net/http/http_cache_transaction.cc

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "net/http/http_cache_transaction.h"
   6
   7 #include "build/build_config.h"
   8
   9 #if defined(OS_POSIX)
  10 #include <unistd.h>
  11 #endif
  12
  13 #include <algorithm>
  14 #include <string>
  15
  16 #include "base/bind.h"
  17 #include "base/compiler_specific.h"
  18 #include "base/format_macros.h"
  19 #include "base/memory/ref_counted.h"
  20 #include "base/memory/scoped_ptr.h"
  21 #include "base/metrics/field_trial.h"
  22 #include "base/metrics/histogram.h"
  23 #include "base/metrics/sparse_histogram.h"
  24 #include "base/profiler/scoped_tracker.h"
  25 #include "base/rand_util.h"
  26 #include "base/strings/string_number_conversions.h"
  27 #include "base/strings/string_piece.h"
  28 #include "base/strings/string_util.h"
  29 #include "base/strings/stringprintf.h"
  30 #include "base/time/clock.h"
  31 #include "base/time/time.h"
  32 #include "base/values.h"
  33 #include "net/base/completion_callback.h"
  34 #include "net/base/io_buffer.h"
  35 #include "net/base/load_flags.h"
  36 #include "net/base/load_timing_info.h"
  37 #include "net/base/net_errors.h"
  38 #include "net/base/upload_data_stream.h"
  39 #include "net/cert/cert_status_flags.h"
  40 #include "net/disk_cache/disk_cache.h"
  41 #include "net/http/disk_based_cert_cache.h"
  42 #include "net/http/http_network_session.h"
  43 #include "net/http/http_request_info.h"
  44 #include "net/http/http_response_headers.h"
  45 #include "net/http/http_transaction.h"
  46 #include "net/http/http_util.h"
  47 #include "net/http/partial_data.h"
  48 #include "net/log/net_log.h"
  49 #include "net/ssl/ssl_cert_request_info.h"
  50 #include "net/ssl/ssl_config_service.h"
  51
  52 using base::Time;
  53 using base::TimeDelta;
  54 using base::TimeTicks;
  55
  56 namespace net {
  57
  58 namespace {
  59
  60 // TODO(ricea): Move this to HttpResponseHeaders once it is standardised.
  61 static const char kFreshnessHeader[] = "Resource-Freshness";
  62
  63 // Stores data relevant to the statistics of writing and reading entire
  64 // certificate chains using DiskBasedCertCache. |num_pending_ops| is the number
  65 // of certificates in the chain that have pending operations in the
  66 // DiskBasedCertCache. |start_time| is the time that the read and write
  67 // commands began being issued to the DiskBasedCertCache.
  68 // TODO(brandonsalmon): Remove this when it is no longer necessary to
  69 // collect data.
  70 class SharedChainData : public base::RefCounted<SharedChainData> {
  71  public:
  72   SharedChainData(int num_ops, TimeTicks start)
  73       : num_pending_ops(num_ops), start_time(start) {}
  74
  75   int num_pending_ops;
  76   TimeTicks start_time;
  77
  78  private:
  79   friend class base::RefCounted<SharedChainData>;
  80   ~SharedChainData() {}
  81   DISALLOW_COPY_AND_ASSIGN(SharedChainData);
  82 };
  83
  84 // Used to obtain a cache entry key for an OSCertHandle.
  85 // TODO(brandonsalmon): Remove this when cache keys are stored
  86 // and no longer have to be recomputed to retrieve the OSCertHandle
  87 // from the disk.
  88 std::string GetCacheKeyForCert(X509Certificate::OSCertHandle cert_handle) {
  89   SHA1HashValue fingerprint =
  90       X509Certificate::CalculateFingerprint(cert_handle);
  91
  92   return "cert:" +
  93          base::HexEncode(fingerprint.data, arraysize(fingerprint.data));
  94 }
  95
  96 // |dist_from_root| indicates the position of the read certificate in the
  97 // certificate chain, 0 indicating it is the root. |is_leaf| indicates
  98 // whether or not the read certificate was the leaf of the chain.
  99 // |shared_chain_data| contains data shared by each certificate in
 100 // the chain.
 101 void OnCertReadIOComplete(
 102     int dist_from_root,
 103     bool is_leaf,
 104     const scoped_refptr<SharedChainData>& shared_chain_data,
 105     X509Certificate::OSCertHandle cert_handle) {
 106   // If |num_pending_ops| is one, this was the last pending read operation
 107   // for this chain of certificates. The total time used to read the chain
 108   // can be calculated by subtracting the starting time from Now().
 109   shared_chain_data->num_pending_ops--;
 110   if (!shared_chain_data->num_pending_ops) {
 111     const TimeDelta read_chain_wait =
 112         TimeTicks::Now() - shared_chain_data->start_time;
 113     UMA_HISTOGRAM_CUSTOM_TIMES("DiskBasedCertCache.ChainReadTime",
 114                                read_chain_wait,
 115                                base::TimeDelta::FromMilliseconds(1),
 116                                base::TimeDelta::FromMinutes(10),
 117                                50);
 118   }
 119
 120   bool success = (cert_handle != NULL);
 121   if (is_leaf)
 122     UMA_HISTOGRAM_BOOLEAN("DiskBasedCertCache.CertIoReadSuccessLeaf", success);
 123
 124   if (success)
 125     UMA_HISTOGRAM_CUSTOM_COUNTS(
 126         "DiskBasedCertCache.CertIoReadSuccess", dist_from_root, 0, 10, 7);
 127   else
 128     UMA_HISTOGRAM_CUSTOM_COUNTS(
 129         "DiskBasedCertCache.CertIoReadFailure", dist_from_root, 0, 10, 7);
 130 }
 131
 132 // |dist_from_root| indicates the position of the written certificate in the
 133 // certificate chain, 0 indicating it is the root. |is_leaf| indicates
 134 // whether or not the written certificate was the leaf of the chain.
 135 // |shared_chain_data| contains data shared by each certificate in
 136 // the chain.
 137 void OnCertWriteIOComplete(
 138     int dist_from_root,
 139     bool is_leaf,
 140     const scoped_refptr<SharedChainData>& shared_chain_data,
 141     const std::string& key) {
 142   // If |num_pending_ops| is one, this was the last pending write operation
 143   // for this chain of certificates. The total time used to write the chain
 144   // can be calculated by subtracting the starting time from Now().
 145   shared_chain_data->num_pending_ops--;
 146   if (!shared_chain_data->num_pending_ops) {
 147     const TimeDelta write_chain_wait =
 148         TimeTicks::Now() - shared_chain_data->start_time;
 149     UMA_HISTOGRAM_CUSTOM_TIMES("DiskBasedCertCache.ChainWriteTime",
 150                                write_chain_wait,
 151                                base::TimeDelta::FromMilliseconds(1),
 152                                base::TimeDelta::FromMinutes(10),
 153                                50);
 154   }
 155
 156   bool success = !key.empty();
 157   if (is_leaf)
 158     UMA_HISTOGRAM_BOOLEAN("DiskBasedCertCache.CertIoWriteSuccessLeaf", success);
 159
 160   if (success)
 161     UMA_HISTOGRAM_CUSTOM_COUNTS(
 162         "DiskBasedCertCache.CertIoWriteSuccess", dist_from_root, 0, 10, 7);
 163   else
 164     UMA_HISTOGRAM_CUSTOM_COUNTS(
 165         "DiskBasedCertCache.CertIoWriteFailure", dist_from_root, 0, 10, 7);
 166 }
 167
 168 // From http://tools.ietf.org/html/draft-ietf-httpbis-p6-cache-21#section-6
 169 //      a "non-error response" is one with a 2xx (Successful) or 3xx
 170 //      (Redirection) status code.
 171 bool NonErrorResponse(int status_code) {
 172   int status_code_range = status_code / 100;
 173   return status_code_range == 2 || status_code_range == 3;
 174 }
 175
 176 void RecordNoStoreHeaderHistogram(int load_flags,
 177                                   const HttpResponseInfo* response) {
 178   if (load_flags & LOAD_MAIN_FRAME) {
 179     UMA_HISTOGRAM_BOOLEAN(
 180         "Net.MainFrameNoStore",
 181         response->headers->HasHeaderValue("cache-control", "no-store"));
 182   }
 183 }
 184
 185 scoped_ptr<base::Value> NetLogAsyncRevalidationInfoCallback(
 186     const NetLog::Source& source,
 187     const HttpRequestInfo* request,
 188     NetLogCaptureMode capture_mode) {
 189   scoped_ptr<base::DictionaryValue> dict(new base::DictionaryValue());
 190   source.AddToEventParameters(dict.get());
 191
 192   dict->SetString("url", request->url.possibly_invalid_spec());
 193   dict->SetString("method", request->method);
 194   return dict.Pass();
 195 }
 196
 197 enum ExternallyConditionalizedType {
 198   EXTERNALLY_CONDITIONALIZED_CACHE_REQUIRES_VALIDATION,
 199   EXTERNALLY_CONDITIONALIZED_CACHE_USABLE,
 200   EXTERNALLY_CONDITIONALIZED_MISMATCHED_VALIDATORS,
 201   EXTERNALLY_CONDITIONALIZED_MAX
 202 };
 203
 204 }  // namespace
 205
 206 struct HeaderNameAndValue {
 207   const char* name;
 208   const char* value;
 209 };
 210
 211 // If the request includes one of these request headers, then avoid caching
 212 // to avoid getting confused.
 213 static const HeaderNameAndValue kPassThroughHeaders[] = {
 214   { "if-unmodified-since", NULL },  // causes unexpected 412s
 215   { "if-match", NULL },             // causes unexpected 412s
 216   { "if-range", NULL },
 217   { NULL, NULL }
 218 };
 219
 220 struct ValidationHeaderInfo {
 221   const char* request_header_name;
 222   const char* related_response_header_name;
 223 };
 224
 225 static const ValidationHeaderInfo kValidationHeaders[] = {
 226   { "if-modified-since", "last-modified" },
 227   { "if-none-match", "etag" },
 228 };
 229
 230 // If the request includes one of these request headers, then avoid reusing
 231 // our cached copy if any.
 232 static const HeaderNameAndValue kForceFetchHeaders[] = {
 233   { "cache-control", "no-cache" },
 234   { "pragma", "no-cache" },
 235   { NULL, NULL }
 236 };
 237
 238 // If the request includes one of these request headers, then force our
 239 // cached copy (if any) to be revalidated before reusing it.
 240 static const HeaderNameAndValue kForceValidateHeaders[] = {
 241   { "cache-control", "max-age=0" },
 242   { NULL, NULL }
 243 };
 244
 245 static bool HeaderMatches(const HttpRequestHeaders& headers,
 246                           const HeaderNameAndValue* search) {
 247   for (; search->name; ++search) {
 248     std::string header_value;
 249     if (!headers.GetHeader(search->name, &header_value))
 250       continue;
 251
 252     if (!search->value)
 253       return true;
 254
 255     HttpUtil::ValuesIterator v(header_value.begin(), header_value.end(), ',');
 256     while (v.GetNext()) {
 257       if (LowerCaseEqualsASCII(v.value_begin(), v.value_end(), search->value))
 258         return true;
 259     }
 260   }
 261   return false;
 262 }
 263
 264 //-----------------------------------------------------------------------------
 265
 266 HttpCache::Transaction::Transaction(RequestPriority priority, HttpCache* cache)
 267     : next_state_(STATE_NONE),
 268       request_(NULL),
 269       priority_(priority),
 270       cache_(cache->GetWeakPtr()),
 271       entry_(NULL),
 272       new_entry_(NULL),
 273       new_response_(NULL),
 274       mode_(NONE),
 275       target_state_(STATE_NONE),
 276       reading_(false),
 277       invalid_range_(false),
 278       truncated_(false),
 279       is_sparse_(false),
 280       range_requested_(false),
 281       handling_206_(false),
 282       cache_pending_(false),
 283       done_reading_(false),
 284       vary_mismatch_(false),
 285       couldnt_conditionalize_request_(false),
 286       bypass_lock_for_test_(false),
 287       fail_conditionalization_for_test_(false),
 288       io_buf_len_(0),
 289       read_offset_(0),
 290       effective_load_flags_(0),
 291       write_len_(0),
 292       transaction_pattern_(PATTERN_UNDEFINED),
 293       total_received_bytes_(0),
 294       websocket_handshake_stream_base_create_helper_(NULL),
 295       weak_factory_(this) {
 296   static_assert(HttpCache::Transaction::kNumValidationHeaders ==
 297                     arraysize(kValidationHeaders),
 298                 "invalid number of validation headers");
 299
 300   io_callback_ = base::Bind(&Transaction::OnIOComplete,
 301                               weak_factory_.GetWeakPtr());
 302 }
 303
 304 HttpCache::Transaction::~Transaction() {
 305   // We may have to issue another IO, but we should never invoke the callback_
 306   // after this point.
 307   callback_.Reset();
 308
 309   if (cache_) {
 310     if (entry_) {
 311       bool cancel_request = reading_ && response_.headers.get();
 312       if (cancel_request) {
 313         if (partial_) {
 314           entry_->disk_entry->CancelSparseIO();
 315         } else {
 316           cancel_request &= (response_.headers->response_code() == 200);
 317         }
 318       }
 319
 320       cache_->DoneWithEntry(entry_, this, cancel_request);
 321     } else if (cache_pending_) {
 322       cache_->RemovePendingTransaction(this);
 323     }
 324   }
 325 }
 326
 327 int HttpCache::Transaction::WriteMetadata(IOBuffer* buf, int buf_len,
 328                                           const CompletionCallback& callback) {
 329   DCHECK(buf);
 330   DCHECK_GT(buf_len, 0);
 331   DCHECK(!callback.is_null());
 332   if (!cache_.get() || !entry_)
 333     return ERR_UNEXPECTED;
 334
 335   // We don't need to track this operation for anything.
 336   // It could be possible to check if there is something already written and
 337   // avoid writing again (it should be the same, right?), but let's allow the
 338   // caller to "update" the contents with something new.
 339   return entry_->disk_entry->WriteData(kMetadataIndex, 0, buf, buf_len,
 340                                        callback, true);
 341 }
 342
 343 bool HttpCache::Transaction::AddTruncatedFlag() {
 344   DCHECK(mode_ & WRITE || mode_ == NONE);
 345
 346   // Don't set the flag for sparse entries.
 347   if (partial_.get() && !truncated_)
 348     return true;
 349
 350   if (!CanResume(true))
 351     return false;
 352
 353   // We may have received the whole resource already.
 354   if (done_reading_)
 355     return true;
 356
 357   truncated_ = true;
 358   target_state_ = STATE_NONE;
 359   next_state_ = STATE_CACHE_WRITE_TRUNCATED_RESPONSE;
 360   DoLoop(OK);
 361   return true;
 362 }
 363
 364 LoadState HttpCache::Transaction::GetWriterLoadState() const {
 365   if (network_trans_.get())
 366     return network_trans_->GetLoadState();
 367   if (entry_ || !request_)
 368     return LOAD_STATE_IDLE;
 369   return LOAD_STATE_WAITING_FOR_CACHE;
 370 }
 371
 372 const BoundNetLog& HttpCache::Transaction::net_log() const {
 373   return net_log_;
 374 }
 375
 376 int HttpCache::Transaction::Start(const HttpRequestInfo* request,
 377                                   const CompletionCallback& callback,
 378                                   const BoundNetLog& net_log) {
 379   DCHECK(request);
 380   DCHECK(!callback.is_null());
 381
 382   // Ensure that we only have one asynchronous call at a time.
