SIZE_ERROR:
      return ERROR_CODE_FRAME_SIZE_ERROR;
    case ERR_SPDY_COMPRESSION_ERROR:
      return ERROR_CODE_COMPRESSION_ERROR;
    case ERR_SPDY_INADEQUATE_TRANSPORT_SECURITY:
      return ERROR_CODE_INADEQUATE_SECURITY;
    default:
      return ERROR_CODE_PROTOCOL_ERROR;
  }
}

SpdyStreamRequest::SpdyStreamRequest() : weak_ptr_factory_(this) {
  Reset();
}

SpdyStreamRequest::~SpdyStreamRequest() {
  CancelRequest();
}

int SpdyStreamRequest::StartRequest(SpdyStreamType type,
                                    const base::WeakPtr<SpdySession>& session,
                                    const GURL& url,
                                    RequestPriority priority,
                                    const NetLogWithSource& net_log,
                                    const CompletionCallback& callback) {
  DCHECK(session);
  DCHECK(!session_);
  DCHECK(!stream_);
  DCHECK(callback_.is_null());

  type_ = type;
  session_ = session;
  url_ = url;
  priority_ = priority;
  net_log_ = net_log;
  callback_ = callback;

  base::WeakPtr<SpdyStream> stream;
  int rv = session->TryCreateStream(weak_ptr_factory_.GetWeakPtr(), &stream);
  if (rv == OK) {
    Reset();
    stream_ = stream;
  }
  return rv;
}

void SpdyStreamRequest::CancelRequest() {
  if (session_)
    session_->CancelStreamRequest(weak_ptr_factory_.GetWeakPtr());
  Reset();
  // Do this to cancel any pending CompleteStreamRequest() tasks.
  weak_ptr_factory_.InvalidateWeakPtrs();
}

base::WeakPtr<SpdyStream> SpdyStreamRequest::ReleaseStream() {
  DCHECK(!session_);
  base::WeakPtr<SpdyStream> stream = stream_;
  DCHECK(stream);
  Reset();
  return stream;
}

size_t SpdyStreamRequest::EstimateMemoryUsage() const {
  return base::trace_event::EstimateItemMemoryUsage(url_);
}

void SpdyStreamRequest::OnRequestCompleteSuccess(
    const base::WeakPtr<SpdyStream>& stream) {
  DCHECK(session_);
  DCHECK(!stream_);
  DCHECK(!callback_.is_null());
  CompletionCallback callback = callback_;
  Reset();
  DCHECK(stream);
  stream_ = stream;
  callback.Run(OK);
}

void SpdyStreamRequest::OnRequestCompleteFailure(int rv) {
  DCHECK(session_);
  DCHECK(!stream_);
  DCHECK(!callback_.is_null());
  CompletionCallback callback = callback_;
  Reset();
  DCHECK_NE(rv, OK);
  callback.Run(rv);
}

void SpdyStreamRequest::Reset() {
  type_ = SPDY_BIDIRECTIONAL_STREAM;
  session_.reset();
  stream_.reset();
  url_ = GURL();
  priority_ = MINIMUM_PRIORITY;
  net_log_ = NetLogWithSource();
  callback_.Reset();
}

// static
bool SpdySession::CanPool(TransportSecurityState* transport_security_state,
                          const SSLInfo& ssl_info,
                          const SpdyString& old_hostname,
                          const SpdyString& new_hostname) {
  // Pooling is prohibited if the server cert is not valid for the new domain,
  // and for connections on which client certs were sent. It is also prohibited
  // when channel ID was sent if the hosts are from different eTLDs+1.
  if (IsCertStatusError(ssl_info.cert_status))
    return false;

  if (ssl_info.client_cert_sent)
    return false;

  if (ssl_info.channel_id_sent &&
      ChannelIDService::GetDomainForHost(new_hostname) !=
          ChannelIDService::GetDomainForHost(old_hostname)) {
    return false;
  }

  if (!ssl_info.cert->VerifyNameMatch(new_hostname, false))
    return false;

  SpdyString pinning_failure_log;
  // DISABLE_PIN_REPORTS is set here because this check can fail in
  // normal operation without being indicative of a misconfiguration or
  // attack. Port is left at 0 as it is never used.
  if (transport_security_state->CheckPublicKeyPins(
          HostPortPair(new_hostname, 0), ssl_info.is_issued_by_known_root,
          ssl_info.public_key_hashes, ssl_info.unverified_cert.get(),
          ssl_info.cert.get(), TransportSecurityState::DISABLE_PIN_REPORTS,
          &pinning_failure_log) ==
      TransportSecurityState::PKPStatus::VIOLATED) {
    return false;
  }

  // As with CheckPublicKeyPins above, disable Expect-CT reports.
  switch (transport_security_state->CheckCTRequirements(
      HostPortPair(new_hostname, 0), ssl_info.is_issued_by_known_root,
      ssl_info.public_key_hashes, ssl_info.cert.get(),
      ssl_info.unverified_cert.get(), ssl_info.signed_certificate_timestamps,
      TransportSecurityState::DISABLE_EXPECT_CT_REPORTS,
      ssl_info.ct_policy_compliance)) {
    case TransportSecurityState::CT_REQUIREMENTS_NOT_MET:
      return false;
    case TransportSecurityState::CT_REQUIREMENTS_MET:
    case TransportSecurityState::CT_NOT_REQUIRED:
      // Intentional fallthrough; this case is just here to make sure that all
      // possible values of CheckCTRequirements() are handled.
      break;
  }

  return true;
}

SpdySession::SpdySession(
    const SpdySessionKey& spdy_session_key,
    HttpServerProperties* http_server_properties,
    TransportSecurityState* transport_security_state,
    const QuicTransportVersionVector& quic_supported_versions,
    bool enable_sending_initial_data,
    bool enable_ping_based_connection_checking,
    bool support_ietf_format_quic_altsvc,
    size_t session_max_recv_window_size,
    const SettingsMap& initial_settings,
    TimeFunc time_func,
    ServerPushDelegate* push_delegate,
    ProxyDelegate* proxy_delegate,
    NetLog* net_log)
    : in_io_loop_(false),
      spdy_session_key_(spdy_session_key),
      pool_(NULL),
      http_server_properties_(http_server_properties),
      transport_security_state_(transport_security_state),
      stream_hi_water_mark_(kFirstStreamId),
      last_accepted_push_stream_id_(0),
      unclaimed_pushed_streams_(this),
      push_delegate_(push_delegate),
      num_pushed_streams_(0u),
      num_active_pushed_streams_(0u),
      bytes_pushed_count_(0u),
      bytes_pushed_and_unclaimed_count_(0u),
      in_flight_write_frame_type_(SpdyFrameType::DATA),
      in_flight_write_frame_size_(0),
      availability_state_(STATE_AVAILABLE),
      read_state_(READ_STATE_DO_READ),
      write_state_(WRITE_STATE_IDLE),
      error_on_close_(OK),
      initial_settings_(initial_settings),
      max_concurrent_streams_(kInitialMaxConcurrentStreams),
      max_concurrent_pushed_streams_(
          initial_settings.at(SETTINGS_MAX_CONCURRENT_STREAMS)),
      streams_initiated_count_(0),
      streams_pushed_count_(0),
      streams_pushed_and_claimed_count_(0),
      streams_abandoned_count_(0),
      pings_in_flight_(0),
      next_ping_id_(1),
      last_read_time_(time_func()),
      last_compressed_frame_len_(0),
      check_ping_status_pending_(false),
      session_send_window_size_(0),
      session_max_recv_window_size_(session_max_recv_window_size),
      session_recv_window_size_(0),
      session_unacked_recv_window_bytes_(0),
      stream_initial_send_window_size_(kDefaultInitialWindowSize),
      max_header_table_size_(initial_settings.at(SETTINGS_HEADER_TABLE_SIZE)),
      stream_max_recv_window_size_(
          initial_settings.at(SETTINGS_INITIAL_WINDOW_SIZE)),
      net_log_(
          NetLogWithSource::Make(net_log, NetLogSourceType::HTTP2_SESSION)),
      quic_supported_versions_(quic_supported_versions),
      enable_sending_initial_data_(enable_sending_initial_data),
      enable_ping_based_connection_checking_(
          enable_ping_based_connection_checking),
      support_ietf_format_quic_altsvc_(support_ietf_format_quic_altsvc),
      connection_at_risk_of_loss_time_(
          base::TimeDelta::FromSeconds(kDefaultConnectionAtRiskOfLossSeconds)),
      hung_interval_(base::TimeDelta::FromSeconds(kHungIntervalSeconds)),
      proxy_delegate_(proxy_delegate),
      time_func_(time_func),
      weak_factory_(this) {
  net_log_.BeginEvent(
      NetLogEventType::HTTP2_SESSION,
      base::Bind(&NetLogSpdySessionCallback, &host_port_proxy_pair()));

  DCHECK(base::ContainsKey(initial_settings_, SETTINGS_HEADER_TABLE_SIZE));
  DCHECK(base::ContainsKey(initial_settings_, SETTINGS_MAX_CONCURRENT_STREAMS));
  DCHECK(base::ContainsKey(initial_settings_, SETTINGS_INITIAL_WINDOW_SIZE));

  // TODO(mbelshe): consider randomization of the stream_hi_water_mark.
}

SpdySession::~SpdySession() {
  CHECK(!in_io_loop_);
  DcheckDraining();

  // TODO(akalin): Check connection->is_initialized() instead. This
  // requires re-working CreateFakeSpdySession(), though.
  DCHECK(connection_->socket());
  // With SPDY we can't recycle sockets.
  connection_->socket()->Disconnect();

  RecordHistograms();

  net_log_.EndEvent(NetLogEventType::HTTP2_SESSION);
}

int SpdySession::GetPushStream(const GURL& url,
                               RequestPriority priority,
                               SpdyStream** stream,
                               const NetLogWithSource& stream_net_log) {
  CHECK(!in_io_loop_);

  if (availability_state_ == STATE_DRAINING) {
    *stream = nullptr;
    return ERR_CONNECTION_CLOSED;
  }

  *stream = GetActivePushStream(url);
  if (!*stream)
    return OK;

  DCHECK_LT(streams_pushed_and_claimed_count_, streams_pushed_count_);
  streams_pushed_and_claimed_count_++;

  if ((*stream)->IsClosed() || (*stream)->priority() == priority)
    return OK;

  // If the stream is still open, update its priority to that of the request.
  (*stream)->set_priority(priority);

  // Send PRIORITY updates.
  auto updates = priority_dependency_state_.OnStreamUpdate(
      (*stream)->stream_id(), ConvertRequestPriorityToSpdyPriority(priority));
  for (auto u : updates) {
    ActiveStreamMap::iterator it = active_streams_.find(u.id);
    DCHECK(it != active_streams_.end());
    int weight = Spdy3PriorityToHttp2Weight(
        ConvertRequestPriorityToSpdyPriority(it->second->priority()));
    EnqueuePriorityFrame(u.id, u.dependent_stream_id, weight, u.exclusive);
  }

  return OK;
}

void SpdySession::CancelPush(const GURL& url) {
  UnclaimedPushedStreamContainer::const_iterator unclaimed_it =
      unclaimed_pushed_streams_.find(url);
  if (unclaimed_it == unclaimed_pushed_streams_.end())
    return;

  const SpdyStreamId stream_id = unclaimed_it->second;
  DCHECK(active_streams_.find(stream_id) != active_streams_.end());
  ResetStream(stream_id, ERROR_CODE_CANCEL, "Cancelled push stream.");
}

void SpdySession::InitializeWithSocket(
    std::unique_ptr<ClientSocketHandle> connection,
    SpdySessionPool* pool) {
  CHECK(!in_io_loop_);
  DCHECK_EQ(availability_state_, STATE_AVAILABLE);
  DCHECK_EQ(read_state_, READ_STATE_DO_READ);
  DCHECK_EQ(write_state_, WRITE_STATE_IDLE);
  DCHECK(!connection_);

  // TODO(akalin): Check connection->is_initialized() instead. This
  // requires re-working CreateFakeSpdySession(), though.
  DCHECK(connection->socket());

  connection_ = std::move(connection);

  session_send_window_size_ = kDefaultInitialWindowSize;
  session_recv_window_size_ = kDefaultInitialWindowSize;

  SettingsMap::const_iterator it =
      initial_settings_.find(SETTINGS_MAX_HEADER_LIST_SIZE);
  uint32_t spdy_max_header_list_size =
      (it == initial_settings_.end()) ? kSpdyMaxHeaderListSize : it->second;
  buffered_spdy_framer_ =
      std::make_unique<BufferedSpdyFramer>(spdy_max_header_list_size, net_log_);
  buffered_spdy_framer_->set_visitor(this);
  buffered_spdy_framer_->set_debug_visitor(this);
  buffered_spdy_framer_->UpdateHeaderDecoderTableSize(max_header_table_size_);

  net_log_.AddEvent(NetLogEventType::HTTP2_SESSION_INITIALIZED,
                    base::Bind(&NetLogSpdyInitializedCallback,
                               connection_->socket()->NetLog().source()));

  DCHECK_EQ(availability_state_, STATE_AVAILABLE);
  connection_->AddHigherLayeredPool(this);
  if (enable_sending_initial_data_)
    SendInitialData();
  pool_ = pool;

