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/net_log.h"
  39 #include "net/base/upload_data_stream.h"
  40 #include "net/cert/cert_status_flags.h"
  41 #include "net/disk_cache/disk_cache.h"
  42 #include "net/http/disk_based_cert_cache.h"
  43 #include "net/http/http_network_session.h"
  44 #include "net/http/http_request_info.h"
  45 #include "net/http/http_response_headers.h"
  46 #include "net/http/http_transaction.h"
  47 #include "net/http/http_util.h"
  48 #include "net/http/partial_data.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 {
  57
  58 // TODO(ricea): Move this to HttpResponseHeaders once it is standardised.
  59 static const char kFreshnessHeader[] = "Resource-Freshness";
  60
  61 // Stores data relevant to the statistics of writing and reading entire
  62 // certificate chains using DiskBasedCertCache. |num_pending_ops| is the number
  63 // of certificates in the chain that have pending operations in the
  64 // DiskBasedCertCache. |start_time| is the time that the read and write
  65 // commands began being issued to the DiskBasedCertCache.
  66 // TODO(brandonsalmon): Remove this when it is no longer necessary to
  67 // collect data.
  68 class SharedChainData : public base::RefCounted<SharedChainData> {
  69  public:
  70   SharedChainData(int num_ops, TimeTicks start)
  71       : num_pending_ops(num_ops), start_time(start) {}
  72
  73   int num_pending_ops;
  74   TimeTicks start_time;
  75
  76  private:
  77   friend class base::RefCounted<SharedChainData>;
  78   ~SharedChainData() {}
  79   DISALLOW_COPY_AND_ASSIGN(SharedChainData);
  80 };
  81
  82 // Used to obtain a cache entry key for an OSCertHandle.
  83 // TODO(brandonsalmon): Remove this when cache keys are stored
  84 // and no longer have to be recomputed to retrieve the OSCertHandle
  85 // from the disk.
  86 std::string GetCacheKeyForCert(net::X509Certificate::OSCertHandle cert_handle) {
  87   net::SHA1HashValue fingerprint =
  88       net::X509Certificate::CalculateFingerprint(cert_handle);
  89
  90   return "cert:" +
  91          base::HexEncode(fingerprint.data, arraysize(fingerprint.data));
  92 }
  93
  94 // |dist_from_root| indicates the position of the read certificate in the
  95 // certificate chain, 0 indicating it is the root. |is_leaf| indicates
  96 // whether or not the read certificate was the leaf of the chain.
  97 // |shared_chain_data| contains data shared by each certificate in
  98 // the chain.
  99 void OnCertReadIOComplete(
 100     int dist_from_root,
 101     bool is_leaf,
 102     const scoped_refptr<SharedChainData>& shared_chain_data,
 103     net::X509Certificate::OSCertHandle cert_handle) {
 104   // If |num_pending_ops| is one, this was the last pending read operation
 105   // for this chain of certificates. The total time used to read the chain
 106   // can be calculated by subtracting the starting time from Now().
 107   shared_chain_data->num_pending_ops--;
 108   if (!shared_chain_data->num_pending_ops) {
 109     const TimeDelta read_chain_wait =
 110         TimeTicks::Now() - shared_chain_data->start_time;
 111     UMA_HISTOGRAM_CUSTOM_TIMES("DiskBasedCertCache.ChainReadTime",
 112                                read_chain_wait,
 113                                base::TimeDelta::FromMilliseconds(1),
 114                                base::TimeDelta::FromMinutes(10),
 115                                50);
 116   }
 117
 118   bool success = (cert_handle != NULL);
 119   if (is_leaf)
 120     UMA_HISTOGRAM_BOOLEAN("DiskBasedCertCache.CertIoReadSuccessLeaf", success);
 121
 122   if (success)
 123     UMA_HISTOGRAM_CUSTOM_COUNTS(
 124         "DiskBasedCertCache.CertIoReadSuccess", dist_from_root, 0, 10, 7);
 125   else
 126     UMA_HISTOGRAM_CUSTOM_COUNTS(
 127         "DiskBasedCertCache.CertIoReadFailure", dist_from_root, 0, 10, 7);
 128 }
 129
 130 // |dist_from_root| indicates the position of the written certificate in the
 131 // certificate chain, 0 indicating it is the root. |is_leaf| indicates
 132 // whether or not the written certificate was the leaf of the chain.
 133 // |shared_chain_data| contains data shared by each certificate in
 134 // the chain.
 135 void OnCertWriteIOComplete(
 136     int dist_from_root,
 137     bool is_leaf,
 138     const scoped_refptr<SharedChainData>& shared_chain_data,
 139     const std::string& key) {
 140   // If |num_pending_ops| is one, this was the last pending write operation
 141   // for this chain of certificates. The total time used to write the chain
 142   // can be calculated by subtracting the starting time from Now().
 143   shared_chain_data->num_pending_ops--;
 144   if (!shared_chain_data->num_pending_ops) {
 145     const TimeDelta write_chain_wait =
 146         TimeTicks::Now() - shared_chain_data->start_time;
 147     UMA_HISTOGRAM_CUSTOM_TIMES("DiskBasedCertCache.ChainWriteTime",
 148                                write_chain_wait,
 149                                base::TimeDelta::FromMilliseconds(1),
 150                                base::TimeDelta::FromMinutes(10),
 151                                50);
 152   }
 153
 154   bool success = !key.empty();
 155   if (is_leaf)
 156     UMA_HISTOGRAM_BOOLEAN("DiskBasedCertCache.CertIoWriteSuccessLeaf", success);
 157
 158   if (success)
 159     UMA_HISTOGRAM_CUSTOM_COUNTS(
 160         "DiskBasedCertCache.CertIoWriteSuccess", dist_from_root, 0, 10, 7);
 161   else
 162     UMA_HISTOGRAM_CUSTOM_COUNTS(
 163         "DiskBasedCertCache.CertIoWriteFailure", dist_from_root, 0, 10, 7);
 164 }
 165
 166 // From http://tools.ietf.org/html/draft-ietf-httpbis-p6-cache-21#section-6
 167 //      a "non-error response" is one with a 2xx (Successful) or 3xx
 168 //      (Redirection) status code.
 169 bool NonErrorResponse(int status_code) {
 170   int status_code_range = status_code / 100;
 171   return status_code_range == 2 || status_code_range == 3;
 172 }
 173
 174 // Error codes that will be considered indicative of a page being offline/
 175 // unreachable for LOAD_FROM_CACHE_IF_OFFLINE.
 176 bool IsOfflineError(int error) {
 177   return (error == net::ERR_NAME_NOT_RESOLVED ||
 178           error == net::ERR_INTERNET_DISCONNECTED ||
 179           error == net::ERR_ADDRESS_UNREACHABLE ||
 180           error == net::ERR_CONNECTION_TIMED_OUT);
 181 }
 182
 183 // Enum for UMA, indicating the status (with regard to offline mode) of
 184 // a particular request.
 185 enum RequestOfflineStatus {
 186   // A cache transaction hit in cache (data was present and not stale)
 187   // and returned it.
 188   OFFLINE_STATUS_FRESH_CACHE,
 189
 190   // A network request was required for a cache entry, and it succeeded.
 191   OFFLINE_STATUS_NETWORK_SUCCEEDED,
 192
 193   // A network request was required for a cache entry, and it failed with
 194   // a non-offline error.
 195   OFFLINE_STATUS_NETWORK_FAILED,
 196
 197   // A network request was required for a cache entry, it failed with an
 198   // offline error, and we could serve stale data if
 199   // LOAD_FROM_CACHE_IF_OFFLINE was set.
 200   OFFLINE_STATUS_DATA_AVAILABLE_OFFLINE,
 201
 202   // A network request was required for a cache entry, it failed with
 203   // an offline error, and there was no servable data in cache (even
 204   // stale data).
 205   OFFLINE_STATUS_DATA_UNAVAILABLE_OFFLINE,
 206
 207   OFFLINE_STATUS_MAX_ENTRIES
 208 };
 209
 210 void RecordOfflineStatus(int load_flags, RequestOfflineStatus status) {
 211   // Restrict to main frame to keep statistics close to
 212   // "would have shown them something useful if offline mode was enabled".
 213   if (load_flags & net::LOAD_MAIN_FRAME) {
 214     UMA_HISTOGRAM_ENUMERATION("HttpCache.OfflineStatus", status,
 215                               OFFLINE_STATUS_MAX_ENTRIES);
 216   }
 217 }
 218
 219 void RecordNoStoreHeaderHistogram(int load_flags,
 220                                   const net::HttpResponseInfo* response) {
 221   if (load_flags & net::LOAD_MAIN_FRAME) {
 222     UMA_HISTOGRAM_BOOLEAN(
 223         "Net.MainFrameNoStore",
 224         response->headers->HasHeaderValue("cache-control", "no-store"));
 225   }
 226 }
 227
 228 base::Value* NetLogAsyncRevalidationInfoCallback(
 229     const net::NetLog::Source& source,
 230     const net::HttpRequestInfo* request,
 231     net::NetLog::LogLevel log_level) {
 232   base::DictionaryValue* dict = new base::DictionaryValue();
 233   source.AddToEventParameters(dict);
 234
 235   dict->SetString("url", request->url.possibly_invalid_spec());
 236   dict->SetString("method", request->method);
 237   return dict;
 238 }
 239
 240 enum ExternallyConditionalizedType {
 241   EXTERNALLY_CONDITIONALIZED_CACHE_REQUIRES_VALIDATION,
 242   EXTERNALLY_CONDITIONALIZED_CACHE_USABLE,
 243   EXTERNALLY_CONDITIONALIZED_MISMATCHED_VALIDATORS,
 244   EXTERNALLY_CONDITIONALIZED_MAX
 245 };
 246
 247 }  // namespace
 248
 249 namespace net {
 250
 251 struct HeaderNameAndValue {
 252   const char* name;
 253   const char* value;
 254 };
 255
 256 // If the request includes one of these request headers, then avoid caching
 257 // to avoid getting confused.
 258 static const HeaderNameAndValue kPassThroughHeaders[] = {
 259   { "if-unmodified-since", NULL },  // causes unexpected 412s
 260   { "if-match", NULL },             // causes unexpected 412s
 261   { "if-range", NULL },
 262   { NULL, NULL }
 263 };
 264
 265 struct ValidationHeaderInfo {
 266   const char* request_header_name;
 267   const char* related_response_header_name;
 268 };
 269
 270 static const ValidationHeaderInfo kValidationHeaders[] = {
 271   { "if-modified-since", "last-modified" },
 272   { "if-none-match", "etag" },
 273 };
 274
 275 // If the request includes one of these request headers, then avoid reusing
 276 // our cached copy if any.
 277 static const HeaderNameAndValue kForceFetchHeaders[] = {
 278   { "cache-control", "no-cache" },
 279   { "pragma", "no-cache" },
 280   { NULL, NULL }
 281 };
 282
 283 // If the request includes one of these request headers, then force our
 284 // cached copy (if any) to be revalidated before reusing it.
 285 static const HeaderNameAndValue kForceValidateHeaders[] = {
 286   { "cache-control", "max-age=0" },
 287   { NULL, NULL }
 288 };
 289
 290 static bool HeaderMatches(const HttpRequestHeaders& headers,
 291                           const HeaderNameAndValue* search) {
 292   for (; search->name; ++search) {
 293     std::string header_value;
 294     if (!headers.GetHeader(search->name, &header_value))
 295       continue;
 296
 297     if (!search->value)
 298       return true;
 299
 300     HttpUtil::ValuesIterator v(header_value.begin(), header_value.end(), ',');
 301     while (v.GetNext()) {
 302       if (LowerCaseEqualsASCII(v.value_begin(), v.value_end(), search->value))
 303         return true;
 304     }
 305   }
 306   return false;
 307 }
 308
 309 //-----------------------------------------------------------------------------
 310
 311 HttpCache::Transaction::Transaction(RequestPriority priority, HttpCache* cache)
 312     : next_state_(STATE_NONE),
 313       request_(NULL),
 314       priority_(priority),
 315       cache_(cache->GetWeakPtr()),
 316       entry_(NULL),
 317       new_entry_(NULL),
 318       new_response_(NULL),
 319       mode_(NONE),
 320       target_state_(STATE_NONE),
 321       reading_(false),
 322       invalid_range_(false),
 323       truncated_(false),
 324       is_sparse_(false),
 325       range_requested_(false),
 326       handling_206_(false),
 327       cache_pending_(false),
 328       done_reading_(false),
 329       vary_mismatch_(false),
 330       couldnt_conditionalize_request_(false),
 331       bypass_lock_for_test_(false),
 332       fail_conditionalization_for_test_(false),
 333       io_buf_len_(0),
 334       read_offset_(0),
 335       effective_load_flags_(0),
 336       write_len_(0),
 337       transaction_pattern_(PATTERN_UNDEFINED),
 338       total_received_bytes_(0),
 339       websocket_handshake_stream_base_create_helper_(NULL),
 340       weak_factory_(this) {
 341   static_assert(HttpCache::Transaction::kNumValidationHeaders ==
 342                     arraysize(kValidationHeaders),
 343                 "invalid number of validation headers");
 344
 345   io_callback_ = base::Bind(&Transaction::OnIOComplete,
 346                               weak_factory_.GetWeakPtr());
 347 }
 348
 349 HttpCache::Transaction::~Transaction() {
 350   // We may have to issue another IO, but we should never invoke the callback_
 351   // after this point.
 352   callback_.Reset();
 353
 354   if (cache_) {
 355     if (entry_) {
 356       bool cancel_request = reading_ && response_.headers.get();
 357       if (cancel_request) {
 358         if (partial_) {
 359           entry_->disk_entry->CancelSparseIO();
 360         } else {
 361           cancel_request &= (response_.headers->response_code() == 200);
 362         }
 363       }
 364
 365       cache_->DoneWithEntry(entry_, this, cancel_request);
 366     } else if (cache_pending_) {
 367       cache_->RemovePendingTransaction(this);
 368     }
 369   }
 370 }
 371
 372 int HttpCache::Transaction::WriteMetadata(IOBuffer* buf, int buf_len,
 373                                           const CompletionCallback& callback) {
 374   DCHECK(buf);
 375   DCHECK_GT(buf_len, 0);
 376   DCHECK(!callback.is_null());
 377   if (!cache_.get() || !entry_)
 378     return ERR_UNEXPECTED;
 379
 380   // We don't need to track this operation for anything.
 381   // It could be possible to check if there is something already written and
 382   // avoid writing again (it should be the same, right?), but let's allow the
 383   // caller to "update" the contents with something new.
 384   return entry_->disk_entry->WriteData(kMetadataIndex, 0, buf, buf_len,
 385                                        callback, true);
 386 }
 387
 388 bool HttpCache::Transaction::AddTruncatedFlag() {
 389   DCHECK(mode_ & WRITE || mode_ == NONE);
 390
 391   // Don't set the flag for sparse entries.
 392   if (partial_.get() && !truncated_)
 393     return true;
 394
 395   if (!CanResume(true))
 396     return false;
 397
 398   // We may have received the whole resource already.
 399   if (done_reading_)
 400     return true;
 401
 402   truncated_ = true;
 403   target_state_ = STATE_NONE;
 404   next_state_ = STATE_CACHE_WRITE_TRUNCATED_RESPONSE;
 405   DoLoop(OK);
 406   return true;
 407 }
 408
 409 LoadState HttpCache::Transaction::GetWriterLoadState() const {
 410   if (network_trans_.get())
 411     return network_trans_->GetLoadState();
 412   if (entry_ || !request_)
 413     return LOAD_STATE_IDLE;
 414   return LOAD_STATE_WAITING_FOR_CACHE;
 415 }
 416
 417 const BoundNetLog& HttpCache::Transaction::net_log() const {
 418   return net_log_;
 419 }
 420
 421 int HttpCache::Transaction::Start(const HttpRequestInfo* request,
 422                                   const CompletionCallback& callback,
 423                                   const BoundNetLog& net_log) {
 424   DCHECK(request);
 425   DCHECK(!callback.is_null());
 426
 427   // Ensure that we only have one asynchronous call at a time.
 428   DCHECK(callback_.is_null());
 429   DCHECK(!reading_);
 430   DCHECK(!network_trans_.get());
 431   DCHECK(!entry_);
 432
 433   if (!cache_.get())
 434     return ERR_UNEXPECTED;
 435
 436   SetRequest(net_log, request);
 437
 438   // We have to wait until the backend is initialized so we start the SM.
 439   next_state_ = STATE_GET_BACKEND;
 440   int rv = DoLoop(OK);
 441
 442   // Setting this here allows us to check for the existence of a callback_ to
 443   // determine if we are still inside Start.
 444   if (rv == ERR_IO_PENDING) {
 445     callback_ = tracked_objects::ScopedTracker::TrackCallback(
 446         FROM_HERE_WITH_EXPLICIT_FUNCTION(
 447             "422516 HttpCache::Transaction::Start"),
 448         callback);
 449   }
 450
 451   return rv;
 452 }
 453
 454 int HttpCache::Transaction::RestartIgnoringLastError(
 455     const CompletionCallback& callback) {
 456   DCHECK(!callback.is_null());
 457
 458   // Ensure that we only have one asynchronous call at a time.
