4 files changed, 1105 insertions, 0 deletions
diff --git a/uriloader/prefetch/moz.build b/uriloader/prefetch/moz.build
new file mode 100644
index 0000000000..8185124da0
--- /dev/null
+++ b/uriloader/prefetch/moz.build
@@ -0,0 +1,26 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+with Files("**"):
+    BUG_COMPONENT = ("Core", "Networking: Cache")
+
+XPIDL_SOURCES += [
+    "nsIPrefetchService.idl",
+]
+
+XPIDL_MODULE = "prefetch"
+
+UNIFIED_SOURCES += [
+    "nsPrefetchService.cpp",
+]
+
+include("/ipc/chromium/chromium-config.mozbuild")
+
+FINAL_LIBRARY = "xul"
+
+LOCAL_INCLUDES += [
+    "/dom/base",
+]
diff --git a/uriloader/prefetch/nsIPrefetchService.idl b/uriloader/prefetch/nsIPrefetchService.idl
new file mode 100644
index 0000000000..160d051116
--- /dev/null
+++ b/uriloader/prefetch/nsIPrefetchService.idl
@@ -0,0 +1,54 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsISupports.idl"
+#include "nsIContentPolicy.idl"
+
+interface nsIURI;
+interface nsISimpleEnumerator;
+interface nsIReferrerInfo;
+
+webidl Node;
+
+[scriptable, uuid(422a1807-4e7f-463d-b8d7-ca2ceb9b5d53)]
+interface nsIPrefetchService : nsISupports
+{
+    /**
+     * Enqueue a request to prefetch the specified URI.
+     *
+     * @param aURI the URI of the document to prefetch
+     * @param aReferrerInfo the referrerInfo of the request
+     * @param aSource the DOM node (such as a <link> tag) that requested this
+     *        fetch, or null if the prefetch was not requested by a DOM node.
+     * @param aExplicit the link element has an explicit prefetch link type
+     */
+    void prefetchURI(in nsIURI aURI,
+                     in nsIReferrerInfo aReferrerInfo,
+                     in Node aSource,
+                     in boolean aExplicit);
+
+    /**
+     * Start a preload of the specified URI.
+     *
+     * @param aURI the URI of the document to preload
+     * @param aReferrerInfo the referrerInfo of the request
+     * @param aSource the DOM node (such as a <link> tag) that requested this
+     *        fetch, or null if the prefetch was not requested by a DOM node.
+     * @param aPolicyType content policy to be used for this load.
+     */
+    void preloadURI(in nsIURI aURI,
+                    in nsIReferrerInfo aReferrerInfo,
+                    in Node aSource,
+                    in nsContentPolicyType aPolicyType);
+
+    /**
+     * Find out if there are any prefetches running or queued
+     */
+    boolean hasMoreElements();
+
+    /**
+     * Cancel prefetch or preload for a Node.
+     */
+    void cancelPrefetchPreloadURI(in nsIURI aURI, in Node aSource);
+};
diff --git a/uriloader/prefetch/nsPrefetchService.cpp b/uriloader/prefetch/nsPrefetchService.cpp
new file mode 100644
index 0000000000..635e4e34a9
--- /dev/null
+++ b/uriloader/prefetch/nsPrefetchService.cpp
@@ -0,0 +1,895 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsPrefetchService.h"
+
+#include "mozilla/AsyncEventDispatcher.h"
+#include "mozilla/Attributes.h"
+#include "mozilla/CORSMode.h"
+#include "mozilla/Components.h"
+#include "mozilla/dom/ClientInfo.h"
+#include "mozilla/dom/HTMLLinkElement.h"
+#include "mozilla/dom/ServiceWorkerDescriptor.h"
+#include "mozilla/Preferences.h"
+#include "ReferrerInfo.h"
+
+#include "nsIObserverService.h"
+#include "nsIWebProgress.h"
+#include "nsICacheInfoChannel.h"
+#include "nsIHttpChannel.h"
+#include "nsIURL.h"
+#include "nsISupportsPriority.h"
+#include "nsNetUtil.h"
+#include "nsString.h"
+#include "nsReadableUtils.h"
+#include "nsStreamUtils.h"
+#include "prtime.h"
+#include "mozilla/Logging.h"
+#include "nsIAsyncVerifyRedirectCallback.h"