  // Bootstrap the read loop.
  base::ThreadTaskRunnerHandle::Get()->PostTask(
      FROM_HERE,
      base::Bind(&SpdySession::PumpReadLoop, weak_factory_.GetWeakPtr(),
                 READ_STATE_DO_READ, OK));
}

bool SpdySession::VerifyDomainAuthentication(const SpdyString& domain) {
  if (availability_state_ == STATE_DRAINING)
    return false;

  SSLInfo ssl_info;
  if (!GetSSLInfo(&ssl_info))
    return true;  // This is not a secure session, so all domains are okay.

  return CanPool(transport_security_state_, ssl_info, host_port_pair().host(),
                 domain);
}

void SpdySession::EnqueueStreamWrite(
    const base::WeakPtr<SpdyStream>& stream,
    SpdyFrameType frame_type,
    std::unique_ptr<SpdyBufferProducer> producer) {
  DCHECK(frame_type == SpdyFrameType::HEADERS ||
         frame_type == SpdyFrameType::DATA);
  EnqueueWrite(stream->priority(), frame_type, std::move(producer), stream);
}

std::unique_ptr<SpdySerializedFrame> SpdySession::CreateHeaders(
    SpdyStreamId stream_id,
    RequestPriority priority,
    SpdyControlFlags flags,
    SpdyHeaderBlock block,
    NetLogSource source_dependency) {
  ActiveStreamMap::const_iterator it = active_streams_.find(stream_id);
  CHECK(it != active_streams_.end());
  CHECK_EQ(it->second->stream_id(), stream_id);

  MaybeSendPrefacePing();

  DCHECK(buffered_spdy_framer_.get());
  SpdyPriority spdy_priority = ConvertRequestPriorityToSpdyPriority(priority);

  bool has_priority = true;
  int weight = Spdy3PriorityToHttp2Weight(spdy_priority);
  SpdyStreamId dependent_stream_id = 0;
  bool exclusive = false;

  priority_dependency_state_.OnStreamCreation(stream_id, spdy_priority,
                                              &dependent_stream_id, &exclusive);

  if (net_log().IsCapturing()) {
    net_log().AddEvent(
        NetLogEventType::HTTP2_SESSION_SEND_HEADERS,
        base::Bind(&NetLogSpdyHeadersSentCallback, &block,
                   (flags & CONTROL_FLAG_FIN) != 0, stream_id, has_priority,
                   weight, dependent_stream_id, exclusive, source_dependency));
  }

  SpdyHeadersIR headers(stream_id, std::move(block));
  headers.set_has_priority(has_priority);
  headers.set_weight(weight);
  headers.set_parent_stream_id(dependent_stream_id);
  headers.set_exclusive(exclusive);
  headers.set_fin((flags & CONTROL_FLAG_FIN) != 0);

  streams_initiated_count_++;

  return std::make_unique<SpdySerializedFrame>(
      buffered_spdy_framer_->SerializeFrame(headers));
}

std::unique_ptr<SpdyBuffer> SpdySession::CreateDataBuffer(
    SpdyStreamId stream_id,
    IOBuffer* data,
    int len,
    SpdyDataFlags flags) {
  if (availability_state_ == STATE_DRAINING) {
    return std::unique_ptr<SpdyBuffer>();
  }

  ActiveStreamMap::const_iterator it = active_streams_.find(stream_id);
  CHECK(it != active_streams_.end());
  SpdyStream* stream = it->second;
  CHECK_EQ(stream->stream_id(), stream_id);

  if (len < 0) {
    NOTREACHED();
    return std::unique_ptr<SpdyBuffer>();
  }

  int effective_len = std::min(len, kMaxSpdyFrameChunkSize);

  bool send_stalled_by_stream = (stream->send_window_size() <= 0);
  bool send_stalled_by_session = IsSendStalled();

  // NOTE: There's an enum of the same name in histograms.xml.
  enum SpdyFrameFlowControlState {
    SEND_NOT_STALLED,
    SEND_STALLED_BY_STREAM,
    SEND_STALLED_BY_SESSION,
    SEND_STALLED_BY_STREAM_AND_SESSION,
  };

  SpdyFrameFlowControlState frame_flow_control_state = SEND_NOT_STALLED;
  if (send_stalled_by_stream) {
    if (send_stalled_by_session) {
      frame_flow_control_state = SEND_STALLED_BY_STREAM_AND_SESSION;
    } else {
      frame_flow_control_state = SEND_STALLED_BY_STREAM;
    }
  } else if (send_stalled_by_session) {
    frame_flow_control_state = SEND_STALLED_BY_SESSION;
  }

  UMA_HISTOGRAM_ENUMERATION("Net.SpdyFrameStreamAndSessionFlowControlState",
                            frame_flow_control_state,
                            SEND_STALLED_BY_STREAM_AND_SESSION + 1);

  // Obey send window size of the stream.
  if (send_stalled_by_stream) {
    stream->set_send_stalled_by_flow_control(true);
    // Even though we're currently stalled only by the stream, we
    // might end up being stalled by the session also.
    QueueSendStalledStream(*stream);
    net_log().AddEvent(
        NetLogEventType::HTTP2_SESSION_STREAM_STALLED_BY_STREAM_SEND_WINDOW,
        NetLog::IntCallback("stream_id", stream_id));
    return std::unique_ptr<SpdyBuffer>();
  }

  effective_len = std::min(effective_len, stream->send_window_size());

  // Obey send window size of the session.
  if (send_stalled_by_session) {
    stream->set_send_stalled_by_flow_control(true);
    QueueSendStalledStream(*stream);
    net_log().AddEvent(
        NetLogEventType::HTTP2_SESSION_STREAM_STALLED_BY_SESSION_SEND_WINDOW,
        NetLog::IntCallback("stream_id", stream_id));
    return std::unique_ptr<SpdyBuffer>();
  }

  effective_len = std::min(effective_len, session_send_window_size_);

  DCHECK_GE(effective_len, 0);

  // Clear FIN flag if only some of the data will be in the data
  // frame.
  if (effective_len < len)
    flags = static_cast<SpdyDataFlags>(flags & ~DATA_FLAG_FIN);

  if (net_log().IsCapturing()) {
    net_log().AddEvent(NetLogEventType::HTTP2_SESSION_SEND_DATA,
                       base::Bind(&NetLogSpdyDataCallback, stream_id,
                                  effective_len, (flags & DATA_FLAG_FIN) != 0));
  }

  // Send PrefacePing for DATA_FRAMEs with nonzero payload size.
  if (effective_len > 0)
    MaybeSendPrefacePing();

  // TODO(mbelshe): reduce memory copies here.
  DCHECK(buffered_spdy_framer_.get());
  std::unique_ptr<SpdySerializedFrame> frame(
      buffered_spdy_framer_->CreateDataFrame(
          stream_id, data->data(), static_cast<uint32_t>(effective_len),
          flags));

  auto data_buffer = std::make_unique<SpdyBuffer>(std::move(frame));

  // Send window size is based on payload size, so nothing to do if this is
  // just a FIN with no payload.
  if (effective_len != 0) {
    DecreaseSendWindowSize(static_cast<int32_t>(effective_len));
    data_buffer->AddConsumeCallback(base::Bind(
        &SpdySession::OnWriteBufferConsumed, weak_factory_.GetWeakPtr(),
        static_cast<size_t>(effective_len)));
  }

  return data_buffer;
}

void SpdySession::CloseActiveStream(SpdyStreamId stream_id, int status) {
  DCHECK_NE(stream_id, 0u);

  ActiveStreamMap::iterator it = active_streams_.find(stream_id);
  if (it == active_streams_.end()) {
    NOTREACHED();
    return;
  }

  CloseActiveStreamIterator(it, status);
}

void SpdySession::CloseCreatedStream(const base::WeakPtr<SpdyStream>& stream,
                                     int status) {
  DCHECK_EQ(stream->stream_id(), 0u);

  CreatedStreamSet::iterator it = created_streams_.find(stream.get());
  if (it == created_streams_.end()) {
    NOTREACHED();
    return;
  }

  CloseCreatedStreamIterator(it, status);
}

void SpdySession::ResetStream(SpdyStreamId stream_id,
                              SpdyErrorCode error_code,
                              const SpdyString& description) {
  DCHECK_NE(stream_id, 0u);

  ActiveStreamMap::iterator it = active_streams_.find(stream_id);
  if (it == active_streams_.end()) {
    NOTREACHED();
    return;
  }

  ResetStreamIterator(it, error_code, description);
}

bool SpdySession::IsStreamActive(SpdyStreamId stream_id) const {
  return base::ContainsKey(active_streams_, stream_id);
}

LoadState SpdySession::GetLoadState() const {
  // Just report that we're idle since the session could be doing
  // many things concurrently.
  return LOAD_STATE_IDLE;
}

bool SpdySession::GetRemoteEndpoint(IPEndPoint* endpoint) {
  return GetPeerAddress(endpoint) == OK;
}

bool SpdySession::GetSSLInfo(SSLInfo* ssl_info) const {
  return connection_->socket()->GetSSLInfo(ssl_info);
}

Error SpdySession::GetTokenBindingSignature(crypto::ECPrivateKey* key,
                                            TokenBindingType tb_type,
                                            std::vector<uint8_t>* out) {
  SSLClientSocket* ssl_socket =
      static_cast<SSLClientSocket*>(connection_->socket());
  return ssl_socket->GetTokenBindingSignature(key, tb_type, out);
}

bool SpdySession::WasAlpnNegotiated() const {
  return connection_->socket()->WasAlpnNegotiated();
}

NextProto SpdySession::GetNegotiatedProtocol() const {
  return connection_->socket()->GetNegotiatedProtocol();
}

void SpdySession::SendStreamWindowUpdate(SpdyStreamId stream_id,
                                         uint32_t delta_window_size) {
  ActiveStreamMap::const_iterator it = active_streams_.find(stream_id);
  CHECK(it != active_streams_.end());
  CHECK_EQ(it->second->stream_id(), stream_id);
  SendWindowUpdateFrame(stream_id, delta_window_size, it->second->priority());
}

void SpdySession::CloseSessionOnError(Error err,
                                      const SpdyString& description) {
  DCHECK_LT(err, ERR_IO_PENDING);
  DoDrainSession(err, description);
}

void SpdySession::MakeUnavailable() {
  if (availability_state_ == STATE_AVAILABLE) {
    availability_state_ = STATE_GOING_AWAY;
    pool_->MakeSessionUnavailable(GetWeakPtr());
  }
}

void SpdySession::StartGoingAway(SpdyStreamId last_good_stream_id,
                                 Error status) {
  DCHECK_GE(availability_state_, STATE_GOING_AWAY);

  // The loops below are carefully written to avoid reentrancy problems.

  while (true) {
    size_t old_size = GetTotalSize(pending_create_stream_queues_);
    base::WeakPtr<SpdyStreamRequest> pending_request =
        GetNextPendingStreamRequest();
    if (!pending_request)
      break;
    // No new stream requests should be added while the session is
    // going away.
    DCHECK_GT(old_size, GetTotalSize(pending_create_stream_queues_));
    pending_request->OnRequestCompleteFailure(ERR_ABORTED);
  }

  while (true) {
    size_t old_size = active_streams_.size();
    ActiveStreamMap::iterator it =
        active_streams_.lower_bound(last_good_stream_id + 1);
    if (it == active_streams_.end())
      break;
    LogAbandonedActiveStream(it, status);
    CloseActiveStreamIterator(it, status);
    // No new streams should be activated while the session is going
    // away.
    DCHECK_GT(old_size, active_streams_.size());
  }

  while (!created_streams_.empty()) {
    size_t old_size = created_streams_.size();
    CreatedStreamSet::iterator it = created_streams_.begin();
    LogAbandonedStream(*it, status);
    CloseCreatedStreamIterator(it, status);
    // No new streams should be created while the session is going
    // away.
    DCHECK_GT(old_size, created_streams_.size());
  }

  write_queue_.RemovePendingWritesForStreamsAfter(last_good_stream_id);

