Serve offline page for online URL on disconnected or bad networks

chrome/browser/android/offline_pages/offline_page_request_job.cc

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "chrome/browser/android/offline_pages/offline_page_request_job.h"
+
+#include <string>
+
+#include "base/bind.h"
+#include "base/files/file_path.h"
+#include "base/logging.h"
+#include "base/metrics/histogram_macros.h"
+#include "base/strings/string_tokenizer.h"
+#include "base/strings/string_util.h"
+#include "base/threading/thread_task_runner_handle.h"
+#include "chrome/browser/android/offline_pages/offline_page_model_factory.h"
+#include "chrome/browser/android/offline_pages/offline_page_tab_helper.h"
+#include "chrome/browser/android/offline_pages/offline_page_utils.h"
+#include "chrome/browser/browser_process.h"
+#include "chrome/browser/profiles/profile.h"
+#include "chrome/browser/profiles/profile_manager.h"
+#include "components/offline_pages/offline_page_model.h"
+#include "components/previews/previews_experiments.h"
+#include "content/public/browser/browser_thread.h"
+#include "content/public/browser/resource_request_info.h"
+#include "content/public/browser/web_contents.h"
+#include "content/public/common/resource_type.h"
+#include "net/base/network_change_notifier.h"
+#include "net/http/http_request_headers.h"
+#include "net/nqe/network_quality_estimator.h"
+#include "net/url_request/url_request.h"
+#include "net/url_request/url_request_context.h"
+
+namespace offline_pages {
+
+const char kLoadingOfflinePageHeader[] = "X-chromium-offline";
+const char kLoadingOfflinePageReason[] = "reason=";
+const char kLoadingOfflinePageDueToNetError[] = "error";
+
+namespace {
+
+enum class NetworkState {
+  // No network connection.
+  DISCONNECTED_NETWORK,
+  // Prohibitively slow means that the NetworkQualityEstimator reported a
+  // connection slow enough to warrant showing an offline page if available.
+  PROHIBITIVELY_SLOW_NETWORK,
+  // Network error received due to bad network, i.e. connected to a hotspot or
+  // proxy that does not have a working network.
+  FLAKY_NETWORK,
+  // Network is in working condition.
+  CONNECTED_NETWORK,
+  // Force to load the offline page if it is available, though network is in
+  // working condition.
+  FORCE_OFFLINE_ON_CONNECTED_NETWORK
+};
+
+// This enum is used to tell all possible outcomes of handling network requests
+// that might serve offline contents.
+enum class RequestResult {
+  OFFLINE_PAGE_SERVED,
+  NO_TAB_ID,
+  NO_WEB_CONTENTS,
+  PAGE_NOT_FRESH,
+  OFFLINE_PAGE_NOT_FOUND
+};
+
+int kUserDataKey;  // Only address is used.
+
+// Contains the info to handle offline page request.
+struct OfflinePageRequestInfo : public base::SupportsUserData::Data {
+  OfflinePageRequestInfo() : use_default(false) {}
+  ~OfflinePageRequestInfo() override {}
+
+  static OfflinePageRequestInfo* GetFromRequest(net::URLRequest* request) {
+    return static_cast<OfflinePageRequestInfo*>(
+        request->GetUserData(&kUserDataKey));
+  }
+
+  // True if the next time this request is started, the request should be
+  // serviced from the default handler.
+  bool use_default;
+};
+
+class DefaultDelegate : public OfflinePageRequestJob::Delegate {
+ public:
+  DefaultDelegate() {}
+
+  content::ResourceRequestInfo::WebContentsGetter
+  GetWebContentsGetter(net::URLRequest* request) const override {
+    const content::ResourceRequestInfo* info =
+        content::ResourceRequestInfo::ForRequest(request);
+    return info ? info->GetWebContentsGetterForRequest()
+                : content::ResourceRequestInfo::WebContentsGetter();
+  }
+
+  OfflinePageRequestJob::Delegate::TabIdGetter GetTabIdGetter() const override {
+    return base::Bind(&DefaultDelegate::GetTabId);
+  }
+
+ private:
+  static bool GetTabId(content::WebContents* web_contents, int* tab_id) {
+    return OfflinePageUtils::GetTabId(web_contents, tab_id);
+  }
+
+  DISALLOW_COPY_AND_ASSIGN(DefaultDelegate);
+};
+
+// Returns true if custom offline header is present.