 383   DCHECK(callback_.is_null());
 384   DCHECK(!reading_);
 385   DCHECK(!network_trans_.get());
 386   DCHECK(!entry_);
 387
 388   if (!cache_.get())
 389     return ERR_UNEXPECTED;
 390
 391   SetRequest(net_log, request);
 392
 393   // We have to wait until the backend is initialized so we start the SM.
 394   next_state_ = STATE_GET_BACKEND;
 395   int rv = DoLoop(OK);
 396
 397   // Setting this here allows us to check for the existence of a callback_ to
 398   // determine if we are still inside Start.
 399   if (rv == ERR_IO_PENDING)
 400     callback_ = callback;
 401
 402   return rv;
 403 }
 404
 405 int HttpCache::Transaction::RestartIgnoringLastError(
 406     const CompletionCallback& callback) {
 407   DCHECK(!callback.is_null());
 408
 409   // Ensure that we only have one asynchronous call at a time.
 410   DCHECK(callback_.is_null());
 411
 412   if (!cache_.get())
 413     return ERR_UNEXPECTED;
 414
 415   int rv = RestartNetworkRequest();
 416
 417   if (rv == ERR_IO_PENDING)
 418     callback_ = callback;
 419
 420   return rv;
 421 }
 422
 423 int HttpCache::Transaction::RestartWithCertificate(
 424     X509Certificate* client_cert,
 425     const CompletionCallback& callback) {
 426   DCHECK(!callback.is_null());
 427
 428   // Ensure that we only have one asynchronous call at a time.
 429   DCHECK(callback_.is_null());
 430
 431   if (!cache_.get())
 432     return ERR_UNEXPECTED;
 433
 434   int rv = RestartNetworkRequestWithCertificate(client_cert);
 435
 436   if (rv == ERR_IO_PENDING)
 437     callback_ = callback;
 438
 439   return rv;
 440 }
 441
 442 int HttpCache::Transaction::RestartWithAuth(
 443     const AuthCredentials& credentials,
 444     const CompletionCallback& callback) {
 445   DCHECK(auth_response_.headers.get());
 446   DCHECK(!callback.is_null());
 447
 448   // Ensure that we only have one asynchronous call at a time.
 449   DCHECK(callback_.is_null());
 450
 451   if (!cache_.get())
 452     return ERR_UNEXPECTED;
 453
 454   // Clear the intermediate response since we are going to start over.
 455   auth_response_ = HttpResponseInfo();
 456
 457   int rv = RestartNetworkRequestWithAuth(credentials);
 458
 459   if (rv == ERR_IO_PENDING)
 460     callback_ = callback;
 461
 462   return rv;
 463 }
 464
 465 bool HttpCache::Transaction::IsReadyToRestartForAuth() {
 466   if (!network_trans_.get())
 467     return false;
 468   return network_trans_->IsReadyToRestartForAuth();
 469 }
 470
 471 int HttpCache::Transaction::Read(IOBuffer* buf, int buf_len,
 472                                  const CompletionCallback& callback) {
 473   DCHECK(buf);
 474   DCHECK_GT(buf_len, 0);
 475   DCHECK(!callback.is_null());
 476
 477   DCHECK(callback_.is_null());
 478
 479   if (!cache_.get())
 480     return ERR_UNEXPECTED;
 481
 482   // If we have an intermediate auth response at this point, then it means the
 483   // user wishes to read the network response (the error page).  If there is a
 484   // previous response in the cache then we should leave it intact.
 485   if (auth_response_.headers.get() && mode_ != NONE) {
 486     UpdateTransactionPattern(PATTERN_NOT_COVERED);
 487     DCHECK(mode_ & WRITE);
 488     DoneWritingToEntry(mode_ == READ_WRITE);
 489     mode_ = NONE;
 490   }
 491
 492   reading_ = true;
 493   int rv;
 494
 495   switch (mode_) {
 496     case READ_WRITE:
 497       DCHECK(partial_.get());
 498       if (!network_trans_.get()) {
 499         // We are just reading from the cache, but we may be writing later.
 500         rv = ReadFromEntry(buf, buf_len);
 501         break;
 502       }
 503     case NONE:
 504     case WRITE:
 505       DCHECK(network_trans_.get());
 506       rv = ReadFromNetwork(buf, buf_len);
 507       break;
 508     case READ:
 509       rv = ReadFromEntry(buf, buf_len);
 510       break;
 511     default:
 512       NOTREACHED();
 513       rv = ERR_FAILED;
 514   }
 515
 516   if (rv == ERR_IO_PENDING) {
 517     DCHECK(callback_.is_null());
 518     callback_ = callback;
 519   }
 520   return rv;
 521 }
 522
 523 void HttpCache::Transaction::StopCaching() {
 524   // We really don't know where we are now. Hopefully there is no operation in
 525   // progress, but nothing really prevents this method to be called after we
 526   // returned ERR_IO_PENDING. We cannot attempt to truncate the entry at this
 527   // point because we need the state machine for that (and even if we are really
 528   // free, that would be an asynchronous operation). In other words, keep the
 529   // entry how it is (it will be marked as truncated at destruction), and let
 530   // the next piece of code that executes know that we are now reading directly
 531   // from the net.
 532   // TODO(mmenke):  This doesn't release the lock on the cache entry, so a
 533   //                future request for the resource will be blocked on this one.
 534   //                Fix this.
 535   if (cache_.get() && entry_ && (mode_ & WRITE) && network_trans_.get() &&
 536       !is_sparse_ && !range_requested_) {
 537     mode_ = NONE;
 538   }
 539 }
 540
 541 bool HttpCache::Transaction::GetFullRequestHeaders(
 542     HttpRequestHeaders* headers) const {
 543   if (network_trans_)
 544     return network_trans_->GetFullRequestHeaders(headers);
 545
 546   // TODO(ttuttle): Read headers from cache.
 547   return false;
 548 }
 549
 550 int64 HttpCache::Transaction::GetTotalReceivedBytes() const {
 551   int64 total_received_bytes = total_received_bytes_;
 552   if (network_trans_)
 553     total_received_bytes += network_trans_->GetTotalReceivedBytes();
 554   return total_received_bytes;
 555 }
 556
 557 void HttpCache::Transaction::DoneReading() {
 558   if (cache_.get() && entry_) {
 559     DCHECK_NE(mode_, UPDATE);
 560     if (mode_ & WRITE) {
 561       DoneWritingToEntry(true);
 562     } else if (mode_ & READ) {
 563       // It is necessary to check mode_ & READ because it is possible
 564       // for mode_ to be NONE and entry_ non-NULL with a write entry
 565       // if StopCaching was called.
 566       cache_->DoneReadingFromEntry(entry_, this);
 567       entry_ = NULL;
 568     }
 569   }
 570 }
 571
 572 const HttpResponseInfo* HttpCache::Transaction::GetResponseInfo() const {
 573   // Null headers means we encountered an error or haven't a response yet
 574   if (auth_response_.headers.get())
 575     return &auth_response_;
 576   return &response_;
 577 }
 578
 579 LoadState HttpCache::Transaction::GetLoadState() const {
 580   LoadState state = GetWriterLoadState();
 581   if (state != LOAD_STATE_WAITING_FOR_CACHE)
 582     return state;
 583
 584   if (cache_.get())
 585     return cache_->GetLoadStateForPendingTransaction(this);
 586
 587   return LOAD_STATE_IDLE;
 588 }
 589
 590 UploadProgress HttpCache::Transaction::GetUploadProgress() const {
 591   if (network_trans_.get())
 592     return network_trans_->GetUploadProgress();
 593   return final_upload_progress_;
 594 }
 595
 596 void HttpCache::Transaction::SetQuicServerInfo(
 597     QuicServerInfo* quic_server_info) {}
 598
 599 bool HttpCache::Transaction::GetLoadTimingInfo(
 600     LoadTimingInfo* load_timing_info) const {
 601   if (network_trans_)
 602     return network_trans_->GetLoadTimingInfo(load_timing_info);
 603
 604   if (old_network_trans_load_timing_) {
 605     *load_timing_info = *old_network_trans_load_timing_;
 606     return true;
 607   }
 608
 609   if (first_cache_access_since_.is_null())
 610     return false;
 611
 612   // If the cache entry was opened, return that time.
 613   load_timing_info->send_start = first_cache_access_since_;
 614   // This time doesn't make much sense when reading from the cache, so just use
 615   // the same time as send_start.
 616   load_timing_info->send_end = first_cache_access_since_;
 617   return true;
 618 }
 619
 620 void HttpCache::Transaction::SetPriority(RequestPriority priority) {
 621   priority_ = priority;
 622   if (network_trans_)
 623     network_trans_->SetPriority(priority_);
 624 }
 625
 626 void HttpCache::Transaction::SetWebSocketHandshakeStreamCreateHelper(
 627     WebSocketHandshakeStreamBase::CreateHelper* create_helper) {
 628   websocket_handshake_stream_base_create_helper_ = create_helper;
 629   if (network_trans_)
 630     network_trans_->SetWebSocketHandshakeStreamCreateHelper(create_helper);
 631 }
 632
 633 void HttpCache::Transaction::SetBeforeNetworkStartCallback(
 634     const BeforeNetworkStartCallback& callback) {
 635   DCHECK(!network_trans_);
 636   before_network_start_callback_ = callback;
 637 }
 638
 639 void HttpCache::Transaction::SetBeforeProxyHeadersSentCallback(
 640     const BeforeProxyHeadersSentCallback& callback) {
 641   DCHECK(!network_trans_);
 642   before_proxy_headers_sent_callback_ = callback;
 643 }
 644
 645 int HttpCache::Transaction::ResumeNetworkStart() {
 646   if (network_trans_)
 647     return network_trans_->ResumeNetworkStart();
 648   return ERR_UNEXPECTED;
 649 }
 650
 651 void HttpCache::Transaction::GetConnectionAttempts(
 652     ConnectionAttempts* out) const {
 653   ConnectionAttempts new_connection_attempts;
 654   if (network_trans_)
 655     network_trans_->GetConnectionAttempts(&new_connection_attempts);
 656
 657   out->swap(new_connection_attempts);
 658   out->insert(out->begin(), old_connection_attempts_.begin(),
 659               old_connection_attempts_.end());
 660 }
 661
 662 //-----------------------------------------------------------------------------
 663
 664 void HttpCache::Transaction::DoCallback(int rv) {
 665   DCHECK(rv != ERR_IO_PENDING);
 666   DCHECK(!callback_.is_null());
 667
 668   read_buf_ = NULL;  // Release the buffer before invoking the callback.
 669
 670   // Since Run may result in Read being called, clear callback_ up front.
 671   CompletionCallback c = callback_;
 672   callback_.Reset();
 673   c.Run(rv);
 674 }
 675
 676 int HttpCache::Transaction::HandleResult(int rv) {
 677   DCHECK(rv != ERR_IO_PENDING);
 678   if (!callback_.is_null())
 679     DoCallback(rv);
 680
 681   return rv;
 682 }
 683
 684 // A few common patterns: (Foo* means Foo -> FooComplete)
 685 //
 686 // 1. Not-cached entry:
 687 //   Start():
 688 //   GetBackend* -> InitEntry -> OpenEntry* -> CreateEntry* -> AddToEntry* ->
 689 //   SendRequest* -> SuccessfulSendRequest -> OverwriteCachedResponse ->
 690 //   CacheWriteResponse* -> TruncateCachedData* -> TruncateCachedMetadata* ->
 691 //   PartialHeadersReceived
 692 //
 693 //   Read():
 694 //   NetworkRead* -> CacheWriteData*
 695 //
 696 // 2. Cached entry, no validation:
 697 //   Start():
 698 //   GetBackend* -> InitEntry -> OpenEntry* -> AddToEntry* -> CacheReadResponse*
 699 //   -> CacheDispatchValidation -> BeginPartialCacheValidation() ->
 700 //   BeginCacheValidation() -> SetupEntryForRead()
 701 //
 702 //   Read():
 703 //   CacheReadData*
 704 //
 705 // 3. Cached entry, validation (304):
 706 //   Start():
 707 //   GetBackend* -> InitEntry -> OpenEntry* -> AddToEntry* -> CacheReadResponse*
 708 //   -> CacheDispatchValidation -> BeginPartialCacheValidation() ->
 709 //   BeginCacheValidation() -> SendRequest* -> SuccessfulSendRequest ->
 710 //   UpdateCachedResponse -> CacheWriteResponse* -> UpdateCachedResponseComplete
 711 //   -> OverwriteCachedResponse -> PartialHeadersReceived
 712 //
 713 //   Read():
 714 //   CacheReadData*
 715 //
 716 // 4. Cached entry, validation and replace (200):
 717 //   Start():
 718 //   GetBackend* -> InitEntry -> OpenEntry* -> AddToEntry* -> CacheReadResponse*
 719 //   -> CacheDispatchValidation -> BeginPartialCacheValidation() ->
 720 //   BeginCacheValidation() -> SendRequest* -> SuccessfulSendRequest ->
 721 //   OverwriteCachedResponse -> CacheWriteResponse* -> DoTruncateCachedData* ->
 722 //   TruncateCachedMetadata* -> PartialHeadersReceived
 723 //
 724 //   Read():
 725 //   NetworkRead* -> CacheWriteData*
 726 //
 727 // 5. Sparse entry, partially cached, byte range request:
 728 //   Start():
 729 //   GetBackend* -> InitEntry -> OpenEntry* -> AddToEntry* -> CacheReadResponse*
 730 //   -> CacheDispatchValidation -> BeginPartialCacheValidation() ->
 731 //   CacheQueryData* -> ValidateEntryHeadersAndContinue() ->
 732 //   StartPartialCacheValidation -> CompletePartialCacheValidation ->
 733 //   BeginCacheValidation() -> SendRequest* -> SuccessfulSendRequest ->
 734 //   UpdateCachedResponse -> CacheWriteResponse* -> UpdateCachedResponseComplete
 735 //   -> OverwriteCachedResponse -> PartialHeadersReceived
 736 //
 737 //   Read() 1:
 738 //   NetworkRead* -> CacheWriteData*
 739 //
 740 //   Read() 2:
 741 //   NetworkRead* -> CacheWriteData* -> StartPartialCacheValidation ->
 742 //   CompletePartialCacheValidation -> CacheReadData* ->
 743 //
 744 //   Read() 3:
 745 //   CacheReadData* -> StartPartialCacheValidation ->
 746 //   CompletePartialCacheValidation -> BeginCacheValidation() -> SendRequest* ->
 747 //   SuccessfulSendRequest -> UpdateCachedResponse* -> OverwriteCachedResponse
 748 //   -> PartialHeadersReceived -> NetworkRead* -> CacheWriteData*
 749 //
 750 // 6. HEAD. Not-cached entry:
 751 //   Pass through. Don't save a HEAD by itself.
 752 //   Start():
 753 //   GetBackend* -> InitEntry -> OpenEntry* -> SendRequest*
 754 //
 755 // 7. HEAD. Cached entry, no validation:
 756 //   Start():
 757 //   The same flow as for a GET request (example #2)
 758 //
 759 //   Read():
 760 //   CacheReadData (returns 0)
 761 //
 762 // 8. HEAD. Cached entry, validation (304):
 763 //   The request updates the stored headers.
 764 //   Start(): Same as for a GET request (example #3)
 765 //
 766 //   Read():
 767 //   CacheReadData (returns 0)
 768 //
 769 // 9. HEAD. Cached entry, validation and replace (200):
 770 //   Pass through. The request dooms the old entry, as a HEAD won't be stored by
 771 //   itself.