  DcheckGoingAway();
  MaybeFinishGoingAway();
}

void SpdySession::MaybeFinishGoingAway() {
  if (active_streams_.empty() && created_streams_.empty() &&
      availability_state_ == STATE_GOING_AWAY) {
    DoDrainSession(OK, "Finished going away");
  }
}

std::unique_ptr<base::Value> SpdySession::GetInfoAsValue() const {
  auto dict = std::make_unique<base::DictionaryValue>();

  dict->SetInteger("source_id", net_log_.source().id);

  dict->SetString("host_port_pair", host_port_pair().ToString());
  if (!pooled_aliases_.empty()) {
    auto alias_list = std::make_unique<base::ListValue>();
    for (const auto& alias : pooled_aliases_) {
      alias_list->AppendString(alias.host_port_pair().ToString());
    }
    dict->Set("aliases", std::move(alias_list));
  }
  dict->SetString("proxy", host_port_proxy_pair().second.ToURI());

  dict->SetInteger("active_streams", active_streams_.size());

  dict->SetInteger("unclaimed_pushed_streams",
                   unclaimed_pushed_streams_.size());

  dict->SetString(
      "negotiated_protocol",
      NextProtoToString(connection_->socket()->GetNegotiatedProtocol()));

  dict->SetInteger("error", error_on_close_);
  dict->SetInteger("max_concurrent_streams", max_concurrent_streams_);

  dict->SetInteger("streams_initiated_count", streams_initiated_count_);
  dict->SetInteger("streams_pushed_count", streams_pushed_count_);
  dict->SetInteger("streams_pushed_and_claimed_count",
                   streams_pushed_and_claimed_count_);
  dict->SetInteger("streams_abandoned_count", streams_abandoned_count_);
  DCHECK(buffered_spdy_framer_.get());
  dict->SetInteger("frames_received", buffered_spdy_framer_->frames_received());

  dict->SetInteger("send_window_size", session_send_window_size_);
  dict->SetInteger("recv_window_size", session_recv_window_size_);
  dict->SetInteger("unacked_recv_window_bytes",
                   session_unacked_recv_window_bytes_);
  return std::move(dict);
}

bool SpdySession::IsReused() const {
  return buffered_spdy_framer_->frames_received() > 0 ||
         connection_->reuse_type() == ClientSocketHandle::UNUSED_IDLE;
}

bool SpdySession::GetLoadTimingInfo(SpdyStreamId stream_id,
                                    LoadTimingInfo* load_timing_info) const {
  return connection_->GetLoadTimingInfo(stream_id != kFirstStreamId,
                                        load_timing_info);
}

size_t SpdySession::num_unclaimed_pushed_streams() const {
  return unclaimed_pushed_streams_.size();
}

size_t SpdySession::count_unclaimed_pushed_streams_for_url(
    const GURL& url) const {
  return unclaimed_pushed_streams_.count(url);
}

int SpdySession::GetPeerAddress(IPEndPoint* address) const {
  if (connection_->socket())
    return connection_->socket()->GetPeerAddress(address);

  return ERR_SOCKET_NOT_CONNECTED;
}

int SpdySession::GetLocalAddress(IPEndPoint* address) const {
  if (connection_->socket())
    return connection_->socket()->GetLocalAddress(address);

  return ERR_SOCKET_NOT_CONNECTED;
}

void SpdySession::AddPooledAlias(const SpdySessionKey& alias_key) {
  pooled_aliases_.insert(alias_key);
}

void SpdySession::RemovePooledAlias(const SpdySessionKey& alias_key) {
  pooled_aliases_.erase(alias_key);
}

bool SpdySession::HasAcceptableTransportSecurity() const {
  SSLInfo ssl_info;
  CHECK(GetSSLInfo(&ssl_info));

  // HTTP/2 requires TLS 1.2+
  if (SSLConnectionStatusToVersion(ssl_info.connection_status) <
      SSL_CONNECTION_VERSION_TLS1_2) {
    return false;
  }

  if (!IsTLSCipherSuiteAllowedByHTTP2(
          SSLConnectionStatusToCipherSuite(ssl_info.connection_status))) {
    return false;
  }

  return true;
}

base::WeakPtr<SpdySession> SpdySession::GetWeakPtr() {
  return weak_factory_.GetWeakPtr();
}

bool SpdySession::CloseOneIdleConnection() {
  CHECK(!in_io_loop_);
  DCHECK(pool_);
  if (active_streams_.empty()) {
    DoDrainSession(ERR_CONNECTION_CLOSED, "Closing idle connection.");
  }
  // Return false as the socket wasn't immediately closed.
  return false;
}

size_t SpdySession::DumpMemoryStats(StreamSocket::SocketMemoryStats* stats,
                                    bool* is_session_active) const {
  // TODO(xunjieli): Include |pending_create_stream_queues_| when WeakPtr is
  // supported in memory_usage_estimator.h.
  *is_session_active = is_active();
  connection_->DumpMemoryStats(stats);

  // |connection_| is estimated in stats->total_size. |read_buffer_| is
  // estimated in |read_buffer_size|. TODO(xunjieli): Make them use EMU().
  size_t read_buffer_size = read_buffer_ ? kReadBufferSize : 0;
  return stats->total_size + read_buffer_size +
         SpdyEstimateMemoryUsage(spdy_session_key_) +
         SpdyEstimateMemoryUsage(pooled_aliases_) +
         SpdyEstimateMemoryUsage(active_streams_) +
         SpdyEstimateMemoryUsage(unclaimed_pushed_streams_) +
         SpdyEstimateMemoryUsage(created_streams_) +
         SpdyEstimateMemoryUsage(write_queue_) +
         SpdyEstimateMemoryUsage(in_flight_write_) +
         SpdyEstimateMemoryUsage(buffered_spdy_framer_) +
         SpdyEstimateMemoryUsage(initial_settings_) +
         SpdyEstimateMemoryUsage(stream_send_unstall_queue_) +
         SpdyEstimateMemoryUsage(priority_dependency_state_);
}

SpdySession::UnclaimedPushedStreamContainer::UnclaimedPushedStreamContainer(
    SpdySession* spdy_session)
    : spdy_session_(spdy_session) {}
SpdySession::UnclaimedPushedStreamContainer::~UnclaimedPushedStreamContainer() {
}

bool SpdySession::UnclaimedPushedStreamContainer::erase(const GURL& url) {
  const_iterator it = find(url);
  if (it == end())
    return false;

  erase(it);
  return true;
}

SpdySession::UnclaimedPushedStreamContainer::iterator
SpdySession::UnclaimedPushedStreamContainer::erase(const_iterator it) {
  DCHECK(spdy_session_->pool_);
  DCHECK(it != end());
  // Only allow cross-origin push for secure resources.
  if (it->first.SchemeIsCryptographic()) {
    spdy_session_->pool_->push_promise_index()->UnregisterUnclaimedPushedStream(
        it->first, spdy_session_);
  }
  return streams_.erase(it);
}

bool SpdySession::UnclaimedPushedStreamContainer::insert(
    const GURL& url,
    SpdyStreamId stream_id) {
  DCHECK(spdy_session_->pool_);
  auto result = streams_.insert(std::make_pair(url, stream_id));
  if (!result.second) {
    // Only one pushed stream is allowed for each URL.
    return false;
  }
  // Only allow cross-origin push for https resources.
  if (url.SchemeIsCryptographic()) {
    spdy_session_->pool_->push_promise_index()->RegisterUnclaimedPushedStream(
        url, spdy_session_->GetWeakPtr());
  }
  return true;
}

size_t SpdySession::UnclaimedPushedStreamContainer::EstimateMemoryUsage()
    const {
  return SpdyEstimateMemoryUsage(streams_);
}

// {,Try}CreateStream() can be called with |in_io_loop_| set if a stream is
// being created in response to another being closed due to received data.

int SpdySession::TryCreateStream(
    const base::WeakPtr<SpdyStreamRequest>& request,
    base::WeakPtr<SpdyStream>* stream) {
  DCHECK(request);

  if (availability_state_ == STATE_GOING_AWAY)
    return ERR_FAILED;

  if (availability_state_ == STATE_DRAINING)
    return ERR_CONNECTION_CLOSED;

  if ((active_streams_.size() + created_streams_.size() - num_pushed_streams_ <
       max_concurrent_streams_)) {
    return CreateStream(*request, stream);
  }

  if (net_log().IsCapturing()) {
    net_log().AddEvent(
        NetLogEventType::HTTP2_SESSION_STALLED_MAX_STREAMS,
        base::Bind(&NetLogSpdySessionStalledCallback, active_streams_.size(),
                   created_streams_.size(), num_pushed_streams_,
                   max_concurrent_streams_, request->url().spec()));
  }
  RequestPriority priority = request->priority();
  CHECK_GE(priority, MINIMUM_PRIORITY);
  CHECK_LE(priority, MAXIMUM_PRIORITY);
  pending_create_stream_queues_[priority].push_back(request);
  return ERR_IO_PENDING;
}

int SpdySession::CreateStream(const SpdyStreamRequest& request,
                              base::WeakPtr<SpdyStream>* stream) {
  DCHECK_GE(request.priority(), MINIMUM_PRIORITY);
  DCHECK_LE(request.priority(), MAXIMUM_PRIORITY);

  if (availability_state_ == STATE_GOING_AWAY)
    return ERR_FAILED;

  if (availability_state_ == STATE_DRAINING)
    return ERR_CONNECTION_CLOSED;

  DCHECK(connection_->socket());
  UMA_HISTOGRAM_BOOLEAN("Net.SpdySession.CreateStreamWithSocketConnected",
                        connection_->socket()->IsConnected());
  if (!connection_->socket()->IsConnected()) {
    DoDrainSession(
        ERR_CONNECTION_CLOSED,
        "Tried to create SPDY stream for a closed socket connection.");
    return ERR_CONNECTION_CLOSED;
  }

  auto new_stream = std::make_unique<SpdyStream>(
      request.type(), GetWeakPtr(), request.url(), request.priority(),
      stream_initial_send_window_size_, stream_max_recv_window_size_,
      request.net_log());
  *stream = new_stream->GetWeakPtr();
  InsertCreatedStream(std::move(new_stream));

  return OK;
}

void SpdySession::CancelStreamRequest(
    const base::WeakPtr<SpdyStreamRequest>& request) {
  DCHECK(request);
  RequestPriority priority = request->priority();
  CHECK_GE(priority, MINIMUM_PRIORITY);
  CHECK_LE(priority, MAXIMUM_PRIORITY);

#if DCHECK_IS_ON()
  // |request| should not be in a queue not matching its priority.
  for (int i = MINIMUM_PRIORITY; i <= MAXIMUM_PRIORITY; ++i) {
    if (priority == i)
      continue;
    PendingStreamRequestQueue* queue = &pending_create_stream_queues_[i];
    DCHECK(std::find_if(queue->begin(), queue->end(), RequestEquals(request)) ==
           queue->end());
  }
#endif

  PendingStreamRequestQueue* queue = &pending_create_stream_queues_[priority];
  // Remove |request| from |queue| while preserving the order of the
  // other elements.
  PendingStreamRequestQueue::iterator it =
      std::find_if(queue->begin(), queue->end(), RequestEquals(request));
  // The request may already be removed if there's a
  // CompleteStreamRequest() in flight.
  if (it != queue->end()) {
    it = queue->erase(it);
    // |request| should be in the queue at most once, and if it is
    // present, should not be pending completion.
    DCHECK(std::find_if(it, queue->end(), RequestEquals(request)) ==
           queue->end());
  }
}

base::WeakPtr<SpdyStreamRequest> SpdySession::GetNextPendingStreamRequest() {
  for (int j = MAXIMUM_PRIORITY; j >= MINIMUM_PRIORITY; --j) {
    if (pending_create_stream_queues_[j].empty())
      continue;

    base::WeakPtr<SpdyStreamRequest> pending_request =
        pending_create_stream_queues_[j].front();
    DCHECK(pending_request);
    pending_create_stream_queues_[j].pop_front();
    return pending_request;
  }
  return base::WeakPtr<SpdyStreamRequest>();
}

void SpdySession::ProcessPendingStreamRequests() {
  size_t max_requests_to_process =
      max_concurrent_streams_ -
      (active_streams_.size() + created_streams_.size());
  for (size_t i = 0; i < max_requests_to_process; ++i) {
    base::WeakPtr<SpdyStreamRequest> pending_request =
        GetNextPendingStreamRequest();
    if (!pending_request)
      break;

    // Note that this post can race with other stream creations, and it's
    // possible that the un-stalled stream will be stalled again if it loses.
    // TODO(jgraettinger): Provide stronger ordering guarantees.
    base::ThreadTaskRunnerHandle::Get()->PostTask(
        FROM_HERE, base::Bind(&SpdySession::CompleteStreamRequest,
                              weak_factory_.GetWeakPtr(), pending_request));
  }
}

void SpdySession::TryCreatePushStream(SpdyStreamId stream_id,
                                      SpdyStreamId associated_stream_id,
                                      SpdyHeaderBlock headers) {
  if ((stream_id & 0x1) != 0) {
    SpdyString description = SpdyStringPrintf(
        "Received invalid pushed stream id %d (must be even) on stream id %d.",
        stream_id, associated_stream_id);
    LOG(WARNING) << description;
    CloseSessionOnError(ERR_SPDY_PROTOCOL_ERROR, description);
    return;
  }

  if ((associated_stream_id & 0x1) != 1) {
    SpdyString description = SpdyStringPrintf(
        "Received pushed stream id %d on invalid stream id %d (must be odd).",
        stream_id, associated_stream_id);
    LOG(WARNING) << description;
    CloseSessionOnError(ERR_SPDY_PROTOCOL_ERROR, description);
    return;
  }

  if (stream_id <= last_accepted_push_stream_id_) {
    SpdyString description = SpdyStringPrintf(
        "Received pushed stream id %d must be larger than last accepted id %d.",
        stream_id, last_accepted_push_stream_id_);
    LOG(WARNING) << description;
    CloseSessionOnError(ERR_SPDY_PROTOCOL_ERROR, description);
    return;
  }

  if (IsStreamActive(stream_id)) {
    // We should not get here, we'll start going away earlier on
    // |last_seen_push_stream_id_| check.
    LOG(WARNING) << "Received push for active stream " << stream_id;
    return;
  }

  last_accepted_push_stream_id_ = stream_id;

  // Pushed streams are speculative, so they start at an IDLE priority.
  const RequestPriority request_priority = IDLE;

  if (availability_state_ == STATE_GOING_AWAY) {
    EnqueueResetStreamFrame(stream_id, request_priority,
                            ERROR_CODE_REFUSED_STREAM,
                            "Push stream request received while going away.");
    return;
  }

  streams_pushed_count_++;