 459   DCHECK(callback_.is_null());
 460
 461   if (!cache_.get())
 462     return ERR_UNEXPECTED;
 463
 464   int rv = RestartNetworkRequest();
 465
 466   if (rv == ERR_IO_PENDING) {
 467     callback_ = tracked_objects::ScopedTracker::TrackCallback(
 468         FROM_HERE_WITH_EXPLICIT_FUNCTION(
 469             "422516 HttpCache::Transaction::RestartIgnoringLastError"),
 470         callback);
 471   }
 472
 473   return rv;
 474 }
 475
 476 int HttpCache::Transaction::RestartWithCertificate(
 477     X509Certificate* client_cert,
 478     const CompletionCallback& callback) {
 479   DCHECK(!callback.is_null());
 480
 481   // Ensure that we only have one asynchronous call at a time.
 482   DCHECK(callback_.is_null());
 483
 484   if (!cache_.get())
 485     return ERR_UNEXPECTED;
 486
 487   int rv = RestartNetworkRequestWithCertificate(client_cert);
 488
 489   if (rv == ERR_IO_PENDING) {
 490     callback_ = tracked_objects::ScopedTracker::TrackCallback(
 491         FROM_HERE_WITH_EXPLICIT_FUNCTION(
 492             "422516 HttpCache::Transaction::RestartWithCertificate"),
 493         callback);
 494   }
 495
 496   return rv;
 497 }
 498
 499 int HttpCache::Transaction::RestartWithAuth(
 500     const AuthCredentials& credentials,
 501     const CompletionCallback& callback) {
 502   DCHECK(auth_response_.headers.get());
 503   DCHECK(!callback.is_null());
 504
 505   // Ensure that we only have one asynchronous call at a time.
 506   DCHECK(callback_.is_null());
 507
 508   if (!cache_.get())
 509     return ERR_UNEXPECTED;
 510
 511   // Clear the intermediate response since we are going to start over.
 512   auth_response_ = HttpResponseInfo();
 513
 514   int rv = RestartNetworkRequestWithAuth(credentials);
 515
 516   if (rv == ERR_IO_PENDING) {
 517     callback_ = tracked_objects::ScopedTracker::TrackCallback(
 518         FROM_HERE_WITH_EXPLICIT_FUNCTION(
 519             "422516 HttpCache::Transaction::RestartWithAuth"),
 520         callback);
 521   }
 522
 523   return rv;
 524 }
 525
 526 bool HttpCache::Transaction::IsReadyToRestartForAuth() {
 527   if (!network_trans_.get())
 528     return false;
 529   return network_trans_->IsReadyToRestartForAuth();
 530 }
 531
 532 int HttpCache::Transaction::Read(IOBuffer* buf, int buf_len,
 533                                  const CompletionCallback& callback) {
 534   DCHECK(buf);
 535   DCHECK_GT(buf_len, 0);
 536   DCHECK(!callback.is_null());
 537
 538   DCHECK(callback_.is_null());
 539
 540   if (!cache_.get())
 541     return ERR_UNEXPECTED;
 542
 543   // If we have an intermediate auth response at this point, then it means the
 544   // user wishes to read the network response (the error page).  If there is a
 545   // previous response in the cache then we should leave it intact.
 546   if (auth_response_.headers.get() && mode_ != NONE) {
 547     UpdateTransactionPattern(PATTERN_NOT_COVERED);
 548     DCHECK(mode_ & WRITE);
 549     DoneWritingToEntry(mode_ == READ_WRITE);
 550     mode_ = NONE;
 551   }
 552
 553   reading_ = true;
 554   int rv;
 555
 556   switch (mode_) {
 557     case READ_WRITE:
 558       DCHECK(partial_.get());
 559       if (!network_trans_.get()) {
 560         // We are just reading from the cache, but we may be writing later.
 561         rv = ReadFromEntry(buf, buf_len);
 562         break;
 563       }
 564     case NONE:
 565     case WRITE:
 566       DCHECK(network_trans_.get());
 567       rv = ReadFromNetwork(buf, buf_len);
 568       break;
 569     case READ:
 570       rv = ReadFromEntry(buf, buf_len);
 571       break;
 572     default:
 573       NOTREACHED();
 574       rv = ERR_FAILED;
 575   }
 576
 577   if (rv == ERR_IO_PENDING) {
 578     DCHECK(callback_.is_null());
 579     callback_ = tracked_objects::ScopedTracker::TrackCallback(
 580         FROM_HERE_WITH_EXPLICIT_FUNCTION("422516 HttpCache::Transaction::Read"),
 581         callback);
 582   }
 583   return rv;
 584 }
 585
 586 void HttpCache::Transaction::StopCaching() {
 587   // We really don't know where we are now. Hopefully there is no operation in
 588   // progress, but nothing really prevents this method to be called after we
 589   // returned ERR_IO_PENDING. We cannot attempt to truncate the entry at this
 590   // point because we need the state machine for that (and even if we are really
 591   // free, that would be an asynchronous operation). In other words, keep the
 592   // entry how it is (it will be marked as truncated at destruction), and let
 593   // the next piece of code that executes know that we are now reading directly
 594   // from the net.
 595   // TODO(mmenke):  This doesn't release the lock on the cache entry, so a
 596   //                future request for the resource will be blocked on this one.
 597   //                Fix this.
 598   if (cache_.get() && entry_ && (mode_ & WRITE) && network_trans_.get() &&
 599       !is_sparse_ && !range_requested_) {
 600     mode_ = NONE;
 601   }
 602 }
 603
 604 bool HttpCache::Transaction::GetFullRequestHeaders(
 605     HttpRequestHeaders* headers) const {
 606   if (network_trans_)
 607     return network_trans_->GetFullRequestHeaders(headers);
 608
 609   // TODO(ttuttle): Read headers from cache.
 610   return false;
 611 }
 612
 613 int64 HttpCache::Transaction::GetTotalReceivedBytes() const {
 614   int64 total_received_bytes = total_received_bytes_;
 615   if (network_trans_)
 616     total_received_bytes += network_trans_->GetTotalReceivedBytes();
 617   return total_received_bytes;
 618 }
 619
 620 void HttpCache::Transaction::DoneReading() {
 621   if (cache_.get() && entry_) {
 622     DCHECK_NE(mode_, UPDATE);
 623     if (mode_ & WRITE) {
 624       DoneWritingToEntry(true);
 625     } else if (mode_ & READ) {
 626       // It is necessary to check mode_ & READ because it is possible
 627       // for mode_ to be NONE and entry_ non-NULL with a write entry
 628       // if StopCaching was called.
 629       cache_->DoneReadingFromEntry(entry_, this);
 630       entry_ = NULL;
 631     }
 632   }
 633 }
 634
 635 const HttpResponseInfo* HttpCache::Transaction::GetResponseInfo() const {
 636   // Null headers means we encountered an error or haven't a response yet
 637   if (auth_response_.headers.get())
 638     return &auth_response_;
 639   return (response_.headers.get() || response_.ssl_info.cert.get() ||
 640           response_.cert_request_info.get())
 641              ? &response_
 642              : NULL;
 643 }
 644
 645 LoadState HttpCache::Transaction::GetLoadState() const {
 646   LoadState state = GetWriterLoadState();
 647   if (state != LOAD_STATE_WAITING_FOR_CACHE)
 648     return state;
 649
 650   if (cache_.get())
 651     return cache_->GetLoadStateForPendingTransaction(this);
 652
 653   return LOAD_STATE_IDLE;
 654 }
 655
 656 UploadProgress HttpCache::Transaction::GetUploadProgress() const {
 657   if (network_trans_.get())
 658     return network_trans_->GetUploadProgress();
 659   return final_upload_progress_;
 660 }
 661
 662 void HttpCache::Transaction::SetQuicServerInfo(
 663     QuicServerInfo* quic_server_info) {}
 664
 665 bool HttpCache::Transaction::GetLoadTimingInfo(
 666     LoadTimingInfo* load_timing_info) const {
 667   if (network_trans_)
 668     return network_trans_->GetLoadTimingInfo(load_timing_info);
 669
 670   if (old_network_trans_load_timing_) {
 671     *load_timing_info = *old_network_trans_load_timing_;
 672     return true;
 673   }
 674
 675   if (first_cache_access_since_.is_null())
 676     return false;
 677
 678   // If the cache entry was opened, return that time.
 679   load_timing_info->send_start = first_cache_access_since_;
 680   // This time doesn't make much sense when reading from the cache, so just use
 681   // the same time as send_start.
 682   load_timing_info->send_end = first_cache_access_since_;
 683   return true;
 684 }
 685
 686 void HttpCache::Transaction::SetPriority(RequestPriority priority) {
 687   priority_ = priority;
 688   if (network_trans_)
 689     network_trans_->SetPriority(priority_);
 690 }
 691
 692 void HttpCache::Transaction::SetWebSocketHandshakeStreamCreateHelper(
 693     WebSocketHandshakeStreamBase::CreateHelper* create_helper) {
 694   websocket_handshake_stream_base_create_helper_ = create_helper;
 695   if (network_trans_)
 696     network_trans_->SetWebSocketHandshakeStreamCreateHelper(create_helper);
 697 }
 698
 699 void HttpCache::Transaction::SetBeforeNetworkStartCallback(
 700     const BeforeNetworkStartCallback& callback) {
 701   DCHECK(!network_trans_);
 702   before_network_start_callback_ = callback;
 703 }
 704
 705 void HttpCache::Transaction::SetBeforeProxyHeadersSentCallback(
 706     const BeforeProxyHeadersSentCallback& callback) {
 707   DCHECK(!network_trans_);
 708   before_proxy_headers_sent_callback_ = callback;
 709 }
 710
 711 int HttpCache::Transaction::ResumeNetworkStart() {
 712   if (network_trans_)
 713     return network_trans_->ResumeNetworkStart();
 714   return ERR_UNEXPECTED;
 715 }
 716
 717 //-----------------------------------------------------------------------------
 718
 719 void HttpCache::Transaction::DoCallback(int rv) {
 720   // TODO(vadimt): Remove ScopedTracker below once crbug.com/422516 is fixed.
 721   tracked_objects::ScopedTracker tracking_profile(
 722       FROM_HERE_WITH_EXPLICIT_FUNCTION(
 723           "422516 HttpCache::Transaction::DoCallback"));
 724
 725   DCHECK(rv != ERR_IO_PENDING);
 726   DCHECK(!callback_.is_null());
 727
 728   read_buf_ = NULL;  // Release the buffer before invoking the callback.
 729
 730   // Since Run may result in Read being called, clear callback_ up front.
 731   CompletionCallback c = callback_;
 732   callback_.Reset();
 733   c.Run(rv);
 734 }
 735
 736 int HttpCache::Transaction::HandleResult(int rv) {
 737   DCHECK(rv != ERR_IO_PENDING);
 738   if (!callback_.is_null())
 739     DoCallback(rv);
 740
 741   return rv;
 742 }
 743
 744 // A few common patterns: (Foo* means Foo -> FooComplete)
 745 //
 746 // 1. Not-cached entry:
 747 //   Start():
 748 //   GetBackend* -> InitEntry -> OpenEntry* -> CreateEntry* -> AddToEntry* ->
 749 //   SendRequest* -> SuccessfulSendRequest -> OverwriteCachedResponse ->
 750 //   CacheWriteResponse* -> TruncateCachedData* -> TruncateCachedMetadata* ->
 751 //   PartialHeadersReceived
 752 //
 753 //   Read():
 754 //   NetworkRead* -> CacheWriteData*
 755 //
 756 // 2. Cached entry, no validation:
 757 //   Start():
 758 //   GetBackend* -> InitEntry -> OpenEntry* -> AddToEntry* -> CacheReadResponse*
 759 //   -> CacheDispatchValidation -> BeginPartialCacheValidation() ->
 760 //   BeginCacheValidation() -> SetupEntryForRead()
 761 //
 762 //   Read():
 763 //   CacheReadData*
 764 //
 765 // 3. Cached entry, validation (304):
 766 //   Start():
 767 //   GetBackend* -> InitEntry -> OpenEntry* -> AddToEntry* -> CacheReadResponse*
 768 //   -> CacheDispatchValidation -> BeginPartialCacheValidation() ->
 769 //   BeginCacheValidation() -> SendRequest* -> SuccessfulSendRequest ->
 770 //   UpdateCachedResponse -> CacheWriteResponse* -> UpdateCachedResponseComplete
 771 //   -> OverwriteCachedResponse -> PartialHeadersReceived
 772 //
 773 //   Read():
 774 //   CacheReadData*
 775 //
 776 // 4. Cached entry, validation and replace (200):
 777 //   Start():
 778 //   GetBackend* -> InitEntry -> OpenEntry* -> AddToEntry* -> CacheReadResponse*
 779 //   -> CacheDispatchValidation -> BeginPartialCacheValidation() ->
 780 //   BeginCacheValidation() -> SendRequest* -> SuccessfulSendRequest ->
 781 //   OverwriteCachedResponse -> CacheWriteResponse* -> DoTruncateCachedData* ->
 782 //   TruncateCachedMetadata* -> PartialHeadersReceived
 783 //
 784 //   Read():
 785 //   NetworkRead* -> CacheWriteData*
 786 //
 787 // 5. Sparse entry, partially cached, byte range request:
 788 //   Start():
 789 //   GetBackend* -> InitEntry -> OpenEntry* -> AddToEntry* -> CacheReadResponse*
 790 //   -> CacheDispatchValidation -> BeginPartialCacheValidation() ->
 791 //   CacheQueryData* -> ValidateEntryHeadersAndContinue() ->
 792 //   StartPartialCacheValidation -> CompletePartialCacheValidation ->
 793 //   BeginCacheValidation() -> SendRequest* -> SuccessfulSendRequest ->
 794 //   UpdateCachedResponse -> CacheWriteResponse* -> UpdateCachedResponseComplete
 795 //   -> OverwriteCachedResponse -> PartialHeadersReceived
 796 //
 797 //   Read() 1:
 798 //   NetworkRead* -> CacheWriteData*
 799 //
 800 //   Read() 2:
 801 //   NetworkRead* -> CacheWriteData* -> StartPartialCacheValidation ->
 802 //   CompletePartialCacheValidation -> CacheReadData* ->
 803 //
 804 //   Read() 3:
 805 //   CacheReadData* -> StartPartialCacheValidation ->
 806 //   CompletePartialCacheValidation -> BeginCacheValidation() -> SendRequest* ->
 807 //   SuccessfulSendRequest -> UpdateCachedResponse* -> OverwriteCachedResponse
 808 //   -> PartialHeadersReceived -> NetworkRead* -> CacheWriteData*
 809 //
 810 // 6. HEAD. Not-cached entry:
 811 //   Pass through. Don't save a HEAD by itself.
 812 //   Start():
 813 //   GetBackend* -> InitEntry -> OpenEntry* -> SendRequest*
 814 //
 815 // 7. HEAD. Cached entry, no validation:
 816 //   Start():
 817 //   The same flow as for a GET request (example #2)
 818 //
 819 //   Read():
 820 //   CacheReadData (returns 0)
 821 //
 822 // 8. HEAD. Cached entry, validation (304):
 823 //   The request updates the stored headers.
 824 //   Start(): Same as for a GET request (example #3)
 825 //
 826 //   Read():
 827 //   CacheReadData (returns 0)
 828 //
 829 // 9. HEAD. Cached entry, validation and replace (200):
 830 //   Pass through. The request dooms the old entry, as a HEAD won't be stored by
 831 //   itself.
 832 //   Start():
 833 //   GetBackend* -> InitEntry -> OpenEntry* -> AddToEntry* -> CacheReadResponse*
 834 //   -> CacheDispatchValidation -> BeginPartialCacheValidation() ->
 835 //   BeginCacheValidation() -> SendRequest* -> SuccessfulSendRequest ->
 836 //   OverwriteCachedResponse
 837 //
 838 // 10. HEAD. Sparse entry, partially cached:
 839 //   Serve the request from the cache, as long as it doesn't require
 840 //   revalidation. Ignore missing ranges when deciding to revalidate. If the
 841 //   entry requires revalidation, ignore the whole request and go to full pass
 842 //   through (the result of the HEAD request will NOT update the entry).
 843 //
 844 //   Start(): Basically the same as example 7, as we never create a partial_
 845 //   object for this request.
 846 //
 847 // 11. Prefetch, not-cached entry:
 848 //   The same as example 1. The "unused_since_prefetch" bit is stored as true in
 849 //   UpdateCachedResponse.
 850 //
 851 // 12. Prefetch, cached entry:
 852 //   Like examples 2-4, only CacheToggleUnusedSincePrefetch* is inserted between
 853 //   CacheReadResponse* and CacheDispatchValidation if the unused_since_prefetch
 854 //   bit is unset.
 855 //
 856 // 13. Cached entry less than 5 minutes old, unused_since_prefetch is true:
 857 //   Skip validation, similar to example 2.
 858 //   GetBackend* -> InitEntry -> OpenEntry* -> AddToEntry* -> CacheReadResponse*
 859 //   -> CacheToggleUnusedSincePrefetch* -> CacheDispatchValidation ->
 860 //   BeginPartialCacheValidation() -> BeginCacheValidation() ->
 861 //   SetupEntryForRead()
 862 //
 863 //   Read():
 864 //   CacheReadData*
 865 //
 866 // 14. Cached entry more than 5 minutes old, unused_since_prefetch is true:
 867 //   Like examples 2-4, only CacheToggleUnusedSincePrefetch* is inserted between
 868 //   CacheReadResponse* and CacheDispatchValidation.