 772 //   Start():
 773 //   GetBackend* -> InitEntry -> OpenEntry* -> AddToEntry* -> CacheReadResponse*
 774 //   -> CacheDispatchValidation -> BeginPartialCacheValidation() ->
 775 //   BeginCacheValidation() -> SendRequest* -> SuccessfulSendRequest ->
 776 //   OverwriteCachedResponse
 777 //
 778 // 10. HEAD. Sparse entry, partially cached:
 779 //   Serve the request from the cache, as long as it doesn't require
 780 //   revalidation. Ignore missing ranges when deciding to revalidate. If the
 781 //   entry requires revalidation, ignore the whole request and go to full pass
 782 //   through (the result of the HEAD request will NOT update the entry).
 783 //
 784 //   Start(): Basically the same as example 7, as we never create a partial_
 785 //   object for this request.
 786 //
 787 // 11. Prefetch, not-cached entry:
 788 //   The same as example 1. The "unused_since_prefetch" bit is stored as true in
 789 //   UpdateCachedResponse.
 790 //
 791 // 12. Prefetch, cached entry:
 792 //   Like examples 2-4, only CacheToggleUnusedSincePrefetch* is inserted between
 793 //   CacheReadResponse* and CacheDispatchValidation if the unused_since_prefetch
 794 //   bit is unset.
 795 //
 796 // 13. Cached entry less than 5 minutes old, unused_since_prefetch is true:
 797 //   Skip validation, similar to example 2.
 798 //   GetBackend* -> InitEntry -> OpenEntry* -> AddToEntry* -> CacheReadResponse*
 799 //   -> CacheToggleUnusedSincePrefetch* -> CacheDispatchValidation ->
 800 //   BeginPartialCacheValidation() -> BeginCacheValidation() ->
 801 //   SetupEntryForRead()
 802 //
 803 //   Read():
 804 //   CacheReadData*
 805 //
 806 // 14. Cached entry more than 5 minutes old, unused_since_prefetch is true:
 807 //   Like examples 2-4, only CacheToggleUnusedSincePrefetch* is inserted between
 808 //   CacheReadResponse* and CacheDispatchValidation.
 809 int HttpCache::Transaction::DoLoop(int result) {
 810   DCHECK(next_state_ != STATE_NONE);
 811
 812   int rv = result;
 813   do {
 814     State state = next_state_;
 815     next_state_ = STATE_NONE;
 816     switch (state) {
 817       case STATE_GET_BACKEND:
 818         DCHECK_EQ(OK, rv);
 819         rv = DoGetBackend();
 820         break;
 821       case STATE_GET_BACKEND_COMPLETE:
 822         rv = DoGetBackendComplete(rv);
 823         break;
 824       case STATE_SEND_REQUEST:
 825         DCHECK_EQ(OK, rv);
 826         rv = DoSendRequest();
 827         break;
 828       case STATE_SEND_REQUEST_COMPLETE:
 829         rv = DoSendRequestComplete(rv);
 830         break;
 831       case STATE_SUCCESSFUL_SEND_REQUEST:
 832         DCHECK_EQ(OK, rv);
 833         rv = DoSuccessfulSendRequest();
 834         break;
 835       case STATE_NETWORK_READ:
 836         DCHECK_EQ(OK, rv);
 837         rv = DoNetworkRead();
 838         break;
 839       case STATE_NETWORK_READ_COMPLETE:
 840         rv = DoNetworkReadComplete(rv);
 841         break;
 842       case STATE_INIT_ENTRY:
 843         DCHECK_EQ(OK, rv);
 844         rv = DoInitEntry();
 845         break;
 846       case STATE_OPEN_ENTRY:
 847         DCHECK_EQ(OK, rv);
 848         rv = DoOpenEntry();
 849         break;
 850       case STATE_OPEN_ENTRY_COMPLETE:
 851         rv = DoOpenEntryComplete(rv);
 852         break;
 853       case STATE_CREATE_ENTRY:
 854         DCHECK_EQ(OK, rv);
 855         rv = DoCreateEntry();
 856         break;
 857       case STATE_CREATE_ENTRY_COMPLETE:
 858         rv = DoCreateEntryComplete(rv);
 859         break;
 860       case STATE_DOOM_ENTRY:
 861         DCHECK_EQ(OK, rv);
 862         rv = DoDoomEntry();
 863         break;
 864       case STATE_DOOM_ENTRY_COMPLETE:
 865         rv = DoDoomEntryComplete(rv);
 866         break;
 867       case STATE_ADD_TO_ENTRY:
 868         DCHECK_EQ(OK, rv);
 869         rv = DoAddToEntry();
 870         break;
 871       case STATE_ADD_TO_ENTRY_COMPLETE:
 872         rv = DoAddToEntryComplete(rv);
 873         break;
 874       case STATE_START_PARTIAL_CACHE_VALIDATION:
 875         DCHECK_EQ(OK, rv);
 876         rv = DoStartPartialCacheValidation();
 877         break;
 878       case STATE_COMPLETE_PARTIAL_CACHE_VALIDATION:
 879         rv = DoCompletePartialCacheValidation(rv);
 880         break;
 881       case STATE_UPDATE_CACHED_RESPONSE:
 882         DCHECK_EQ(OK, rv);
 883         rv = DoUpdateCachedResponse();
 884         break;
 885       case STATE_UPDATE_CACHED_RESPONSE_COMPLETE:
 886         rv = DoUpdateCachedResponseComplete(rv);
 887         break;
 888       case STATE_OVERWRITE_CACHED_RESPONSE:
 889         DCHECK_EQ(OK, rv);
 890         rv = DoOverwriteCachedResponse();
 891         break;
 892       case STATE_TRUNCATE_CACHED_DATA:
 893         DCHECK_EQ(OK, rv);
 894         rv = DoTruncateCachedData();
 895         break;
 896       case STATE_TRUNCATE_CACHED_DATA_COMPLETE:
 897         rv = DoTruncateCachedDataComplete(rv);
 898         break;
 899       case STATE_TRUNCATE_CACHED_METADATA:
 900         DCHECK_EQ(OK, rv);
 901         rv = DoTruncateCachedMetadata();
 902         break;
 903       case STATE_TRUNCATE_CACHED_METADATA_COMPLETE:
 904         rv = DoTruncateCachedMetadataComplete(rv);
 905         break;
 906       case STATE_PARTIAL_HEADERS_RECEIVED:
 907         DCHECK_EQ(OK, rv);
 908         rv = DoPartialHeadersReceived();
 909         break;
 910       case STATE_CACHE_READ_RESPONSE:
 911         DCHECK_EQ(OK, rv);
 912         rv = DoCacheReadResponse();
 913         break;
 914       case STATE_CACHE_READ_RESPONSE_COMPLETE:
 915         rv = DoCacheReadResponseComplete(rv);
 916         break;
 917       case STATE_CACHE_DISPATCH_VALIDATION:
 918         DCHECK_EQ(OK, rv);
 919         rv = DoCacheDispatchValidation();
 920         break;
 921       case STATE_TOGGLE_UNUSED_SINCE_PREFETCH:
 922         DCHECK_EQ(OK, rv);
 923         rv = DoCacheToggleUnusedSincePrefetch();
 924         break;
 925       case STATE_TOGGLE_UNUSED_SINCE_PREFETCH_COMPLETE:
 926         rv = DoCacheToggleUnusedSincePrefetchComplete(rv);
 927         break;
 928       case STATE_CACHE_WRITE_RESPONSE:
 929         DCHECK_EQ(OK, rv);
 930         rv = DoCacheWriteResponse();
 931         break;
 932       case STATE_CACHE_WRITE_TRUNCATED_RESPONSE:
 933         DCHECK_EQ(OK, rv);
 934         rv = DoCacheWriteTruncatedResponse();
 935         break;
 936       case STATE_CACHE_WRITE_RESPONSE_COMPLETE:
 937         rv = DoCacheWriteResponseComplete(rv);
 938         break;
 939       case STATE_CACHE_READ_METADATA:
 940         DCHECK_EQ(OK, rv);
 941         rv = DoCacheReadMetadata();
 942         break;
 943       case STATE_CACHE_READ_METADATA_COMPLETE:
 944         rv = DoCacheReadMetadataComplete(rv);
 945         break;
 946       case STATE_CACHE_QUERY_DATA:
 947         DCHECK_EQ(OK, rv);
 948         rv = DoCacheQueryData();
 949         break;
 950       case STATE_CACHE_QUERY_DATA_COMPLETE:
 951         rv = DoCacheQueryDataComplete(rv);
 952         break;
 953       case STATE_CACHE_READ_DATA:
 954         DCHECK_EQ(OK, rv);
 955         rv = DoCacheReadData();
 956         break;
 957       case STATE_CACHE_READ_DATA_COMPLETE:
 958         rv = DoCacheReadDataComplete(rv);
 959         break;
 960       case STATE_CACHE_WRITE_DATA:
 961         rv = DoCacheWriteData(rv);
 962         break;
 963       case STATE_CACHE_WRITE_DATA_COMPLETE:
 964         rv = DoCacheWriteDataComplete(rv);
 965         break;
 966       default:
 967         NOTREACHED() << "bad state";
 968         rv = ERR_FAILED;
 969         break;
 970     }
 971   } while (rv != ERR_IO_PENDING && next_state_ != STATE_NONE);
 972
 973   if (rv != ERR_IO_PENDING)
 974     HandleResult(rv);
 975
 976   return rv;
 977 }
 978
 979 int HttpCache::Transaction::DoGetBackend() {
 980   cache_pending_ = true;
 981   next_state_ = STATE_GET_BACKEND_COMPLETE;
 982   net_log_.BeginEvent(NetLog::TYPE_HTTP_CACHE_GET_BACKEND);
 983   return cache_->GetBackendForTransaction(this);
 984 }
 985
 986 int HttpCache::Transaction::DoGetBackendComplete(int result) {
 987   DCHECK(result == OK || result == ERR_FAILED);
 988   net_log_.EndEventWithNetErrorCode(NetLog::TYPE_HTTP_CACHE_GET_BACKEND,
 989                                     result);
 990   cache_pending_ = false;
 991
 992   if (!ShouldPassThrough()) {
 993     cache_key_ = cache_->GenerateCacheKey(request_);
 994
 995     // Requested cache access mode.
 996     if (effective_load_flags_ & LOAD_ONLY_FROM_CACHE) {
 997       mode_ = READ;
 998     } else if (effective_load_flags_ & LOAD_BYPASS_CACHE) {
 999       mode_ = WRITE;
1000     } else {
1001       mode_ = READ_WRITE;
1002     }
1003
1004     // Downgrade to UPDATE if the request has been externally conditionalized.
1005     if (external_validation_.initialized) {
1006       if (mode_ & WRITE) {
1007         // Strip off the READ_DATA bit (and maybe add back a READ_META bit
1008         // in case READ was off).
1009         mode_ = UPDATE;
1010       } else {
1011         mode_ = NONE;
1012       }
1013     }
1014   }
1015
1016   // Use PUT and DELETE only to invalidate existing stored entries.
1017   if ((request_->method == "PUT" || request_->method == "DELETE") &&
1018       mode_ != READ_WRITE && mode_ != WRITE) {
1019     mode_ = NONE;
1020   }
1021
1022   // Note that if mode_ == UPDATE (which is tied to external_validation_), the
1023   // transaction behaves the same for GET and HEAD requests at this point: if it
1024   // was not modified, the entry is updated and a response is not returned from
1025   // the cache. If we receive 200, it doesn't matter if there was a validation
1026   // header or not.
1027   if (request_->method == "HEAD" && mode_ == WRITE)
1028     mode_ = NONE;
1029
1030   // If must use cache, then we must fail.  This can happen for back/forward
1031   // navigations to a page generated via a form post.
1032   if (!(mode_ & READ) && effective_load_flags_ & LOAD_ONLY_FROM_CACHE)
1033     return ERR_CACHE_MISS;
1034
1035   if (mode_ == NONE) {
1036     if (partial_.get()) {
1037       partial_->RestoreHeaders(&custom_request_->extra_headers);
1038       partial_.reset();
1039     }
1040     next_state_ = STATE_SEND_REQUEST;
1041   } else {
1042     next_state_ = STATE_INIT_ENTRY;
1043   }
1044
1045   // This is only set if we have something to do with the response.
1046   range_requested_ = (partial_.get() != NULL);
1047
1048   return OK;
1049 }
1050
1051 int HttpCache::Transaction::DoSendRequest() {
1052   DCHECK(mode_ & WRITE || mode_ == NONE);
1053   DCHECK(!network_trans_.get());
1054
1055   send_request_since_ = TimeTicks::Now();
1056
1057   // Create a network transaction.
1058   int rv = cache_->network_layer_->CreateTransaction(priority_,
1059                                                      &network_trans_);
1060   if (rv != OK)
1061     return rv;
1062   network_trans_->SetBeforeNetworkStartCallback(before_network_start_callback_);
1063   network_trans_->SetBeforeProxyHeadersSentCallback(
1064       before_proxy_headers_sent_callback_);
1065
1066   // Old load timing information, if any, is now obsolete.
1067   old_network_trans_load_timing_.reset();
1068
1069   if (websocket_handshake_stream_base_create_helper_)
1070     network_trans_->SetWebSocketHandshakeStreamCreateHelper(
1071         websocket_handshake_stream_base_create_helper_);
1072
1073   next_state_ = STATE_SEND_REQUEST_COMPLETE;
1074   rv = network_trans_->Start(request_, io_callback_, net_log_);
1075   return rv;
1076 }
1077
1078 int HttpCache::Transaction::DoSendRequestComplete(int result) {
1079   if (!cache_.get())
1080     return ERR_UNEXPECTED;
1081
1082   // If we tried to conditionalize the request and failed, we know
1083   // we won't be reading from the cache after this point.
1084   if (couldnt_conditionalize_request_)
1085     mode_ = WRITE;
1086
1087   if (result == OK) {
1088     next_state_ = STATE_SUCCESSFUL_SEND_REQUEST;
1089     return OK;
1090   }
1091
1092   const HttpResponseInfo* response = network_trans_->GetResponseInfo();
1093   response_.network_accessed = response->network_accessed;
1094
1095   // Do not record requests that have network errors or restarts.
1096   UpdateTransactionPattern(PATTERN_NOT_COVERED);
1097   if (IsCertificateError(result)) {
1098     // If we get a certificate error, then there is a certificate in ssl_info,
1099     // so GetResponseInfo() should never return NULL here.
1100     DCHECK(response);
1101     response_.ssl_info = response->ssl_info;
1102   } else if (result == ERR_SSL_CLIENT_AUTH_CERT_NEEDED) {
1103     DCHECK(response);
1104     response_.cert_request_info = response->cert_request_info;
1105   } else if (response_.was_cached) {
1106     DoneWritingToEntry(true);
1107   }
1108
1109   return result;
1110 }
1111
1112 // We received the response headers and there is no error.
1113 int HttpCache::Transaction::DoSuccessfulSendRequest() {
1114   DCHECK(!new_response_);
1115   const HttpResponseInfo* new_response = network_trans_->GetResponseInfo();
1116   bool authentication_failure = false;
1117
1118   if (new_response->headers->response_code() == 401 ||
1119       new_response->headers->response_code() == 407) {
1120     auth_response_ = *new_response;
1121     if (!reading_)
1122       return OK;
1123
1124     // We initiated a second request the caller doesn't know about. We should be
1125     // able to authenticate this request because we should have authenticated
1126     // this URL moments ago.
1127     if (IsReadyToRestartForAuth()) {
1128       DCHECK(!response_.auth_challenge.get());
1129       next_state_ = STATE_SEND_REQUEST_COMPLETE;
1130       // In theory we should check to see if there are new cookies, but there
1131       // is no way to do that from here.