+// |reason| may be set with the reason to trigger the offline page loading.
+bool ParseOfflineHeader(net::URLRequest* request, std::string* reason) {
+  std::string value;
+  if (!request->extra_request_headers().GetHeader(kLoadingOfflinePageHeader,
+                                                  &value)) {
+    return false;
+  }
+
+  // Currently we only support reason field.
+  base::StringTokenizer tokenizer(value, ", ");
+  while (tokenizer.GetNext()) {
+    if (base::StartsWith(tokenizer.token(),
+                         kLoadingOfflinePageReason,
+                         base::CompareCase::INSENSITIVE_ASCII)) {
+      *reason = tokenizer.token().substr(
+          arraysize(kLoadingOfflinePageReason) - 1);
+      break;
+    }
+  }
+  return true;
+}
+
+bool IsNetworkProhibitivelySlow(net::URLRequest* request) {
+  // NetworkQualityEstimator only works when it is enabled.
+  if (!previews::IsOfflinePreviewsEnabled())
+    return false;
+
+  if (!request->context())
+    return false;
+
+  net::NetworkQualityEstimator* network_quality_estimator =
+      request->context()->network_quality_estimator();
+  if (network_quality_estimator)
+    return false;
+
+  net::EffectiveConnectionType effective_connection_type =
+      network_quality_estimator->GetEffectiveConnectionType();
+  return effective_connection_type >= net::EFFECTIVE_CONNECTION_TYPE_OFFLINE &&
+         effective_connection_type <= net::EFFECTIVE_CONNECTION_TYPE_SLOW_2G;
+}
+
+NetworkState GetNetworkState(net::URLRequest* request) {
+  DCHECK_CURRENTLY_ON(content::BrowserThread::IO);
+
+  std::string reason;
+  bool has_offline_header = ParseOfflineHeader(request, &reason);
+  if (has_offline_header &&
+      base::EqualsCaseInsensitiveASCII(reason,
+                                       kLoadingOfflinePageDueToNetError)) {
+    return NetworkState::FLAKY_NETWORK;
+  }
+
+  if (net::NetworkChangeNotifier::IsOffline())
+    return NetworkState::DISCONNECTED_NETWORK;
+
+  if (IsNetworkProhibitivelySlow(request))
+    return NetworkState::PROHIBITIVELY_SLOW_NETWORK;
+
+  return has_offline_header ? NetworkState::FORCE_OFFLINE_ON_CONNECTED_NETWORK
+                            : NetworkState::CONNECTED_NETWORK;
+}
+
+AggregatedRequestResult RequestResultToAggregatedRequestResult(
+    RequestResult request_result, NetworkState network_state) {
+  if (request_result == RequestResult::NO_TAB_ID)
+    return AggregatedRequestResult::NO_TAB_ID;
+
+  if (request_result == RequestResult::NO_WEB_CONTENTS)
+    return AggregatedRequestResult::NO_WEB_CONTENTS;
+
+  if (request_result == RequestResult::PAGE_NOT_FRESH) {
+    DCHECK_EQ(NetworkState::PROHIBITIVELY_SLOW_NETWORK, network_state);
+    return
+        AggregatedRequestResult::PAGE_NOT_FRESH_ON_PROHIBITIVELY_SLOW_NETWORK;
+  }
+
+  if (request_result == RequestResult::OFFLINE_PAGE_NOT_FOUND) {
+    switch (network_state) {
+      case NetworkState::DISCONNECTED_NETWORK:
+        return AggregatedRequestResult::PAGE_NOT_FOUND_ON_DISCONNECTED_NETWORK;
+      case NetworkState::PROHIBITIVELY_SLOW_NETWORK:
+        return AggregatedRequestResult::
+            PAGE_NOT_FOUND_ON_PROHIBITIVELY_SLOW_NETWORK;
+      case NetworkState::FLAKY_NETWORK:
+        return AggregatedRequestResult::PAGE_NOT_FOUND_ON_FLAKY_NETWORK;