 869 int HttpCache::Transaction::DoLoop(int result) {
 870   DCHECK(next_state_ != STATE_NONE);
 871
 872   int rv = result;
 873   do {
 874     State state = next_state_;
 875     next_state_ = STATE_NONE;
 876     switch (state) {
 877       case STATE_GET_BACKEND:
 878         DCHECK_EQ(OK, rv);
 879         rv = DoGetBackend();
 880         break;
 881       case STATE_GET_BACKEND_COMPLETE:
 882         rv = DoGetBackendComplete(rv);
 883         break;
 884       case STATE_SEND_REQUEST:
 885         DCHECK_EQ(OK, rv);
 886         rv = DoSendRequest();
 887         break;
 888       case STATE_SEND_REQUEST_COMPLETE:
 889         rv = DoSendRequestComplete(rv);
 890         break;
 891       case STATE_SUCCESSFUL_SEND_REQUEST:
 892         DCHECK_EQ(OK, rv);
 893         rv = DoSuccessfulSendRequest();
 894         break;
 895       case STATE_NETWORK_READ:
 896         DCHECK_EQ(OK, rv);
 897         rv = DoNetworkRead();
 898         break;
 899       case STATE_NETWORK_READ_COMPLETE:
 900         rv = DoNetworkReadComplete(rv);
 901         break;
 902       case STATE_INIT_ENTRY:
 903         DCHECK_EQ(OK, rv);
 904         rv = DoInitEntry();
 905         break;
 906       case STATE_OPEN_ENTRY:
 907         DCHECK_EQ(OK, rv);
 908         rv = DoOpenEntry();
 909         break;
 910       case STATE_OPEN_ENTRY_COMPLETE:
 911         rv = DoOpenEntryComplete(rv);
 912         break;
 913       case STATE_CREATE_ENTRY:
 914         DCHECK_EQ(OK, rv);
 915         rv = DoCreateEntry();
 916         break;
 917       case STATE_CREATE_ENTRY_COMPLETE:
 918         rv = DoCreateEntryComplete(rv);
 919         break;
 920       case STATE_DOOM_ENTRY:
 921         DCHECK_EQ(OK, rv);
 922         rv = DoDoomEntry();
 923         break;
 924       case STATE_DOOM_ENTRY_COMPLETE:
 925         rv = DoDoomEntryComplete(rv);
 926         break;
 927       case STATE_ADD_TO_ENTRY:
 928         DCHECK_EQ(OK, rv);
 929         rv = DoAddToEntry();
 930         break;
 931       case STATE_ADD_TO_ENTRY_COMPLETE:
 932         rv = DoAddToEntryComplete(rv);
 933         break;
 934       case STATE_START_PARTIAL_CACHE_VALIDATION:
 935         DCHECK_EQ(OK, rv);
 936         rv = DoStartPartialCacheValidation();
 937         break;
 938       case STATE_COMPLETE_PARTIAL_CACHE_VALIDATION:
 939         rv = DoCompletePartialCacheValidation(rv);
 940         break;
 941       case STATE_UPDATE_CACHED_RESPONSE:
 942         DCHECK_EQ(OK, rv);
 943         rv = DoUpdateCachedResponse();
 944         break;
 945       case STATE_UPDATE_CACHED_RESPONSE_COMPLETE:
 946         rv = DoUpdateCachedResponseComplete(rv);
 947         break;
 948       case STATE_OVERWRITE_CACHED_RESPONSE:
 949         DCHECK_EQ(OK, rv);
 950         rv = DoOverwriteCachedResponse();
 951         break;
 952       case STATE_TRUNCATE_CACHED_DATA:
 953         DCHECK_EQ(OK, rv);
 954         rv = DoTruncateCachedData();
 955         break;
 956       case STATE_TRUNCATE_CACHED_DATA_COMPLETE:
 957         rv = DoTruncateCachedDataComplete(rv);
 958         break;
 959       case STATE_TRUNCATE_CACHED_METADATA:
 960         DCHECK_EQ(OK, rv);
 961         rv = DoTruncateCachedMetadata();
 962         break;
 963       case STATE_TRUNCATE_CACHED_METADATA_COMPLETE:
 964         rv = DoTruncateCachedMetadataComplete(rv);
 965         break;
 966       case STATE_PARTIAL_HEADERS_RECEIVED:
 967         DCHECK_EQ(OK, rv);
 968         rv = DoPartialHeadersReceived();
 969         break;
 970       case STATE_CACHE_READ_RESPONSE:
 971         DCHECK_EQ(OK, rv);
 972         rv = DoCacheReadResponse();
 973         break;
 974       case STATE_CACHE_READ_RESPONSE_COMPLETE:
 975         rv = DoCacheReadResponseComplete(rv);
 976         break;
 977       case STATE_CACHE_DISPATCH_VALIDATION:
 978         DCHECK_EQ(OK, rv);
 979         rv = DoCacheDispatchValidation();
 980         break;
 981       case STATE_TOGGLE_UNUSED_SINCE_PREFETCH:
 982         DCHECK_EQ(OK, rv);
 983         rv = DoCacheToggleUnusedSincePrefetch();
 984         break;
 985       case STATE_TOGGLE_UNUSED_SINCE_PREFETCH_COMPLETE:
 986         rv = DoCacheToggleUnusedSincePrefetchComplete(rv);
 987         break;
 988       case STATE_CACHE_WRITE_RESPONSE:
 989         DCHECK_EQ(OK, rv);
 990         rv = DoCacheWriteResponse();
 991         break;
 992       case STATE_CACHE_WRITE_TRUNCATED_RESPONSE:
 993         DCHECK_EQ(OK, rv);
 994         rv = DoCacheWriteTruncatedResponse();
 995         break;
 996       case STATE_CACHE_WRITE_RESPONSE_COMPLETE:
 997         rv = DoCacheWriteResponseComplete(rv);
 998         break;
 999       case STATE_CACHE_READ_METADATA:
1000         DCHECK_EQ(OK, rv);
1001         rv = DoCacheReadMetadata();
1002         break;
1003       case STATE_CACHE_READ_METADATA_COMPLETE:
1004         rv = DoCacheReadMetadataComplete(rv);
1005         break;
1006       case STATE_CACHE_QUERY_DATA:
1007         DCHECK_EQ(OK, rv);
1008         rv = DoCacheQueryData();
1009         break;
1010       case STATE_CACHE_QUERY_DATA_COMPLETE:
1011         rv = DoCacheQueryDataComplete(rv);
1012         break;
1013       case STATE_CACHE_READ_DATA:
1014         DCHECK_EQ(OK, rv);
1015         rv = DoCacheReadData();
1016         break;
1017       case STATE_CACHE_READ_DATA_COMPLETE:
1018         rv = DoCacheReadDataComplete(rv);
1019         break;
1020       case STATE_CACHE_WRITE_DATA:
1021         rv = DoCacheWriteData(rv);
1022         break;
1023       case STATE_CACHE_WRITE_DATA_COMPLETE:
1024         rv = DoCacheWriteDataComplete(rv);
1025         break;
1026       default:
1027         NOTREACHED() << "bad state";
1028         rv = ERR_FAILED;
1029         break;
1030     }
1031   } while (rv != ERR_IO_PENDING && next_state_ != STATE_NONE);
1032
1033   if (rv != ERR_IO_PENDING)
1034     HandleResult(rv);
1035
1036   return rv;
1037 }
1038
1039 int HttpCache::Transaction::DoGetBackend() {
1040   // TODO(vadimt): Remove ScopedTracker below once crbug.com/422516 is fixed.
1041   tracked_objects::ScopedTracker tracking_profile(
1042       FROM_HERE_WITH_EXPLICIT_FUNCTION(
1043           "422516 HttpCache::Transaction::DoGetBackend"));
1044
1045   cache_pending_ = true;
1046   next_state_ = STATE_GET_BACKEND_COMPLETE;
1047   net_log_.BeginEvent(NetLog::TYPE_HTTP_CACHE_GET_BACKEND);
1048   return cache_->GetBackendForTransaction(this);
1049 }
1050
1051 int HttpCache::Transaction::DoGetBackendComplete(int result) {
1052   // TODO(vadimt): Remove ScopedTracker below once crbug.com/422516 is fixed.
1053   tracked_objects::ScopedTracker tracking_profile(
1054       FROM_HERE_WITH_EXPLICIT_FUNCTION(
1055           "422516 HttpCache::Transaction::DoGetBackendComplete"));
1056
1057   DCHECK(result == OK || result == ERR_FAILED);
1058   net_log_.EndEventWithNetErrorCode(NetLog::TYPE_HTTP_CACHE_GET_BACKEND,
1059                                     result);
1060   cache_pending_ = false;
1061
1062   if (!ShouldPassThrough()) {
1063     cache_key_ = cache_->GenerateCacheKey(request_);
1064
1065     // Requested cache access mode.
1066     if (effective_load_flags_ & LOAD_ONLY_FROM_CACHE) {
1067       mode_ = READ;
1068     } else if (effective_load_flags_ & LOAD_BYPASS_CACHE) {
1069       mode_ = WRITE;
1070     } else {
1071       mode_ = READ_WRITE;
1072     }
1073
1074     // Downgrade to UPDATE if the request has been externally conditionalized.
1075     if (external_validation_.initialized) {
1076       if (mode_ & WRITE) {
1077         // Strip off the READ_DATA bit (and maybe add back a READ_META bit
1078         // in case READ was off).
1079         mode_ = UPDATE;
1080       } else {
1081         mode_ = NONE;
1082       }
1083     }
1084   }
1085
1086   // Use PUT and DELETE only to invalidate existing stored entries.
1087   if ((request_->method == "PUT" || request_->method == "DELETE") &&
1088       mode_ != READ_WRITE && mode_ != WRITE) {
1089     mode_ = NONE;
1090   }
1091
1092   // Note that if mode_ == UPDATE (which is tied to external_validation_), the
1093   // transaction behaves the same for GET and HEAD requests at this point: if it
1094   // was not modified, the entry is updated and a response is not returned from
1095   // the cache. If we receive 200, it doesn't matter if there was a validation
1096   // header or not.
1097   if (request_->method == "HEAD" && mode_ == WRITE)
1098     mode_ = NONE;
1099
1100   // If must use cache, then we must fail.  This can happen for back/forward
1101   // navigations to a page generated via a form post.
1102   if (!(mode_ & READ) && effective_load_flags_ & LOAD_ONLY_FROM_CACHE)
1103     return ERR_CACHE_MISS;
1104
1105   if (mode_ == NONE) {
1106     if (partial_.get()) {
1107       partial_->RestoreHeaders(&custom_request_->extra_headers);
1108       partial_.reset();
1109     }
1110     next_state_ = STATE_SEND_REQUEST;
1111   } else {
1112     next_state_ = STATE_INIT_ENTRY;
1113   }
1114
1115   // This is only set if we have something to do with the response.
1116   range_requested_ = (partial_.get() != NULL);
1117
1118   return OK;
1119 }
1120
1121 int HttpCache::Transaction::DoSendRequest() {
1122   // TODO(vadimt): Remove ScopedTracker below once crbug.com/422516 is fixed.
1123   tracked_objects::ScopedTracker tracking_profile(
1124       FROM_HERE_WITH_EXPLICIT_FUNCTION(
1125           "422516 HttpCache::Transaction::DoSendRequest"));
1126
1127   DCHECK(mode_ & WRITE || mode_ == NONE);
1128   DCHECK(!network_trans_.get());
1129
1130   send_request_since_ = TimeTicks::Now();
1131
1132   // Create a network transaction.
1133   int rv = cache_->network_layer_->CreateTransaction(priority_,
1134                                                      &network_trans_);
1135   if (rv != OK)
1136     return rv;
1137   network_trans_->SetBeforeNetworkStartCallback(before_network_start_callback_);
1138   network_trans_->SetBeforeProxyHeadersSentCallback(
1139       before_proxy_headers_sent_callback_);
1140
1141   // Old load timing information, if any, is now obsolete.
1142   old_network_trans_load_timing_.reset();
1143
1144   if (websocket_handshake_stream_base_create_helper_)
1145     network_trans_->SetWebSocketHandshakeStreamCreateHelper(
1146         websocket_handshake_stream_base_create_helper_);
1147
1148   next_state_ = STATE_SEND_REQUEST_COMPLETE;
1149   rv = network_trans_->Start(request_, io_callback_, net_log_);
1150   return rv;
1151 }
1152
1153 int HttpCache::Transaction::DoSendRequestComplete(int result) {
1154   // TODO(vadimt): Remove ScopedTracker below once crbug.com/422516 is fixed.
1155   tracked_objects::ScopedTracker tracking_profile(
1156       FROM_HERE_WITH_EXPLICIT_FUNCTION(
1157           "422516 HttpCache::Transaction::DoSendRequestComplete"));
1158
1159   if (!cache_.get())
1160     return ERR_UNEXPECTED;
1161
1162   // If requested, and we have a readable cache entry, and we have
1163   // an error indicating that we're offline as opposed to in contact
1164   // with a bad server, read from cache anyway.
1165   if (IsOfflineError(result)) {
1166     if (mode_ == READ_WRITE && entry_ && !partial_) {
1167       RecordOfflineStatus(effective_load_flags_,
1168                           OFFLINE_STATUS_DATA_AVAILABLE_OFFLINE);
1169       if (effective_load_flags_ & LOAD_FROM_CACHE_IF_OFFLINE) {
1170         UpdateTransactionPattern(PATTERN_NOT_COVERED);
1171         response_.server_data_unavailable = true;
1172         return SetupEntryForRead();
1173       }
1174     } else {
1175       RecordOfflineStatus(effective_load_flags_,
1176                           OFFLINE_STATUS_DATA_UNAVAILABLE_OFFLINE);
1177     }
1178   } else {
1179     RecordOfflineStatus(effective_load_flags_,
1180                         (result == OK ? OFFLINE_STATUS_NETWORK_SUCCEEDED :
1181                                         OFFLINE_STATUS_NETWORK_FAILED));
1182   }
1183
1184   // If we tried to conditionalize the request and failed, we know
1185   // we won't be reading from the cache after this point.
1186   if (couldnt_conditionalize_request_)
1187     mode_ = WRITE;
1188
1189   if (result == OK) {
1190     next_state_ = STATE_SUCCESSFUL_SEND_REQUEST;
1191     return OK;
1192   }
1193
1194   // Do not record requests that have network errors or restarts.
1195   UpdateTransactionPattern(PATTERN_NOT_COVERED);
1196   if (IsCertificateError(result)) {
1197     const HttpResponseInfo* response = network_trans_->GetResponseInfo();
1198     // If we get a certificate error, then there is a certificate in ssl_info,
1199     // so GetResponseInfo() should never return NULL here.
1200     DCHECK(response);
1201     response_.ssl_info = response->ssl_info;
1202   } else if (result == ERR_SSL_CLIENT_AUTH_CERT_NEEDED) {
1203     const HttpResponseInfo* response = network_trans_->GetResponseInfo();
1204     DCHECK(response);
1205     response_.cert_request_info = response->cert_request_info;
1206   } else if (response_.was_cached) {
1207     DoneWritingToEntry(true);
1208   }
1209   return result;
1210 }
1211
1212 // We received the response headers and there is no error.
1213 int HttpCache::Transaction::DoSuccessfulSendRequest() {
1214   // TODO(vadimt): Remove ScopedTracker below once crbug.com/422516 is fixed.
1215   tracked_objects::ScopedTracker tracking_profile(
1216       FROM_HERE_WITH_EXPLICIT_FUNCTION(
1217           "422516 HttpCache::Transaction::DoSuccessfulSendRequest"));
1218
1219   DCHECK(!new_response_);
1220   const HttpResponseInfo* new_response = network_trans_->GetResponseInfo();
1221   bool authentication_failure = false;
1222
1223   if (new_response->headers->response_code() == 401 ||
1224       new_response->headers->response_code() == 407) {
1225     auth_response_ = *new_response;
1226     if (!reading_)
1227       return OK;
1228
1229     // We initiated a second request the caller doesn't know about. We should be
1230     // able to authenticate this request because we should have authenticated
1231     // this URL moments ago.
1232     if (IsReadyToRestartForAuth()) {
1233       DCHECK(!response_.auth_challenge.get());
1234       next_state_ = STATE_SEND_REQUEST_COMPLETE;
1235       // In theory we should check to see if there are new cookies, but there
1236       // is no way to do that from here.
1237       return network_trans_->RestartWithAuth(AuthCredentials(), io_callback_);
1238     }
1239
1240     // We have to perform cleanup at this point so that at least the next
1241     // request can succeed.
1242     authentication_failure = true;
1243     if (entry_)
1244       DoomPartialEntry(false);
1245     mode_ = NONE;
1246     partial_.reset();
1247   }
1248
1249   new_response_ = new_response;
1250   if (authentication_failure ||
1251       (!ValidatePartialResponse() && !auth_response_.headers.get())) {
1252     // Something went wrong with this request and we have to restart it.
1253     // If we have an authentication response, we are exposed to weird things
1254     // hapenning if the user cancels the authentication before we receive
1255     // the new response.
1256     net_log_.AddEvent(NetLog::TYPE_HTTP_CACHE_RE_SEND_PARTIAL_REQUEST);
1257     UpdateTransactionPattern(PATTERN_NOT_COVERED);
1258     response_ = HttpResponseInfo();
1259     ResetNetworkTransaction();
1260     new_response_ = NULL;
1261     next_state_ = STATE_SEND_REQUEST;
1262     return OK;
1263   }
1264
1265   if (handling_206_ && mode_ == READ_WRITE && !truncated_ && !is_sparse_) {
1266     // We have stored the full entry, but it changed and the server is
1267     // sending a range. We have to delete the old entry.