  // Verify that the response had a URL for us.
  GURL gurl = GetUrlFromHeaderBlock(headers);
  if (!gurl.is_valid()) {
    EnqueueResetStreamFrame(
        stream_id, request_priority, ERROR_CODE_REFUSED_STREAM,
        "Pushed stream url was invalid: " + gurl.possibly_invalid_spec());
    return;
  }

  // Verify we have a valid stream association.
  ActiveStreamMap::iterator associated_it =
      active_streams_.find(associated_stream_id);
  if (associated_it == active_streams_.end()) {
    EnqueueResetStreamFrame(stream_id, request_priority,
                            ERROR_CODE_STREAM_CLOSED,
                            "Inactive associated stream.");
    return;
  }

  DCHECK(gurl.is_valid());

  // Cross-origin push validation.
  GURL associated_url(associated_it->second->GetUrlFromHeaders());
  if (associated_url.GetOrigin() != gurl.GetOrigin()) {
    if (proxy_delegate_ &&
        proxy_delegate_->IsTrustedSpdyProxy(
            ProxyServer(ProxyServer::SCHEME_HTTPS, host_port_pair()))) {
      // Disallow pushing of HTTPS content by trusted proxy.
      if (gurl.SchemeIs("https")) {
        EnqueueResetStreamFrame(
            stream_id, request_priority, ERROR_CODE_REFUSED_STREAM,
            "Cross origin HTTPS content from trusted proxy.");
        return;
      }
    } else {
      if (!gurl.SchemeIs("https") || !associated_url.SchemeIs("https")) {
        EnqueueResetStreamFrame(
            stream_id, request_priority, ERROR_CODE_REFUSED_STREAM,
            "Both pushed URL and associated URL must have https scheme.");
        return;
      }
      SSLInfo ssl_info;
      CHECK(GetSSLInfo(&ssl_info));
      if (!CanPool(transport_security_state_, ssl_info, associated_url.host(),
                   gurl.host())) {
        EnqueueResetStreamFrame(stream_id, request_priority,
                                ERROR_CODE_REFUSED_STREAM,
                                "Certificate does not match pushed URL.");
        return;
      }
    }
  }

  // "Promised requests MUST be cacheable and MUST be safe [...]" (RFC7540
  // Section 8.2).  Only cacheable safe request methods are GET and HEAD.
  SpdyHeaderBlock::const_iterator it = headers.find(kHttp2MethodHeader);
  if (it == headers.end() ||
      (it->second.compare("GET") != 0 && it->second.compare("HEAD") != 0)) {
    EnqueueResetStreamFrame(stream_id, request_priority,
                            ERROR_CODE_REFUSED_STREAM,
                            "Inadequate request method.");
    return;
  }

  // Insertion fails if there already is a pushed stream with the same path.
  if (!unclaimed_pushed_streams_.insert(gurl, stream_id)) {
    EnqueueResetStreamFrame(stream_id, request_priority,
                            ERROR_CODE_REFUSED_STREAM,
                            "Duplicate pushed stream with url: " + gurl.spec());
    return;
  }

  base::ThreadTaskRunnerHandle::Get()->PostDelayedTask(
      FROM_HERE,
      base::Bind(&SpdySession::CancelPushedStreamIfUnclaimed, GetWeakPtr(),
                 stream_id),
      base::TimeDelta::FromSeconds(kPushedStreamLifetimeSeconds));

  auto stream = std::make_unique<SpdyStream>(
      SPDY_PUSH_STREAM, GetWeakPtr(), gurl, request_priority,
      stream_initial_send_window_size_, stream_max_recv_window_size_, net_log_);
  stream->set_stream_id(stream_id);

  // Convert RequestPriority to a SpdyPriority to send in a PRIORITY frame.
  SpdyPriority spdy_priority =
      ConvertRequestPriorityToSpdyPriority(request_priority);
  SpdyStreamId dependency_id = 0;
  bool exclusive = false;
  priority_dependency_state_.OnStreamCreation(stream_id, spdy_priority,
                                              &dependency_id, &exclusive);
  EnqueuePriorityFrame(stream_id, dependency_id,
                       Spdy3PriorityToHttp2Weight(spdy_priority), exclusive);

  // PUSH_PROMISE arrives on associated stream.
  associated_it->second->AddRawReceivedBytes(last_compressed_frame_len_);
  last_compressed_frame_len_ = 0;

  InsertActivatedStream(std::move(stream));

  ActiveStreamMap::iterator active_it = active_streams_.find(stream_id);
  if (active_it == active_streams_.end()) {
    NOTREACHED();
    return;
  }

  // Notify the push_delegate that a push promise has been received.
  if (push_delegate_) {
    push_delegate_->OnPush(std::make_unique<SpdyServerPushHelper>(
                               weak_factory_.GetWeakPtr(), gurl),
                           net_log_);
  }

  active_it->second->OnPushPromiseHeadersReceived(std::move(headers));
  DCHECK(active_it->second->IsReservedRemote());
  num_pushed_streams_++;
  return;
}

void SpdySession::CloseActiveStreamIterator(ActiveStreamMap::iterator it,
                                            int status) {
  // TODO(mbelshe): We should send a RST_STREAM control frame here
  //                so that the server can cancel a large send.

  std::unique_ptr<SpdyStream> owned_stream(it->second);
  active_streams_.erase(it);
  priority_dependency_state_.OnStreamDestruction(owned_stream->stream_id());

  // TODO(akalin): When SpdyStream was ref-counted (and
  // |unclaimed_pushed_streams_| held scoped_refptr<SpdyStream>), this
  // was only done when status was not OK. This meant that pushed
  // streams can still be claimed after they're closed. This is
  // probably something that we still want to support, although server
  // push is hardly used. Write tests for this and fix this. (See
  // http://crbug.com/261712 .)
  if (owned_stream->type() == SPDY_PUSH_STREAM) {
    if (unclaimed_pushed_streams_.erase(owned_stream->url())) {
      bytes_pushed_and_unclaimed_count_ += owned_stream->recv_bytes();
    }
    bytes_pushed_count_ += owned_stream->recv_bytes();
    num_pushed_streams_--;
    if (!owned_stream->IsReservedRemote())
      num_active_pushed_streams_--;
  }

  DeleteStream(std::move(owned_stream), status);

  // If there are no active streams and the socket pool is stalled, close the
  // session to free up a socket slot.
  if (active_streams_.empty() && created_streams_.empty() &&
      connection_->IsPoolStalled()) {
    DoDrainSession(ERR_CONNECTION_CLOSED, "Closing idle connection.");
  }
}

void SpdySession::CloseCreatedStreamIterator(CreatedStreamSet::iterator it,
                                             int status) {
  std::unique_ptr<SpdyStream> owned_stream(*it);
  created_streams_.erase(it);
  DeleteStream(std::move(owned_stream), status);
}

void SpdySession::ResetStreamIterator(ActiveStreamMap::iterator it,
                                      SpdyErrorCode error_code,
                                      const SpdyString& description) {
  // Send the RST_STREAM frame first as CloseActiveStreamIterator()
  // may close us.
  SpdyStreamId stream_id = it->first;
  RequestPriority priority = it->second->priority();
  EnqueueResetStreamFrame(stream_id, priority, error_code, description);

  // Removes any pending writes for the stream except for possibly an
  // in-flight one.
  CloseActiveStreamIterator(it, ERR_SPDY_PROTOCOL_ERROR);
}

void SpdySession::EnqueueResetStreamFrame(SpdyStreamId stream_id,
                                          RequestPriority priority,
                                          SpdyErrorCode error_code,
                                          const SpdyString& description) {
  DCHECK_NE(stream_id, 0u);

  net_log().AddEvent(NetLogEventType::HTTP2_SESSION_SEND_RST_STREAM,
                     base::Bind(&NetLogSpdySendRstStreamCallback, stream_id,
                                error_code, &description));

  DCHECK(buffered_spdy_framer_.get());
  std::unique_ptr<SpdySerializedFrame> rst_frame(
      buffered_spdy_framer_->CreateRstStream(stream_id, error_code));

  EnqueueSessionWrite(priority, SpdyFrameType::RST_STREAM,
                      std::move(rst_frame));
  RecordProtocolErrorHistogram(MapRstStreamStatusToProtocolError(error_code));
}

void SpdySession::EnqueuePriorityFrame(SpdyStreamId stream_id,
                                       SpdyStreamId dependency_id,
                                       int weight,
                                       bool exclusive) {
  net_log().AddEvent(NetLogEventType::HTTP2_STREAM_SEND_PRIORITY,
                     base::Bind(&NetLogSpdyPriorityCallback, stream_id,
                                dependency_id, weight, exclusive));

  DCHECK(buffered_spdy_framer_.get());
  std::unique_ptr<SpdySerializedFrame> frame(
      buffered_spdy_framer_->CreatePriority(stream_id, dependency_id, weight,
                                            exclusive));

  // PRIORITY frames describe sequenced updates to the tree, so they must
  // be serialized. We do this by queueing all PRIORITY frames at HIGHEST
  // priority.
  EnqueueWrite(HIGHEST, SpdyFrameType::PRIORITY,
               std::make_unique<SimpleBufferProducer>(
                   std::make_unique<SpdyBuffer>(std::move(frame))),
               base::WeakPtr<SpdyStream>());
}

void SpdySession::PumpReadLoop(ReadState expected_read_state, int result) {
  CHECK(!in_io_loop_);
  if (availability_state_ == STATE_DRAINING) {
    return;
  }
  ignore_result(DoReadLoop(expected_read_state, result));
}

int SpdySession::DoReadLoop(ReadState expected_read_state, int result) {
  CHECK(!in_io_loop_);
  CHECK_EQ(read_state_, expected_read_state);

  in_io_loop_ = true;

  int bytes_read_without_yielding = 0;
  const base::TimeTicks yield_after_time =
      time_func_() +
      base::TimeDelta::FromMilliseconds(kYieldAfterDurationMilliseconds);

  // Loop until the session is draining, the read becomes blocked, or
  // the read limit is exceeded.
  while (true) {
    switch (read_state_) {
      case READ_STATE_DO_READ:
        CHECK_EQ(result, OK);
        result = DoRead();
        break;
      case READ_STATE_DO_READ_COMPLETE:
        if (result > 0)
          bytes_read_without_yielding += result;
        result = DoReadComplete(result);
        break;
      default:
        NOTREACHED() << "read_state_: " << read_state_;
        break;
    }

    if (availability_state_ == STATE_DRAINING)
      break;

    if (result == ERR_IO_PENDING)
      break;

    if (read_state_ == READ_STATE_DO_READ &&
        (bytes_read_without_yielding > kYieldAfterBytesRead ||
         time_func_() > yield_after_time)) {
      base::ThreadTaskRunnerHandle::Get()->PostTask(
          FROM_HERE,
          base::Bind(&SpdySession::PumpReadLoop, weak_factory_.GetWeakPtr(),
                     READ_STATE_DO_READ, OK));
      result = ERR_IO_PENDING;
      break;
    }
  }

  CHECK(in_io_loop_);
  in_io_loop_ = false;

  return result;
}

int SpdySession::DoRead() {
  DCHECK(!read_buffer_);
  CHECK(in_io_loop_);

  CHECK(connection_);
  CHECK(connection_->socket());
  read_state_ = READ_STATE_DO_READ_COMPLETE;
  int rv = ERR_READ_IF_READY_NOT_IMPLEMENTED;
  read_buffer_ = new IOBuffer(kReadBufferSize);
  if (base::FeatureList::IsEnabled(Socket::kReadIfReadyExperiment)) {
    rv = connection_->socket()->ReadIfReady(
        read_buffer_.get(), kReadBufferSize,
        base::Bind(&SpdySession::PumpReadLoop, weak_factory_.GetWeakPtr(),
                   READ_STATE_DO_READ));
    if (rv == ERR_IO_PENDING) {
      read_buffer_ = nullptr;
      read_state_ = READ_STATE_DO_READ;
      return rv;
    }
  }
  if (rv == ERR_READ_IF_READY_NOT_IMPLEMENTED) {
    // Fallback to regular Read().
    return connection_->socket()->Read(
        read_buffer_.get(), kReadBufferSize,
        base::Bind(&SpdySession::PumpReadLoop, weak_factory_.GetWeakPtr(),
                   READ_STATE_DO_READ_COMPLETE));
  }
  return rv;
}

int SpdySession::DoReadComplete(int result) {
  DCHECK(read_buffer_);
  CHECK(in_io_loop_);

  // Parse a frame.  For now this code requires that the frame fit into our
  // buffer (kReadBufferSize).
  // TODO(mbelshe): support arbitrarily large frames!

  if (result == 0) {
    DoDrainSession(ERR_CONNECTION_CLOSED, "Connection closed");
    return ERR_CONNECTION_CLOSED;
  }

  if (result < 0) {
    DoDrainSession(static_cast<Error>(result),
                   SpdyStringPrintf("Error %d reading from socket.", -result));
    return result;
  }
  CHECK_LE(result, kReadBufferSize);

  last_read_time_ = time_func_();

  DCHECK(buffered_spdy_framer_.get());
  char* data = read_buffer_->data();
  while (result > 0) {
    uint32_t bytes_processed =
        buffered_spdy_framer_->ProcessInput(data, result);
    result -= bytes_processed;
    data += bytes_processed;

    if (availability_state_ == STATE_DRAINING) {
      return ERR_CONNECTION_CLOSED;
    }