1132       return network_trans_->RestartWithAuth(AuthCredentials(), io_callback_);
1133     }
1134
1135     // We have to perform cleanup at this point so that at least the next
1136     // request can succeed.
1137     authentication_failure = true;
1138     if (entry_)
1139       DoomPartialEntry(false);
1140     mode_ = NONE;
1141     partial_.reset();
1142   }
1143
1144   new_response_ = new_response;
1145   if (authentication_failure ||
1146       (!ValidatePartialResponse() && !auth_response_.headers.get())) {
1147     // Something went wrong with this request and we have to restart it.
1148     // If we have an authentication response, we are exposed to weird things
1149     // hapenning if the user cancels the authentication before we receive
1150     // the new response.
1151     net_log_.AddEvent(NetLog::TYPE_HTTP_CACHE_RE_SEND_PARTIAL_REQUEST);
1152     UpdateTransactionPattern(PATTERN_NOT_COVERED);
1153     response_ = HttpResponseInfo();
1154     ResetNetworkTransaction();
1155     new_response_ = NULL;
1156     next_state_ = STATE_SEND_REQUEST;
1157     return OK;
1158   }
1159
1160   if (handling_206_ && mode_ == READ_WRITE && !truncated_ && !is_sparse_) {
1161     // We have stored the full entry, but it changed and the server is
1162     // sending a range. We have to delete the old entry.
1163     UpdateTransactionPattern(PATTERN_NOT_COVERED);
1164     DoneWritingToEntry(false);
1165   }
1166
1167   if (mode_ == WRITE &&
1168       transaction_pattern_ != PATTERN_ENTRY_CANT_CONDITIONALIZE) {
1169     UpdateTransactionPattern(PATTERN_ENTRY_NOT_CACHED);
1170   }
1171
1172   // Invalidate any cached GET with a successful PUT or DELETE.
1173   if (mode_ == WRITE &&
1174       (request_->method == "PUT" || request_->method == "DELETE")) {
1175     if (NonErrorResponse(new_response->headers->response_code())) {
1176       int ret = cache_->DoomEntry(cache_key_, NULL);
1177       DCHECK_EQ(OK, ret);
1178     }
1179     cache_->DoneWritingToEntry(entry_, true);
1180     entry_ = NULL;
1181     mode_ = NONE;
1182   }
1183
1184   // Invalidate any cached GET with a successful POST.
1185   if (!(effective_load_flags_ & LOAD_DISABLE_CACHE) &&
1186       request_->method == "POST" &&
1187       NonErrorResponse(new_response->headers->response_code())) {
1188     cache_->DoomMainEntryForUrl(request_->url);
1189   }
1190
1191   RecordNoStoreHeaderHistogram(request_->load_flags, new_response);
1192
1193   if (new_response_->headers->response_code() == 416 &&
1194       (request_->method == "GET" || request_->method == "POST")) {
1195     // If there is an active entry it may be destroyed with this transaction.
1196     response_ = *new_response_;
1197     return OK;
1198   }
1199
1200   // Are we expecting a response to a conditional query?
1201   if (mode_ == READ_WRITE || mode_ == UPDATE) {
1202     if (new_response->headers->response_code() == 304 || handling_206_) {
1203       UpdateTransactionPattern(PATTERN_ENTRY_VALIDATED);
1204       next_state_ = STATE_UPDATE_CACHED_RESPONSE;
1205       return OK;
1206     }
1207     UpdateTransactionPattern(PATTERN_ENTRY_UPDATED);
1208     mode_ = WRITE;
1209   }
1210
1211   next_state_ = STATE_OVERWRITE_CACHED_RESPONSE;
1212   return OK;
1213 }
1214
1215 int HttpCache::Transaction::DoNetworkRead() {
1216   next_state_ = STATE_NETWORK_READ_COMPLETE;
1217   return network_trans_->Read(read_buf_.get(), io_buf_len_, io_callback_);
1218 }
1219
1220 int HttpCache::Transaction::DoNetworkReadComplete(int result) {
1221   DCHECK(mode_ & WRITE || mode_ == NONE);
1222
1223   if (!cache_.get())
1224     return ERR_UNEXPECTED;
1225
1226   // If there is an error or we aren't saving the data, we are done; just wait
1227   // until the destructor runs to see if we can keep the data.
1228   if (mode_ == NONE || result < 0)
1229     return result;
1230
1231   next_state_ = STATE_CACHE_WRITE_DATA;
1232   return result;
1233 }
1234
1235 int HttpCache::Transaction::DoInitEntry() {
1236   DCHECK(!new_entry_);
1237
1238   if (!cache_.get())
1239     return ERR_UNEXPECTED;
1240
1241   if (mode_ == WRITE) {
1242     next_state_ = STATE_DOOM_ENTRY;
1243     return OK;
1244   }
1245
1246   next_state_ = STATE_OPEN_ENTRY;
1247   return OK;
1248 }
1249
1250 int HttpCache::Transaction::DoOpenEntry() {
1251   DCHECK(!new_entry_);
1252   next_state_ = STATE_OPEN_ENTRY_COMPLETE;
1253   cache_pending_ = true;
1254   net_log_.BeginEvent(NetLog::TYPE_HTTP_CACHE_OPEN_ENTRY);
1255   first_cache_access_since_ = TimeTicks::Now();
1256   return cache_->OpenEntry(cache_key_, &new_entry_, this);
1257 }
1258
1259 int HttpCache::Transaction::DoOpenEntryComplete(int result) {
1260   // It is important that we go to STATE_ADD_TO_ENTRY whenever the result is
1261   // OK, otherwise the cache will end up with an active entry without any
1262   // transaction attached.
1263   net_log_.EndEventWithNetErrorCode(NetLog::TYPE_HTTP_CACHE_OPEN_ENTRY, result);
1264   cache_pending_ = false;
1265   if (result == OK) {
1266     next_state_ = STATE_ADD_TO_ENTRY;
1267     return OK;
1268   }
1269
1270   if (result == ERR_CACHE_RACE) {
1271     next_state_ = STATE_INIT_ENTRY;
1272     return OK;
1273   }
1274
1275   if (request_->method == "PUT" || request_->method == "DELETE" ||
1276       (request_->method == "HEAD" && mode_ == READ_WRITE)) {
1277     DCHECK(mode_ == READ_WRITE || mode_ == WRITE || request_->method == "HEAD");
1278     mode_ = NONE;
1279     next_state_ = STATE_SEND_REQUEST;
1280     return OK;
1281   }
1282
1283   if (mode_ == READ_WRITE) {
1284     mode_ = WRITE;
1285     next_state_ = STATE_CREATE_ENTRY;
1286     return OK;
1287   }
1288   if (mode_ == UPDATE) {
1289     // There is no cache entry to update; proceed without caching.
1290     mode_ = NONE;
1291     next_state_ = STATE_SEND_REQUEST;
1292     return OK;
1293   }
1294
1295   // The entry does not exist, and we are not permitted to create a new entry,
1296   // so we must fail.
1297   return ERR_CACHE_MISS;
1298 }
1299
1300 int HttpCache::Transaction::DoCreateEntry() {
1301   DCHECK(!new_entry_);
1302   next_state_ = STATE_CREATE_ENTRY_COMPLETE;
1303   cache_pending_ = true;
1304   net_log_.BeginEvent(NetLog::TYPE_HTTP_CACHE_CREATE_ENTRY);
1305   return cache_->CreateEntry(cache_key_, &new_entry_, this);
1306 }
1307
1308 int HttpCache::Transaction::DoCreateEntryComplete(int result) {
1309   // It is important that we go to STATE_ADD_TO_ENTRY whenever the result is
1310   // OK, otherwise the cache will end up with an active entry without any
1311   // transaction attached.
1312   net_log_.EndEventWithNetErrorCode(NetLog::TYPE_HTTP_CACHE_CREATE_ENTRY,
1313                                     result);
1314   cache_pending_ = false;
1315   next_state_ = STATE_ADD_TO_ENTRY;
1316
1317   if (result == ERR_CACHE_RACE) {
1318     next_state_ = STATE_INIT_ENTRY;
1319     return OK;
1320   }
1321
1322   if (result != OK) {
1323     // We have a race here: Maybe we failed to open the entry and decided to
1324     // create one, but by the time we called create, another transaction already
1325     // created the entry. If we want to eliminate this issue, we need an atomic
1326     // OpenOrCreate() method exposed by the disk cache.
1327     DLOG(WARNING) << "Unable to create cache entry";
1328     mode_ = NONE;
1329     if (partial_.get())
1330       partial_->RestoreHeaders(&custom_request_->extra_headers);
1331     next_state_ = STATE_SEND_REQUEST;
1332   }
1333   return OK;
1334 }
1335
1336 int HttpCache::Transaction::DoDoomEntry() {
1337   next_state_ = STATE_DOOM_ENTRY_COMPLETE;
1338   cache_pending_ = true;
1339   if (first_cache_access_since_.is_null())
1340     first_cache_access_since_ = TimeTicks::Now();
1341   net_log_.BeginEvent(NetLog::TYPE_HTTP_CACHE_DOOM_ENTRY);
1342   return cache_->DoomEntry(cache_key_, this);
1343 }
1344
1345 int HttpCache::Transaction::DoDoomEntryComplete(int result) {
1346   net_log_.EndEventWithNetErrorCode(NetLog::TYPE_HTTP_CACHE_DOOM_ENTRY, result);
1347   next_state_ = STATE_CREATE_ENTRY;
1348   cache_pending_ = false;
1349   if (result == ERR_CACHE_RACE)
1350     next_state_ = STATE_INIT_ENTRY;
1351   return OK;
1352 }
1353
1354 int HttpCache::Transaction::DoAddToEntry() {
1355   DCHECK(new_entry_);
1356   cache_pending_ = true;
1357   next_state_ = STATE_ADD_TO_ENTRY_COMPLETE;
1358   net_log_.BeginEvent(NetLog::TYPE_HTTP_CACHE_ADD_TO_ENTRY);
1359   DCHECK(entry_lock_waiting_since_.is_null());
1360   entry_lock_waiting_since_ = TimeTicks::Now();
1361   int rv = cache_->AddTransactionToEntry(new_entry_, this);
1362   if (rv == ERR_IO_PENDING) {
1363     if (bypass_lock_for_test_) {
1364       OnAddToEntryTimeout(entry_lock_waiting_since_);
1365     } else {
1366       int timeout_milliseconds = 20 * 1000;
1367       if (partial_ && new_entry_->writer &&
1368           new_entry_->writer->range_requested_) {
1369         // Quickly timeout and bypass the cache if we're a range request and
1370         // we're blocked by the reader/writer lock. Doing so eliminates a long
1371         // running issue, http://crbug.com/31014, where two of the same media
1372         // resources could not be played back simultaneously due to one locking
1373         // the cache entry until the entire video was downloaded.
1374         //
1375         // Bypassing the cache is not ideal, as we are now ignoring the cache
1376         // entirely for all range requests to a resource beyond the first. This
1377         // is however a much more succinct solution than the alternatives, which
1378         // would require somewhat significant changes to the http caching logic.
1379         //
1380         // Allow some timeout slack for the entry addition to complete in case
1381         // the writer lock is imminently released; we want to avoid skipping
1382         // the cache if at all possible. See http://crbug.com/408765
1383         timeout_milliseconds = 25;
1384       }
1385       base::MessageLoop::current()->PostDelayedTask(
1386           FROM_HERE,
1387           base::Bind(&HttpCache::Transaction::OnAddToEntryTimeout,
1388                      weak_factory_.GetWeakPtr(), entry_lock_waiting_since_),
1389           TimeDelta::FromMilliseconds(timeout_milliseconds));
1390     }
1391   }
1392   return rv;
1393 }
1394
1395 int HttpCache::Transaction::DoAddToEntryComplete(int result) {
1396   net_log_.EndEventWithNetErrorCode(NetLog::TYPE_HTTP_CACHE_ADD_TO_ENTRY,
1397                                     result);
1398   const TimeDelta entry_lock_wait =
1399       TimeTicks::Now() - entry_lock_waiting_since_;
1400   UMA_HISTOGRAM_TIMES("HttpCache.EntryLockWait", entry_lock_wait);
1401
1402   entry_lock_waiting_since_ = TimeTicks();
1403   DCHECK(new_entry_);
1404   cache_pending_ = false;
1405
1406   if (result == OK)
1407     entry_ = new_entry_;
1408
1409   // If there is a failure, the cache should have taken care of new_entry_.
1410   new_entry_ = NULL;
1411
1412   if (result == ERR_CACHE_RACE) {
1413     next_state_ = STATE_INIT_ENTRY;
1414     return OK;
1415   }
1416
1417   if (result == ERR_CACHE_LOCK_TIMEOUT) {
1418     // The cache is busy, bypass it for this transaction.
1419     mode_ = NONE;
1420     next_state_ = STATE_SEND_REQUEST;
1421     if (partial_) {
1422       partial_->RestoreHeaders(&custom_request_->extra_headers);
1423       partial_.reset();
1424     }
1425     return OK;
1426   }
1427
1428   if (result != OK) {
1429     NOTREACHED();
1430     return result;
1431   }
1432
1433   if (mode_ == WRITE) {
1434     if (partial_.get())
1435       partial_->RestoreHeaders(&custom_request_->extra_headers);
1436     next_state_ = STATE_SEND_REQUEST;
1437   } else {
1438     // We have to read the headers from the cached entry.
1439     DCHECK(mode_ & READ_META);
1440     next_state_ = STATE_CACHE_READ_RESPONSE;
1441   }
1442   return OK;
1443 }
1444
1445 // We may end up here multiple times for a given request.
1446 int HttpCache::Transaction::DoStartPartialCacheValidation() {
1447   if (mode_ == NONE)
1448     return OK;
1449
1450   next_state_ = STATE_COMPLETE_PARTIAL_CACHE_VALIDATION;
1451   return partial_->ShouldValidateCache(entry_->disk_entry, io_callback_);
1452 }
1453
1454 int HttpCache::Transaction::DoCompletePartialCacheValidation(int result) {
1455   if (!result) {
1456     // This is the end of the request.
1457     if (mode_ & WRITE) {
1458       DoneWritingToEntry(true);
1459     } else {
1460       cache_->DoneReadingFromEntry(entry_, this);
1461       entry_ = NULL;
1462     }
1463     return result;
1464   }
1465
1466   if (result < 0)
1467     return result;
1468
1469   partial_->PrepareCacheValidation(entry_->disk_entry,
1470                                    &custom_request_->extra_headers);
1471
1472   if (reading_ && partial_->IsCurrentRangeCached()) {
1473     next_state_ = STATE_CACHE_READ_DATA;
1474     return OK;
1475   }
1476
1477   return BeginCacheValidation();
1478 }
1479
1480 // We received 304 or 206 and we want to update the cached response headers.
1481 int HttpCache::Transaction::DoUpdateCachedResponse() {
1482   next_state_ = STATE_UPDATE_CACHED_RESPONSE_COMPLETE;
1483   int rv = OK;
1484   // Update cached response based on headers in new_response.
1485   // TODO(wtc): should we update cached certificate (response_.ssl_info), too?
1486   response_.headers->Update(*new_response_->headers.get());
1487   response_.response_time = new_response_->response_time;
1488   response_.request_time = new_response_->request_time;
1489   response_.network_accessed = new_response_->network_accessed;
1490   response_.unused_since_prefetch = new_response_->unused_since_prefetch;
1491   if (new_response_->vary_data.is_valid()) {
1492     response_.vary_data = new_response_->vary_data;
1493   } else if (response_.vary_data.is_valid()) {
1494     // There is a vary header in the stored response but not in the current one.
1495     // Update the data with the new request headers.