1268     UpdateTransactionPattern(PATTERN_NOT_COVERED);
1269     DoneWritingToEntry(false);
1270   }
1271
1272   if (mode_ == WRITE &&
1273       transaction_pattern_ != PATTERN_ENTRY_CANT_CONDITIONALIZE) {
1274     UpdateTransactionPattern(PATTERN_ENTRY_NOT_CACHED);
1275   }
1276
1277   // Invalidate any cached GET with a successful PUT or DELETE.
1278   if (mode_ == WRITE &&
1279       (request_->method == "PUT" || request_->method == "DELETE")) {
1280     if (NonErrorResponse(new_response->headers->response_code())) {
1281       int ret = cache_->DoomEntry(cache_key_, NULL);
1282       DCHECK_EQ(OK, ret);
1283     }
1284     cache_->DoneWritingToEntry(entry_, true);
1285     entry_ = NULL;
1286     mode_ = NONE;
1287   }
1288
1289   // Invalidate any cached GET with a successful POST.
1290   if (!(effective_load_flags_ & LOAD_DISABLE_CACHE) &&
1291       request_->method == "POST" &&
1292       NonErrorResponse(new_response->headers->response_code())) {
1293     cache_->DoomMainEntryForUrl(request_->url);
1294   }
1295
1296   RecordNoStoreHeaderHistogram(request_->load_flags, new_response);
1297
1298   if (new_response_->headers->response_code() == 416 &&
1299       (request_->method == "GET" || request_->method == "POST")) {
1300     // If there is an active entry it may be destroyed with this transaction.
1301     response_ = *new_response_;
1302     return OK;
1303   }
1304
1305   // Are we expecting a response to a conditional query?
1306   if (mode_ == READ_WRITE || mode_ == UPDATE) {
1307     if (new_response->headers->response_code() == 304 || handling_206_) {
1308       UpdateTransactionPattern(PATTERN_ENTRY_VALIDATED);
1309       next_state_ = STATE_UPDATE_CACHED_RESPONSE;
1310       return OK;
1311     }
1312     UpdateTransactionPattern(PATTERN_ENTRY_UPDATED);
1313     mode_ = WRITE;
1314   }
1315
1316   next_state_ = STATE_OVERWRITE_CACHED_RESPONSE;
1317   return OK;
1318 }
1319
1320 int HttpCache::Transaction::DoNetworkRead() {
1321   // TODO(vadimt): Remove ScopedTracker below once crbug.com/422516 is fixed.
1322   tracked_objects::ScopedTracker tracking_profile(
1323       FROM_HERE_WITH_EXPLICIT_FUNCTION(
1324           "422516 HttpCache::Transaction::DoNetworkRead"));
1325
1326   next_state_ = STATE_NETWORK_READ_COMPLETE;
1327   return network_trans_->Read(read_buf_.get(), io_buf_len_, io_callback_);
1328 }
1329
1330 int HttpCache::Transaction::DoNetworkReadComplete(int result) {
1331   // TODO(vadimt): Remove ScopedTracker below once crbug.com/422516 is fixed.
1332   tracked_objects::ScopedTracker tracking_profile(
1333       FROM_HERE_WITH_EXPLICIT_FUNCTION(
1334           "422516 HttpCache::Transaction::DoNetworkReadComplete"));
1335
1336   DCHECK(mode_ & WRITE || mode_ == NONE);
1337
1338   if (!cache_.get())
1339     return ERR_UNEXPECTED;
1340
1341   // If there is an error or we aren't saving the data, we are done; just wait
1342   // until the destructor runs to see if we can keep the data.
1343   if (mode_ == NONE || result < 0)
1344     return result;
1345
1346   next_state_ = STATE_CACHE_WRITE_DATA;
1347   return result;
1348 }
1349
1350 int HttpCache::Transaction::DoInitEntry() {
1351   // TODO(vadimt): Remove ScopedTracker below once crbug.com/422516 is fixed.
1352   tracked_objects::ScopedTracker tracking_profile(
1353       FROM_HERE_WITH_EXPLICIT_FUNCTION(
1354           "422516 HttpCache::Transaction::DoInitEntry"));
1355
1356   DCHECK(!new_entry_);
1357
1358   if (!cache_.get())
1359     return ERR_UNEXPECTED;
1360
1361   if (mode_ == WRITE) {
1362     next_state_ = STATE_DOOM_ENTRY;
1363     return OK;
1364   }
1365
1366   next_state_ = STATE_OPEN_ENTRY;
1367   return OK;
1368 }
1369
1370 int HttpCache::Transaction::DoOpenEntry() {
1371   // TODO(vadimt): Remove ScopedTracker below once crbug.com/422516 is fixed.
1372   tracked_objects::ScopedTracker tracking_profile(
1373       FROM_HERE_WITH_EXPLICIT_FUNCTION(
1374           "422516 HttpCache::Transaction::DoOpenEntry"));
1375
1376   DCHECK(!new_entry_);
1377   next_state_ = STATE_OPEN_ENTRY_COMPLETE;
1378   cache_pending_ = true;
1379   net_log_.BeginEvent(NetLog::TYPE_HTTP_CACHE_OPEN_ENTRY);
1380   first_cache_access_since_ = TimeTicks::Now();
1381   return cache_->OpenEntry(cache_key_, &new_entry_, this);
1382 }
1383
1384 int HttpCache::Transaction::DoOpenEntryComplete(int result) {
1385   // TODO(vadimt): Remove ScopedTracker below once crbug.com/422516 is fixed.
1386   tracked_objects::ScopedTracker tracking_profile(
1387       FROM_HERE_WITH_EXPLICIT_FUNCTION(
1388           "422516 HttpCache::Transaction::DoOpenEntryComplete"));
1389
1390   // It is important that we go to STATE_ADD_TO_ENTRY whenever the result is
1391   // OK, otherwise the cache will end up with an active entry without any
1392   // transaction attached.
1393   net_log_.EndEventWithNetErrorCode(NetLog::TYPE_HTTP_CACHE_OPEN_ENTRY, result);
1394   cache_pending_ = false;
1395   if (result == OK) {
1396     next_state_ = STATE_ADD_TO_ENTRY;
1397     return OK;
1398   }
1399
1400   if (result == ERR_CACHE_RACE) {
1401     next_state_ = STATE_INIT_ENTRY;
1402     return OK;
1403   }
1404
1405   if (request_->method == "PUT" || request_->method == "DELETE" ||
1406       (request_->method == "HEAD" && mode_ == READ_WRITE)) {
1407     DCHECK(mode_ == READ_WRITE || mode_ == WRITE || request_->method == "HEAD");
1408     mode_ = NONE;
1409     next_state_ = STATE_SEND_REQUEST;
1410     return OK;
1411   }
1412
1413   if (mode_ == READ_WRITE) {
1414     mode_ = WRITE;
1415     next_state_ = STATE_CREATE_ENTRY;
1416     return OK;
1417   }
1418   if (mode_ == UPDATE) {
1419     // There is no cache entry to update; proceed without caching.
1420     mode_ = NONE;
1421     next_state_ = STATE_SEND_REQUEST;
1422     return OK;
1423   }
1424
1425   // The entry does not exist, and we are not permitted to create a new entry,
1426   // so we must fail.
1427   return ERR_CACHE_MISS;
1428 }
1429
1430 int HttpCache::Transaction::DoCreateEntry() {
1431   // TODO(vadimt): Remove ScopedTracker below once crbug.com/422516 is fixed.
1432   tracked_objects::ScopedTracker tracking_profile(
1433       FROM_HERE_WITH_EXPLICIT_FUNCTION(
1434           "422516 HttpCache::Transaction::DoCreateEntry"));
1435
1436   DCHECK(!new_entry_);
1437   next_state_ = STATE_CREATE_ENTRY_COMPLETE;
1438   cache_pending_ = true;
1439   net_log_.BeginEvent(NetLog::TYPE_HTTP_CACHE_CREATE_ENTRY);
1440   return cache_->CreateEntry(cache_key_, &new_entry_, this);
1441 }
1442
1443 int HttpCache::Transaction::DoCreateEntryComplete(int result) {
1444   // TODO(vadimt): Remove ScopedTracker below once crbug.com/422516 is fixed.
1445   tracked_objects::ScopedTracker tracking_profile(
1446       FROM_HERE_WITH_EXPLICIT_FUNCTION(
1447           "422516 HttpCache::Transaction::DoCreateEntryComplete"));
1448
1449   // It is important that we go to STATE_ADD_TO_ENTRY whenever the result is
1450   // OK, otherwise the cache will end up with an active entry without any
1451   // transaction attached.
1452   net_log_.EndEventWithNetErrorCode(NetLog::TYPE_HTTP_CACHE_CREATE_ENTRY,
1453                                     result);
1454   cache_pending_ = false;
1455   next_state_ = STATE_ADD_TO_ENTRY;
1456
1457   if (result == ERR_CACHE_RACE) {
1458     next_state_ = STATE_INIT_ENTRY;
1459     return OK;
1460   }
1461
1462   if (result != OK) {
1463     // We have a race here: Maybe we failed to open the entry and decided to
1464     // create one, but by the time we called create, another transaction already
1465     // created the entry. If we want to eliminate this issue, we need an atomic
1466     // OpenOrCreate() method exposed by the disk cache.
1467     DLOG(WARNING) << "Unable to create cache entry";
1468     mode_ = NONE;
1469     if (partial_.get())
1470       partial_->RestoreHeaders(&custom_request_->extra_headers);
1471     next_state_ = STATE_SEND_REQUEST;
1472   }
1473   return OK;
1474 }
1475
1476 int HttpCache::Transaction::DoDoomEntry() {
1477   // TODO(vadimt): Remove ScopedTracker below once crbug.com/422516 is fixed.
1478   tracked_objects::ScopedTracker tracking_profile(
1479       FROM_HERE_WITH_EXPLICIT_FUNCTION(
1480           "422516 HttpCache::Transaction::DoDoomEntry"));
1481
1482   next_state_ = STATE_DOOM_ENTRY_COMPLETE;
1483   cache_pending_ = true;
1484   if (first_cache_access_since_.is_null())
1485     first_cache_access_since_ = TimeTicks::Now();
1486   net_log_.BeginEvent(NetLog::TYPE_HTTP_CACHE_DOOM_ENTRY);
1487   return cache_->DoomEntry(cache_key_, this);
1488 }
1489
1490 int HttpCache::Transaction::DoDoomEntryComplete(int result) {
1491   // TODO(vadimt): Remove ScopedTracker below once crbug.com/422516 is fixed.
1492   tracked_objects::ScopedTracker tracking_profile(
1493       FROM_HERE_WITH_EXPLICIT_FUNCTION(
1494           "422516 HttpCache::Transaction::DoDoomEntryComplete"));
1495
1496   net_log_.EndEventWithNetErrorCode(NetLog::TYPE_HTTP_CACHE_DOOM_ENTRY, result);
1497   next_state_ = STATE_CREATE_ENTRY;
1498   cache_pending_ = false;
1499   if (result == ERR_CACHE_RACE)
1500     next_state_ = STATE_INIT_ENTRY;
1501   return OK;
1502 }
1503
1504 int HttpCache::Transaction::DoAddToEntry() {
1505   // TODO(vadimt): Remove ScopedTracker below once crbug.com/422516 is fixed.
1506   tracked_objects::ScopedTracker tracking_profile(
1507       FROM_HERE_WITH_EXPLICIT_FUNCTION(
1508           "422516 HttpCache::Transaction::DoAddToEntry"));
1509
1510   DCHECK(new_entry_);
1511   cache_pending_ = true;
1512   next_state_ = STATE_ADD_TO_ENTRY_COMPLETE;
1513   net_log_.BeginEvent(NetLog::TYPE_HTTP_CACHE_ADD_TO_ENTRY);
1514   DCHECK(entry_lock_waiting_since_.is_null());
1515   entry_lock_waiting_since_ = TimeTicks::Now();
1516   int rv = cache_->AddTransactionToEntry(new_entry_, this);
1517   if (rv == ERR_IO_PENDING) {
1518     if (bypass_lock_for_test_) {
1519       OnAddToEntryTimeout(entry_lock_waiting_since_);
1520     } else {
1521       int timeout_milliseconds = 20 * 1000;
1522       if (partial_ && new_entry_->writer &&
1523           new_entry_->writer->range_requested_) {
1524         // Quickly timeout and bypass the cache if we're a range request and
1525         // we're blocked by the reader/writer lock. Doing so eliminates a long
1526         // running issue, http://crbug.com/31014, where two of the same media
1527         // resources could not be played back simultaneously due to one locking
1528         // the cache entry until the entire video was downloaded.
1529         //
1530         // Bypassing the cache is not ideal, as we are now ignoring the cache
1531         // entirely for all range requests to a resource beyond the first. This
1532         // is however a much more succinct solution than the alternatives, which
1533         // would require somewhat significant changes to the http caching logic.
1534         //
1535         // Allow some timeout slack for the entry addition to complete in case
1536         // the writer lock is imminently released; we want to avoid skipping
1537         // the cache if at all possible. See http://crbug.com/408765
1538         timeout_milliseconds = 25;
1539       }
1540       base::MessageLoop::current()->PostDelayedTask(
1541           FROM_HERE,
1542           base::Bind(&HttpCache::Transaction::OnAddToEntryTimeout,
1543                      weak_factory_.GetWeakPtr(), entry_lock_waiting_since_),
1544           TimeDelta::FromMilliseconds(timeout_milliseconds));
1545     }
1546   }
1547   return rv;
1548 }
1549
1550 int HttpCache::Transaction::DoAddToEntryComplete(int result) {
1551   // TODO(vadimt): Remove ScopedTracker below once crbug.com/422516 is fixed.
1552   tracked_objects::ScopedTracker tracking_profile(
1553       FROM_HERE_WITH_EXPLICIT_FUNCTION(
1554           "422516 HttpCache::Transaction::DoAddToEntryComplete"));
1555
1556   net_log_.EndEventWithNetErrorCode(NetLog::TYPE_HTTP_CACHE_ADD_TO_ENTRY,
1557                                     result);
1558   const TimeDelta entry_lock_wait =
1559       TimeTicks::Now() - entry_lock_waiting_since_;
1560   UMA_HISTOGRAM_TIMES("HttpCache.EntryLockWait", entry_lock_wait);
1561
1562   entry_lock_waiting_since_ = TimeTicks();
1563   DCHECK(new_entry_);
1564   cache_pending_ = false;
1565
1566   if (result == OK)
1567     entry_ = new_entry_;
1568
1569   // If there is a failure, the cache should have taken care of new_entry_.
1570   new_entry_ = NULL;
1571
1572   if (result == ERR_CACHE_RACE) {
1573     next_state_ = STATE_INIT_ENTRY;
1574     return OK;
1575   }
1576
1577   if (result == ERR_CACHE_LOCK_TIMEOUT) {
1578     // The cache is busy, bypass it for this transaction.
1579     mode_ = NONE;
1580     next_state_ = STATE_SEND_REQUEST;
1581     if (partial_) {
1582       partial_->RestoreHeaders(&custom_request_->extra_headers);
1583       partial_.reset();
1584     }
1585     return OK;
1586   }
1587
1588   if (result != OK) {
1589     NOTREACHED();
1590     return result;
1591   }
1592
1593   if (mode_ == WRITE) {
1594     if (partial_.get())
1595       partial_->RestoreHeaders(&custom_request_->extra_headers);
1596     next_state_ = STATE_SEND_REQUEST;
1597   } else {
1598     // We have to read the headers from the cached entry.
1599     DCHECK(mode_ & READ_META);
1600     next_state_ = STATE_CACHE_READ_RESPONSE;
1601   }
1602   return OK;
1603 }
1604
1605 // We may end up here multiple times for a given request.
1606 int HttpCache::Transaction::DoStartPartialCacheValidation() {
1607   // TODO(vadimt): Remove ScopedTracker below once crbug.com/422516 is fixed.
1608   tracked_objects::ScopedTracker tracking_profile(
1609       FROM_HERE_WITH_EXPLICIT_FUNCTION(
1610           "422516 HttpCache::Transaction::DoStartPartialCacheValidation"));
1611
1612   if (mode_ == NONE)
1613     return OK;
1614
1615   next_state_ = STATE_COMPLETE_PARTIAL_CACHE_VALIDATION;
1616   return partial_->ShouldValidateCache(entry_->disk_entry, io_callback_);
1617 }
1618
1619 int HttpCache::Transaction::DoCompletePartialCacheValidation(int result) {
1620   // TODO(vadimt): Remove ScopedTracker below once crbug.com/422516 is fixed.
1621   tracked_objects::ScopedTracker tracking_profile(
1622       FROM_HERE_WITH_EXPLICIT_FUNCTION(
1623           "422516 HttpCache::Transaction::DoCompletePartialCacheValidation"));
1624
1625   if (!result) {
1626     // This is the end of the request.
1627     if (mode_ & WRITE) {
1628       DoneWritingToEntry(true);
1629     } else {
1630       cache_->DoneReadingFromEntry(entry_, this);
1631       entry_ = NULL;
1632     }
1633     return result;
1634   }
1635
1636   if (result < 0)
1637     return result;
1638
1639   partial_->PrepareCacheValidation(entry_->disk_entry,
1640                                    &custom_request_->extra_headers);
1641
1642   if (reading_ && partial_->IsCurrentRangeCached()) {
1643     next_state_ = STATE_CACHE_READ_DATA;
1644     return OK;
1645   }
1646
1647   return BeginCacheValidation();
1648 }
1649
1650 // We received 304 or 206 and we want to update the cached response headers.