    DCHECK_EQ(buffered_spdy_framer_->spdy_framer_error(),
              Http2DecoderAdapter::SPDY_NO_ERROR);
  }

  read_buffer_ = nullptr;
  read_state_ = READ_STATE_DO_READ;
  return OK;
}

void SpdySession::PumpWriteLoop(WriteState expected_write_state, int result) {
  CHECK(!in_io_loop_);
  DCHECK_EQ(write_state_, expected_write_state);

  DoWriteLoop(expected_write_state, result);

  if (availability_state_ == STATE_DRAINING && !in_flight_write_ &&
      write_queue_.IsEmpty()) {
    pool_->RemoveUnavailableSession(GetWeakPtr());  // Destroys |this|.
    return;
  }
}

void SpdySession::MaybePostWriteLoop() {
  if (write_state_ == WRITE_STATE_IDLE) {
    CHECK(!in_flight_write_);
    write_state_ = WRITE_STATE_DO_WRITE;
    base::ThreadTaskRunnerHandle::Get()->PostTask(
        FROM_HERE,
        base::Bind(&SpdySession::PumpWriteLoop, weak_factory_.GetWeakPtr(),
                   WRITE_STATE_DO_WRITE, OK));
  }
}

int SpdySession::DoWriteLoop(WriteState expected_write_state, int result) {
  CHECK(!in_io_loop_);
  DCHECK_NE(write_state_, WRITE_STATE_IDLE);
  DCHECK_EQ(write_state_, expected_write_state);

  in_io_loop_ = true;

  // Loop until the session is closed or the write becomes blocked.
  while (true) {
    switch (write_state_) {
      case WRITE_STATE_DO_WRITE:
        DCHECK_EQ(result, OK);
        result = DoWrite();
        break;
      case WRITE_STATE_DO_WRITE_COMPLETE:
        result = DoWriteComplete(result);
        break;
      case WRITE_STATE_IDLE:
      default:
        NOTREACHED() << "write_state_: " << write_state_;
        break;
    }

    if (write_state_ == WRITE_STATE_IDLE) {
      DCHECK_EQ(result, ERR_IO_PENDING);
      break;
    }

    if (result == ERR_IO_PENDING)
      break;
  }

  CHECK(in_io_loop_);
  in_io_loop_ = false;

  return result;
}

int SpdySession::DoWrite() {
  CHECK(in_io_loop_);

  DCHECK(buffered_spdy_framer_);
  if (in_flight_write_) {
    DCHECK_GT(in_flight_write_->GetRemainingSize(), 0u);
  } else {
    // Grab the next frame to send.
    SpdyFrameType frame_type = SpdyFrameType::DATA;
    std::unique_ptr<SpdyBufferProducer> producer;
    base::WeakPtr<SpdyStream> stream;
    if (!write_queue_.Dequeue(&frame_type, &producer, &stream)) {
      write_state_ = WRITE_STATE_IDLE;
      return ERR_IO_PENDING;
    }

    if (stream.get())
      CHECK(!stream->IsClosed());

    // Activate the stream only when sending the HEADERS frame to
    // guarantee monotonically-increasing stream IDs.
    if (frame_type == SpdyFrameType::HEADERS) {
      CHECK(stream.get());
      CHECK_EQ(stream->stream_id(), 0u);
      std::unique_ptr<SpdyStream> owned_stream =
          ActivateCreatedStream(stream.get());
      InsertActivatedStream(std::move(owned_stream));

      if (stream_hi_water_mark_ > kLastStreamId) {
        CHECK_EQ(stream->stream_id(), kLastStreamId);
        // We've exhausted the stream ID space, and no new streams may be
        // created after this one.
        MakeUnavailable();
        StartGoingAway(kLastStreamId, ERR_ABORTED);
      }
    }

    in_flight_write_ = producer->ProduceBuffer();
    if (!in_flight_write_) {
      NOTREACHED();
      return ERR_UNEXPECTED;
    }
    in_flight_write_frame_type_ = frame_type;
    in_flight_write_frame_size_ = in_flight_write_->GetRemainingSize();
    DCHECK_GE(in_flight_write_frame_size_, kFrameMinimumSize);
    in_flight_write_stream_ = stream;
  }

  write_state_ = WRITE_STATE_DO_WRITE_COMPLETE;

  // Explicitly store in a scoped_refptr<IOBuffer> to avoid problems
  // with Socket implementations that don't store their IOBuffer
  // argument in a scoped_refptr<IOBuffer> (see crbug.com/232345).
  scoped_refptr<IOBuffer> write_io_buffer =
      in_flight_write_->GetIOBufferForRemainingData();
  return connection_->socket()->Write(
      write_io_buffer.get(), in_flight_write_->GetRemainingSize(),
      base::Bind(&SpdySession::PumpWriteLoop, weak_factory_.GetWeakPtr(),
                 WRITE_STATE_DO_WRITE_COMPLETE));
}

int SpdySession::DoWriteComplete(int result) {
  CHECK(in_io_loop_);
  DCHECK_NE(result, ERR_IO_PENDING);
  DCHECK_GT(in_flight_write_->GetRemainingSize(), 0u);

  if (result < 0) {
    DCHECK_NE(result, ERR_IO_PENDING);
    in_flight_write_.reset();
    in_flight_write_frame_type_ = SpdyFrameType::DATA;
    in_flight_write_frame_size_ = 0;
    in_flight_write_stream_.reset();
    write_state_ = WRITE_STATE_DO_WRITE;
    DoDrainSession(static_cast<Error>(result), "Write error");
    return OK;
  }

  // It should not be possible to have written more bytes than our
  // in_flight_write_.
  DCHECK_LE(static_cast<size_t>(result), in_flight_write_->GetRemainingSize());

  if (result > 0) {
    in_flight_write_->Consume(static_cast<size_t>(result));
    if (in_flight_write_stream_.get())
      in_flight_write_stream_->AddRawSentBytes(static_cast<size_t>(result));

    // We only notify the stream when we've fully written the pending frame.
    if (in_flight_write_->GetRemainingSize() == 0) {
      // It is possible that the stream was cancelled while we were
      // writing to the socket.
      if (in_flight_write_stream_.get()) {
        DCHECK_GT(in_flight_write_frame_size_, 0u);
        in_flight_write_stream_->OnFrameWriteComplete(
            in_flight_write_frame_type_, in_flight_write_frame_size_);
      }

      // Cleanup the write which just completed.
      in_flight_write_.reset();
      in_flight_write_frame_type_ = SpdyFrameType::DATA;
      in_flight_write_frame_size_ = 0;
      in_flight_write_stream_.reset();
    }
  }

  write_state_ = WRITE_STATE_DO_WRITE;
  return OK;
}

void SpdySession::SendInitialData() {
  DCHECK(enable_sending_initial_data_);
  DCHECK(buffered_spdy_framer_.get());

  // Prepare initial SETTINGS frame.  Only send settings that have a value
  // different from the protocol default value.
  SettingsMap settings_map;
  for (auto setting : initial_settings_) {
    if (!IsSpdySettingAtDefaultInitialValue(setting.first, setting.second)) {
      settings_map.insert(setting);
    }
  }
  net_log_.AddEvent(NetLogEventType::HTTP2_SESSION_SEND_SETTINGS,
                    base::Bind(&NetLogSpdySendSettingsCallback, &settings_map));
  std::unique_ptr<SpdySerializedFrame> settings_frame(
      buffered_spdy_framer_->CreateSettings(settings_map));

  // Prepare initial WINDOW_UPDATE frame.
  // Make sure |session_max_recv_window_size_ - session_recv_window_size_|
  // does not underflow.
  DCHECK_GE(session_max_recv_window_size_, session_recv_window_size_);
  DCHECK_GE(session_recv_window_size_, 0);
  DCHECK_EQ(0, session_unacked_recv_window_bytes_);
  std::unique_ptr<SpdySerializedFrame> window_update_frame;
  const bool send_window_update =
      session_max_recv_window_size_ > session_recv_window_size_;
  if (send_window_update) {
    const int32_t delta_window_size =
        session_max_recv_window_size_ - session_recv_window_size_;
    session_recv_window_size_ += delta_window_size;
    net_log_.AddEvent(NetLogEventType::HTTP2_SESSION_UPDATE_RECV_WINDOW,
                      base::Bind(&NetLogSpdySessionWindowUpdateCallback,
                                 delta_window_size, session_recv_window_size_));

    session_unacked_recv_window_bytes_ += delta_window_size;
    net_log_.AddEvent(NetLogEventType::HTTP2_SESSION_SEND_WINDOW_UPDATE,
                      base::Bind(&NetLogSpdyWindowUpdateFrameCallback,
                                 kSessionFlowControlStreamId,
                                 session_unacked_recv_window_bytes_));
    window_update_frame = buffered_spdy_framer_->CreateWindowUpdate(
        kSessionFlowControlStreamId, session_unacked_recv_window_bytes_);
    session_unacked_recv_window_bytes_ = 0;
  }

  // Create a single frame to hold connection prefix, initial SETTINGS frame,
  // and optional initial WINDOW_UPDATE frame, so that they are sent on the wire
  // in a single packet.
  size_t initial_frame_size =
      kHttp2ConnectionHeaderPrefixSize + settings_frame->size();
  if (send_window_update)
    initial_frame_size += window_update_frame->size();
  auto initial_frame_data = std::make_unique<char[]>(initial_frame_size);
  size_t offset = 0;

  memcpy(initial_frame_data.get() + offset, kHttp2ConnectionHeaderPrefix,
         kHttp2ConnectionHeaderPrefixSize);
  offset += kHttp2ConnectionHeaderPrefixSize;

  memcpy(initial_frame_data.get() + offset, settings_frame->data(),
         settings_frame->size());
  offset += settings_frame->size();

  if (send_window_update) {
    memcpy(initial_frame_data.get() + offset, window_update_frame->data(),
           window_update_frame->size());
  }

  auto initial_frame = std::make_unique<SpdySerializedFrame>(
      initial_frame_data.release(), initial_frame_size,
      /* owns_buffer = */ true);
  EnqueueSessionWrite(HIGHEST, SpdyFrameType::SETTINGS,
                      std::move(initial_frame));
}

void SpdySession::HandleSetting(uint32_t id, uint32_t value) {
  switch (id) {
    case SETTINGS_MAX_CONCURRENT_STREAMS:
      max_concurrent_streams_ =
          std::min(static_cast<size_t>(value), kMaxConcurrentStreamLimit);
      ProcessPendingStreamRequests();
      break;
    case SETTINGS_INITIAL_WINDOW_SIZE: {
      if (value > static_cast<uint32_t>(std::numeric_limits<int32_t>::max())) {
        net_log().AddEvent(
            NetLogEventType::HTTP2_SESSION_INITIAL_WINDOW_SIZE_OUT_OF_RANGE,
            NetLog::IntCallback("initial_window_size", value));
        return;
      }

      // SETTINGS_INITIAL_WINDOW_SIZE updates initial_send_window_size_ only.
      int32_t delta_window_size =
          static_cast<int32_t>(value) - stream_initial_send_window_size_;
      stream_initial_send_window_size_ = static_cast<int32_t>(value);
      UpdateStreamsSendWindowSize(delta_window_size);
      net_log().AddEvent(
          NetLogEventType::HTTP2_SESSION_UPDATE_STREAMS_SEND_WINDOW_SIZE,
          NetLog::IntCallback("delta_window_size", delta_window_size));
      break;
    }
  }
}

void SpdySession::UpdateStreamsSendWindowSize(int32_t delta_window_size) {
  for (const auto& value : active_streams_) {
    if (!value.second->AdjustSendWindowSize(delta_window_size)) {
      DoDrainSession(
          ERR_SPDY_FLOW_CONTROL_ERROR,
          SpdyStringPrintf("New SETTINGS_INITIAL_WINDOW_SIZE value overflows "
                           "flow control window of stream %d.",
                           value.second->stream_id()));
      return;
    }
  }

  for (auto* const stream : created_streams_) {
    if (!stream->AdjustSendWindowSize(delta_window_size)) {
      DoDrainSession(
          ERR_SPDY_FLOW_CONTROL_ERROR,
          SpdyStringPrintf("New SETTINGS_INITIAL_WINDOW_SIZE value overflows "
                           "flow control window of stream %d.",
                           stream->stream_id()));
      return;
    }
  }
}

void SpdySession::MaybeSendPrefacePing() {
  if (pings_in_flight_ > 0 || check_ping_status_pending_ ||
      !enable_ping_based_connection_checking_) {
    return;
  }

  // If there has been no read activity in the session for some time,
  // then send a preface-PING.
  if (time_func_() > last_read_time_ + connection_at_risk_of_loss_time_)
    WritePingFrame(next_ping_id_, false);
}

void SpdySession::SendWindowUpdateFrame(SpdyStreamId stream_id,
                                        uint32_t delta_window_size,
                                        RequestPriority priority) {
  ActiveStreamMap::const_iterator it = active_streams_.find(stream_id);
  if (it != active_streams_.end()) {
    CHECK_EQ(it->second->stream_id(), stream_id);
  } else {
    CHECK_EQ(stream_id, kSessionFlowControlStreamId);
  }

  net_log_.AddEvent(NetLogEventType::HTTP2_SESSION_SEND_WINDOW_UPDATE,
                    base::Bind(&NetLogSpdyWindowUpdateFrameCallback, stream_id,
                               delta_window_size));