1496     HttpVaryData new_vary_data;
1497     new_vary_data.Init(*request_, *response_.headers.get());
1498     response_.vary_data = new_vary_data;
1499   }
1500
1501   if (response_.headers->HasHeaderValue("cache-control", "no-store")) {
1502     if (!entry_->doomed) {
1503       int ret = cache_->DoomEntry(cache_key_, NULL);
1504       DCHECK_EQ(OK, ret);
1505     }
1506   } else {
1507     // If we are already reading, we already updated the headers for this
1508     // request; doing it again will change Content-Length.
1509     if (!reading_) {
1510       target_state_ = STATE_UPDATE_CACHED_RESPONSE_COMPLETE;
1511       next_state_ = STATE_CACHE_WRITE_RESPONSE;
1512       rv = OK;
1513     }
1514   }
1515   return rv;
1516 }
1517
1518 int HttpCache::Transaction::DoUpdateCachedResponseComplete(int result) {
1519   if (mode_ == UPDATE) {
1520     DCHECK(!handling_206_);
1521     // We got a "not modified" response and already updated the corresponding
1522     // cache entry above.
1523     //
1524     // By closing the cached entry now, we make sure that the 304 rather than
1525     // the cached 200 response, is what will be returned to the user.
1526     DoneWritingToEntry(true);
1527   } else if (entry_ && !handling_206_) {
1528     DCHECK_EQ(READ_WRITE, mode_);
1529     if (!partial_.get() || partial_->IsLastRange()) {
1530       cache_->ConvertWriterToReader(entry_);
1531       mode_ = READ;
1532     }
1533     // We no longer need the network transaction, so destroy it.
1534     final_upload_progress_ = network_trans_->GetUploadProgress();
1535     ResetNetworkTransaction();
1536   } else if (entry_ && handling_206_ && truncated_ &&
1537              partial_->initial_validation()) {
1538     // We just finished the validation of a truncated entry, and the server
1539     // is willing to resume the operation. Now we go back and start serving
1540     // the first part to the user.
1541     ResetNetworkTransaction();
1542     new_response_ = NULL;
1543     next_state_ = STATE_START_PARTIAL_CACHE_VALIDATION;
1544     partial_->SetRangeToStartDownload();
1545     return OK;
1546   }
1547   next_state_ = STATE_OVERWRITE_CACHED_RESPONSE;
1548   return OK;
1549 }
1550
1551 int HttpCache::Transaction::DoOverwriteCachedResponse() {
1552   if (mode_ & READ) {
1553     next_state_ = STATE_PARTIAL_HEADERS_RECEIVED;
1554     return OK;
1555   }
1556
1557   // We change the value of Content-Length for partial content.
1558   if (handling_206_ && partial_.get())
1559     partial_->FixContentLength(new_response_->headers.get());
1560
1561   response_ = *new_response_;
1562
1563   if (request_->method == "HEAD") {
1564     // This response is replacing the cached one.
1565     DoneWritingToEntry(false);
1566     mode_ = NONE;
1567     new_response_ = NULL;
1568     return OK;
1569   }
1570
1571   if (handling_206_ && !CanResume(false)) {
1572     // There is no point in storing this resource because it will never be used.
1573     // This may change if we support LOAD_ONLY_FROM_CACHE with sparse entries.
1574     DoneWritingToEntry(false);
1575     if (partial_.get())
1576       partial_->FixResponseHeaders(response_.headers.get(), true);
1577     next_state_ = STATE_PARTIAL_HEADERS_RECEIVED;
1578     return OK;
1579   }
1580
1581   target_state_ = STATE_TRUNCATE_CACHED_DATA;
1582   next_state_ = truncated_ ? STATE_CACHE_WRITE_TRUNCATED_RESPONSE :
1583                              STATE_CACHE_WRITE_RESPONSE;
1584   return OK;
1585 }
1586
1587 int HttpCache::Transaction::DoTruncateCachedData() {
1588   next_state_ = STATE_TRUNCATE_CACHED_DATA_COMPLETE;
1589   if (!entry_)
1590     return OK;
1591   if (net_log_.IsCapturing())
1592     net_log_.BeginEvent(NetLog::TYPE_HTTP_CACHE_WRITE_DATA);
1593   // Truncate the stream.
1594   return WriteToEntry(kResponseContentIndex, 0, NULL, 0, io_callback_);
1595 }
1596
1597 int HttpCache::Transaction::DoTruncateCachedDataComplete(int result) {
1598   if (entry_) {
1599     if (net_log_.IsCapturing()) {
1600       net_log_.EndEventWithNetErrorCode(NetLog::TYPE_HTTP_CACHE_WRITE_DATA,
1601                                         result);
1602     }
1603   }
1604
1605   next_state_ = STATE_TRUNCATE_CACHED_METADATA;
1606   return OK;
1607 }
1608
1609 int HttpCache::Transaction::DoTruncateCachedMetadata() {
1610   next_state_ = STATE_TRUNCATE_CACHED_METADATA_COMPLETE;
1611   if (!entry_)
1612     return OK;
1613
1614   if (net_log_.IsCapturing())
1615     net_log_.BeginEvent(NetLog::TYPE_HTTP_CACHE_WRITE_INFO);
1616   return WriteToEntry(kMetadataIndex, 0, NULL, 0, io_callback_);
1617 }
1618
1619 int HttpCache::Transaction::DoTruncateCachedMetadataComplete(int result) {
1620   if (entry_) {
1621     if (net_log_.IsCapturing()) {
1622       net_log_.EndEventWithNetErrorCode(NetLog::TYPE_HTTP_CACHE_WRITE_INFO,
1623                                         result);
1624     }
1625   }
1626
1627   next_state_ = STATE_PARTIAL_HEADERS_RECEIVED;
1628   return OK;
1629 }
1630
1631 int HttpCache::Transaction::DoPartialHeadersReceived() {
1632   new_response_ = NULL;
1633   if (entry_ && !partial_.get() &&
1634       entry_->disk_entry->GetDataSize(kMetadataIndex))
1635     next_state_ = STATE_CACHE_READ_METADATA;
1636
1637   if (!partial_.get())
1638     return OK;
1639
1640   if (reading_) {
1641     if (network_trans_.get()) {
1642       next_state_ = STATE_NETWORK_READ;
1643     } else {
1644       next_state_ = STATE_CACHE_READ_DATA;
1645     }
1646   } else if (mode_ != NONE) {
1647     // We are about to return the headers for a byte-range request to the user,
1648     // so let's fix them.
1649     partial_->FixResponseHeaders(response_.headers.get(), true);
1650   }
1651   return OK;
1652 }
1653
1654 int HttpCache::Transaction::DoCacheReadResponse() {
1655   DCHECK(entry_);
1656   next_state_ = STATE_CACHE_READ_RESPONSE_COMPLETE;
1657
1658   io_buf_len_ = entry_->disk_entry->GetDataSize(kResponseInfoIndex);
1659   read_buf_ = new IOBuffer(io_buf_len_);
1660
1661   net_log_.BeginEvent(NetLog::TYPE_HTTP_CACHE_READ_INFO);
1662   return entry_->disk_entry->ReadData(kResponseInfoIndex, 0, read_buf_.get(),
1663                                       io_buf_len_, io_callback_);
1664 }
1665
1666 int HttpCache::Transaction::DoCacheReadResponseComplete(int result) {
1667   net_log_.EndEventWithNetErrorCode(NetLog::TYPE_HTTP_CACHE_READ_INFO, result);
1668   if (result != io_buf_len_ ||
1669       !HttpCache::ParseResponseInfo(read_buf_->data(), io_buf_len_,
1670                                     &response_, &truncated_)) {
1671     return OnCacheReadError(result, true);
1672   }
1673
1674   // cert_cache() will be null if the CertCacheTrial field trial is disabled.
1675   if (cache_->cert_cache() && response_.ssl_info.is_valid())
1676     ReadCertChain();
1677
1678   // Some resources may have slipped in as truncated when they're not.
1679   int current_size = entry_->disk_entry->GetDataSize(kResponseContentIndex);
1680   if (response_.headers->GetContentLength() == current_size)
1681     truncated_ = false;
1682
1683   if ((response_.unused_since_prefetch &&
1684        !(request_->load_flags & LOAD_PREFETCH)) ||
1685       (!response_.unused_since_prefetch &&
1686        (request_->load_flags & LOAD_PREFETCH))) {
1687     // Either this is the first use of an entry since it was prefetched or
1688     // this is a prefetch. The value of response.unused_since_prefetch is valid
1689     // for this transaction but the bit needs to be flipped in storage.
1690     next_state_ = STATE_TOGGLE_UNUSED_SINCE_PREFETCH;
1691     return OK;
1692   }
1693
1694   next_state_ = STATE_CACHE_DISPATCH_VALIDATION;
1695   return OK;
1696 }
1697
1698 int HttpCache::Transaction::DoCacheDispatchValidation() {
1699   // We now have access to the cache entry.
1700   //
1701   //  o if we are a reader for the transaction, then we can start reading the
1702   //    cache entry.
1703   //
1704   //  o if we can read or write, then we should check if the cache entry needs
1705   //    to be validated and then issue a network request if needed or just read
1706   //    from the cache if the cache entry is already valid.
1707   //
1708   //  o if we are set to UPDATE, then we are handling an externally
1709   //    conditionalized request (if-modified-since / if-none-match). We check
1710   //    if the request headers define a validation request.
1711   //
1712   int result = ERR_FAILED;
1713   switch (mode_) {
1714     case READ:
1715       UpdateTransactionPattern(PATTERN_ENTRY_USED);
1716       result = BeginCacheRead();
1717       break;
1718     case READ_WRITE:
1719       result = BeginPartialCacheValidation();
1720       break;
1721     case UPDATE:
1722       result = BeginExternallyConditionalizedRequest();
1723       break;
1724     case WRITE:
1725     default:
1726       NOTREACHED();
1727   }
1728   return result;
1729 }
1730
1731 int HttpCache::Transaction::DoCacheToggleUnusedSincePrefetch() {
1732   // Write back the toggled value for the next use of this entry.
1733   response_.unused_since_prefetch = !response_.unused_since_prefetch;
1734
1735   // TODO(jkarlin): If DoUpdateCachedResponse is also called for this
1736   // transaction then metadata will be written to cache twice. If prefetching
1737   // becomes more common, consider combining the writes.
1738   target_state_ = STATE_TOGGLE_UNUSED_SINCE_PREFETCH_COMPLETE;
1739   next_state_ = STATE_CACHE_WRITE_RESPONSE;
1740   return OK;
1741 }
1742
1743 int HttpCache::Transaction::DoCacheToggleUnusedSincePrefetchComplete(
1744     int result) {
1745   // Restore the original value for this transaction.
1746   response_.unused_since_prefetch = !response_.unused_since_prefetch;
1747   next_state_ = STATE_CACHE_DISPATCH_VALIDATION;
1748   return OK;
1749 }
1750
1751 int HttpCache::Transaction::DoCacheWriteResponse() {
1752   // TODO(rtenneti): Remove ScopedTracker below once crbug.com/422516 is fixed.
1753   tracked_objects::ScopedTracker tracking_profile(
1754       FROM_HERE_WITH_EXPLICIT_FUNCTION(
1755           "422516 HttpCache::Transaction::DoCacheWriteResponse"));
1756
1757   if (entry_) {
1758     if (net_log_.IsCapturing())
1759       net_log_.BeginEvent(NetLog::TYPE_HTTP_CACHE_WRITE_INFO);
1760   }
1761   return WriteResponseInfoToEntry(false);
1762 }
1763
1764 int HttpCache::Transaction::DoCacheWriteTruncatedResponse() {
1765   if (entry_) {
1766     if (net_log_.IsCapturing())
1767       net_log_.BeginEvent(NetLog::TYPE_HTTP_CACHE_WRITE_INFO);
1768   }
1769   return WriteResponseInfoToEntry(true);
1770 }
1771
1772 int HttpCache::Transaction::DoCacheWriteResponseComplete(int result) {
1773   next_state_ = target_state_;
1774   target_state_ = STATE_NONE;
1775   if (!entry_)
1776     return OK;
1777   if (net_log_.IsCapturing()) {
1778     net_log_.EndEventWithNetErrorCode(NetLog::TYPE_HTTP_CACHE_WRITE_INFO,
1779                                       result);
1780   }
1781
1782   // Balance the AddRef from WriteResponseInfoToEntry.
1783   if (result != io_buf_len_) {
1784     DLOG(ERROR) << "failed to write response info to cache";
1785     DoneWritingToEntry(false);
1786   }
1787   return OK;
1788 }
1789
1790 int HttpCache::Transaction::DoCacheReadMetadata() {
1791   DCHECK(entry_);
1792   DCHECK(!response_.metadata.get());
1793   next_state_ = STATE_CACHE_READ_METADATA_COMPLETE;
1794
1795   response_.metadata =
1796       new IOBufferWithSize(entry_->disk_entry->GetDataSize(kMetadataIndex));
1797
1798   net_log_.BeginEvent(NetLog::TYPE_HTTP_CACHE_READ_INFO);
1799   return entry_->disk_entry->ReadData(kMetadataIndex, 0,
1800                                       response_.metadata.get(),
1801                                       response_.metadata->size(),
1802                                       io_callback_);
1803 }
1804
1805 int HttpCache::Transaction::DoCacheReadMetadataComplete(int result) {
1806   net_log_.EndEventWithNetErrorCode(NetLog::TYPE_HTTP_CACHE_READ_INFO, result);
1807   if (result != response_.metadata->size())
1808     return OnCacheReadError(result, false);
1809   return OK;
1810 }
1811
1812 int HttpCache::Transaction::DoCacheQueryData() {
1813   next_state_ = STATE_CACHE_QUERY_DATA_COMPLETE;
1814   return entry_->disk_entry->ReadyForSparseIO(io_callback_);
1815 }
1816
1817 int HttpCache::Transaction::DoCacheQueryDataComplete(int result) {
1818   DCHECK_EQ(OK, result);
1819   if (!cache_.get())
1820     return ERR_UNEXPECTED;
1821
1822   return ValidateEntryHeadersAndContinue();
1823 }
1824
1825 int HttpCache::Transaction::DoCacheReadData() {
1826   DCHECK(entry_);
1827   next_state_ = STATE_CACHE_READ_DATA_COMPLETE;
1828
1829   if (net_log_.IsCapturing())
1830     net_log_.BeginEvent(NetLog::TYPE_HTTP_CACHE_READ_DATA);
1831   if (partial_.get()) {
1832     return partial_->CacheRead(entry_->disk_entry, read_buf_.get(), io_buf_len_,
1833                                io_callback_);
1834   }
1835
1836   return entry_->disk_entry->ReadData(kResponseContentIndex, read_offset_,
1837                                       read_buf_.get(), io_buf_len_,
1838                                       io_callback_);
1839 }
1840
1841 int HttpCache::Transaction::DoCacheReadDataComplete(int result) {
1842   if (net_log_.IsCapturing()) {
1843     net_log_.EndEventWithNetErrorCode(NetLog::TYPE_HTTP_CACHE_READ_DATA,
1844                                       result);
1845   }
1846
1847   if (!cache_.get())
1848     return ERR_UNEXPECTED;
1849
1850   if (partial_.get()) {
1851     // Partial requests are confusing to report in histograms because they may
1852     // have multiple underlying requests.
1853     UpdateTransactionPattern(PATTERN_NOT_COVERED);
1854     return DoPartialCacheReadCompleted(result);
1855   }
1856
1857   if (result > 0) {
1858     read_offset_ += result;
1859   } else if (result == 0) {  // End of file.