1651 int HttpCache::Transaction::DoUpdateCachedResponse() {
1652   // TODO(vadimt): Remove ScopedTracker below once crbug.com/422516 is fixed.
1653   tracked_objects::ScopedTracker tracking_profile(
1654       FROM_HERE_WITH_EXPLICIT_FUNCTION(
1655           "422516 HttpCache::Transaction::DoUpdateCachedResponse"));
1656
1657   next_state_ = STATE_UPDATE_CACHED_RESPONSE_COMPLETE;
1658   int rv = OK;
1659   // Update cached response based on headers in new_response.
1660   // TODO(wtc): should we update cached certificate (response_.ssl_info), too?
1661   response_.headers->Update(*new_response_->headers.get());
1662   response_.response_time = new_response_->response_time;
1663   response_.request_time = new_response_->request_time;
1664   response_.network_accessed = new_response_->network_accessed;
1665   response_.unused_since_prefetch = new_response_->unused_since_prefetch;
1666   if (new_response_->vary_data.is_valid()) {
1667     response_.vary_data = new_response_->vary_data;
1668   } else if (response_.vary_data.is_valid()) {
1669     // There is a vary header in the stored response but not in the current one.
1670     // Update the data with the new request headers.
1671     HttpVaryData new_vary_data;
1672     new_vary_data.Init(*request_, *response_.headers.get());
1673     response_.vary_data = new_vary_data;
1674   }
1675
1676   if (response_.headers->HasHeaderValue("cache-control", "no-store")) {
1677     if (!entry_->doomed) {
1678       int ret = cache_->DoomEntry(cache_key_, NULL);
1679       DCHECK_EQ(OK, ret);
1680     }
1681   } else {
1682     // If we are already reading, we already updated the headers for this
1683     // request; doing it again will change Content-Length.
1684     if (!reading_) {
1685       target_state_ = STATE_UPDATE_CACHED_RESPONSE_COMPLETE;
1686       next_state_ = STATE_CACHE_WRITE_RESPONSE;
1687       rv = OK;
1688     }
1689   }
1690   return rv;
1691 }
1692
1693 int HttpCache::Transaction::DoUpdateCachedResponseComplete(int result) {
1694   // TODO(vadimt): Remove ScopedTracker below once crbug.com/422516 is fixed.
1695   tracked_objects::ScopedTracker tracking_profile(
1696       FROM_HERE_WITH_EXPLICIT_FUNCTION(
1697           "422516 HttpCache::Transaction::DoUpdateCachedResponseComplete"));
1698
1699   if (mode_ == UPDATE) {
1700     DCHECK(!handling_206_);
1701     // We got a "not modified" response and already updated the corresponding
1702     // cache entry above.
1703     //
1704     // By closing the cached entry now, we make sure that the 304 rather than
1705     // the cached 200 response, is what will be returned to the user.
1706     DoneWritingToEntry(true);
1707   } else if (entry_ && !handling_206_) {
1708     DCHECK_EQ(READ_WRITE, mode_);
1709     if (!partial_.get() || partial_->IsLastRange()) {
1710       cache_->ConvertWriterToReader(entry_);
1711       mode_ = READ;
1712     }
1713     // We no longer need the network transaction, so destroy it.
1714     final_upload_progress_ = network_trans_->GetUploadProgress();
1715     ResetNetworkTransaction();
1716   } else if (entry_ && handling_206_ && truncated_ &&
1717              partial_->initial_validation()) {
1718     // We just finished the validation of a truncated entry, and the server
1719     // is willing to resume the operation. Now we go back and start serving
1720     // the first part to the user.
1721     ResetNetworkTransaction();
1722     new_response_ = NULL;
1723     next_state_ = STATE_START_PARTIAL_CACHE_VALIDATION;
1724     partial_->SetRangeToStartDownload();
1725     return OK;
1726   }
1727   next_state_ = STATE_OVERWRITE_CACHED_RESPONSE;
1728   return OK;
1729 }
1730
1731 int HttpCache::Transaction::DoOverwriteCachedResponse() {
1732   // TODO(vadimt): Remove ScopedTracker below once crbug.com/422516 is fixed.
1733   tracked_objects::ScopedTracker tracking_profile(
1734       FROM_HERE_WITH_EXPLICIT_FUNCTION(
1735           "422516 HttpCache::Transaction::DoOverwriteCachedResponse"));
1736
1737   if (mode_ & READ) {
1738     next_state_ = STATE_PARTIAL_HEADERS_RECEIVED;
1739     return OK;
1740   }
1741
1742   // We change the value of Content-Length for partial content.
1743   if (handling_206_ && partial_.get())
1744     partial_->FixContentLength(new_response_->headers.get());
1745
1746   response_ = *new_response_;
1747
1748   if (request_->method == "HEAD") {
1749     // This response is replacing the cached one.
1750     DoneWritingToEntry(false);
1751     mode_ = NONE;
1752     new_response_ = NULL;
1753     return OK;
1754   }
1755
1756   if (handling_206_ && !CanResume(false)) {
1757     // There is no point in storing this resource because it will never be used.
1758     // This may change if we support LOAD_ONLY_FROM_CACHE with sparse entries.
1759     DoneWritingToEntry(false);
1760     if (partial_.get())
1761       partial_->FixResponseHeaders(response_.headers.get(), true);
1762     next_state_ = STATE_PARTIAL_HEADERS_RECEIVED;
1763     return OK;
1764   }
1765
1766   target_state_ = STATE_TRUNCATE_CACHED_DATA;
1767   next_state_ = truncated_ ? STATE_CACHE_WRITE_TRUNCATED_RESPONSE :
1768                              STATE_CACHE_WRITE_RESPONSE;
1769   return OK;
1770 }
1771
1772 int HttpCache::Transaction::DoTruncateCachedData() {
1773   // TODO(vadimt): Remove ScopedTracker below once crbug.com/422516 is fixed.
1774   tracked_objects::ScopedTracker tracking_profile(
1775       FROM_HERE_WITH_EXPLICIT_FUNCTION(
1776           "422516 HttpCache::Transaction::DoTruncateCachedData"));
1777
1778   next_state_ = STATE_TRUNCATE_CACHED_DATA_COMPLETE;
1779   if (!entry_)
1780     return OK;
1781   if (net_log_.IsLogging())
1782     net_log_.BeginEvent(NetLog::TYPE_HTTP_CACHE_WRITE_DATA);
1783   // Truncate the stream.
1784   return WriteToEntry(kResponseContentIndex, 0, NULL, 0, io_callback_);
1785 }
1786
1787 int HttpCache::Transaction::DoTruncateCachedDataComplete(int result) {
1788   // TODO(vadimt): Remove ScopedTracker below once crbug.com/422516 is fixed.
1789   tracked_objects::ScopedTracker tracking_profile(
1790       FROM_HERE_WITH_EXPLICIT_FUNCTION(
1791           "422516 HttpCache::Transaction::DoTruncateCachedDataComplete"));
1792
1793   if (entry_) {
1794     if (net_log_.IsLogging()) {
1795       net_log_.EndEventWithNetErrorCode(NetLog::TYPE_HTTP_CACHE_WRITE_DATA,
1796                                         result);
1797     }
1798   }
1799
1800   next_state_ = STATE_TRUNCATE_CACHED_METADATA;
1801   return OK;
1802 }
1803
1804 int HttpCache::Transaction::DoTruncateCachedMetadata() {
1805   // TODO(vadimt): Remove ScopedTracker below once crbug.com/422516 is fixed.
1806   tracked_objects::ScopedTracker tracking_profile(
1807       FROM_HERE_WITH_EXPLICIT_FUNCTION(
1808           "422516 HttpCache::Transaction::DoTruncateCachedMetadata"));
1809
1810   next_state_ = STATE_TRUNCATE_CACHED_METADATA_COMPLETE;
1811   if (!entry_)
1812     return OK;
1813
1814   if (net_log_.IsLogging())
1815     net_log_.BeginEvent(NetLog::TYPE_HTTP_CACHE_WRITE_INFO);
1816   return WriteToEntry(kMetadataIndex, 0, NULL, 0, io_callback_);
1817 }
1818
1819 int HttpCache::Transaction::DoTruncateCachedMetadataComplete(int result) {
1820   // TODO(vadimt): Remove ScopedTracker below once crbug.com/422516 is fixed.
1821   tracked_objects::ScopedTracker tracking_profile(
1822       FROM_HERE_WITH_EXPLICIT_FUNCTION(
1823           "422516 HttpCache::Transaction::DoTruncateCachedMetadataComplete"));
1824
1825   if (entry_) {
1826     if (net_log_.IsLogging()) {
1827       net_log_.EndEventWithNetErrorCode(NetLog::TYPE_HTTP_CACHE_WRITE_INFO,
1828                                         result);
1829     }
1830   }
1831
1832   next_state_ = STATE_PARTIAL_HEADERS_RECEIVED;
1833   return OK;
1834 }
1835
1836 int HttpCache::Transaction::DoPartialHeadersReceived() {
1837   // TODO(vadimt): Remove ScopedTracker below once crbug.com/422516 is fixed.
1838   tracked_objects::ScopedTracker tracking_profile(
1839       FROM_HERE_WITH_EXPLICIT_FUNCTION(
1840           "422516 HttpCache::Transaction::DoPartialHeadersReceived"));
1841
1842   new_response_ = NULL;
1843   if (entry_ && !partial_.get() &&
1844       entry_->disk_entry->GetDataSize(kMetadataIndex))
1845     next_state_ = STATE_CACHE_READ_METADATA;
1846
1847   if (!partial_.get())
1848     return OK;
1849
1850   if (reading_) {
1851     if (network_trans_.get()) {
1852       next_state_ = STATE_NETWORK_READ;
1853     } else {
1854       next_state_ = STATE_CACHE_READ_DATA;
1855     }
1856   } else if (mode_ != NONE) {
1857     // We are about to return the headers for a byte-range request to the user,
1858     // so let's fix them.
1859     partial_->FixResponseHeaders(response_.headers.get(), true);
1860   }
1861   return OK;
1862 }
1863
1864 int HttpCache::Transaction::DoCacheReadResponse() {
1865   // TODO(vadimt): Remove ScopedTracker below once crbug.com/422516 is fixed.
1866   tracked_objects::ScopedTracker tracking_profile(
1867       FROM_HERE_WITH_EXPLICIT_FUNCTION(
1868           "422516 HttpCache::Transaction::DoCacheReadResponse"));
1869
1870   DCHECK(entry_);
1871   next_state_ = STATE_CACHE_READ_RESPONSE_COMPLETE;
1872
1873   io_buf_len_ = entry_->disk_entry->GetDataSize(kResponseInfoIndex);
1874   read_buf_ = new IOBuffer(io_buf_len_);
1875
1876   net_log_.BeginEvent(NetLog::TYPE_HTTP_CACHE_READ_INFO);
1877   return entry_->disk_entry->ReadData(kResponseInfoIndex, 0, read_buf_.get(),
1878                                       io_buf_len_, io_callback_);
1879 }
1880
1881 int HttpCache::Transaction::DoCacheReadResponseComplete(int result) {
1882   // TODO(vadimt): Remove ScopedTracker below once crbug.com/422516 is fixed.
1883   tracked_objects::ScopedTracker tracking_profile(
1884       FROM_HERE_WITH_EXPLICIT_FUNCTION(
1885           "422516 HttpCache::Transaction::DoCacheReadResponseComplete"));
1886
1887   net_log_.EndEventWithNetErrorCode(NetLog::TYPE_HTTP_CACHE_READ_INFO, result);
1888   if (result != io_buf_len_ ||
1889       !HttpCache::ParseResponseInfo(read_buf_->data(), io_buf_len_,
1890                                     &response_, &truncated_)) {
1891     return OnCacheReadError(result, true);
1892   }
1893
1894   // cert_cache() will be null if the CertCacheTrial field trial is disabled.
1895   if (cache_->cert_cache() && response_.ssl_info.is_valid())
1896     ReadCertChain();
1897
1898   // Some resources may have slipped in as truncated when they're not.
1899   int current_size = entry_->disk_entry->GetDataSize(kResponseContentIndex);
1900   if (response_.headers->GetContentLength() == current_size)
1901     truncated_ = false;
1902
1903   if ((response_.unused_since_prefetch &&
1904        !(request_->load_flags & LOAD_PREFETCH)) ||
1905       (!response_.unused_since_prefetch &&
1906        (request_->load_flags & LOAD_PREFETCH))) {
1907     // Either this is the first use of an entry since it was prefetched or
1908     // this is a prefetch. The value of response.unused_since_prefetch is valid
1909     // for this transaction but the bit needs to be flipped in storage.
1910     next_state_ = STATE_TOGGLE_UNUSED_SINCE_PREFETCH;
1911     return OK;
1912   }
1913
1914   next_state_ = STATE_CACHE_DISPATCH_VALIDATION;
1915   return OK;
1916 }
1917
1918 int HttpCache::Transaction::DoCacheDispatchValidation() {
1919   // We now have access to the cache entry.
1920   //
1921   //  o if we are a reader for the transaction, then we can start reading the
1922   //    cache entry.
1923   //
1924   //  o if we can read or write, then we should check if the cache entry needs
1925   //    to be validated and then issue a network request if needed or just read
1926   //    from the cache if the cache entry is already valid.
1927   //
1928   //  o if we are set to UPDATE, then we are handling an externally
1929   //    conditionalized request (if-modified-since / if-none-match). We check
1930   //    if the request headers define a validation request.
1931   //
1932   int result = ERR_FAILED;
1933   switch (mode_) {
1934     case READ:
1935       UpdateTransactionPattern(PATTERN_ENTRY_USED);
1936       result = BeginCacheRead();
1937       break;
1938     case READ_WRITE:
1939       result = BeginPartialCacheValidation();
1940       break;
1941     case UPDATE:
1942       result = BeginExternallyConditionalizedRequest();
1943       break;
1944     case WRITE:
1945     default:
1946       NOTREACHED();
1947   }
1948   return result;
1949 }
1950
1951 int HttpCache::Transaction::DoCacheToggleUnusedSincePrefetch() {
1952   // Write back the toggled value for the next use of this entry.
1953   response_.unused_since_prefetch = !response_.unused_since_prefetch;
1954
1955   // TODO(jkarlin): If DoUpdateCachedResponse is also called for this
1956   // transaction then metadata will be written to cache twice. If prefetching
1957   // becomes more common, consider combining the writes.
1958   target_state_ = STATE_TOGGLE_UNUSED_SINCE_PREFETCH_COMPLETE;
1959   next_state_ = STATE_CACHE_WRITE_RESPONSE;
1960   return OK;
1961 }
1962
1963 int HttpCache::Transaction::DoCacheToggleUnusedSincePrefetchComplete(
1964     int result) {
1965   // Restore the original value for this transaction.
1966   response_.unused_since_prefetch = !response_.unused_since_prefetch;
1967   next_state_ = STATE_CACHE_DISPATCH_VALIDATION;
1968   return OK;
1969 }
1970
1971 int HttpCache::Transaction::DoCacheWriteResponse() {
1972   // TODO(vadimt): Remove ScopedTracker below once crbug.com/422516 is fixed.
1973   tracked_objects::ScopedTracker tracking_profile(
1974       FROM_HERE_WITH_EXPLICIT_FUNCTION(
1975           "422516 HttpCache::Transaction::DoCacheWriteResponse"));
1976
1977   if (entry_) {
1978     if (net_log_.IsLogging())
1979       net_log_.BeginEvent(NetLog::TYPE_HTTP_CACHE_WRITE_INFO);
1980   }
1981   return WriteResponseInfoToEntry(false);
1982 }
1983
1984 int HttpCache::Transaction::DoCacheWriteTruncatedResponse() {
1985   // TODO(vadimt): Remove ScopedTracker below once crbug.com/422516 is fixed.
1986   tracked_objects::ScopedTracker tracking_profile(
1987       FROM_HERE_WITH_EXPLICIT_FUNCTION(
1988           "422516 HttpCache::Transaction::DoCacheWriteTruncatedResponse"));
1989
1990   if (entry_) {
1991     if (net_log_.IsLogging())
1992       net_log_.BeginEvent(NetLog::TYPE_HTTP_CACHE_WRITE_INFO);
1993   }
1994   return WriteResponseInfoToEntry(true);
1995 }
1996
1997 int HttpCache::Transaction::DoCacheWriteResponseComplete(int result) {
1998   // TODO(vadimt): Remove ScopedTracker below once crbug.com/422516 is fixed.
1999   tracked_objects::ScopedTracker tracking_profile(
2000       FROM_HERE_WITH_EXPLICIT_FUNCTION(
2001           "422516 HttpCache::Transaction::DoCacheWriteResponseComplete"));
2002
2003   next_state_ = target_state_;
2004   target_state_ = STATE_NONE;
2005   if (!entry_)
2006     return OK;
2007   if (net_log_.IsLogging()) {
2008     net_log_.EndEventWithNetErrorCode(NetLog::TYPE_HTTP_CACHE_WRITE_INFO,
2009                                       result);
2010   }
2011
2012   // Balance the AddRef from WriteResponseInfoToEntry.
2013   if (result != io_buf_len_) {
2014     DLOG(ERROR) << "failed to write response info to cache";
2015     DoneWritingToEntry(false);
2016   }
2017   return OK;
2018 }
2019
2020 int HttpCache::Transaction::DoCacheReadMetadata() {
2021   // TODO(vadimt): Remove ScopedTracker below once crbug.com/422516 is fixed.