  DCHECK(buffered_spdy_framer_.get());
  std::unique_ptr<SpdySerializedFrame> window_update_frame(
      buffered_spdy_framer_->CreateWindowUpdate(stream_id, delta_window_size));
  EnqueueSessionWrite(priority, SpdyFrameType::WINDOW_UPDATE,
                      std::move(window_update_frame));
}

void SpdySession::WritePingFrame(SpdyPingId unique_id, bool is_ack) {
  DCHECK(buffered_spdy_framer_.get());
  std::unique_ptr<SpdySerializedFrame> ping_frame(
      buffered_spdy_framer_->CreatePingFrame(unique_id, is_ack));
  EnqueueSessionWrite(HIGHEST, SpdyFrameType::PING, std::move(ping_frame));

  if (net_log().IsCapturing()) {
    net_log().AddEvent(
        NetLogEventType::HTTP2_SESSION_PING,
        base::Bind(&NetLogSpdyPingCallback, unique_id, is_ack, "sent"));
  }
  if (!is_ack) {
    ++next_ping_id_;
    ++pings_in_flight_;
    PlanToCheckPingStatus();
    last_ping_sent_time_ = time_func_();
  }
}

void SpdySession::PlanToCheckPingStatus() {
  if (check_ping_status_pending_)
    return;

  check_ping_status_pending_ = true;
  base::ThreadTaskRunnerHandle::Get()->PostDelayedTask(
      FROM_HERE, base::Bind(&SpdySession::CheckPingStatus,
                            weak_factory_.GetWeakPtr(), time_func_()),
      hung_interval_);
}

void SpdySession::CheckPingStatus(base::TimeTicks last_check_time) {
  CHECK(!in_io_loop_);
  DCHECK(check_ping_status_pending_);

  // Check if we got a response back for all PINGs we had sent.
  if (pings_in_flight_ == 0) {
    check_ping_status_pending_ = false;
    return;
  }

  const base::TimeTicks now = time_func_();
  if (now > last_read_time_ + hung_interval_ ||
      last_read_time_ < last_check_time) {
    check_ping_status_pending_ = false;
    DoDrainSession(ERR_SPDY_PING_FAILED, "Failed ping.");
    return;
  }

  // Check the status of connection after a delay.
  const base::TimeDelta delay = last_read_time_ + hung_interval_ - now;
  base::ThreadTaskRunnerHandle::Get()->PostDelayedTask(
      FROM_HERE, base::Bind(&SpdySession::CheckPingStatus,
                            weak_factory_.GetWeakPtr(), now),
      delay);
}

SpdyStreamId SpdySession::GetNewStreamId() {
  CHECK_LE(stream_hi_water_mark_, kLastStreamId);
  SpdyStreamId id = stream_hi_water_mark_;
  stream_hi_water_mark_ += 2;
  return id;
}

void SpdySession::EnqueueSessionWrite(
    RequestPriority priority,
    SpdyFrameType frame_type,
    std::unique_ptr<SpdySerializedFrame> frame) {
  DCHECK(frame_type == SpdyFrameType::RST_STREAM ||
         frame_type == SpdyFrameType::SETTINGS ||
         frame_type == SpdyFrameType::WINDOW_UPDATE ||
         frame_type == SpdyFrameType::PING ||
         frame_type == SpdyFrameType::GOAWAY);
  auto buffer = std::make_unique<SpdyBuffer>(std::move(frame));
  EnqueueWrite(priority, frame_type,
               std::make_unique<SimpleBufferProducer>(std::move(buffer)),
               base::WeakPtr<SpdyStream>());
}

void SpdySession::EnqueueWrite(RequestPriority priority,
                               SpdyFrameType frame_type,
                               std::unique_ptr<SpdyBufferProducer> producer,
                               const base::WeakPtr<SpdyStream>& stream) {
  if (availability_state_ == STATE_DRAINING)
    return;

  write_queue_.Enqueue(priority, frame_type, std::move(producer), stream);
  MaybePostWriteLoop();
}

void SpdySession::InsertCreatedStream(std::unique_ptr<SpdyStream> stream) {
  CHECK_EQ(stream->stream_id(), 0u);
  CHECK(created_streams_.find(stream.get()) == created_streams_.end());
  created_streams_.insert(stream.release());
}

std::unique_ptr<SpdyStream> SpdySession::ActivateCreatedStream(
    SpdyStream* stream) {
  CHECK_EQ(stream->stream_id(), 0u);
  CHECK(created_streams_.find(stream) != created_streams_.end());
  stream->set_stream_id(GetNewStreamId());
  std::unique_ptr<SpdyStream> owned_stream(stream);
  created_streams_.erase(stream);
  return owned_stream;
}

void SpdySession::InsertActivatedStream(std::unique_ptr<SpdyStream> stream) {
  SpdyStreamId stream_id = stream->stream_id();
  CHECK_NE(stream_id, 0u);
  std::pair<ActiveStreamMap::iterator, bool> result =
      active_streams_.insert(std::make_pair(stream_id, stream.get()));
  CHECK(result.second);
  ignore_result(stream.release());
}

void SpdySession::DeleteStream(std::unique_ptr<SpdyStream> stream, int status) {
  if (in_flight_write_stream_.get() == stream.get()) {
    // If we're deleting the stream for the in-flight write, we still
    // need to let the write complete, so we clear
    // |in_flight_write_stream_| and let the write finish on its own
    // without notifying |in_flight_write_stream_|.
    in_flight_write_stream_.reset();
  }

  write_queue_.RemovePendingWritesForStream(stream->GetWeakPtr());
  stream->OnClose(status);

  if (availability_state_ == STATE_AVAILABLE) {
    ProcessPendingStreamRequests();
  }
}

SpdyStream* SpdySession::GetActivePushStream(const GURL& url) {
  UnclaimedPushedStreamContainer::const_iterator unclaimed_it =
      unclaimed_pushed_streams_.find(url);
  if (unclaimed_it == unclaimed_pushed_streams_.end())
    return nullptr;

  const SpdyStreamId stream_id = unclaimed_it->second;
  unclaimed_pushed_streams_.erase(unclaimed_it);

  ActiveStreamMap::iterator active_it = active_streams_.find(stream_id);
  if (active_it == active_streams_.end()) {
    NOTREACHED();
    return nullptr;
  }

  SpdyStream* stream = active_it->second;
  net_log_.AddEvent(
      NetLogEventType::HTTP2_STREAM_ADOPTED_PUSH_STREAM,
      base::Bind(&NetLogSpdyAdoptedPushStreamCallback, stream_id, &url));
  return stream;
}

void SpdySession::RecordPingRTTHistogram(base::TimeDelta duration) {
  UMA_HISTOGRAM_CUSTOM_TIMES("Net.SpdyPing.RTT", duration,
                             base::TimeDelta::FromMilliseconds(1),
                             base::TimeDelta::FromMinutes(10), 100);
}

void SpdySession::RecordHistograms() {
  UMA_HISTOGRAM_CUSTOM_COUNTS("Net.SpdyStreamsPerSession",
                              streams_initiated_count_, 1, 300, 50);
  UMA_HISTOGRAM_CUSTOM_COUNTS("Net.SpdyStreamsPushedPerSession",
                              streams_pushed_count_, 1, 300, 50);
  UMA_HISTOGRAM_CUSTOM_COUNTS("Net.SpdyStreamsPushedAndClaimedPerSession",
                              streams_pushed_and_claimed_count_, 1, 300, 50);
  UMA_HISTOGRAM_CUSTOM_COUNTS("Net.SpdyStreamsAbandonedPerSession",
                              streams_abandoned_count_, 1, 300, 50);
  UMA_HISTOGRAM_COUNTS_1M("Net.SpdySession.PushedBytes", bytes_pushed_count_);
  DCHECK_LE(bytes_pushed_and_unclaimed_count_, bytes_pushed_count_);
  UMA_HISTOGRAM_COUNTS_1M("Net.SpdySession.PushedAndUnclaimedBytes",
                          bytes_pushed_and_unclaimed_count_);
}

void SpdySession::RecordProtocolErrorHistogram(
    SpdyProtocolErrorDetails details) {
  UMA_HISTOGRAM_ENUMERATION("Net.SpdySessionErrorDetails2", details,
                            NUM_SPDY_PROTOCOL_ERROR_DETAILS);
  if (base::EndsWith(host_port_pair().host(), "google.com",
                     base::CompareCase::INSENSITIVE_ASCII)) {
    UMA_HISTOGRAM_ENUMERATION("Net.SpdySessionErrorDetails_Google2", details,
                              NUM_SPDY_PROTOCOL_ERROR_DETAILS);
  }
}

// static
void SpdySession::RecordPushedStreamVaryResponseHeaderHistogram(
    const SpdyHeaderBlock& headers) {
  UMA_HISTOGRAM_ENUMERATION("Net.PushedStreamVaryResponseHeader",
                            ParseVaryInPushedResponse(headers),
                            kNumberOfVaryEntries);
}

void SpdySession::DcheckGoingAway() const {
#if DCHECK_IS_ON()
  DCHECK_GE(availability_state_, STATE_GOING_AWAY);
  for (int i = MINIMUM_PRIORITY; i <= MAXIMUM_PRIORITY; ++i) {
    DCHECK(pending_create_stream_queues_[i].empty());
  }
  DCHECK(created_streams_.empty());
#endif
}

void SpdySession::DcheckDraining() const {
  DcheckGoingAway();
  DCHECK_EQ(availability_state_, STATE_DRAINING);
  DCHECK(active_streams_.empty());
  DCHECK(unclaimed_pushed_streams_.empty());
}

void SpdySession::DoDrainSession(Error err, const SpdyString& description) {
  if (availability_state_ == STATE_DRAINING) {
    return;
  }
  MakeUnavailable();

  // Mark host_port_pair requiring HTTP/1.1 for subsequent connections.
  if (err == ERR_HTTP_1_1_REQUIRED) {
    http_server_properties_->SetHTTP11Required(host_port_pair());
  }

  // If |err| indicates an error occurred, inform the peer that we're closing
  // and why. Don't GOAWAY on a graceful or idle close, as that may
  // unnecessarily wake the radio. We could technically GOAWAY on network errors
  // (we'll probably fail to actually write it, but that's okay), however many
  // unit-tests would need to be updated.
  if (err != OK &&
      err != ERR_ABORTED &&  // Used by SpdySessionPool to close idle sessions.
      err != ERR_NETWORK_CHANGED &&  // Used to deprecate sessions on IP change.
      err != ERR_SOCKET_NOT_CONNECTED && err != ERR_HTTP_1_1_REQUIRED &&
      err != ERR_CONNECTION_CLOSED && err != ERR_CONNECTION_RESET) {
    // Enqueue a GOAWAY to inform the peer of why we're closing the connection.
    SpdyGoAwayIR goaway_ir(last_accepted_push_stream_id_,
                           MapNetErrorToGoAwayStatus(err), description);
    auto frame = std::make_unique<SpdySerializedFrame>(
        buffered_spdy_framer_->SerializeFrame(goaway_ir));
    EnqueueSessionWrite(HIGHEST, SpdyFrameType::GOAWAY, std::move(frame));
  }

  availability_state_ = STATE_DRAINING;
  error_on_close_ = err;

  net_log_.AddEvent(
      NetLogEventType::HTTP2_SESSION_CLOSE,
      base::Bind(&NetLogSpdySessionCloseCallback, err, &description));

  UMA_HISTOGRAM_SPARSE_SLOWLY("Net.SpdySession.ClosedOnError", -err);

  if (err == OK) {
    // We ought to be going away already, as this is a graceful close.
    DcheckGoingAway();
  } else {
    StartGoingAway(0, err);
  }
  DcheckDraining();
  MaybePostWriteLoop();
}

void SpdySession::LogAbandonedStream(SpdyStream* stream, Error status) {
  DCHECK(stream);
  stream->LogStreamError(status, "Abandoned.");
  // We don't increment the streams abandoned counter here. If the
  // stream isn't active (i.e., it hasn't written anything to the wire
  // yet) then it's as if it never existed. If it is active, then
  // LogAbandonedActiveStream() will increment the counters.
}

void SpdySession::LogAbandonedActiveStream(ActiveStreamMap::const_iterator it,
                                           Error status) {
  DCHECK_GT(it->first, 0u);
  LogAbandonedStream(it->second, status);
  ++streams_abandoned_count_;
}

void SpdySession::CompleteStreamRequest(
    const base::WeakPtr<SpdyStreamRequest>& pending_request) {
  // Abort if the request has already been cancelled.
  if (!pending_request)
    return;

  base::WeakPtr<SpdyStream> stream;
  int rv = TryCreateStream(pending_request, &stream);

  if (rv == OK) {
    DCHECK(stream);
    pending_request->OnRequestCompleteSuccess(stream);
    return;
  }
  DCHECK(!stream);

  if (rv != ERR_IO_PENDING) {
    pending_request->OnRequestCompleteFailure(rv);
  }
}

void SpdySession::CancelPushedStreamIfUnclaimed(SpdyStreamId stream_id) {
  ActiveStreamMap::iterator active_it = active_streams_.find(stream_id);
  if (active_it == active_streams_.end())
    return;

  // Grab URL for faster lookup in unclaimed_pushed_streams_.
  const GURL& url = active_it->second->url();
  UnclaimedPushedStreamContainer::const_iterator unclaimed_it =
      unclaimed_pushed_streams_.find(url);
  // Make sure to cancel the correct stream.  It is possible that the pushed
  // stream |stream_id| is already claimed, and another stream has been pushed
  // for the same URL.
  if (unclaimed_it == unclaimed_pushed_streams_.end() ||
      unclaimed_it->second != stream_id) {
    return;
  }