1860     RecordHistograms();
1861     cache_->DoneReadingFromEntry(entry_, this);
1862     entry_ = NULL;
1863   } else {
1864     return OnCacheReadError(result, false);
1865   }
1866   return result;
1867 }
1868
1869 int HttpCache::Transaction::DoCacheWriteData(int num_bytes) {
1870   next_state_ = STATE_CACHE_WRITE_DATA_COMPLETE;
1871   write_len_ = num_bytes;
1872   if (entry_) {
1873     if (net_log_.IsCapturing())
1874       net_log_.BeginEvent(NetLog::TYPE_HTTP_CACHE_WRITE_DATA);
1875   }
1876
1877   return AppendResponseDataToEntry(read_buf_.get(), num_bytes, io_callback_);
1878 }
1879
1880 int HttpCache::Transaction::DoCacheWriteDataComplete(int result) {
1881   if (entry_) {
1882     if (net_log_.IsCapturing()) {
1883       net_log_.EndEventWithNetErrorCode(NetLog::TYPE_HTTP_CACHE_WRITE_DATA,
1884                                         result);
1885     }
1886   }
1887   // Balance the AddRef from DoCacheWriteData.
1888   if (!cache_.get())
1889     return ERR_UNEXPECTED;
1890
1891   if (result != write_len_) {
1892     DLOG(ERROR) << "failed to write response data to cache";
1893     DoneWritingToEntry(false);
1894
1895     // We want to ignore errors writing to disk and just keep reading from
1896     // the network.
1897     result = write_len_;
1898   } else if (!done_reading_ && entry_) {
1899     int current_size = entry_->disk_entry->GetDataSize(kResponseContentIndex);
1900     int64 body_size = response_.headers->GetContentLength();
1901     if (body_size >= 0 && body_size <= current_size)
1902       done_reading_ = true;
1903   }
1904
1905   if (partial_.get()) {
1906     // This may be the last request.
1907     if (!(result == 0 && !truncated_ &&
1908           (partial_->IsLastRange() || mode_ == WRITE)))
1909       return DoPartialNetworkReadCompleted(result);
1910   }
1911
1912   if (result == 0) {
1913     // End of file. This may be the result of a connection problem so see if we
1914     // have to keep the entry around to be flagged as truncated later on.
1915     if (done_reading_ || !entry_ || partial_.get() ||
1916         response_.headers->GetContentLength() <= 0)
1917       DoneWritingToEntry(true);
1918   }
1919
1920   return result;
1921 }
1922
1923 //-----------------------------------------------------------------------------
1924
1925 void HttpCache::Transaction::ReadCertChain() {
1926   std::string key =
1927       GetCacheKeyForCert(response_.ssl_info.cert->os_cert_handle());
1928   const X509Certificate::OSCertHandles& intermediates =
1929       response_.ssl_info.cert->GetIntermediateCertificates();
1930   int dist_from_root = intermediates.size();
1931
1932   scoped_refptr<SharedChainData> shared_chain_data(
1933       new SharedChainData(intermediates.size() + 1, TimeTicks::Now()));
1934   cache_->cert_cache()->GetCertificate(key,
1935                                        base::Bind(&OnCertReadIOComplete,
1936                                                   dist_from_root,
1937                                                   true /* is leaf */,
1938                                                   shared_chain_data));
1939
1940   for (X509Certificate::OSCertHandles::const_iterator it =
1941            intermediates.begin();
1942        it != intermediates.end();
1943        ++it) {
1944     --dist_from_root;
1945     key = GetCacheKeyForCert(*it);
1946     cache_->cert_cache()->GetCertificate(key,
1947                                          base::Bind(&OnCertReadIOComplete,
1948                                                     dist_from_root,
1949                                                     false /* is not leaf */,
1950                                                     shared_chain_data));
1951   }
1952   DCHECK_EQ(0, dist_from_root);
1953 }
1954
1955 void HttpCache::Transaction::WriteCertChain() {
1956   const X509Certificate::OSCertHandles& intermediates =
1957       response_.ssl_info.cert->GetIntermediateCertificates();
1958   int dist_from_root = intermediates.size();
1959
1960   scoped_refptr<SharedChainData> shared_chain_data(
1961       new SharedChainData(intermediates.size() + 1, TimeTicks::Now()));
1962   cache_->cert_cache()->SetCertificate(
1963       response_.ssl_info.cert->os_cert_handle(),
1964       base::Bind(&OnCertWriteIOComplete,
1965                  dist_from_root,
1966                  true /* is leaf */,
1967                  shared_chain_data));
1968   for (X509Certificate::OSCertHandles::const_iterator it =
1969            intermediates.begin();
1970        it != intermediates.end();
1971        ++it) {
1972     --dist_from_root;
1973     cache_->cert_cache()->SetCertificate(*it,
1974                                          base::Bind(&OnCertWriteIOComplete,
1975                                                     dist_from_root,
1976                                                     false /* is not leaf */,
1977                                                     shared_chain_data));
1978   }
1979   DCHECK_EQ(0, dist_from_root);
1980 }
1981
1982 void HttpCache::Transaction::SetRequest(const BoundNetLog& net_log,
1983                                         const HttpRequestInfo* request) {
1984   net_log_ = net_log;
1985   request_ = request;
1986   effective_load_flags_ = request_->load_flags;
1987
1988   if (cache_->mode() == DISABLE)
1989     effective_load_flags_ |= LOAD_DISABLE_CACHE;
1990
1991   // Some headers imply load flags.  The order here is significant.
1992   //
1993   //   LOAD_DISABLE_CACHE   : no cache read or write
1994   //   LOAD_BYPASS_CACHE    : no cache read
1995   //   LOAD_VALIDATE_CACHE  : no cache read unless validation
1996   //
1997   // The former modes trump latter modes, so if we find a matching header we
1998   // can stop iterating kSpecialHeaders.
1999   //
2000   static const struct {
2001     const HeaderNameAndValue* search;
2002     int load_flag;
2003   } kSpecialHeaders[] = {
2004     { kPassThroughHeaders, LOAD_DISABLE_CACHE },
2005     { kForceFetchHeaders, LOAD_BYPASS_CACHE },
2006     { kForceValidateHeaders, LOAD_VALIDATE_CACHE },
2007   };
2008
2009   bool range_found = false;
2010   bool external_validation_error = false;
2011   bool special_headers = false;
2012
2013   if (request_->extra_headers.HasHeader(HttpRequestHeaders::kRange))
2014     range_found = true;
2015
2016   for (size_t i = 0; i < arraysize(kSpecialHeaders); ++i) {
2017     if (HeaderMatches(request_->extra_headers, kSpecialHeaders[i].search)) {
2018       effective_load_flags_ |= kSpecialHeaders[i].load_flag;
2019       special_headers = true;
2020       break;
2021     }
2022   }
2023
2024   // Check for conditionalization headers which may correspond with a
2025   // cache validation request.
2026   for (size_t i = 0; i < arraysize(kValidationHeaders); ++i) {
2027     const ValidationHeaderInfo& info = kValidationHeaders[i];
2028     std::string validation_value;
2029     if (request_->extra_headers.GetHeader(
2030             info.request_header_name, &validation_value)) {
2031       if (!external_validation_.values[i].empty() ||
2032           validation_value.empty()) {
2033         external_validation_error = true;
2034       }
2035       external_validation_.values[i] = validation_value;
2036       external_validation_.initialized = true;
2037     }
2038   }
2039
2040   if (range_found || special_headers || external_validation_.initialized) {
2041     // Log the headers before request_ is modified.
2042     std::string empty;
2043     net_log_.AddEvent(
2044         NetLog::TYPE_HTTP_CACHE_CALLER_REQUEST_HEADERS,
2045         base::Bind(&HttpRequestHeaders::NetLogCallback,
2046                    base::Unretained(&request_->extra_headers), &empty));
2047   }
2048
2049   // We don't support ranges and validation headers.
2050   if (range_found && external_validation_.initialized) {
2051     LOG(WARNING) << "Byte ranges AND validation headers found.";
2052     effective_load_flags_ |= LOAD_DISABLE_CACHE;
2053   }
2054
2055   // If there is more than one validation header, we can't treat this request as
2056   // a cache validation, since we don't know for sure which header the server
2057   // will give us a response for (and they could be contradictory).
2058   if (external_validation_error) {
2059     LOG(WARNING) << "Multiple or malformed validation headers found.";
2060     effective_load_flags_ |= LOAD_DISABLE_CACHE;
2061   }
2062
2063   if (range_found && !(effective_load_flags_ & LOAD_DISABLE_CACHE)) {
2064     UpdateTransactionPattern(PATTERN_NOT_COVERED);
2065     partial_.reset(new PartialData);
2066     if (request_->method == "GET" && partial_->Init(request_->extra_headers)) {
2067       // We will be modifying the actual range requested to the server, so
2068       // let's remove the header here.
2069       custom_request_.reset(new HttpRequestInfo(*request_));
2070       custom_request_->extra_headers.RemoveHeader(HttpRequestHeaders::kRange);
2071       request_ = custom_request_.get();
2072       partial_->SetHeaders(custom_request_->extra_headers);
2073     } else {
2074       // The range is invalid or we cannot handle it properly.
2075       VLOG(1) << "Invalid byte range found.";
2076       effective_load_flags_ |= LOAD_DISABLE_CACHE;
2077       partial_.reset(NULL);
2078     }
2079   }
2080 }
2081
2082 bool HttpCache::Transaction::ShouldPassThrough() {
2083   // We may have a null disk_cache if there is an error we cannot recover from,
2084   // like not enough disk space, or sharing violations.
2085   if (!cache_->disk_cache_.get())
2086     return true;
2087
2088   if (effective_load_flags_ & LOAD_DISABLE_CACHE)
2089     return true;
2090
2091   if (request_->method == "GET" || request_->method == "HEAD")
2092     return false;
2093
2094   if (request_->method == "POST" && request_->upload_data_stream &&
2095       request_->upload_data_stream->identifier()) {
2096     return false;
2097   }
2098
2099   if (request_->method == "PUT" && request_->upload_data_stream)
2100     return false;
2101
2102   if (request_->method == "DELETE")
2103     return false;
2104
2105   return true;
2106 }
2107
2108 int HttpCache::Transaction::BeginCacheRead() {
2109   // We don't support any combination of LOAD_ONLY_FROM_CACHE and byte ranges.
2110   if (response_.headers->response_code() == 206 || partial_.get()) {
2111     NOTREACHED();
2112     return ERR_CACHE_MISS;
2113   }
2114
2115   if (request_->method == "HEAD")
2116     FixHeadersForHead();
2117
2118   // We don't have the whole resource.
2119   if (truncated_)
2120     return ERR_CACHE_MISS;
2121
2122   if (entry_->disk_entry->GetDataSize(kMetadataIndex))
2123     next_state_ = STATE_CACHE_READ_METADATA;
2124
2125   return OK;
2126 }
2127
2128 int HttpCache::Transaction::BeginCacheValidation() {
2129   DCHECK(mode_ == READ_WRITE);
2130
2131   ValidationType required_validation = RequiresValidation();
2132
2133   bool skip_validation = (required_validation == VALIDATION_NONE);
2134
2135   if (required_validation == VALIDATION_ASYNCHRONOUS &&
2136       !(request_->method == "GET" && (truncated_ || partial_)) && cache_ &&
2137       cache_->use_stale_while_revalidate()) {
2138     TriggerAsyncValidation();
2139     skip_validation = true;
2140   }
2141
2142   if (request_->method == "HEAD" &&
2143       (truncated_ || response_.headers->response_code() == 206)) {
2144     DCHECK(!partial_);
2145     if (skip_validation)
2146       return SetupEntryForRead();
2147
2148     // Bail out!
2149     next_state_ = STATE_SEND_REQUEST;
2150     mode_ = NONE;
2151     return OK;
2152   }
2153
2154   if (truncated_) {
2155     // Truncated entries can cause partial gets, so we shouldn't record this
2156     // load in histograms.
2157     UpdateTransactionPattern(PATTERN_NOT_COVERED);
2158     skip_validation = !partial_->initial_validation();
2159   }
2160
2161   if (partial_.get() && (is_sparse_ || truncated_) &&
2162       (!partial_->IsCurrentRangeCached() || invalid_range_)) {
2163     // Force revalidation for sparse or truncated entries. Note that we don't
2164     // want to ignore the regular validation logic just because a byte range was
2165     // part of the request.
2166     skip_validation = false;
2167   }
2168
2169   if (skip_validation) {
2170     // TODO(ricea): Is this pattern okay for asynchronous revalidations?
2171     UpdateTransactionPattern(PATTERN_ENTRY_USED);
2172     return SetupEntryForRead();
2173   } else {
2174     // Make the network request conditional, to see if we may reuse our cached
2175     // response.  If we cannot do so, then we just resort to a normal fetch.
2176     // Our mode remains READ_WRITE for a conditional request.  Even if the
2177     // conditionalization fails, we don't switch to WRITE mode until we
2178     // know we won't be falling back to using the cache entry in the
2179     // LOAD_FROM_CACHE_IF_OFFLINE case.
2180     if (!ConditionalizeRequest()) {
2181       couldnt_conditionalize_request_ = true;
2182       UpdateTransactionPattern(PATTERN_ENTRY_CANT_CONDITIONALIZE);
2183       if (partial_.get())
2184         return DoRestartPartialRequest();
2185
2186       DCHECK_NE(206, response_.headers->response_code());
2187     }
2188     next_state_ = STATE_SEND_REQUEST;
2189   }
2190   return OK;
2191 }
2192
2193 int HttpCache::Transaction::BeginPartialCacheValidation() {
2194   DCHECK(mode_ == READ_WRITE);
2195
2196   if (response_.headers->response_code() != 206 && !partial_.get() &&
2197       !truncated_) {
2198     return BeginCacheValidation();
2199   }
2200
2201   // Partial requests should not be recorded in histograms.
2202   UpdateTransactionPattern(PATTERN_NOT_COVERED);
2203   if (range_requested_) {
2204     next_state_ = STATE_CACHE_QUERY_DATA;
2205     return OK;
2206   }
2207
2208   // The request is not for a range, but we have stored just ranges.
2209
2210   if (request_->method == "HEAD")
2211     return BeginCacheValidation();
2212
2213   partial_.reset(new PartialData());
2214   partial_->SetHeaders(request_->extra_headers);
2215   if (!custom_request_.get()) {
2216     custom_request_.reset(new HttpRequestInfo(*request_));
2217     request_ = custom_request_.get();
2218   }
2219
2220   return ValidateEntryHeadersAndContinue();
2221 }
2222
2223 // This should only be called once per request.
2224 int HttpCache::Transaction::ValidateEntryHeadersAndContinue() {
2225   DCHECK(mode_ == READ_WRITE);
2226
2227   if (!partial_->UpdateFromStoredHeaders(
2228           response_.headers.get(), entry_->disk_entry, truncated_)) {
2229     return DoRestartPartialRequest();
2230   }
2231
2232   if (response_.headers->response_code() == 206)
2233     is_sparse_ = true;
2234
2235   if (!partial_->IsRequestedRangeOK()) {
2236     // The stored data is fine, but the request may be invalid.
2237     invalid_range_ = true;
2238   }
2239
2240   next_state_ = STATE_START_PARTIAL_CACHE_VALIDATION;
2241   return OK;
2242 }
2243
2244 int HttpCache::Transaction::BeginExternallyConditionalizedRequest() {
2245   DCHECK_EQ(UPDATE, mode_);
2246   DCHECK(external_validation_.initialized);
2247
2248   for (size_t i = 0;  i < arraysize(kValidationHeaders); i++) {
2249     if (external_validation_.values[i].empty())
2250       continue;
2251     // Retrieve either the cached response's "etag" or "last-modified" header.