2022   tracked_objects::ScopedTracker tracking_profile(
2023       FROM_HERE_WITH_EXPLICIT_FUNCTION(
2024           "422516 HttpCache::Transaction::DoCacheReadMetadata"));
2025
2026   DCHECK(entry_);
2027   DCHECK(!response_.metadata.get());
2028   next_state_ = STATE_CACHE_READ_METADATA_COMPLETE;
2029
2030   response_.metadata =
2031       new IOBufferWithSize(entry_->disk_entry->GetDataSize(kMetadataIndex));
2032
2033   net_log_.BeginEvent(NetLog::TYPE_HTTP_CACHE_READ_INFO);
2034   return entry_->disk_entry->ReadData(kMetadataIndex, 0,
2035                                       response_.metadata.get(),
2036                                       response_.metadata->size(),
2037                                       io_callback_);
2038 }
2039
2040 int HttpCache::Transaction::DoCacheReadMetadataComplete(int result) {
2041   // TODO(vadimt): Remove ScopedTracker below once crbug.com/422516 is fixed.
2042   tracked_objects::ScopedTracker tracking_profile(
2043       FROM_HERE_WITH_EXPLICIT_FUNCTION(
2044           "422516 HttpCache::Transaction::DoCacheReadMetadataComplete"));
2045
2046   net_log_.EndEventWithNetErrorCode(NetLog::TYPE_HTTP_CACHE_READ_INFO, result);
2047   if (result != response_.metadata->size())
2048     return OnCacheReadError(result, false);
2049   return OK;
2050 }
2051
2052 int HttpCache::Transaction::DoCacheQueryData() {
2053   // TODO(vadimt): Remove ScopedTracker below once crbug.com/422516 is fixed.
2054   tracked_objects::ScopedTracker tracking_profile(
2055       FROM_HERE_WITH_EXPLICIT_FUNCTION(
2056           "422516 HttpCache::Transaction::DoCacheQueryData"));
2057
2058   next_state_ = STATE_CACHE_QUERY_DATA_COMPLETE;
2059   return entry_->disk_entry->ReadyForSparseIO(io_callback_);
2060 }
2061
2062 int HttpCache::Transaction::DoCacheQueryDataComplete(int result) {
2063   // TODO(vadimt): Remove ScopedTracker below once crbug.com/422516 is fixed.
2064   tracked_objects::ScopedTracker tracking_profile(
2065       FROM_HERE_WITH_EXPLICIT_FUNCTION(
2066           "422516 HttpCache::Transaction::DoCacheQueryDataComplete"));
2067
2068   DCHECK_EQ(OK, result);
2069   if (!cache_.get())
2070     return ERR_UNEXPECTED;
2071
2072   return ValidateEntryHeadersAndContinue();
2073 }
2074
2075 int HttpCache::Transaction::DoCacheReadData() {
2076   // TODO(vadimt): Remove ScopedTracker below once crbug.com/422516 is fixed.
2077   tracked_objects::ScopedTracker tracking_profile(
2078       FROM_HERE_WITH_EXPLICIT_FUNCTION(
2079           "422516 HttpCache::Transaction::DoCacheReadData"));
2080
2081   DCHECK(entry_);
2082   next_state_ = STATE_CACHE_READ_DATA_COMPLETE;
2083
2084   if (net_log_.IsLogging())
2085     net_log_.BeginEvent(NetLog::TYPE_HTTP_CACHE_READ_DATA);
2086   if (partial_.get()) {
2087     return partial_->CacheRead(entry_->disk_entry, read_buf_.get(), io_buf_len_,
2088                                io_callback_);
2089   }
2090
2091   return entry_->disk_entry->ReadData(kResponseContentIndex, read_offset_,
2092                                       read_buf_.get(), io_buf_len_,
2093                                       io_callback_);
2094 }
2095
2096 int HttpCache::Transaction::DoCacheReadDataComplete(int result) {
2097   // TODO(vadimt): Remove ScopedTracker below once crbug.com/422516 is fixed.
2098   tracked_objects::ScopedTracker tracking_profile(
2099       FROM_HERE_WITH_EXPLICIT_FUNCTION(
2100           "422516 HttpCache::Transaction::DoCacheReadDataComplete"));
2101
2102   if (net_log_.IsLogging()) {
2103     net_log_.EndEventWithNetErrorCode(NetLog::TYPE_HTTP_CACHE_READ_DATA,
2104                                       result);
2105   }
2106
2107   if (!cache_.get())
2108     return ERR_UNEXPECTED;
2109
2110   if (partial_.get()) {
2111     // Partial requests are confusing to report in histograms because they may
2112     // have multiple underlying requests.
2113     UpdateTransactionPattern(PATTERN_NOT_COVERED);
2114     return DoPartialCacheReadCompleted(result);
2115   }
2116
2117   if (result > 0) {
2118     read_offset_ += result;
2119   } else if (result == 0) {  // End of file.
2120     RecordHistograms();
2121     cache_->DoneReadingFromEntry(entry_, this);
2122     entry_ = NULL;
2123   } else {
2124     return OnCacheReadError(result, false);
2125   }
2126   return result;
2127 }
2128
2129 int HttpCache::Transaction::DoCacheWriteData(int num_bytes) {
2130   // TODO(vadimt): Remove ScopedTracker below once crbug.com/422516 is fixed.
2131   tracked_objects::ScopedTracker tracking_profile(
2132       FROM_HERE_WITH_EXPLICIT_FUNCTION(
2133           "422516 HttpCache::Transaction::DoCacheWriteData"));
2134
2135   next_state_ = STATE_CACHE_WRITE_DATA_COMPLETE;
2136   write_len_ = num_bytes;
2137   if (entry_) {
2138     if (net_log_.IsLogging())
2139       net_log_.BeginEvent(NetLog::TYPE_HTTP_CACHE_WRITE_DATA);
2140   }
2141
2142   return AppendResponseDataToEntry(read_buf_.get(), num_bytes, io_callback_);
2143 }
2144
2145 int HttpCache::Transaction::DoCacheWriteDataComplete(int result) {
2146   // TODO(vadimt): Remove ScopedTracker below once crbug.com/422516 is fixed.
2147   tracked_objects::ScopedTracker tracking_profile(
2148       FROM_HERE_WITH_EXPLICIT_FUNCTION(
2149           "422516 HttpCache::Transaction::DoCacheWriteDataComplete"));
2150
2151   if (entry_) {
2152     if (net_log_.IsLogging()) {
2153       net_log_.EndEventWithNetErrorCode(NetLog::TYPE_HTTP_CACHE_WRITE_DATA,
2154                                         result);
2155     }
2156   }
2157   // Balance the AddRef from DoCacheWriteData.
2158   if (!cache_.get())
2159     return ERR_UNEXPECTED;
2160
2161   if (result != write_len_) {
2162     DLOG(ERROR) << "failed to write response data to cache";
2163     DoneWritingToEntry(false);
2164
2165     // We want to ignore errors writing to disk and just keep reading from
2166     // the network.
2167     result = write_len_;
2168   } else if (!done_reading_ && entry_) {
2169     int current_size = entry_->disk_entry->GetDataSize(kResponseContentIndex);
2170     int64 body_size = response_.headers->GetContentLength();
2171     if (body_size >= 0 && body_size <= current_size)
2172       done_reading_ = true;
2173   }
2174
2175   if (partial_.get()) {
2176     // This may be the last request.
2177     if (!(result == 0 && !truncated_ &&
2178           (partial_->IsLastRange() || mode_ == WRITE)))
2179       return DoPartialNetworkReadCompleted(result);
2180   }
2181
2182   if (result == 0) {
2183     // End of file. This may be the result of a connection problem so see if we
2184     // have to keep the entry around to be flagged as truncated later on.
2185     if (done_reading_ || !entry_ || partial_.get() ||
2186         response_.headers->GetContentLength() <= 0)
2187       DoneWritingToEntry(true);
2188   }
2189
2190   return result;
2191 }
2192
2193 //-----------------------------------------------------------------------------
2194
2195 void HttpCache::Transaction::ReadCertChain() {
2196   std::string key =
2197       GetCacheKeyForCert(response_.ssl_info.cert->os_cert_handle());
2198   const X509Certificate::OSCertHandles& intermediates =
2199       response_.ssl_info.cert->GetIntermediateCertificates();
2200   int dist_from_root = intermediates.size();
2201
2202   scoped_refptr<SharedChainData> shared_chain_data(
2203       new SharedChainData(intermediates.size() + 1, TimeTicks::Now()));
2204   cache_->cert_cache()->GetCertificate(key,
2205                                        base::Bind(&OnCertReadIOComplete,
2206                                                   dist_from_root,
2207                                                   true /* is leaf */,
2208                                                   shared_chain_data));
2209
2210   for (X509Certificate::OSCertHandles::const_iterator it =
2211            intermediates.begin();
2212        it != intermediates.end();
2213        ++it) {
2214     --dist_from_root;
2215     key = GetCacheKeyForCert(*it);
2216     cache_->cert_cache()->GetCertificate(key,
2217                                          base::Bind(&OnCertReadIOComplete,
2218                                                     dist_from_root,
2219                                                     false /* is not leaf */,
2220                                                     shared_chain_data));
2221   }
2222   DCHECK_EQ(0, dist_from_root);
2223 }
2224
2225 void HttpCache::Transaction::WriteCertChain() {
2226   const X509Certificate::OSCertHandles& intermediates =
2227       response_.ssl_info.cert->GetIntermediateCertificates();
2228   int dist_from_root = intermediates.size();
2229
2230   scoped_refptr<SharedChainData> shared_chain_data(
2231       new SharedChainData(intermediates.size() + 1, TimeTicks::Now()));
2232   cache_->cert_cache()->SetCertificate(
2233       response_.ssl_info.cert->os_cert_handle(),
2234       base::Bind(&OnCertWriteIOComplete,
2235                  dist_from_root,
2236                  true /* is leaf */,
2237                  shared_chain_data));
2238   for (X509Certificate::OSCertHandles::const_iterator it =
2239            intermediates.begin();
2240        it != intermediates.end();
2241        ++it) {
2242     --dist_from_root;
2243     cache_->cert_cache()->SetCertificate(*it,
2244                                          base::Bind(&OnCertWriteIOComplete,
2245                                                     dist_from_root,
2246                                                     false /* is not leaf */,
2247                                                     shared_chain_data));
2248   }
2249   DCHECK_EQ(0, dist_from_root);
2250 }
2251
2252 void HttpCache::Transaction::SetRequest(const BoundNetLog& net_log,
2253                                         const HttpRequestInfo* request) {
2254   net_log_ = net_log;
2255   request_ = request;
2256   effective_load_flags_ = request_->load_flags;
2257
2258   if (cache_->mode() == DISABLE)
2259     effective_load_flags_ |= LOAD_DISABLE_CACHE;
2260
2261   // Some headers imply load flags.  The order here is significant.
2262   //
2263   //   LOAD_DISABLE_CACHE   : no cache read or write
2264   //   LOAD_BYPASS_CACHE    : no cache read
2265   //   LOAD_VALIDATE_CACHE  : no cache read unless validation
2266   //
2267   // The former modes trump latter modes, so if we find a matching header we
2268   // can stop iterating kSpecialHeaders.
2269   //
2270   static const struct {
2271     const HeaderNameAndValue* search;
2272     int load_flag;
2273   } kSpecialHeaders[] = {
2274     { kPassThroughHeaders, LOAD_DISABLE_CACHE },
2275     { kForceFetchHeaders, LOAD_BYPASS_CACHE },
2276     { kForceValidateHeaders, LOAD_VALIDATE_CACHE },
2277   };
2278
2279   bool range_found = false;
2280   bool external_validation_error = false;
2281   bool special_headers = false;
2282
2283   if (request_->extra_headers.HasHeader(HttpRequestHeaders::kRange))
2284     range_found = true;
2285
2286   for (size_t i = 0; i < arraysize(kSpecialHeaders); ++i) {
2287     if (HeaderMatches(request_->extra_headers, kSpecialHeaders[i].search)) {
2288       effective_load_flags_ |= kSpecialHeaders[i].load_flag;
2289       special_headers = true;
2290       break;
2291     }
2292   }
2293
2294   // Check for conditionalization headers which may correspond with a
2295   // cache validation request.
2296   for (size_t i = 0; i < arraysize(kValidationHeaders); ++i) {
2297     const ValidationHeaderInfo& info = kValidationHeaders[i];
2298     std::string validation_value;
2299     if (request_->extra_headers.GetHeader(
2300             info.request_header_name, &validation_value)) {
2301       if (!external_validation_.values[i].empty() ||
2302           validation_value.empty()) {
2303         external_validation_error = true;
2304       }
2305       external_validation_.values[i] = validation_value;
2306       external_validation_.initialized = true;
2307     }
2308   }
2309
2310   if (range_found || special_headers || external_validation_.initialized) {
2311     // Log the headers before request_ is modified.
2312     std::string empty;
2313     net_log_.AddEvent(
2314         NetLog::TYPE_HTTP_CACHE_CALLER_REQUEST_HEADERS,
2315         base::Bind(&HttpRequestHeaders::NetLogCallback,
2316                    base::Unretained(&request_->extra_headers), &empty));
2317   }
2318
2319   // We don't support ranges and validation headers.
2320   if (range_found && external_validation_.initialized) {
2321     LOG(WARNING) << "Byte ranges AND validation headers found.";
2322     effective_load_flags_ |= LOAD_DISABLE_CACHE;
2323   }
2324
2325   // If there is more than one validation header, we can't treat this request as
2326   // a cache validation, since we don't know for sure which header the server
2327   // will give us a response for (and they could be contradictory).
2328   if (external_validation_error) {
2329     LOG(WARNING) << "Multiple or malformed validation headers found.";
2330     effective_load_flags_ |= LOAD_DISABLE_CACHE;
2331   }
2332
2333   if (range_found && !(effective_load_flags_ & LOAD_DISABLE_CACHE)) {
2334     UpdateTransactionPattern(PATTERN_NOT_COVERED);
2335     partial_.reset(new PartialData);
2336     if (request_->method == "GET" && partial_->Init(request_->extra_headers)) {
2337       // We will be modifying the actual range requested to the server, so
2338       // let's remove the header here.
2339       custom_request_.reset(new HttpRequestInfo(*request_));
2340       custom_request_->extra_headers.RemoveHeader(HttpRequestHeaders::kRange);
2341       request_ = custom_request_.get();
2342       partial_->SetHeaders(custom_request_->extra_headers);
2343     } else {
2344       // The range is invalid or we cannot handle it properly.
2345       VLOG(1) << "Invalid byte range found.";
2346       effective_load_flags_ |= LOAD_DISABLE_CACHE;
2347       partial_.reset(NULL);
2348     }
2349   }
2350 }
2351
2352 bool HttpCache::Transaction::ShouldPassThrough() {
2353   // We may have a null disk_cache if there is an error we cannot recover from,
2354   // like not enough disk space, or sharing violations.
2355   if (!cache_->disk_cache_.get())
2356     return true;
2357
2358   if (effective_load_flags_ & LOAD_DISABLE_CACHE)
2359     return true;
2360
2361   if (request_->method == "GET" || request_->method == "HEAD")
2362     return false;
2363
2364   if (request_->method == "POST" && request_->upload_data_stream &&
2365       request_->upload_data_stream->identifier()) {
2366     return false;
2367   }
2368
2369   if (request_->method == "PUT" && request_->upload_data_stream)
2370     return false;
2371
2372   if (request_->method == "DELETE")
2373     return false;
2374
2375   return true;
2376 }
2377
2378 int HttpCache::Transaction::BeginCacheRead() {
2379   // We don't support any combination of LOAD_ONLY_FROM_CACHE and byte ranges.
2380   if (response_.headers->response_code() == 206 || partial_.get()) {
2381     NOTREACHED();
2382     return ERR_CACHE_MISS;
2383   }
2384
2385   if (request_->method == "HEAD")
2386     FixHeadersForHead();
2387
2388   // We don't have the whole resource.
2389   if (truncated_)
2390     return ERR_CACHE_MISS;
2391
2392   if (entry_->disk_entry->GetDataSize(kMetadataIndex))
2393     next_state_ = STATE_CACHE_READ_METADATA;
2394
2395   return OK;
2396 }
2397
2398 int HttpCache::Transaction::BeginCacheValidation() {
2399   DCHECK(mode_ == READ_WRITE);
2400
2401   ValidationType required_validation = RequiresValidation();
2402
2403   bool skip_validation = (required_validation == VALIDATION_NONE);
2404
2405   if (required_validation == VALIDATION_ASYNCHRONOUS &&
2406       !(request_->method == "GET" && (truncated_ || partial_)) && cache_ &&
2407       cache_->use_stale_while_revalidate()) {
2408     TriggerAsyncValidation();
2409     skip_validation = true;
2410   }
2411
2412   if (request_->method == "HEAD" &&
2413       (truncated_ || response_.headers->response_code() == 206)) {
2414     DCHECK(!partial_);
2415     if (skip_validation)
2416       return SetupEntryForRead();
2417
2418     // Bail out!
2419     next_state_ = STATE_SEND_REQUEST;
2420     mode_ = NONE;
2421     return OK;
2422   }
2423
2424   if (truncated_) {
2425     // Truncated entries can cause partial gets, so we shouldn't record this
2426     // load in histograms.