+      case NetworkState::FORCE_OFFLINE_ON_CONNECTED_NETWORK:
+        return AggregatedRequestResult::PAGE_NOT_FOUND_ON_CONNECTED_NETWORK;
+      default:
+        NOTREACHED();
+    }
+  }
+
+  DCHECK_EQ(RequestResult::OFFLINE_PAGE_SERVED, request_result);
+  DCHECK_NE(NetworkState::CONNECTED_NETWORK, network_state);
+  switch (network_state) {
+    case NetworkState::DISCONNECTED_NETWORK:
+      return AggregatedRequestResult::SHOW_OFFLINE_ON_DISCONNECTED_NETWORK;
+    case NetworkState::PROHIBITIVELY_SLOW_NETWORK:
+      return AggregatedRequestResult::
+          SHOW_OFFLINE_ON_PROHIBITIVELY_SLOW_NETWORK;
+    case NetworkState::FLAKY_NETWORK:
+      return AggregatedRequestResult::SHOW_OFFLINE_ON_FLAKY_NETWORK;
+    case NetworkState::FORCE_OFFLINE_ON_CONNECTED_NETWORK:
+      return AggregatedRequestResult::SHOW_OFFLINE_ON_CONNECTED_NETWORK;
+    default:
+      NOTREACHED();
+   }
+
+   return AggregatedRequestResult::AGGREGATED_REQUEST_RESULT_MAX;
+}
+
+void ReportRequestResult(
+    RequestResult request_result, NetworkState network_state) {
+  OfflinePageRequestJob::ReportAggregatedRequestResult(
+      RequestResultToAggregatedRequestResult(request_result, network_state));
+}
+
+void NotifyOfflineFilePathOnIO(base::WeakPtr<OfflinePageRequestJob> job,
+                               const base::FilePath& offline_file_path) {
+  DCHECK_CURRENTLY_ON(content::BrowserThread::IO);
+
+  if (!job)
+    return;
+  job->OnOfflineFilePathAvailable(offline_file_path);
+}
+
+// Notifies OfflinePageRequestJob about the offline file path. Note that the
+// file path may be empty if not found or on error.
+void NotifyOfflineFilePathOnUI(base::WeakPtr<OfflinePageRequestJob> job,
+                               const base::FilePath& offline_file_path) {
+  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
+
+  // Delegates to IO thread since OfflinePageRequestJob should only be accessed
+  // from IO thread.
+  content::BrowserThread::PostTask(
+      content::BrowserThread::IO,
+      FROM_HERE,
+      base::Bind(&NotifyOfflineFilePathOnIO, job, offline_file_path));
+}
+
+// Finds the offline file path based on the select page result and network
+// state.
+RequestResult GetOfflineFilePath(
+    NetworkState network_state,
+    base::WeakPtr<OfflinePageRequestJob> job,
+    content::ResourceRequestInfo::WebContentsGetter web_contents_getter,
+    const OfflinePageItem* offline_page,
+    base::FilePath* offline_file_path) {
+  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
+
+  if (!offline_page)
+    return RequestResult::OFFLINE_PAGE_NOT_FOUND;
+
+  // |web_contents_getter| is passed from IO thread. We neeed to check if
+  // web contents is still valid.
+  content::WebContents* web_contents = web_contents_getter.Run();
+  if (!web_contents)
+    return RequestResult::NO_WEB_CONTENTS;
+
+  // If the page is being loaded on a slow network, only use the offline page
+  // if it was created within the past day.
+  // TODO(romax): Make the constant be policy driven.
+  if (network_state == NetworkState::PROHIBITIVELY_SLOW_NETWORK &&
+      base::Time::Now() - offline_page->creation_time >
+          base::TimeDelta::FromDays(1)) {
+    return RequestResult::PAGE_NOT_FRESH;
+  }
+
+  // Since offline page will be loaded, it should be marked as accessed.