2252     std::string validator;
2253     response_.headers->EnumerateHeader(
2254         NULL,
2255         kValidationHeaders[i].related_response_header_name,
2256         &validator);
2257
2258     if (response_.headers->response_code() != 200 || truncated_ ||
2259         validator.empty() || validator != external_validation_.values[i]) {
2260       // The externally conditionalized request is not a validation request
2261       // for our existing cache entry. Proceed with caching disabled.
2262       UpdateTransactionPattern(PATTERN_NOT_COVERED);
2263       DoneWritingToEntry(true);
2264     }
2265   }
2266
2267   // TODO(ricea): This calculation is expensive to perform just to collect
2268   // statistics. Either remove it or use the result, depending on the result of
2269   // the experiment.
2270   ExternallyConditionalizedType type =
2271       EXTERNALLY_CONDITIONALIZED_CACHE_USABLE;
2272   if (mode_ == NONE)
2273     type = EXTERNALLY_CONDITIONALIZED_MISMATCHED_VALIDATORS;
2274   else if (RequiresValidation())
2275     type = EXTERNALLY_CONDITIONALIZED_CACHE_REQUIRES_VALIDATION;
2276
2277   // TODO(ricea): Add CACHE_USABLE_STALE once stale-while-revalidate CL landed.
2278   // TODO(ricea): Either remove this histogram or make it permanent by M40.
2279   UMA_HISTOGRAM_ENUMERATION("HttpCache.ExternallyConditionalized",
2280                             type,
2281                             EXTERNALLY_CONDITIONALIZED_MAX);
2282
2283   next_state_ = STATE_SEND_REQUEST;
2284   return OK;
2285 }
2286
2287 int HttpCache::Transaction::RestartNetworkRequest() {
2288   DCHECK(mode_ & WRITE || mode_ == NONE);
2289   DCHECK(network_trans_.get());
2290   DCHECK_EQ(STATE_NONE, next_state_);
2291
2292   next_state_ = STATE_SEND_REQUEST_COMPLETE;
2293   int rv = network_trans_->RestartIgnoringLastError(io_callback_);
2294   if (rv != ERR_IO_PENDING)
2295     return DoLoop(rv);
2296   return rv;
2297 }
2298
2299 int HttpCache::Transaction::RestartNetworkRequestWithCertificate(
2300     X509Certificate* client_cert) {
2301   DCHECK(mode_ & WRITE || mode_ == NONE);
2302   DCHECK(network_trans_.get());
2303   DCHECK_EQ(STATE_NONE, next_state_);
2304
2305   next_state_ = STATE_SEND_REQUEST_COMPLETE;
2306   int rv = network_trans_->RestartWithCertificate(client_cert, io_callback_);
2307   if (rv != ERR_IO_PENDING)
2308     return DoLoop(rv);
2309   return rv;
2310 }
2311
2312 int HttpCache::Transaction::RestartNetworkRequestWithAuth(
2313     const AuthCredentials& credentials) {
2314   DCHECK(mode_ & WRITE || mode_ == NONE);
2315   DCHECK(network_trans_.get());
2316   DCHECK_EQ(STATE_NONE, next_state_);
2317
2318   next_state_ = STATE_SEND_REQUEST_COMPLETE;
2319   int rv = network_trans_->RestartWithAuth(credentials, io_callback_);
2320   if (rv != ERR_IO_PENDING)
2321     return DoLoop(rv);
2322   return rv;
2323 }
2324
2325 ValidationType HttpCache::Transaction::RequiresValidation() {
2326   // TODO(darin): need to do more work here:
2327   //  - make sure we have a matching request method
2328   //  - watch out for cached responses that depend on authentication
2329
2330   if (response_.vary_data.is_valid() &&
2331       !response_.vary_data.MatchesRequest(*request_,
2332                                           *response_.headers.get())) {
2333     vary_mismatch_ = true;
2334     return VALIDATION_SYNCHRONOUS;
2335   }
2336
2337   if (effective_load_flags_ & LOAD_PREFERRING_CACHE)
2338     return VALIDATION_NONE;
2339
2340   if (response_.unused_since_prefetch &&
2341       !(effective_load_flags_ & LOAD_PREFETCH) &&
2342       response_.headers->GetCurrentAge(
2343           response_.request_time, response_.response_time,
2344           cache_->clock_->Now()) < TimeDelta::FromMinutes(kPrefetchReuseMins)) {
2345     // The first use of a resource after prefetch within a short window skips
2346     // validation.
2347     return VALIDATION_NONE;
2348   }
2349
2350   if (effective_load_flags_ & (LOAD_VALIDATE_CACHE | LOAD_ASYNC_REVALIDATION))
2351     return VALIDATION_SYNCHRONOUS;
2352
2353   if (request_->method == "PUT" || request_->method == "DELETE")
2354     return VALIDATION_SYNCHRONOUS;
2355
2356   ValidationType validation_required_by_headers =
2357       response_.headers->RequiresValidation(response_.request_time,
2358                                             response_.response_time,
2359                                             cache_->clock_->Now());
2360
2361   if (validation_required_by_headers == VALIDATION_ASYNCHRONOUS) {
2362     // Asynchronous revalidation is only supported for GET and HEAD methods.
2363     if (request_->method != "GET" && request_->method != "HEAD")
2364       return VALIDATION_SYNCHRONOUS;
2365   }
2366
2367   return validation_required_by_headers;
2368 }
2369
2370 bool HttpCache::Transaction::ConditionalizeRequest() {
2371   DCHECK(response_.headers.get());
2372
2373   if (request_->method == "PUT" || request_->method == "DELETE")
2374     return false;
2375
2376   // This only makes sense for cached 200 or 206 responses.
2377   if (response_.headers->response_code() != 200 &&
2378       response_.headers->response_code() != 206) {
2379     return false;
2380   }
2381
2382   if (fail_conditionalization_for_test_)
2383     return false;
2384
2385   DCHECK(response_.headers->response_code() != 206 ||
2386          response_.headers->HasStrongValidators());
2387
2388   // Just use the first available ETag and/or Last-Modified header value.
2389   // TODO(darin): Or should we use the last?
2390
2391   std::string etag_value;
2392   if (response_.headers->GetHttpVersion() >= HttpVersion(1, 1))
2393     response_.headers->EnumerateHeader(NULL, "etag", &etag_value);
2394
2395   std::string last_modified_value;
2396   if (!vary_mismatch_) {
2397     response_.headers->EnumerateHeader(NULL, "last-modified",
2398                                        &last_modified_value);
2399   }
2400
2401   if (etag_value.empty() && last_modified_value.empty())
2402     return false;
2403
2404   if (!partial_.get()) {
2405     // Need to customize the request, so this forces us to allocate :(
2406     custom_request_.reset(new HttpRequestInfo(*request_));
2407     request_ = custom_request_.get();
2408   }
2409   DCHECK(custom_request_.get());
2410
2411   bool use_if_range = partial_.get() && !partial_->IsCurrentRangeCached() &&
2412                       !invalid_range_;
2413
2414   if (!use_if_range) {
2415     // stale-while-revalidate is not useful when we only have a partial response
2416     // cached, so don't set the header in that case.
2417     HttpResponseHeaders::FreshnessLifetimes lifetimes =
2418         response_.headers->GetFreshnessLifetimes(response_.response_time);
2419     if (lifetimes.staleness > TimeDelta()) {
2420       TimeDelta current_age = response_.headers->GetCurrentAge(
2421           response_.request_time, response_.response_time,
2422           cache_->clock_->Now());
2423
2424       custom_request_->extra_headers.SetHeader(
2425           kFreshnessHeader,
2426           base::StringPrintf("max-age=%" PRId64
2427                              ",stale-while-revalidate=%" PRId64 ",age=%" PRId64,
2428                              lifetimes.freshness.InSeconds(),
2429                              lifetimes.staleness.InSeconds(),
2430                              current_age.InSeconds()));
2431     }
2432   }
2433
2434   if (!etag_value.empty()) {
2435     if (use_if_range) {
2436       // We don't want to switch to WRITE mode if we don't have this block of a
2437       // byte-range request because we may have other parts cached.
2438       custom_request_->extra_headers.SetHeader(
2439           HttpRequestHeaders::kIfRange, etag_value);
2440     } else {
2441       custom_request_->extra_headers.SetHeader(
2442           HttpRequestHeaders::kIfNoneMatch, etag_value);
2443     }
2444     // For byte-range requests, make sure that we use only one way to validate
2445     // the request.
2446     if (partial_.get() && !partial_->IsCurrentRangeCached())
2447       return true;
2448   }
2449
2450   if (!last_modified_value.empty()) {
2451     if (use_if_range) {
2452       custom_request_->extra_headers.SetHeader(
2453           HttpRequestHeaders::kIfRange, last_modified_value);
2454     } else {
2455       custom_request_->extra_headers.SetHeader(
2456           HttpRequestHeaders::kIfModifiedSince, last_modified_value);
2457     }
2458   }
2459
2460   return true;
2461 }
2462
2463 // We just received some headers from the server. We may have asked for a range,
2464 // in which case partial_ has an object. This could be the first network request
2465 // we make to fulfill the original request, or we may be already reading (from
2466 // the net and / or the cache). If we are not expecting a certain response, we
2467 // just bypass the cache for this request (but again, maybe we are reading), and
2468 // delete partial_ (so we are not able to "fix" the headers that we return to
2469 // the user). This results in either a weird response for the caller (we don't
2470 // expect it after all), or maybe a range that was not exactly what it was asked
2471 // for.
2472 //
2473 // If the server is simply telling us that the resource has changed, we delete
2474 // the cached entry and restart the request as the caller intended (by returning
2475 // false from this method). However, we may not be able to do that at any point,
2476 // for instance if we already returned the headers to the user.
2477 //
2478 // WARNING: Whenever this code returns false, it has to make sure that the next
2479 // time it is called it will return true so that we don't keep retrying the
2480 // request.
2481 bool HttpCache::Transaction::ValidatePartialResponse() {
2482   const HttpResponseHeaders* headers = new_response_->headers.get();
2483   int response_code = headers->response_code();
2484   bool partial_response = (response_code == 206);
2485   handling_206_ = false;
2486
2487   if (!entry_ || request_->method != "GET")
2488     return true;
2489
2490   if (invalid_range_) {
2491     // We gave up trying to match this request with the stored data. If the
2492     // server is ok with the request, delete the entry, otherwise just ignore
2493     // this request
2494     DCHECK(!reading_);
2495     if (partial_response || response_code == 200) {
2496       DoomPartialEntry(true);
2497       mode_ = NONE;
2498     } else {
2499       if (response_code == 304)
2500         FailRangeRequest();
2501       IgnoreRangeRequest();
2502     }
2503     return true;
2504   }
2505
2506   if (!partial_.get()) {
2507     // We are not expecting 206 but we may have one.
2508     if (partial_response)
2509       IgnoreRangeRequest();
2510
2511     return true;
2512   }
2513
2514   // TODO(rvargas): Do we need to consider other results here?.
2515   bool failure = response_code == 200 || response_code == 416;
2516
2517   if (partial_->IsCurrentRangeCached()) {
2518     // We asked for "If-None-Match: " so a 206 means a new object.
2519     if (partial_response)
2520       failure = true;
2521
2522     if (response_code == 304 && partial_->ResponseHeadersOK(headers))
2523       return true;
2524   } else {
2525     // We asked for "If-Range: " so a 206 means just another range.
2526     if (partial_response) {
2527       if (partial_->ResponseHeadersOK(headers)) {
2528         handling_206_ = true;
2529         return true;
2530       } else {
2531         failure = true;
2532       }
2533     }
2534
2535     if (!reading_ && !is_sparse_ && !partial_response) {
2536       // See if we can ignore the fact that we issued a byte range request.
2537       // If the server sends 200, just store it. If it sends an error, redirect
2538       // or something else, we may store the response as long as we didn't have
2539       // anything already stored.
2540       if (response_code == 200 ||
2541           (!truncated_ && response_code != 304 && response_code != 416)) {
2542         // The server is sending something else, and we can save it.
2543         DCHECK((truncated_ && !partial_->IsLastRange()) || range_requested_);
2544         partial_.reset();
2545         truncated_ = false;
2546         return true;
2547       }
2548     }
2549
2550     // 304 is not expected here, but we'll spare the entry (unless it was
2551     // truncated).
2552     if (truncated_)
2553       failure = true;
2554   }
2555
2556   if (failure) {
2557     // We cannot truncate this entry, it has to be deleted.
2558     UpdateTransactionPattern(PATTERN_NOT_COVERED);
2559     mode_ = NONE;
2560     if (is_sparse_ || truncated_) {
2561       // There was something cached to start with, either sparsed data (206), or
2562       // a truncated 200, which means that we probably modified the request,
2563       // adding a byte range or modifying the range requested by the caller.
2564       if (!reading_ && !partial_->IsLastRange()) {
2565         // We have not returned anything to the caller yet so it should be safe
2566         // to issue another network request, this time without us messing up the
2567         // headers.
2568         ResetPartialState(true);
2569         return false;
2570       }
2571       LOG(WARNING) << "Failed to revalidate partial entry";
2572     }
2573     DoomPartialEntry(true);
2574     return true;
2575   }
2576
2577   IgnoreRangeRequest();
2578   return true;
2579 }
2580
2581 void HttpCache::Transaction::IgnoreRangeRequest() {
2582   // We have a problem. We may or may not be reading already (in which case we
2583   // returned the headers), but we'll just pretend that this request is not
2584   // using the cache and see what happens. Most likely this is the first
2585   // response from the server (it's not changing its mind midway, right?).
2586   UpdateTransactionPattern(PATTERN_NOT_COVERED);
2587   if (mode_ & WRITE)
2588     DoneWritingToEntry(mode_ != WRITE);
2589   else if (mode_ & READ && entry_)
2590     cache_->DoneReadingFromEntry(entry_, this);
2591
2592   partial_.reset(NULL);
2593   entry_ = NULL;
2594   mode_ = NONE;
2595 }
2596
2597 void HttpCache::Transaction::FixHeadersForHead() {
2598   if (response_.headers->response_code() == 206) {
2599     response_.headers->RemoveHeader("Content-Range");
2600     response_.headers->ReplaceStatusLine("HTTP/1.1 200 OK");
2601   }
2602 }
2603
2604 void HttpCache::Transaction::TriggerAsyncValidation() {
2605   DCHECK(!request_->upload_data_stream);
2606   BoundNetLog async_revalidation_net_log(
2607       BoundNetLog::Make(net_log_.net_log(), NetLog::SOURCE_ASYNC_REVALIDATION));
2608   net_log_.AddEvent(
2609       NetLog::TYPE_HTTP_CACHE_VALIDATE_RESOURCE_ASYNC,
2610       async_revalidation_net_log.source().ToEventParametersCallback());
2611   async_revalidation_net_log.BeginEvent(
2612       NetLog::TYPE_ASYNC_REVALIDATION,
2613       base::Bind(
2614           &NetLogAsyncRevalidationInfoCallback, net_log_.source(), request_));
2615   base::MessageLoop::current()->PostTask(
2616       FROM_HERE,
2617       base::Bind(&HttpCache::PerformAsyncValidation,
2618                  cache_,  // cache_ is a weak pointer.
2619                  *request_,
2620                  async_revalidation_net_log));
2621 }
2622
2623 void HttpCache::Transaction::FailRangeRequest() {
2624   response_ = *new_response_;
2625   partial_->FixResponseHeaders(response_.headers.get(), false);
2626 }
2627
2628 int HttpCache::Transaction::SetupEntryForRead() {
2629   if (network_trans_)
2630     ResetNetworkTransaction();
2631   if (partial_.get()) {
2632     if (truncated_ || is_sparse_ || !invalid_range_) {
2633       // We are going to return the saved response headers to the caller, so
2634       // we may need to adjust them first.