2427     UpdateTransactionPattern(PATTERN_NOT_COVERED);
2428     skip_validation = !partial_->initial_validation();
2429   }
2430
2431   if (partial_.get() && (is_sparse_ || truncated_) &&
2432       (!partial_->IsCurrentRangeCached() || invalid_range_)) {
2433     // Force revalidation for sparse or truncated entries. Note that we don't
2434     // want to ignore the regular validation logic just because a byte range was
2435     // part of the request.
2436     skip_validation = false;
2437   }
2438
2439   if (skip_validation) {
2440     // TODO(ricea): Is this pattern okay for asynchronous revalidations?
2441     UpdateTransactionPattern(PATTERN_ENTRY_USED);
2442     RecordOfflineStatus(effective_load_flags_, OFFLINE_STATUS_FRESH_CACHE);
2443     return SetupEntryForRead();
2444   } else {
2445     // Make the network request conditional, to see if we may reuse our cached
2446     // response.  If we cannot do so, then we just resort to a normal fetch.
2447     // Our mode remains READ_WRITE for a conditional request.  Even if the
2448     // conditionalization fails, we don't switch to WRITE mode until we
2449     // know we won't be falling back to using the cache entry in the
2450     // LOAD_FROM_CACHE_IF_OFFLINE case.
2451     if (!ConditionalizeRequest()) {
2452       couldnt_conditionalize_request_ = true;
2453       UpdateTransactionPattern(PATTERN_ENTRY_CANT_CONDITIONALIZE);
2454       if (partial_.get())
2455         return DoRestartPartialRequest();
2456
2457       DCHECK_NE(206, response_.headers->response_code());
2458     }
2459     next_state_ = STATE_SEND_REQUEST;
2460   }
2461   return OK;
2462 }
2463
2464 int HttpCache::Transaction::BeginPartialCacheValidation() {
2465   DCHECK(mode_ == READ_WRITE);
2466
2467   if (response_.headers->response_code() != 206 && !partial_.get() &&
2468       !truncated_) {
2469     return BeginCacheValidation();
2470   }
2471
2472   // Partial requests should not be recorded in histograms.
2473   UpdateTransactionPattern(PATTERN_NOT_COVERED);
2474   if (range_requested_) {
2475     next_state_ = STATE_CACHE_QUERY_DATA;
2476     return OK;
2477   }
2478
2479   // The request is not for a range, but we have stored just ranges.
2480
2481   if (request_->method == "HEAD")
2482     return BeginCacheValidation();
2483
2484   partial_.reset(new PartialData());
2485   partial_->SetHeaders(request_->extra_headers);
2486   if (!custom_request_.get()) {
2487     custom_request_.reset(new HttpRequestInfo(*request_));
2488     request_ = custom_request_.get();
2489   }
2490
2491   return ValidateEntryHeadersAndContinue();
2492 }
2493
2494 // This should only be called once per request.
2495 int HttpCache::Transaction::ValidateEntryHeadersAndContinue() {
2496   DCHECK(mode_ == READ_WRITE);
2497
2498   if (!partial_->UpdateFromStoredHeaders(
2499           response_.headers.get(), entry_->disk_entry, truncated_)) {
2500     return DoRestartPartialRequest();
2501   }
2502
2503   if (response_.headers->response_code() == 206)
2504     is_sparse_ = true;
2505
2506   if (!partial_->IsRequestedRangeOK()) {
2507     // The stored data is fine, but the request may be invalid.
2508     invalid_range_ = true;
2509   }
2510
2511   next_state_ = STATE_START_PARTIAL_CACHE_VALIDATION;
2512   return OK;
2513 }
2514
2515 int HttpCache::Transaction::BeginExternallyConditionalizedRequest() {
2516   DCHECK_EQ(UPDATE, mode_);
2517   DCHECK(external_validation_.initialized);
2518
2519   for (size_t i = 0;  i < arraysize(kValidationHeaders); i++) {
2520     if (external_validation_.values[i].empty())
2521       continue;
2522     // Retrieve either the cached response's "etag" or "last-modified" header.
2523     std::string validator;
2524     response_.headers->EnumerateHeader(
2525         NULL,
2526         kValidationHeaders[i].related_response_header_name,
2527         &validator);
2528
2529     if (response_.headers->response_code() != 200 || truncated_ ||
2530         validator.empty() || validator != external_validation_.values[i]) {
2531       // The externally conditionalized request is not a validation request
2532       // for our existing cache entry. Proceed with caching disabled.
2533       UpdateTransactionPattern(PATTERN_NOT_COVERED);
2534       DoneWritingToEntry(true);
2535     }
2536   }
2537
2538   // TODO(ricea): This calculation is expensive to perform just to collect
2539   // statistics. Either remove it or use the result, depending on the result of
2540   // the experiment.
2541   ExternallyConditionalizedType type =
2542       EXTERNALLY_CONDITIONALIZED_CACHE_USABLE;
2543   if (mode_ == NONE)
2544     type = EXTERNALLY_CONDITIONALIZED_MISMATCHED_VALIDATORS;
2545   else if (RequiresValidation())
2546     type = EXTERNALLY_CONDITIONALIZED_CACHE_REQUIRES_VALIDATION;
2547
2548   // TODO(ricea): Add CACHE_USABLE_STALE once stale-while-revalidate CL landed.
2549   // TODO(ricea): Either remove this histogram or make it permanent by M40.
2550   UMA_HISTOGRAM_ENUMERATION("HttpCache.ExternallyConditionalized",
2551                             type,
2552                             EXTERNALLY_CONDITIONALIZED_MAX);
2553
2554   next_state_ = STATE_SEND_REQUEST;
2555   return OK;
2556 }
2557
2558 int HttpCache::Transaction::RestartNetworkRequest() {
2559   DCHECK(mode_ & WRITE || mode_ == NONE);
2560   DCHECK(network_trans_.get());
2561   DCHECK_EQ(STATE_NONE, next_state_);
2562
2563   next_state_ = STATE_SEND_REQUEST_COMPLETE;
2564   int rv = network_trans_->RestartIgnoringLastError(io_callback_);
2565   if (rv != ERR_IO_PENDING)
2566     return DoLoop(rv);
2567   return rv;
2568 }
2569
2570 int HttpCache::Transaction::RestartNetworkRequestWithCertificate(
2571     X509Certificate* client_cert) {
2572   DCHECK(mode_ & WRITE || mode_ == NONE);
2573   DCHECK(network_trans_.get());
2574   DCHECK_EQ(STATE_NONE, next_state_);
2575
2576   next_state_ = STATE_SEND_REQUEST_COMPLETE;
2577   int rv = network_trans_->RestartWithCertificate(client_cert, io_callback_);
2578   if (rv != ERR_IO_PENDING)
2579     return DoLoop(rv);
2580   return rv;
2581 }
2582
2583 int HttpCache::Transaction::RestartNetworkRequestWithAuth(
2584     const AuthCredentials& credentials) {
2585   DCHECK(mode_ & WRITE || mode_ == NONE);
2586   DCHECK(network_trans_.get());
2587   DCHECK_EQ(STATE_NONE, next_state_);
2588
2589   next_state_ = STATE_SEND_REQUEST_COMPLETE;
2590   int rv = network_trans_->RestartWithAuth(credentials, io_callback_);
2591   if (rv != ERR_IO_PENDING)
2592     return DoLoop(rv);
2593   return rv;
2594 }
2595
2596 ValidationType HttpCache::Transaction::RequiresValidation() {
2597   // TODO(darin): need to do more work here:
2598   //  - make sure we have a matching request method
2599   //  - watch out for cached responses that depend on authentication
2600
2601   if (response_.vary_data.is_valid() &&
2602       !response_.vary_data.MatchesRequest(*request_,
2603                                           *response_.headers.get())) {
2604     vary_mismatch_ = true;
2605     return VALIDATION_SYNCHRONOUS;
2606   }
2607
2608   if (effective_load_flags_ & LOAD_PREFERRING_CACHE)
2609     return VALIDATION_NONE;
2610
2611   if (response_.unused_since_prefetch &&
2612       !(effective_load_flags_ & LOAD_PREFETCH) &&
2613       response_.headers->GetCurrentAge(
2614           response_.request_time, response_.response_time,
2615           cache_->clock_->Now()) < TimeDelta::FromMinutes(kPrefetchReuseMins)) {
2616     // The first use of a resource after prefetch within a short window skips
2617     // validation.
2618     return VALIDATION_NONE;
2619   }
2620
2621   if (effective_load_flags_ & (LOAD_VALIDATE_CACHE | LOAD_ASYNC_REVALIDATION))
2622     return VALIDATION_SYNCHRONOUS;
2623
2624   if (request_->method == "PUT" || request_->method == "DELETE")
2625     return VALIDATION_SYNCHRONOUS;
2626
2627   ValidationType validation_required_by_headers =
2628       response_.headers->RequiresValidation(response_.request_time,
2629                                             response_.response_time,
2630                                             cache_->clock_->Now());
2631
2632   if (validation_required_by_headers == VALIDATION_ASYNCHRONOUS) {
2633     // Asynchronous revalidation is only supported for GET and HEAD methods.
2634     if (request_->method != "GET" && request_->method != "HEAD")
2635       return VALIDATION_SYNCHRONOUS;
2636   }
2637
2638   return validation_required_by_headers;
2639 }
2640
2641 bool HttpCache::Transaction::ConditionalizeRequest() {
2642   DCHECK(response_.headers.get());
2643
2644   if (request_->method == "PUT" || request_->method == "DELETE")
2645     return false;
2646
2647   // This only makes sense for cached 200 or 206 responses.
2648   if (response_.headers->response_code() != 200 &&
2649       response_.headers->response_code() != 206) {
2650     return false;
2651   }
2652
2653   if (fail_conditionalization_for_test_)
2654     return false;
2655
2656   DCHECK(response_.headers->response_code() != 206 ||
2657          response_.headers->HasStrongValidators());
2658
2659   // Just use the first available ETag and/or Last-Modified header value.
2660   // TODO(darin): Or should we use the last?
2661
2662   std::string etag_value;
2663   if (response_.headers->GetHttpVersion() >= HttpVersion(1, 1))
2664     response_.headers->EnumerateHeader(NULL, "etag", &etag_value);
2665
2666   std::string last_modified_value;
2667   if (!vary_mismatch_) {
2668     response_.headers->EnumerateHeader(NULL, "last-modified",
2669                                        &last_modified_value);
2670   }
2671
2672   if (etag_value.empty() && last_modified_value.empty())
2673     return false;
2674
2675   if (!partial_.get()) {
2676     // Need to customize the request, so this forces us to allocate :(
2677     custom_request_.reset(new HttpRequestInfo(*request_));
2678     request_ = custom_request_.get();
2679   }
2680   DCHECK(custom_request_.get());
2681
2682   bool use_if_range = partial_.get() && !partial_->IsCurrentRangeCached() &&
2683                       !invalid_range_;
2684
2685   if (!use_if_range) {
2686     // stale-while-revalidate is not useful when we only have a partial response
2687     // cached, so don't set the header in that case.
2688     HttpResponseHeaders::FreshnessLifetimes lifetimes =
2689         response_.headers->GetFreshnessLifetimes(response_.response_time);
2690     if (lifetimes.staleness > TimeDelta()) {
2691       TimeDelta current_age = response_.headers->GetCurrentAge(
2692           response_.request_time, response_.response_time,
2693           cache_->clock_->Now());
2694
2695       custom_request_->extra_headers.SetHeader(
2696           kFreshnessHeader,
2697           base::StringPrintf("max-age=%" PRId64
2698                              ",stale-while-revalidate=%" PRId64 ",age=%" PRId64,
2699                              lifetimes.freshness.InSeconds(),
2700                              lifetimes.staleness.InSeconds(),
2701                              current_age.InSeconds()));
2702     }
2703   }
2704
2705   if (!etag_value.empty()) {
2706     if (use_if_range) {
2707       // We don't want to switch to WRITE mode if we don't have this block of a
2708       // byte-range request because we may have other parts cached.
2709       custom_request_->extra_headers.SetHeader(
2710           HttpRequestHeaders::kIfRange, etag_value);
2711     } else {
2712       custom_request_->extra_headers.SetHeader(
2713           HttpRequestHeaders::kIfNoneMatch, etag_value);
2714     }
2715     // For byte-range requests, make sure that we use only one way to validate
2716     // the request.
2717     if (partial_.get() && !partial_->IsCurrentRangeCached())
2718       return true;
2719   }
2720
2721   if (!last_modified_value.empty()) {
2722     if (use_if_range) {
2723       custom_request_->extra_headers.SetHeader(
2724           HttpRequestHeaders::kIfRange, last_modified_value);
2725     } else {
2726       custom_request_->extra_headers.SetHeader(
2727           HttpRequestHeaders::kIfModifiedSince, last_modified_value);
2728     }
2729   }
2730
2731   return true;
2732 }
2733
2734 // We just received some headers from the server. We may have asked for a range,
2735 // in which case partial_ has an object. This could be the first network request
2736 // we make to fulfill the original request, or we may be already reading (from
2737 // the net and / or the cache). If we are not expecting a certain response, we
2738 // just bypass the cache for this request (but again, maybe we are reading), and
2739 // delete partial_ (so we are not able to "fix" the headers that we return to
2740 // the user). This results in either a weird response for the caller (we don't
2741 // expect it after all), or maybe a range that was not exactly what it was asked
2742 // for.
2743 //
2744 // If the server is simply telling us that the resource has changed, we delete
2745 // the cached entry and restart the request as the caller intended (by returning
2746 // false from this method). However, we may not be able to do that at any point,
2747 // for instance if we already returned the headers to the user.
2748 //
2749 // WARNING: Whenever this code returns false, it has to make sure that the next
2750 // time it is called it will return true so that we don't keep retrying the
2751 // request.
2752 bool HttpCache::Transaction::ValidatePartialResponse() {
2753   const HttpResponseHeaders* headers = new_response_->headers.get();
2754   int response_code = headers->response_code();
2755   bool partial_response = (response_code == 206);
2756   handling_206_ = false;
2757
2758   if (!entry_ || request_->method != "GET")
2759     return true;
2760
2761   if (invalid_range_) {
2762     // We gave up trying to match this request with the stored data. If the
2763     // server is ok with the request, delete the entry, otherwise just ignore
2764     // this request
2765     DCHECK(!reading_);
2766     if (partial_response || response_code == 200) {
2767       DoomPartialEntry(true);
2768       mode_ = NONE;
2769     } else {
2770       if (response_code == 304)
2771         FailRangeRequest();
2772       IgnoreRangeRequest();
2773     }
2774     return true;
2775   }
2776
2777   if (!partial_.get()) {
2778     // We are not expecting 206 but we may have one.
2779     if (partial_response)
2780       IgnoreRangeRequest();
2781
2782     return true;
2783   }
2784
2785   // TODO(rvargas): Do we need to consider other results here?.
2786   bool failure = response_code == 200 || response_code == 416;
2787
2788   if (partial_->IsCurrentRangeCached()) {
2789     // We asked for "If-None-Match: " so a 206 means a new object.
2790     if (partial_response)
2791       failure = true;
2792
2793     if (response_code == 304 && partial_->ResponseHeadersOK(headers))
2794       return true;
2795   } else {
2796     // We asked for "If-Range: " so a 206 means just another range.
2797     if (partial_response) {
2798       if (partial_->ResponseHeadersOK(headers)) {
2799         handling_206_ = true;
2800         return true;
2801       } else {
2802         failure = true;
2803       }
2804     }
2805
2806     if (!reading_ && !is_sparse_ && !partial_response) {
2807       // See if we can ignore the fact that we issued a byte range request.
2808       // If the server sends 200, just store it. If it sends an error, redirect
2809       // or something else, we may store the response as long as we didn't have
2810       // anything already stored.
2811       if (response_code == 200 ||
2812           (!truncated_ && response_code != 304 && response_code != 416)) {
2813         // The server is sending something else, and we can save it.
2814         DCHECK((truncated_ && !partial_->IsLastRange()) || range_requested_);
2815         partial_.reset();
2816         truncated_ = false;
2817         return true;
2818       }
2819     }
2820
2821     // 304 is not expected here, but we'll spare the entry (unless it was
2822     // truncated).
2823     if (truncated_)
2824       failure = true;
2825   }
2826
2827   if (failure) {
2828     // We cannot truncate this entry, it has to be deleted.
2829     UpdateTransactionPattern(PATTERN_NOT_COVERED);
2830     mode_ = NONE;
2831     if (is_sparse_ || truncated_) {
2832       // There was something cached to start with, either sparsed data (206), or
2833       // a truncated 200, which means that we probably modified the request,
2834       // adding a byte range or modifying the range requested by the caller.
2835       if (!reading_ && !partial_->IsLastRange()) {
2836         // We have not returned anything to the caller yet so it should be safe
2837         // to issue another network request, this time without us messing up the
2838         // headers.
2839         ResetPartialState(true);
2840         return false;
2841       }
2842       LOG(WARNING) << "Failed to revalidate partial entry";
2843     }
2844     DoomPartialEntry(true);
2845     return true;
2846   }
2847
2848   IgnoreRangeRequest();
2849   return true;
2850 }
2851
2852 void HttpCache::Transaction::IgnoreRangeRequest() {
2853   // We have a problem. We may or may not be reading already (in which case we
2854   // returned the headers), but we'll just pretend that this request is not
2855   // using the cache and see what happens. Most likely this is the first
2856   // response from the server (it's not changing its mind midway, right?).