+  OfflinePageModel* offline_page_model =
+      OfflinePageModelFactory::GetForBrowserContext(
+          web_contents->GetBrowserContext());
+  DCHECK(offline_page_model);
+  offline_page_model->MarkPageAccessed(offline_page->offline_id);
+
+  // Save an cached copy of OfflinePageItem such that Tab code can get
+  // the loaded offline page immediately.
+  OfflinePageTabHelper* tab_helper =
+      OfflinePageTabHelper::FromWebContents(web_contents);
+  DCHECK(tab_helper);
+  tab_helper->SetOfflinePage(*offline_page);
+
+  *offline_file_path = offline_page->file_path;
+  return RequestResult::OFFLINE_PAGE_SERVED;
+}
+
+// Handles the result of finding an offline page.
+void SelectPageForOnlineURLDone(
+    NetworkState network_state,
+    base::WeakPtr<OfflinePageRequestJob> job,
+    content::ResourceRequestInfo::WebContentsGetter web_contents_getter,
+    const OfflinePageItem* offline_page) {
+  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
+
+  base::FilePath offline_file_path;
+  RequestResult request_result = GetOfflineFilePath(
+      network_state, job, web_contents_getter, offline_page,
+      &offline_file_path);
+
+  ReportRequestResult(request_result, network_state);
+
+  // NotifyOfflineFilePathOnUI should always be called regardless the failure
+  // result and empty file path such that OfflinePageRequestJob will be notified
+  // on failure.
+  NotifyOfflineFilePathOnUI(job, offline_file_path);
+}
+
+void FailedToSelectOfflinePage(base::WeakPtr<OfflinePageRequestJob> job) {
+  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
+
+  // Proceed with empty file path in order to notify the OfflinePageRequestJob
+  // about the failure.
+  base::FilePath empty_file_path;
+  NotifyOfflineFilePathOnUI(job, empty_file_path);
+}
+
+// Tries to find the offline page to serve for |online_url|.
+void SelectOfflinePage(
+    const GURL& online_url,
+    NetworkState network_state,
+    void* profile_id,
+    content::ResourceRequestInfo::WebContentsGetter web_contents_getter,
+    OfflinePageRequestJob::Delegate::TabIdGetter tab_id_getter,
+    base::WeakPtr<OfflinePageRequestJob> job) {
+  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
+
+  // |profile_id| needs to be checked with ProfileManager::IsValidProfile
+  // before using it.
+  if (!g_browser_process->profile_manager()->IsValidProfile(profile_id)) {
+    FailedToSelectOfflinePage(job);
+    return;
+  }
+  Profile* profile = reinterpret_cast<Profile*>(profile_id);
+
+  content::WebContents* web_contents = web_contents_getter.Run();
+  if (!web_contents){
+    ReportRequestResult(RequestResult::NO_WEB_CONTENTS, network_state);
+    FailedToSelectOfflinePage(job);
+    return;
+  }
+  int tab_id;
+  if (!tab_id_getter.Run(web_contents, &tab_id)) {
+    ReportRequestResult(RequestResult::NO_TAB_ID, network_state);
+    FailedToSelectOfflinePage(job);
+    return;
+  }
+
+  OfflinePageUtils::SelectPageForOnlineURL(
+      profile,
+      online_url,
+      tab_id,
+      base::Bind(&SelectPageForOnlineURLDone,
+                 network_state,
+                 job,
+                 web_contents_getter));
+}
+
+}  // namespace
+
+// static
+void OfflinePageRequestJob::ReportAggregatedRequestResult(
+    AggregatedRequestResult result) {
+  UMA_HISTOGRAM_ENUMERATION("OfflinePages.AggregatedRequestResult",
+      static_cast<int>(result),
+      static_cast<int>(AggregatedRequestResult::AGGREGATED_REQUEST_RESULT_MAX));
+}
+
+// static
+OfflinePageRequestJob* OfflinePageRequestJob::Create(
+    void* profile_id,
+    net::URLRequest* request,
+    net::NetworkDelegate* network_delegate) {
+  const content::ResourceRequestInfo* resource_request_info =
+      content::ResourceRequestInfo::ForRequest(request);
+  if (!resource_request_info)
+    return nullptr;
+
+  // Ignore the requests not for the main resource.