2635       next_state_ = STATE_PARTIAL_HEADERS_RECEIVED;
2636       return OK;
2637     } else {
2638       partial_.reset();
2639     }
2640   }
2641   cache_->ConvertWriterToReader(entry_);
2642   mode_ = READ;
2643
2644   if (request_->method == "HEAD")
2645     FixHeadersForHead();
2646
2647   if (entry_->disk_entry->GetDataSize(kMetadataIndex))
2648     next_state_ = STATE_CACHE_READ_METADATA;
2649   return OK;
2650 }
2651
2652
2653 int HttpCache::Transaction::ReadFromNetwork(IOBuffer* data, int data_len) {
2654   read_buf_ = data;
2655   io_buf_len_ = data_len;
2656   next_state_ = STATE_NETWORK_READ;
2657   return DoLoop(OK);
2658 }
2659
2660 int HttpCache::Transaction::ReadFromEntry(IOBuffer* data, int data_len) {
2661   if (request_->method == "HEAD")
2662     return 0;
2663
2664   read_buf_ = data;
2665   io_buf_len_ = data_len;
2666   next_state_ = STATE_CACHE_READ_DATA;
2667   return DoLoop(OK);
2668 }
2669
2670 int HttpCache::Transaction::WriteToEntry(int index, int offset,
2671                                          IOBuffer* data, int data_len,
2672                                          const CompletionCallback& callback) {
2673   if (!entry_)
2674     return data_len;
2675
2676   int rv = 0;
2677   if (!partial_.get() || !data_len) {
2678     rv = entry_->disk_entry->WriteData(index, offset, data, data_len, callback,
2679                                        true);
2680   } else {
2681     rv = partial_->CacheWrite(entry_->disk_entry, data, data_len, callback);
2682   }
2683   return rv;
2684 }
2685
2686 int HttpCache::Transaction::WriteResponseInfoToEntry(bool truncated) {
2687   next_state_ = STATE_CACHE_WRITE_RESPONSE_COMPLETE;
2688   if (!entry_)
2689     return OK;
2690
2691   // Do not cache no-store content.  Do not cache content with cert errors
2692   // either.  This is to prevent not reporting net errors when loading a
2693   // resource from the cache.  When we load a page over HTTPS with a cert error
2694   // we show an SSL blocking page.  If the user clicks proceed we reload the
2695   // resource ignoring the errors.  The loaded resource is then cached.  If that
2696   // resource is subsequently loaded from the cache, no net error is reported
2697   // (even though the cert status contains the actual errors) and no SSL
2698   // blocking page is shown.  An alternative would be to reverse-map the cert
2699   // status to a net error and replay the net error.
2700   if ((response_.headers->HasHeaderValue("cache-control", "no-store")) ||
2701       IsCertStatusError(response_.ssl_info.cert_status)) {
2702     DoneWritingToEntry(false);
2703     if (net_log_.IsCapturing())
2704       net_log_.EndEvent(NetLog::TYPE_HTTP_CACHE_WRITE_INFO);
2705     return OK;
2706   }
2707
2708   // cert_cache() will be null if the CertCacheTrial field trial is disabled.
2709   if (cache_->cert_cache() && response_.ssl_info.is_valid())
2710     WriteCertChain();
2711
2712   if (truncated)
2713     DCHECK_EQ(200, response_.headers->response_code());
2714
2715   // When writing headers, we normally only write the non-transient headers.
2716   bool skip_transient_headers = true;
2717   scoped_refptr<PickledIOBuffer> data(new PickledIOBuffer());
2718   response_.Persist(data->pickle(), skip_transient_headers, truncated);
2719   data->Done();
2720
2721   io_buf_len_ = data->pickle()->size();
2722   return entry_->disk_entry->WriteData(kResponseInfoIndex, 0, data.get(),
2723                                        io_buf_len_, io_callback_, true);
2724 }
2725
2726 int HttpCache::Transaction::AppendResponseDataToEntry(
2727     IOBuffer* data, int data_len, const CompletionCallback& callback) {
2728   if (!entry_ || !data_len)
2729     return data_len;
2730
2731   int current_size = entry_->disk_entry->GetDataSize(kResponseContentIndex);
2732   return WriteToEntry(kResponseContentIndex, current_size, data, data_len,
2733                       callback);
2734 }
2735
2736 void HttpCache::Transaction::DoneWritingToEntry(bool success) {
2737   if (!entry_)
2738     return;
2739
2740   RecordHistograms();
2741
2742   cache_->DoneWritingToEntry(entry_, success);
2743   entry_ = NULL;
2744   mode_ = NONE;  // switch to 'pass through' mode
2745 }
2746
2747 int HttpCache::Transaction::OnCacheReadError(int result, bool restart) {
2748   DLOG(ERROR) << "ReadData failed: " << result;
2749   const int result_for_histogram = std::max(0, -result);
2750   if (restart) {
2751     UMA_HISTOGRAM_SPARSE_SLOWLY("HttpCache.ReadErrorRestartable",
2752                                 result_for_histogram);
2753   } else {
2754     UMA_HISTOGRAM_SPARSE_SLOWLY("HttpCache.ReadErrorNonRestartable",
2755                                 result_for_histogram);
2756   }
2757
2758   // Avoid using this entry in the future.
2759   if (cache_.get())
2760     cache_->DoomActiveEntry(cache_key_);
2761
2762   if (restart) {
2763     DCHECK(!reading_);
2764     DCHECK(!network_trans_.get());
2765     cache_->DoneWithEntry(entry_, this, false);
2766     entry_ = NULL;
2767     is_sparse_ = false;
2768     partial_.reset();
2769     next_state_ = STATE_GET_BACKEND;
2770     return OK;
2771   }
2772
2773   return ERR_CACHE_READ_FAILURE;
2774 }
2775
2776 void HttpCache::Transaction::OnAddToEntryTimeout(base::TimeTicks start_time) {
2777   if (entry_lock_waiting_since_ != start_time)
2778     return;
2779
2780   DCHECK_EQ(next_state_, STATE_ADD_TO_ENTRY_COMPLETE);
2781
2782   if (!cache_)
2783     return;
2784
2785   cache_->RemovePendingTransaction(this);
2786   OnIOComplete(ERR_CACHE_LOCK_TIMEOUT);
2787 }
2788
2789 void HttpCache::Transaction::DoomPartialEntry(bool delete_object) {
2790   DVLOG(2) << "DoomPartialEntry";
2791   int rv = cache_->DoomEntry(cache_key_, NULL);
2792   DCHECK_EQ(OK, rv);
2793   cache_->DoneWithEntry(entry_, this, false);
2794   entry_ = NULL;
2795   is_sparse_ = false;
2796   truncated_ = false;
2797   if (delete_object)
2798     partial_.reset(NULL);
2799 }
2800
2801 int HttpCache::Transaction::DoPartialNetworkReadCompleted(int result) {
2802   partial_->OnNetworkReadCompleted(result);
2803
2804   if (result == 0) {
2805     // We need to move on to the next range.
2806     ResetNetworkTransaction();
2807     next_state_ = STATE_START_PARTIAL_CACHE_VALIDATION;
2808   }
2809   return result;
2810 }
2811
2812 int HttpCache::Transaction::DoPartialCacheReadCompleted(int result) {
2813   partial_->OnCacheReadCompleted(result);
2814
2815   if (result == 0 && mode_ == READ_WRITE) {
2816     // We need to move on to the next range.
2817     next_state_ = STATE_START_PARTIAL_CACHE_VALIDATION;
2818   } else if (result < 0) {
2819     return OnCacheReadError(result, false);
2820   }
2821   return result;
2822 }
2823
2824 int HttpCache::Transaction::DoRestartPartialRequest() {
2825   // The stored data cannot be used. Get rid of it and restart this request.
2826   net_log_.AddEvent(NetLog::TYPE_HTTP_CACHE_RESTART_PARTIAL_REQUEST);
2827
2828   // WRITE + Doom + STATE_INIT_ENTRY == STATE_CREATE_ENTRY (without an attempt
2829   // to Doom the entry again).
2830   mode_ = WRITE;
2831   ResetPartialState(!range_requested_);
2832   next_state_ = STATE_CREATE_ENTRY;
2833   return OK;
2834 }
2835
2836 void HttpCache::Transaction::ResetPartialState(bool delete_object) {
2837   partial_->RestoreHeaders(&custom_request_->extra_headers);
2838   DoomPartialEntry(delete_object);
2839
2840   if (!delete_object) {
2841     // The simplest way to re-initialize partial_ is to create a new object.
2842     partial_.reset(new PartialData());
2843     if (partial_->Init(request_->extra_headers))
2844       partial_->SetHeaders(custom_request_->extra_headers);
2845     else
2846       partial_.reset();
2847   }
2848 }
2849
2850 void HttpCache::Transaction::ResetNetworkTransaction() {
2851   DCHECK(!old_network_trans_load_timing_);
2852   DCHECK(network_trans_);
2853   LoadTimingInfo load_timing;
2854   if (network_trans_->GetLoadTimingInfo(&load_timing))
2855     old_network_trans_load_timing_.reset(new LoadTimingInfo(load_timing));
2856   total_received_bytes_ += network_trans_->GetTotalReceivedBytes();
2857   ConnectionAttempts attempts;
2858   network_trans_->GetConnectionAttempts(&attempts);
2859   for (const auto& attempt : attempts)
2860     old_connection_attempts_.push_back(attempt);
2861   network_trans_.reset();
2862 }
2863
2864 // Histogram data from the end of 2010 show the following distribution of
2865 // response headers:
2866 //
2867 //   Content-Length............... 87%
2868 //   Date......................... 98%
2869 //   Last-Modified................ 49%
2870 //   Etag......................... 19%
2871 //   Accept-Ranges: bytes......... 25%
2872 //   Accept-Ranges: none.......... 0.4%
2873 //   Strong Validator............. 50%
2874 //   Strong Validator + ranges.... 24%
2875 //   Strong Validator + CL........ 49%
2876 //
2877 bool HttpCache::Transaction::CanResume(bool has_data) {
2878   // Double check that there is something worth keeping.
2879   if (has_data && !entry_->disk_entry->GetDataSize(kResponseContentIndex))
2880     return false;
2881
2882   if (request_->method != "GET")
2883     return false;
2884
2885   // Note that if this is a 206, content-length was already fixed after calling
2886   // PartialData::ResponseHeadersOK().
2887   if (response_.headers->GetContentLength() <= 0 ||
2888       response_.headers->HasHeaderValue("Accept-Ranges", "none") ||
2889       !response_.headers->HasStrongValidators()) {
2890     return false;
2891   }
2892
2893   return true;
2894 }
2895
2896 void HttpCache::Transaction::UpdateTransactionPattern(
2897     TransactionPattern new_transaction_pattern) {
2898   if (transaction_pattern_ == PATTERN_NOT_COVERED)
2899     return;
2900   DCHECK(transaction_pattern_ == PATTERN_UNDEFINED ||
2901          new_transaction_pattern == PATTERN_NOT_COVERED);
2902   transaction_pattern_ = new_transaction_pattern;
2903 }
2904
2905 void HttpCache::Transaction::RecordHistograms() {
2906   DCHECK_NE(PATTERN_UNDEFINED, transaction_pattern_);
2907   if (!cache_.get() || !cache_->GetCurrentBackend() ||
2908       cache_->GetCurrentBackend()->GetCacheType() != DISK_CACHE ||
2909       cache_->mode() != NORMAL || request_->method != "GET") {
2910     return;
2911   }
2912   UMA_HISTOGRAM_ENUMERATION(
2913       "HttpCache.Pattern", transaction_pattern_, PATTERN_MAX);
2914   if (transaction_pattern_ == PATTERN_NOT_COVERED)
2915     return;
2916   DCHECK(!range_requested_);
2917   DCHECK(!first_cache_access_since_.is_null());
2918
2919   TimeDelta total_time = base::TimeTicks::Now() - first_cache_access_since_;
2920
2921   UMA_HISTOGRAM_TIMES("HttpCache.AccessToDone", total_time);
2922
2923   bool did_send_request = !send_request_since_.is_null();
2924   DCHECK(
2925       (did_send_request &&
2926        (transaction_pattern_ == PATTERN_ENTRY_NOT_CACHED ||
2927         transaction_pattern_ == PATTERN_ENTRY_VALIDATED ||
2928         transaction_pattern_ == PATTERN_ENTRY_UPDATED ||
2929         transaction_pattern_ == PATTERN_ENTRY_CANT_CONDITIONALIZE)) ||
2930       (!did_send_request && transaction_pattern_ == PATTERN_ENTRY_USED));
2931
2932   if (!did_send_request) {
2933     DCHECK(transaction_pattern_ == PATTERN_ENTRY_USED);
2934     UMA_HISTOGRAM_TIMES("HttpCache.AccessToDone.Used", total_time);
2935     return;
2936   }
2937
2938   TimeDelta before_send_time = send_request_since_ - first_cache_access_since_;
2939   int64 before_send_percent = (total_time.ToInternalValue() == 0) ?
2940       0 : before_send_time * 100 / total_time;
2941   DCHECK_GE(before_send_percent, 0);
2942   DCHECK_LE(before_send_percent, 100);
2943   base::HistogramBase::Sample before_send_sample =
2944       static_cast<base::HistogramBase::Sample>(before_send_percent);
2945
2946   UMA_HISTOGRAM_TIMES("HttpCache.AccessToDone.SentRequest", total_time);
2947   UMA_HISTOGRAM_TIMES("HttpCache.BeforeSend", before_send_time);
2948   UMA_HISTOGRAM_PERCENTAGE("HttpCache.PercentBeforeSend", before_send_sample);
2949
2950   // TODO(gavinp): Remove or minimize these histograms, particularly the ones
2951   // below this comment after we have received initial data.
2952   switch (transaction_pattern_) {
2953     case PATTERN_ENTRY_CANT_CONDITIONALIZE: {
2954       UMA_HISTOGRAM_TIMES("HttpCache.BeforeSend.CantConditionalize",
2955                           before_send_time);
2956       UMA_HISTOGRAM_PERCENTAGE("HttpCache.PercentBeforeSend.CantConditionalize",
2957                                before_send_sample);
2958       break;
2959     }
2960     case PATTERN_ENTRY_NOT_CACHED: {
2961       UMA_HISTOGRAM_TIMES("HttpCache.BeforeSend.NotCached", before_send_time);
2962       UMA_HISTOGRAM_PERCENTAGE("HttpCache.PercentBeforeSend.NotCached",
2963                                before_send_sample);
2964       break;
2965     }
2966     case PATTERN_ENTRY_VALIDATED: {
2967       UMA_HISTOGRAM_TIMES("HttpCache.BeforeSend.Validated", before_send_time);
2968       UMA_HISTOGRAM_PERCENTAGE("HttpCache.PercentBeforeSend.Validated",
2969                                before_send_sample);
2970       break;
2971     }
2972     case PATTERN_ENTRY_UPDATED: {
2973       UMA_HISTOGRAM_TIMES("HttpCache.BeforeSend.Updated", before_send_time);
2974       UMA_HISTOGRAM_PERCENTAGE("HttpCache.PercentBeforeSend.Updated",
2975                                before_send_sample);
2976       break;
2977     }
2978     default:
2979       NOTREACHED();
2980   }
2981 }
2982
2983 void HttpCache::Transaction::OnIOComplete(int result) {
2984   DoLoop(result);
2985 }
2986
2987 }  // namespace net