2857   UpdateTransactionPattern(PATTERN_NOT_COVERED);
2858   if (mode_ & WRITE)
2859     DoneWritingToEntry(mode_ != WRITE);
2860   else if (mode_ & READ && entry_)
2861     cache_->DoneReadingFromEntry(entry_, this);
2862
2863   partial_.reset(NULL);
2864   entry_ = NULL;
2865   mode_ = NONE;
2866 }
2867
2868 void HttpCache::Transaction::FixHeadersForHead() {
2869   if (response_.headers->response_code() == 206) {
2870     response_.headers->RemoveHeader("Content-Range");
2871     response_.headers->ReplaceStatusLine("HTTP/1.1 200 OK");
2872   }
2873 }
2874
2875 void HttpCache::Transaction::TriggerAsyncValidation() {
2876   DCHECK(!request_->upload_data_stream);
2877   BoundNetLog async_revalidation_net_log(
2878       BoundNetLog::Make(net_log_.net_log(), NetLog::SOURCE_ASYNC_REVALIDATION));
2879   net_log_.AddEvent(
2880       NetLog::TYPE_HTTP_CACHE_VALIDATE_RESOURCE_ASYNC,
2881       async_revalidation_net_log.source().ToEventParametersCallback());
2882   async_revalidation_net_log.BeginEvent(
2883       NetLog::TYPE_ASYNC_REVALIDATION,
2884       base::Bind(
2885           &NetLogAsyncRevalidationInfoCallback, net_log_.source(), request_));
2886   base::MessageLoop::current()->PostTask(
2887       FROM_HERE,
2888       base::Bind(&HttpCache::PerformAsyncValidation,
2889                  cache_,  // cache_ is a weak pointer.
2890                  *request_,
2891                  async_revalidation_net_log));
2892 }
2893
2894 void HttpCache::Transaction::FailRangeRequest() {
2895   response_ = *new_response_;
2896   partial_->FixResponseHeaders(response_.headers.get(), false);
2897 }
2898
2899 int HttpCache::Transaction::SetupEntryForRead() {
2900   if (network_trans_)
2901     ResetNetworkTransaction();
2902   if (partial_.get()) {
2903     if (truncated_ || is_sparse_ || !invalid_range_) {
2904       // We are going to return the saved response headers to the caller, so
2905       // we may need to adjust them first.
2906       next_state_ = STATE_PARTIAL_HEADERS_RECEIVED;
2907       return OK;
2908     } else {
2909       partial_.reset();
2910     }
2911   }
2912   cache_->ConvertWriterToReader(entry_);
2913   mode_ = READ;
2914
2915   if (request_->method == "HEAD")
2916     FixHeadersForHead();
2917
2918   if (entry_->disk_entry->GetDataSize(kMetadataIndex))
2919     next_state_ = STATE_CACHE_READ_METADATA;
2920   return OK;
2921 }
2922
2923
2924 int HttpCache::Transaction::ReadFromNetwork(IOBuffer* data, int data_len) {
2925   read_buf_ = data;
2926   io_buf_len_ = data_len;
2927   next_state_ = STATE_NETWORK_READ;
2928   return DoLoop(OK);
2929 }
2930
2931 int HttpCache::Transaction::ReadFromEntry(IOBuffer* data, int data_len) {
2932   if (request_->method == "HEAD")
2933     return 0;
2934
2935   read_buf_ = data;
2936   io_buf_len_ = data_len;
2937   next_state_ = STATE_CACHE_READ_DATA;
2938   return DoLoop(OK);
2939 }
2940
2941 int HttpCache::Transaction::WriteToEntry(int index, int offset,
2942                                          IOBuffer* data, int data_len,
2943                                          const CompletionCallback& callback) {
2944   if (!entry_)
2945     return data_len;
2946
2947   int rv = 0;
2948   if (!partial_.get() || !data_len) {
2949     rv = entry_->disk_entry->WriteData(index, offset, data, data_len, callback,
2950                                        true);
2951   } else {
2952     rv = partial_->CacheWrite(entry_->disk_entry, data, data_len, callback);
2953   }
2954   return rv;
2955 }
2956
2957 int HttpCache::Transaction::WriteResponseInfoToEntry(bool truncated) {
2958   next_state_ = STATE_CACHE_WRITE_RESPONSE_COMPLETE;
2959   if (!entry_)
2960     return OK;
2961
2962   // Do not cache no-store content.  Do not cache content with cert errors
2963   // either.  This is to prevent not reporting net errors when loading a
2964   // resource from the cache.  When we load a page over HTTPS with a cert error
2965   // we show an SSL blocking page.  If the user clicks proceed we reload the
2966   // resource ignoring the errors.  The loaded resource is then cached.  If that
2967   // resource is subsequently loaded from the cache, no net error is reported
2968   // (even though the cert status contains the actual errors) and no SSL
2969   // blocking page is shown.  An alternative would be to reverse-map the cert
2970   // status to a net error and replay the net error.
2971   if ((response_.headers->HasHeaderValue("cache-control", "no-store")) ||
2972       net::IsCertStatusError(response_.ssl_info.cert_status)) {
2973     DoneWritingToEntry(false);
2974     if (net_log_.IsLogging())
2975       net_log_.EndEvent(NetLog::TYPE_HTTP_CACHE_WRITE_INFO);
2976     return OK;
2977   }
2978
2979   // cert_cache() will be null if the CertCacheTrial field trial is disabled.
2980   if (cache_->cert_cache() && response_.ssl_info.is_valid())
2981     WriteCertChain();
2982
2983   if (truncated)
2984     DCHECK_EQ(200, response_.headers->response_code());
2985
2986   // When writing headers, we normally only write the non-transient headers.
2987   bool skip_transient_headers = true;
2988   scoped_refptr<PickledIOBuffer> data(new PickledIOBuffer());
2989   response_.Persist(data->pickle(), skip_transient_headers, truncated);
2990   data->Done();
2991
2992   io_buf_len_ = data->pickle()->size();
2993   return entry_->disk_entry->WriteData(kResponseInfoIndex, 0, data.get(),
2994                                        io_buf_len_, io_callback_, true);
2995 }
2996
2997 int HttpCache::Transaction::AppendResponseDataToEntry(
2998     IOBuffer* data, int data_len, const CompletionCallback& callback) {
2999   if (!entry_ || !data_len)
3000     return data_len;
3001
3002   int current_size = entry_->disk_entry->GetDataSize(kResponseContentIndex);
3003   return WriteToEntry(kResponseContentIndex, current_size, data, data_len,
3004                       callback);
3005 }
3006
3007 void HttpCache::Transaction::DoneWritingToEntry(bool success) {
3008   if (!entry_)
3009     return;
3010
3011   RecordHistograms();
3012
3013   cache_->DoneWritingToEntry(entry_, success);
3014   entry_ = NULL;
3015   mode_ = NONE;  // switch to 'pass through' mode
3016 }
3017
3018 int HttpCache::Transaction::OnCacheReadError(int result, bool restart) {
3019   DLOG(ERROR) << "ReadData failed: " << result;
3020   const int result_for_histogram = std::max(0, -result);
3021   if (restart) {
3022     UMA_HISTOGRAM_SPARSE_SLOWLY("HttpCache.ReadErrorRestartable",
3023                                 result_for_histogram);
3024   } else {
3025     UMA_HISTOGRAM_SPARSE_SLOWLY("HttpCache.ReadErrorNonRestartable",
3026                                 result_for_histogram);
3027   }
3028
3029   // Avoid using this entry in the future.
3030   if (cache_.get())
3031     cache_->DoomActiveEntry(cache_key_);
3032
3033   if (restart) {
3034     DCHECK(!reading_);
3035     DCHECK(!network_trans_.get());
3036     cache_->DoneWithEntry(entry_, this, false);
3037     entry_ = NULL;
3038     is_sparse_ = false;
3039     partial_.reset();
3040     next_state_ = STATE_GET_BACKEND;
3041     return OK;
3042   }
3043
3044   return ERR_CACHE_READ_FAILURE;
3045 }
3046
3047 void HttpCache::Transaction::OnAddToEntryTimeout(base::TimeTicks start_time) {
3048   if (entry_lock_waiting_since_ != start_time)
3049     return;
3050
3051   DCHECK_EQ(next_state_, STATE_ADD_TO_ENTRY_COMPLETE);
3052
3053   if (!cache_)
3054     return;
3055
3056   cache_->RemovePendingTransaction(this);
3057   OnIOComplete(ERR_CACHE_LOCK_TIMEOUT);
3058 }
3059
3060 void HttpCache::Transaction::DoomPartialEntry(bool delete_object) {
3061   DVLOG(2) << "DoomPartialEntry";
3062   int rv = cache_->DoomEntry(cache_key_, NULL);
3063   DCHECK_EQ(OK, rv);
3064   cache_->DoneWithEntry(entry_, this, false);
3065   entry_ = NULL;
3066   is_sparse_ = false;
3067   truncated_ = false;
3068   if (delete_object)
3069     partial_.reset(NULL);
3070 }
3071
3072 int HttpCache::Transaction::DoPartialNetworkReadCompleted(int result) {
3073   partial_->OnNetworkReadCompleted(result);
3074
3075   if (result == 0) {
3076     // We need to move on to the next range.
3077     ResetNetworkTransaction();
3078     next_state_ = STATE_START_PARTIAL_CACHE_VALIDATION;
3079   }
3080   return result;
3081 }
3082
3083 int HttpCache::Transaction::DoPartialCacheReadCompleted(int result) {
3084   partial_->OnCacheReadCompleted(result);
3085
3086   if (result == 0 && mode_ == READ_WRITE) {
3087     // We need to move on to the next range.
3088     next_state_ = STATE_START_PARTIAL_CACHE_VALIDATION;
3089   } else if (result < 0) {
3090     return OnCacheReadError(result, false);
3091   }
3092   return result;
3093 }
3094
3095 int HttpCache::Transaction::DoRestartPartialRequest() {
3096   // The stored data cannot be used. Get rid of it and restart this request.
3097   net_log_.AddEvent(NetLog::TYPE_HTTP_CACHE_RESTART_PARTIAL_REQUEST);
3098
3099   // WRITE + Doom + STATE_INIT_ENTRY == STATE_CREATE_ENTRY (without an attempt
3100   // to Doom the entry again).
3101   mode_ = WRITE;
3102   ResetPartialState(!range_requested_);
3103   next_state_ = STATE_CREATE_ENTRY;
3104   return OK;
3105 }
3106
3107 void HttpCache::Transaction::ResetPartialState(bool delete_object) {
3108   partial_->RestoreHeaders(&custom_request_->extra_headers);
3109   DoomPartialEntry(delete_object);
3110
3111   if (!delete_object) {
3112     // The simplest way to re-initialize partial_ is to create a new object.
3113     partial_.reset(new PartialData());
3114     if (partial_->Init(request_->extra_headers))
3115       partial_->SetHeaders(custom_request_->extra_headers);
3116     else
3117       partial_.reset();
3118   }
3119 }
3120
3121 void HttpCache::Transaction::ResetNetworkTransaction() {
3122   DCHECK(!old_network_trans_load_timing_);
3123   DCHECK(network_trans_);
3124   LoadTimingInfo load_timing;
3125   if (network_trans_->GetLoadTimingInfo(&load_timing))
3126     old_network_trans_load_timing_.reset(new LoadTimingInfo(load_timing));
3127   total_received_bytes_ += network_trans_->GetTotalReceivedBytes();
3128   network_trans_.reset();
3129 }
3130
3131 // Histogram data from the end of 2010 show the following distribution of
3132 // response headers:
3133 //
3134 //   Content-Length............... 87%
3135 //   Date......................... 98%
3136 //   Last-Modified................ 49%
3137 //   Etag......................... 19%
3138 //   Accept-Ranges: bytes......... 25%
3139 //   Accept-Ranges: none.......... 0.4%
3140 //   Strong Validator............. 50%
3141 //   Strong Validator + ranges.... 24%
3142 //   Strong Validator + CL........ 49%
3143 //
3144 bool HttpCache::Transaction::CanResume(bool has_data) {
3145   // Double check that there is something worth keeping.
3146   if (has_data && !entry_->disk_entry->GetDataSize(kResponseContentIndex))
3147     return false;
3148
3149   if (request_->method != "GET")
3150     return false;
3151
3152   // Note that if this is a 206, content-length was already fixed after calling
3153   // PartialData::ResponseHeadersOK().
3154   if (response_.headers->GetContentLength() <= 0 ||
3155       response_.headers->HasHeaderValue("Accept-Ranges", "none") ||
3156       !response_.headers->HasStrongValidators()) {
3157     return false;
3158   }
3159
3160   return true;
3161 }
3162
3163 void HttpCache::Transaction::UpdateTransactionPattern(
3164     TransactionPattern new_transaction_pattern) {
3165   if (transaction_pattern_ == PATTERN_NOT_COVERED)
3166     return;
3167   DCHECK(transaction_pattern_ == PATTERN_UNDEFINED ||
3168          new_transaction_pattern == PATTERN_NOT_COVERED);
3169   transaction_pattern_ = new_transaction_pattern;
3170 }
3171
3172 void HttpCache::Transaction::RecordHistograms() {
3173   DCHECK_NE(PATTERN_UNDEFINED, transaction_pattern_);
3174   if (!cache_.get() || !cache_->GetCurrentBackend() ||
3175       cache_->GetCurrentBackend()->GetCacheType() != DISK_CACHE ||
3176       cache_->mode() != NORMAL || request_->method != "GET") {
3177     return;
3178   }
3179   UMA_HISTOGRAM_ENUMERATION(
3180       "HttpCache.Pattern", transaction_pattern_, PATTERN_MAX);
3181   if (transaction_pattern_ == PATTERN_NOT_COVERED)
3182     return;
3183   DCHECK(!range_requested_);
3184   DCHECK(!first_cache_access_since_.is_null());
3185
3186   TimeDelta total_time = base::TimeTicks::Now() - first_cache_access_since_;
3187
3188   UMA_HISTOGRAM_TIMES("HttpCache.AccessToDone", total_time);
3189
3190   bool did_send_request = !send_request_since_.is_null();
3191   DCHECK(
3192       (did_send_request &&
3193        (transaction_pattern_ == PATTERN_ENTRY_NOT_CACHED ||
3194         transaction_pattern_ == PATTERN_ENTRY_VALIDATED ||
3195         transaction_pattern_ == PATTERN_ENTRY_UPDATED ||
3196         transaction_pattern_ == PATTERN_ENTRY_CANT_CONDITIONALIZE)) ||
3197       (!did_send_request && transaction_pattern_ == PATTERN_ENTRY_USED));
3198
3199   if (!did_send_request) {
3200     DCHECK(transaction_pattern_ == PATTERN_ENTRY_USED);
3201     UMA_HISTOGRAM_TIMES("HttpCache.AccessToDone.Used", total_time);
3202     return;
3203   }
3204
3205   TimeDelta before_send_time = send_request_since_ - first_cache_access_since_;
3206   int64 before_send_percent = (total_time.ToInternalValue() == 0) ?
3207       0 : before_send_time * 100 / total_time;
3208   DCHECK_GE(before_send_percent, 0);
3209   DCHECK_LE(before_send_percent, 100);
3210   base::HistogramBase::Sample before_send_sample =
3211       static_cast<base::HistogramBase::Sample>(before_send_percent);
3212
3213   UMA_HISTOGRAM_TIMES("HttpCache.AccessToDone.SentRequest", total_time);
3214   UMA_HISTOGRAM_TIMES("HttpCache.BeforeSend", before_send_time);
3215   UMA_HISTOGRAM_PERCENTAGE("HttpCache.PercentBeforeSend", before_send_sample);
3216
3217   // TODO(gavinp): Remove or minimize these histograms, particularly the ones
3218   // below this comment after we have received initial data.
3219   switch (transaction_pattern_) {
3220     case PATTERN_ENTRY_CANT_CONDITIONALIZE: {
3221       UMA_HISTOGRAM_TIMES("HttpCache.BeforeSend.CantConditionalize",
3222                           before_send_time);
3223       UMA_HISTOGRAM_PERCENTAGE("HttpCache.PercentBeforeSend.CantConditionalize",
3224                                before_send_sample);
3225       break;
3226     }
3227     case PATTERN_ENTRY_NOT_CACHED: {
3228       UMA_HISTOGRAM_TIMES("HttpCache.BeforeSend.NotCached", before_send_time);
3229       UMA_HISTOGRAM_PERCENTAGE("HttpCache.PercentBeforeSend.NotCached",
3230                                before_send_sample);
3231       break;
3232     }
3233     case PATTERN_ENTRY_VALIDATED: {
3234       UMA_HISTOGRAM_TIMES("HttpCache.BeforeSend.Validated", before_send_time);
3235       UMA_HISTOGRAM_PERCENTAGE("HttpCache.PercentBeforeSend.Validated",
3236                                before_send_sample);
3237       break;
3238     }
3239     case PATTERN_ENTRY_UPDATED: {
3240       UMA_HISTOGRAM_TIMES("HttpCache.BeforeSend.Updated", before_send_time);
3241       UMA_HISTOGRAM_PERCENTAGE("HttpCache.PercentBeforeSend.Updated",
3242                                before_send_sample);
3243       break;
3244     }
3245     default:
3246       NOTREACHED();
3247   }
3248 }
3249
3250 void HttpCache::Transaction::OnIOComplete(int result) {
3251   // TODO(vadimt): Remove ScopedTracker below once crbug.com/422516 is fixed.
3252   tracked_objects::ScopedTracker tracking_profile(
3253       FROM_HERE_WITH_EXPLICIT_FUNCTION("422516 Transaction::OnIOComplete"));
3254
3255   DoLoop(result);
3256 }
3257
3258 }  // namespace net