  LogAbandonedActiveStream(active_it, ERR_TIMED_OUT);
  // CloseActiveStreamIterator() will remove the stream from
  // |unclaimed_pushed_streams_|.
  ResetStreamIterator(active_it, ERROR_CODE_REFUSED_STREAM,
                      "Stream not claimed.");
}

void SpdySession::OnError(
    Http2DecoderAdapter::SpdyFramerError spdy_framer_error) {
  CHECK(in_io_loop_);

  RecordProtocolErrorHistogram(
      MapFramerErrorToProtocolError(spdy_framer_error));
  SpdyString description = SpdyStringPrintf(
      "Framer error: %d (%s).", spdy_framer_error,
      Http2DecoderAdapter::SpdyFramerErrorToString(spdy_framer_error));
  DoDrainSession(MapFramerErrorToNetError(spdy_framer_error), description);
}

void SpdySession::OnStreamError(SpdyStreamId stream_id,
                                const SpdyString& description) {
  CHECK(in_io_loop_);

  ActiveStreamMap::iterator it = active_streams_.find(stream_id);
  if (it == active_streams_.end()) {
    // We still want to send a frame to reset the stream even if we
    // don't know anything about it.
    EnqueueResetStreamFrame(stream_id, IDLE, ERROR_CODE_PROTOCOL_ERROR,
                            description);
    return;
  }

  ResetStreamIterator(it, ERROR_CODE_PROTOCOL_ERROR, description);
}

void SpdySession::OnPing(SpdyPingId unique_id, bool is_ack) {
  CHECK(in_io_loop_);

  net_log_.AddEvent(
      NetLogEventType::HTTP2_SESSION_PING,
      base::Bind(&NetLogSpdyPingCallback, unique_id, is_ack, "received"));

  // Send response to a PING from server.
  if (!is_ack) {
    WritePingFrame(unique_id, true);
    return;
  }

  --pings_in_flight_;
  if (pings_in_flight_ < 0) {
    RecordProtocolErrorHistogram(PROTOCOL_ERROR_UNEXPECTED_PING);
    DoDrainSession(ERR_SPDY_PROTOCOL_ERROR, "pings_in_flight_ is < 0.");
    pings_in_flight_ = 0;
    return;
  }

  if (pings_in_flight_ > 0)
    return;

  // Record RTT in histogram when there are no more pings in flight.
  RecordPingRTTHistogram(time_func_() - last_ping_sent_time_);
}

void SpdySession::OnRstStream(SpdyStreamId stream_id,
                              SpdyErrorCode error_code) {
  CHECK(in_io_loop_);

  net_log().AddEvent(
      NetLogEventType::HTTP2_SESSION_RECV_RST_STREAM,
      base::Bind(&NetLogSpdyRecvRstStreamCallback, stream_id, error_code));

  ActiveStreamMap::iterator it = active_streams_.find(stream_id);
  if (it == active_streams_.end()) {
    // NOTE:  it may just be that the stream was cancelled.
    LOG(WARNING) << "Received RST for invalid stream" << stream_id;
    return;
  }

  CHECK_EQ(it->second->stream_id(), stream_id);

  if (error_code == ERROR_CODE_NO_ERROR) {
    CloseActiveStreamIterator(it, ERR_SPDY_RST_STREAM_NO_ERROR_RECEIVED);
  } else if (error_code == ERROR_CODE_REFUSED_STREAM) {
    CloseActiveStreamIterator(it, ERR_SPDY_SERVER_REFUSED_STREAM);
  } else if (error_code == ERROR_CODE_HTTP_1_1_REQUIRED) {
    // TODO(bnc): Record histogram with number of open streams capped at 50.
    if (net_log().IsCapturing()) {
      it->second->LogStreamError(ERR_HTTP_1_1_REQUIRED,
                                 "Closing session because server reset stream "
                                 "with ERR_HTTP_1_1_REQUIRED.");
    }
    DoDrainSession(ERR_HTTP_1_1_REQUIRED, "HTTP_1_1_REQUIRED for stream.");
  } else {
    RecordProtocolErrorHistogram(
        PROTOCOL_ERROR_RST_STREAM_FOR_NON_ACTIVE_STREAM);
    if (net_log().IsCapturing()) {
      it->second->LogStreamError(ERR_SPDY_PROTOCOL_ERROR,
                                 "Server reset stream.");
    }
    // TODO(mbelshe): Map from Spdy-protocol errors to something sensical.
    //                For now, it doesn't matter much - it is a protocol error.
    CloseActiveStreamIterator(it, ERR_SPDY_PROTOCOL_ERROR);
  }
}

void SpdySession::OnGoAway(SpdyStreamId last_accepted_stream_id,
                           SpdyErrorCode error_code,
                           SpdyStringPiece debug_data) {
  CHECK(in_io_loop_);

  // TODO(jgraettinger): UMA histogram on |error_code|.

  net_log_.AddEvent(
      NetLogEventType::HTTP2_SESSION_RECV_GOAWAY,
      base::Bind(&NetLogSpdyRecvGoAwayCallback, last_accepted_stream_id,
                 active_streams_.size(), unclaimed_pushed_streams_.size(),
                 error_code, debug_data));
  MakeUnavailable();
  if (error_code == ERROR_CODE_HTTP_1_1_REQUIRED) {
    // TODO(bnc): Record histogram with number of open streams capped at 50.
    DoDrainSession(ERR_HTTP_1_1_REQUIRED, "HTTP_1_1_REQUIRED for stream.");
  } else if (error_code == ERROR_CODE_NO_ERROR) {
    StartGoingAway(last_accepted_stream_id, ERR_SPDY_SERVER_REFUSED_STREAM);
  } else {
    StartGoingAway(last_accepted_stream_id, ERR_ABORTED);
  }
  // This is to handle the case when we already don't have any active
  // streams (i.e., StartGoingAway() did nothing). Otherwise, we have
  // active streams and so the last one being closed will finish the
  // going away process (see DeleteStream()).
  MaybeFinishGoingAway();
}

void SpdySession::OnDataFrameHeader(SpdyStreamId stream_id,
                                    size_t length,
                                    bool fin) {
  CHECK(in_io_loop_);

  ActiveStreamMap::iterator it = active_streams_.find(stream_id);

  // By the time data comes in, the stream may already be inactive.
  if (it == active_streams_.end())
    return;

  SpdyStream* stream = it->second;
  CHECK_EQ(stream->stream_id(), stream_id);

  DCHECK(buffered_spdy_framer_);
  stream->AddRawReceivedBytes(kDataFrameMinimumSize);
}

void SpdySession::OnStreamFrameData(SpdyStreamId stream_id,
                                    const char* data,
                                    size_t len) {
  CHECK(in_io_loop_);
  DCHECK_LT(len, 1u << 24);
  if (net_log().IsCapturing()) {
    net_log().AddEvent(
        NetLogEventType::HTTP2_SESSION_RECV_DATA,
        base::Bind(&NetLogSpdyDataCallback, stream_id, len, false));
  }

  // Build the buffer as early as possible so that we go through the
  // session flow control checks and update
  // |unacked_recv_window_bytes_| properly even when the stream is
  // inactive (since the other side has still reduced its session send
  // window).
  std::unique_ptr<SpdyBuffer> buffer;
  if (data) {
    DCHECK_GT(len, 0u);
    CHECK_LE(len, static_cast<size_t>(kReadBufferSize));
    buffer = std::make_unique<SpdyBuffer>(data, len);

    DecreaseRecvWindowSize(static_cast<int32_t>(len));
    buffer->AddConsumeCallback(base::Bind(&SpdySession::OnReadBufferConsumed,
                                          weak_factory_.GetWeakPtr()));
  } else {
    DCHECK_EQ(len, 0u);
  }

  ActiveStreamMap::iterator it = active_streams_.find(stream_id);

  // By the time data comes in, the stream may already be inactive.
  if (it == active_streams_.end())
    return;

  SpdyStream* stream = it->second;
  CHECK_EQ(stream->stream_id(), stream_id);

  stream->AddRawReceivedBytes(len);
  stream->OnDataReceived(std::move(buffer));
}

void SpdySession::OnStreamEnd(SpdyStreamId stream_id) {
  CHECK(in_io_loop_);
  if (net_log().IsCapturing()) {
    net_log().AddEvent(NetLogEventType::HTTP2_SESSION_RECV_DATA,
                       base::Bind(&NetLogSpdyDataCallback, stream_id, 0, true));
  }

  ActiveStreamMap::iterator it = active_streams_.find(stream_id);
  // By the time data comes in, the stream may already be inactive.
  if (it == active_streams_.end())
    return;

  SpdyStream* stream = it->second;
  CHECK_EQ(stream->stream_id(), stream_id);

  stream->OnDataReceived(std::unique_ptr<SpdyBuffer>());
}

void SpdySession::OnStreamPadding(SpdyStreamId stream_id, size_t len) {
  CHECK(in_io_loop_);

  // Decrease window size because padding bytes are received.
  // Increase window size because padding bytes are consumed (by discarding).
  // Net result: |session_unacked_recv_window_bytes_| increases by |len|,
  // |session_recv_window_size_| does not change.
  DecreaseRecvWindowSize(static_cast<int32_t>(len));
  IncreaseRecvWindowSize(static_cast<int32_t>(len));

  ActiveStreamMap::iterator it = active_streams_.find(stream_id);
  if (it == active_streams_.end())
    return;
  it->second->OnPaddingConsumed(len);
}

void SpdySession::OnSettings() {
  CHECK(in_io_loop_);

  if (net_log_.IsCapturing()) {
    net_log_.AddEvent(NetLogEventType::HTTP2_SESSION_RECV_SETTINGS);
    net_log_.AddEvent(NetLogEventType::HTTP2_SESSION_SEND_SETTINGS_ACK);
  }

  // Send an acknowledgment of the setting.
  SpdySettingsIR settings_ir;
  settings_ir.set_is_ack(true);
  auto frame = std::make_unique<SpdySerializedFrame>(
      buffered_spdy_framer_->SerializeFrame(settings_ir));
  EnqueueSessionWrite(HIGHEST, SpdyFrameType::SETTINGS, std::move(frame));
}

void SpdySession::OnSettingsAck() {
  CHECK(in_io_loop_);

  if (net_log_.IsCapturing())
    net_log_.AddEvent(NetLogEventType::HTTP2_SESSION_RECV_SETTINGS_ACK);
}

void SpdySession::OnSetting(SpdySettingsIds id, uint32_t value) {
  CHECK(in_io_loop_);

  HandleSetting(id, value);

  // Log the setting.
  net_log_.AddEvent(NetLogEventType::HTTP2_SESSION_RECV_SETTING,
                    base::Bind(&NetLogSpdyRecvSettingCallback, id, value));
}

void SpdySession::OnWindowUpdate(SpdyStreamId stream_id,
                                 int delta_window_size) {
  CHECK(in_io_loop_);

  net_log_.AddEvent(NetLogEventType::HTTP2_SESSION_RECV_WINDOW_UPDATE,
                    base::Bind(&NetLogSpdyWindowUpdateFrameCallback, stream_id,
                               delta_window_size));

  if (stream_id == kSessionFlowControlStreamId) {
    // WINDOW_UPDATE for the session.
    if (delta_window_size < 1) {
      RecordProtocolErrorHistogram(PROTOCOL_ERROR_INVALID_WINDOW_UPDATE_SIZE);
      DoDrainSession(
          ERR_SPDY_PROTOCOL_ERROR,
          "Received WINDOW_UPDATE with an invalid delta_window_size " +
              base::IntToString(delta_window_size));
      return;
    }

    IncreaseSendWindowSize(delta_window_size);
  } else {
    // WINDOW_UPDATE for a stream.
    ActiveStreamMap::iterator it = active_streams_.find(stream_id);

    if (it == active_streams_.end()) {
      // NOTE:  it may just be that the stream was cancelled.
      LOG(WARNING) << "Received WINDOW_UPDATE for invalid stream " << stream_id;
      return;
    }

    SpdyStream* stream = it->second;
    CHECK_EQ(stream->stream_id(), stream_id);

    if (delta_window_size < 1) {
      ResetStreamIterator(
          it, ERROR_CODE_FLOW_CONTROL_ERROR,
          "Received WINDOW_UPDATE with an invalid delta_window_size.");
      return;
    }

    CHECK_EQ(it->second->stream_id(), stream_id);
    it->second->IncreaseSendWindowSize(delta_window_size);
  }
}

void SpdySession::OnPushPromise(SpdyStreamId stream_id,
                                SpdyStreamId promised_stream_id,
                                SpdyHeaderBlock headers) {
  CHECK(in_io_loop_);

  if (net_log_.IsCapturing()) {
    net_log_.AddEvent(NetLogEventType::HTTP2_SESSION_RECV_PUSH_PROMISE,
                      base::Bind(&NetLogSpdyPushPromiseReceivedCallback,
                                 &headers, stream_id, promised_stream_id));
  }

  TryCreatePushStream(promised_stream_id, stream_id, std::move(headers));
}

void SpdySession::OnHeaders(SpdyStreamId stream_id,
                            bool has_priority,
                            int weight,
                            SpdyStreamId parent_stream_id,
                            bool exclusive,
                            bool fin,
                            SpdyHeaderBlock headers) {
  CHECK(in_io_loop_);

  if (net_log().IsCapturing()) {
    net_log().AddEvent(NetLogEventType::HTTP2_SESSION_RECV_HEADERS,
                       base::Bind(&NetLogSpdyHeadersReceivedCallback, &headers,
                                  fin, stream_id));
  }