+  if (resource_request_info->GetResourceType() !=
+      content::RESOURCE_TYPE_MAIN_FRAME) {
+    return nullptr;
+  }
+
+  // Ignore non-http/https requests.
+  if (!request->url().SchemeIsHTTPOrHTTPS())
+    return nullptr;
+
+  // Ignore requests other than GET.
+  if (request->method() != "GET")
+    return nullptr;
+
+  OfflinePageRequestInfo* info =
+      OfflinePageRequestInfo::GetFromRequest(request);
+  if (info) {
+    // Fall back to default which is set when an offline page cannot be served,
+    // either page not found or online version desired.
+    if (info->use_default)
+      return nullptr;
+  } else {
+    request->SetUserData(&kUserDataKey, new OfflinePageRequestInfo());
+  }
+
+  return new OfflinePageRequestJob(profile_id, request, network_delegate);
+}
+
+OfflinePageRequestJob::OfflinePageRequestJob(
+    void* profile_id,
+    net::URLRequest* request,
+    net::NetworkDelegate* network_delegate)
+    : net::URLRequestFileJob(
+          request,
+          network_delegate,
+          base::FilePath(),
+          content::BrowserThread::GetBlockingPool()->
+              GetTaskRunnerWithShutdownBehavior(
+                  base::SequencedWorkerPool::SKIP_ON_SHUTDOWN)),
+      profile_id_(profile_id),
+      delegate_(new DefaultDelegate()),
+      weak_ptr_factory_(this) {
+}
+
+OfflinePageRequestJob::~OfflinePageRequestJob() {
+}
+
+void OfflinePageRequestJob::Start() {
+  base::ThreadTaskRunnerHandle::Get()->PostTask(
+      FROM_HERE, base::Bind(&OfflinePageRequestJob::StartAsync,
+                            weak_ptr_factory_.GetWeakPtr()));
+}
+
+void OfflinePageRequestJob::StartAsync() {
+  NetworkState network_state = GetNetworkState(request());
+  if (network_state == NetworkState::CONNECTED_NETWORK) {
+    FallbackToDefault();
+    return;
+  }
+
+  content::BrowserThread::PostTask(
+      content::BrowserThread::UI,
+      FROM_HERE,
+      base::Bind(&SelectOfflinePage,
+                 request()->url(),
+                 network_state,
+                 profile_id_,
+                 delegate_->GetWebContentsGetter(request()),
+                 delegate_->GetTabIdGetter(),
+                 weak_ptr_factory_.GetWeakPtr()));
+}
+
+void OfflinePageRequestJob::Kill() {
+  net::URLRequestJob::Kill();
+  weak_ptr_factory_.InvalidateWeakPtrs();
+}
+
+void OfflinePageRequestJob::FallbackToDefault() {
+  OfflinePageRequestInfo* info =
+      OfflinePageRequestInfo::GetFromRequest(request());
+  DCHECK(info);
+  info->use_default = true;
+
+  URLRequestJob::NotifyRestartRequired();
+}
+
+void OfflinePageRequestJob::OnOfflineFilePathAvailable(
+    const base::FilePath& offline_file_path) {
+  // If offline file path is empty, it means that offline page cannot be found
+  // and we want to restart the job to fall back to the default handling.
+  if (offline_file_path.empty()) {
+    FallbackToDefault();
+    return;
+  }
+
+  // Sets the file path and lets URLRequestFileJob start to read from the file.
+  file_path_ = offline_file_path;
+  URLRequestFileJob::Start();
+}
+
+void OfflinePageRequestJob::SetDelegateForTesting(
+    std::unique_ptr<Delegate> delegate) {
+  delegate_ = std::move(delegate);
+}
+
+}  // namespace offline_pages