  ActiveStreamMap::iterator it = active_streams_.find(stream_id);
  if (it == active_streams_.end()) {
    // NOTE:  it may just be that the stream was cancelled.
    LOG(WARNING) << "Received HEADERS for invalid stream " << stream_id;
    return;
  }

  SpdyStream* stream = it->second;
  CHECK_EQ(stream->stream_id(), stream_id);

  if (stream->type() == SPDY_PUSH_STREAM)
    RecordPushedStreamVaryResponseHeaderHistogram(headers);

  stream->AddRawReceivedBytes(last_compressed_frame_len_);
  last_compressed_frame_len_ = 0;

  if (it->second->IsReservedRemote()) {
    DCHECK_EQ(SPDY_PUSH_STREAM, stream->type());
    if (max_concurrent_pushed_streams_ &&
        num_active_pushed_streams_ >= max_concurrent_pushed_streams_) {
      ResetStream(stream_id, ERROR_CODE_REFUSED_STREAM,
                  "Stream concurrency limit reached.");
      return;
    }

    // Will be balanced in DeleteStream.
    num_active_pushed_streams_++;
  }

  base::Time response_time = base::Time::Now();
  base::TimeTicks recv_first_byte_time = time_func_();
  // May invalidate |stream|.
  stream->OnHeadersReceived(headers, response_time, recv_first_byte_time);
}

void SpdySession::OnAltSvc(
    SpdyStreamId stream_id,
    SpdyStringPiece origin,
    const SpdyAltSvcWireFormat::AlternativeServiceVector& altsvc_vector) {
  url::SchemeHostPort scheme_host_port;
  if (stream_id == 0) {
    if (origin.empty())
      return;
    const GURL gurl(origin);
    if (!gurl.SchemeIs("https"))
      return;
    SSLInfo ssl_info;
    if (!GetSSLInfo(&ssl_info))
      return;
    if (!CanPool(transport_security_state_, ssl_info, host_port_pair().host(),
                 gurl.host())) {
      return;
    }
    scheme_host_port = url::SchemeHostPort(gurl);
  } else {
    if (!origin.empty())
      return;
    const ActiveStreamMap::iterator it = active_streams_.find(stream_id);
    if (it == active_streams_.end())
      return;
    const GURL& gurl(it->second->url());
    if (!gurl.SchemeIs("https"))
      return;
    scheme_host_port = url::SchemeHostPort(gurl);
  }

  AlternativeServiceInfoVector alternative_service_info_vector;
  alternative_service_info_vector.reserve(altsvc_vector.size());
  const base::Time now(base::Time::Now());
  DCHECK(!quic_supported_versions_.empty());
  for (const SpdyAltSvcWireFormat::AlternativeService& altsvc : altsvc_vector) {
    const NextProto protocol = NextProtoFromString(altsvc.protocol_id);
    if (protocol == kProtoUnknown)
      continue;

    // Check if QUIC version is supported. Filter supported QUIC versions.
    QuicTransportVersionVector advertised_versions;
    if (protocol == kProtoQUIC && !altsvc.version.empty()) {
      advertised_versions = FilterSupportedAltSvcVersions(
          altsvc, quic_supported_versions_, support_ietf_format_quic_altsvc_);
      if (advertised_versions.empty())
        continue;
    }

    const AlternativeService alternative_service(protocol, altsvc.host,
                                                 altsvc.port);
    const base::Time expiration =
        now + base::TimeDelta::FromSeconds(altsvc.max_age);
    AlternativeServiceInfo alternative_service_info;
    if (protocol == kProtoQUIC) {
      alternative_service_info =
          AlternativeServiceInfo::CreateQuicAlternativeServiceInfo(
              alternative_service, expiration, advertised_versions);
    } else {
      alternative_service_info =
          AlternativeServiceInfo::CreateHttp2AlternativeServiceInfo(
              alternative_service, expiration);
    }
    alternative_service_info_vector.push_back(alternative_service_info);
  }

  http_server_properties_->SetAlternativeServices(
      scheme_host_port, alternative_service_info_vector);
}

bool SpdySession::OnUnknownFrame(SpdyStreamId stream_id, uint8_t frame_type) {
  // Validate stream id.
  // Was the frame sent on a stream id that has not been used in this session?
  if (stream_id % 2 == 1 && stream_id > stream_hi_water_mark_)
    return false;

  if (stream_id % 2 == 0 && stream_id > last_accepted_push_stream_id_)
    return false;

  return true;
}

void SpdySession::OnSendCompressedFrame(SpdyStreamId stream_id,
                                        SpdyFrameType type,
                                        size_t payload_len,
                                        size_t frame_len) {
  if (type != SpdyFrameType::HEADERS) {
    return;
  }

  DCHECK(buffered_spdy_framer_.get());
  size_t compressed_len = frame_len - kFrameMinimumSize;

  if (payload_len) {
    // Make sure we avoid early decimal truncation.
    int compression_pct = 100 - (100 * compressed_len) / payload_len;
    UMA_HISTOGRAM_PERCENTAGE("Net.SpdyHeadersCompressionPercentage",
                             compression_pct);
  }
}

void SpdySession::OnReceiveCompressedFrame(SpdyStreamId stream_id,
                                           SpdyFrameType type,
                                           size_t frame_len) {
  last_compressed_frame_len_ = frame_len;
}

void SpdySession::OnWriteBufferConsumed(
    size_t frame_payload_size,
    size_t consume_size,
    SpdyBuffer::ConsumeSource consume_source) {
  // We can be called with |in_io_loop_| set if a write SpdyBuffer is
  // deleted (e.g., a stream is closed due to incoming data).
  if (consume_source == SpdyBuffer::DISCARD) {
    // If we're discarding a frame or part of it, increase the send
    // window by the number of discarded bytes. (Although if we're
    // discarding part of a frame, it's probably because of a write
    // error and we'll be tearing down the session soon.)
    int remaining_payload_bytes = std::min(consume_size, frame_payload_size);
    DCHECK_GT(remaining_payload_bytes, 0);
    IncreaseSendWindowSize(remaining_payload_bytes);
  }
  // For consumed bytes, the send window is increased when we receive
  // a WINDOW_UPDATE frame.
}

void SpdySession::IncreaseSendWindowSize(int delta_window_size) {
  // We can be called with |in_io_loop_| set if a SpdyBuffer is
  // deleted (e.g., a stream is closed due to incoming data).
  DCHECK_GE(delta_window_size, 1);

  // Check for overflow.
  int32_t max_delta_window_size =
      std::numeric_limits<int32_t>::max() - session_send_window_size_;
  if (delta_window_size > max_delta_window_size) {
    RecordProtocolErrorHistogram(PROTOCOL_ERROR_INVALID_WINDOW_UPDATE_SIZE);
    DoDrainSession(
        ERR_SPDY_PROTOCOL_ERROR,
        "Received WINDOW_UPDATE [delta: " +
            base::IntToString(delta_window_size) +
            "] for session overflows session_send_window_size_ [current: " +
            base::IntToString(session_send_window_size_) + "]");
    return;
  }

  session_send_window_size_ += delta_window_size;

  net_log_.AddEvent(NetLogEventType::HTTP2_SESSION_UPDATE_SEND_WINDOW,
                    base::Bind(&NetLogSpdySessionWindowUpdateCallback,
                               delta_window_size, session_send_window_size_));

  DCHECK(!IsSendStalled());
  ResumeSendStalledStreams();
}

void SpdySession::DecreaseSendWindowSize(int32_t delta_window_size) {
  // We only call this method when sending a frame. Therefore,
  // |delta_window_size| should be within the valid frame size range.
  DCHECK_GE(delta_window_size, 1);
  DCHECK_LE(delta_window_size, kMaxSpdyFrameChunkSize);

  // |send_window_size_| should have been at least |delta_window_size| for
  // this call to happen.
  DCHECK_GE(session_send_window_size_, delta_window_size);

  session_send_window_size_ -= delta_window_size;

  net_log_.AddEvent(NetLogEventType::HTTP2_SESSION_UPDATE_SEND_WINDOW,
                    base::Bind(&NetLogSpdySessionWindowUpdateCallback,
                               -delta_window_size, session_send_window_size_));
}

void SpdySession::OnReadBufferConsumed(
    size_t consume_size,
    SpdyBuffer::ConsumeSource consume_source) {
  // We can be called with |in_io_loop_| set if a read SpdyBuffer is
  // deleted (e.g., discarded by a SpdyReadQueue).
  DCHECK_GE(consume_size, 1u);
  DCHECK_LE(consume_size,
            static_cast<size_t>(std::numeric_limits<int32_t>::max()));

  IncreaseRecvWindowSize(static_cast<int32_t>(consume_size));
}

void SpdySession::IncreaseRecvWindowSize(int32_t delta_window_size) {
  DCHECK_GE(session_unacked_recv_window_bytes_, 0);
  DCHECK_GE(session_recv_window_size_, session_unacked_recv_window_bytes_);
  DCHECK_GE(delta_window_size, 1);
  // Check for overflow.
  DCHECK_LE(delta_window_size,
            std::numeric_limits<int32_t>::max() - session_recv_window_size_);

  session_recv_window_size_ += delta_window_size;
  net_log_.AddEvent(NetLogEventType::HTTP2_SESSION_UPDATE_RECV_WINDOW,
                    base::Bind(&NetLogSpdySessionWindowUpdateCallback,
                               delta_window_size, session_recv_window_size_));

  session_unacked_recv_window_bytes_ += delta_window_size;
  if (session_unacked_recv_window_bytes_ > session_max_recv_window_size_ / 2) {
    SendWindowUpdateFrame(kSessionFlowControlStreamId,
                          session_unacked_recv_window_bytes_, HIGHEST);
    session_unacked_recv_window_bytes_ = 0;
  }
}

void SpdySession::DecreaseRecvWindowSize(int32_t delta_window_size) {
  CHECK(in_io_loop_);
  DCHECK_GE(delta_window_size, 1);

  // The receiving window size as the peer knows it is
  // |session_recv_window_size_ - session_unacked_recv_window_bytes_|, if more
  // data are sent by the peer, that means that the receive window is not being
  // respected.
  if (delta_window_size >
      session_recv_window_size_ - session_unacked_recv_window_bytes_) {
    RecordProtocolErrorHistogram(PROTOCOL_ERROR_RECEIVE_WINDOW_VIOLATION);
    DoDrainSession(
        ERR_SPDY_FLOW_CONTROL_ERROR,
        "delta_window_size is " + base::IntToString(delta_window_size) +
            " in DecreaseRecvWindowSize, which is larger than the receive " +
            "window size of " + base::IntToString(session_recv_window_size_));
    return;
  }

  session_recv_window_size_ -= delta_window_size;
  net_log_.AddEvent(NetLogEventType::HTTP2_SESSION_UPDATE_RECV_WINDOW,
                    base::Bind(&NetLogSpdySessionWindowUpdateCallback,
                               -delta_window_size, session_recv_window_size_));
}

void SpdySession::QueueSendStalledStream(const SpdyStream& stream) {
  DCHECK(stream.send_stalled_by_flow_control() || IsSendStalled());
  RequestPriority priority = stream.priority();
  CHECK_GE(priority, MINIMUM_PRIORITY);
  CHECK_LE(priority, MAXIMUM_PRIORITY);
  stream_send_unstall_queue_[priority].push_back(stream.stream_id());
}

void SpdySession::ResumeSendStalledStreams() {
  // We don't have to worry about new streams being queued, since
  // doing so would cause IsSendStalled() to return true. But we do
  // have to worry about streams being closed, as well as ourselves
  // being closed.

  base::circular_deque<SpdyStream*> streams_to_requeue;

  while (!IsSendStalled()) {
    size_t old_size = 0;
#if DCHECK_IS_ON()
    old_size = GetTotalSize(stream_send_unstall_queue_);
#endif

    SpdyStreamId stream_id = PopStreamToPossiblyResume();
    if (stream_id == 0)
      break;
    ActiveStreamMap::const_iterator it = active_streams_.find(stream_id);
    // The stream may actually still be send-stalled after this (due
    // to its own send window) but that's okay -- it'll then be
    // resumed once its send window increases.
    if (it != active_streams_.end()) {
      if (it->second->PossiblyResumeIfSendStalled() == SpdyStream::Requeue)
        streams_to_requeue.push_back(it->second);
    }

    // The size should decrease unless we got send-stalled again.
    if (!IsSendStalled())
      DCHECK_LT(GetTotalSize(stream_send_unstall_queue_), old_size);
  }
  while (!streams_to_requeue.empty()) {
    SpdyStream* stream = streams_to_requeue.front();
    streams_to_requeue.pop_front();
    QueueSendStalledStream(*stream);
  }
}

SpdyStreamId SpdySession::PopStreamToPossiblyResume() {
  for (int i = MAXIMUM_PRIORITY; i >= MINIMUM_PRIORITY; --i) {
    base::circular_deque<SpdyStreamId>* queue = &stream_send_unstall_queue_[i];
    if (!queue->empty()) {
      SpdyStreamId stream_id = queue->front();
      queue->pop_front();
      return stream_id;
    }
  }
  return 0;
}

}  // namespace net