+#include "nsINode.h"
+#include "mozilla/dom/Document.h"
+#include "nsContentUtils.h"
+#include "mozilla/AsyncEventDispatcher.h"
+#include "nsICachingChannel.h"
+#include "nsHttp.h"
+
+using namespace mozilla;
+using namespace mozilla::dom;
+
+//
+// To enable logging (see mozilla/Logging.h for full details):
+//
+//    set MOZ_LOG=nsPrefetch:5
+//    set MOZ_LOG_FILE=prefetch.log
+//
+// this enables LogLevel::Debug level information and places all output in
+// the file prefetch.log
+//
+static LazyLogModule gPrefetchLog("nsPrefetch");
+
+#undef LOG
+#define LOG(args) MOZ_LOG(gPrefetchLog, mozilla::LogLevel::Debug, args)
+
+#undef LOG_ENABLED
+#define LOG_ENABLED() MOZ_LOG_TEST(gPrefetchLog, mozilla::LogLevel::Debug)
+
+#define PREFETCH_PREF "network.prefetch-next"
+#define PARALLELISM_PREF "network.prefetch-next.parallelism"
+#define AGGRESSIVE_PREF "network.prefetch-next.aggressive"
+
+//-----------------------------------------------------------------------------
+// nsPrefetchNode <public>
+//-----------------------------------------------------------------------------
+
+nsPrefetchNode::nsPrefetchNode(nsPrefetchService* aService, nsIURI* aURI,
+                               nsIReferrerInfo* aReferrerInfo, nsINode* aSource,
+                               nsContentPolicyType aPolicyType, bool aPreload)
+    : mURI(aURI),
+      mReferrerInfo(aReferrerInfo),
+      mPolicyType(aPolicyType),
+      mPreload(aPreload),
+      mService(aService),
+      mChannel(nullptr),
+      mBytesRead(0),
+      mShouldFireLoadEvent(false) {
+  nsWeakPtr source = do_GetWeakReference(aSource);
+  mSources.AppendElement(source);
+}
+
+nsresult nsPrefetchNode::OpenChannel() {
+  if (mSources.IsEmpty()) {
+    // Don't attempt to prefetch if we don't have a source node
+    // (which should never happen).
+    return NS_ERROR_FAILURE;
+  }
+  nsCOMPtr<nsINode> source;
+  while (!mSources.IsEmpty() &&
+         !(source = do_QueryReferent(mSources.ElementAt(0)))) {
+    // If source is null remove it.
+    // (which should never happen).
+    mSources.RemoveElementAt(0);
+  }
+
+  if (!source) {
+    // Don't attempt to prefetch if we don't have a source node
+    // (which should never happen).
+
+    return NS_ERROR_FAILURE;
+  }
+  nsCOMPtr<nsILoadGroup> loadGroup = source->OwnerDoc()->GetDocumentLoadGroup();
+  CORSMode corsMode = CORS_NONE;
+  if (auto* link = dom::HTMLLinkElement::FromNode(source)) {
+    corsMode = link->GetCORSMode();
+  }
+
+  uint32_t securityFlags;
+  if (corsMode == CORS_NONE) {
+    securityFlags = nsILoadInfo::SEC_ALLOW_CROSS_ORIGIN_INHERITS_SEC_CONTEXT;
+  } else {
+    securityFlags = nsILoadInfo::SEC_REQUIRE_CORS_INHERITS_SEC_CONTEXT;
+    if (corsMode == CORS_USE_CREDENTIALS) {
+      securityFlags |= nsILoadInfo::SEC_COOKIES_INCLUDE;
+    }
+  }
+  nsresult rv = NS_NewChannelInternal(
+      getter_AddRefs(mChannel), mURI, source, source->NodePrincipal(),
+      nullptr,  // aTriggeringPrincipal
+      Maybe<ClientInfo>(), Maybe<ServiceWorkerDescriptor>(), securityFlags,
+      mPolicyType, source->OwnerDoc()->CookieJarSettings(),
+      nullptr,    // aPerformanceStorage
+      loadGroup,  // aLoadGroup
+      this,       // aCallbacks
+      nsIRequest::LOAD_BACKGROUND | nsICachingChannel::LOAD_ONLY_IF_MODIFIED);
+
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  // configure HTTP specific stuff
+  nsCOMPtr<nsIHttpChannel> httpChannel = do_QueryInterface(mChannel);
+  if (httpChannel) {
+    DebugOnly<nsresult> success = httpChannel->SetReferrerInfo(mReferrerInfo);
+    MOZ_ASSERT(NS_SUCCEEDED(success));
+
+    // https://fetch.spec.whatwg.org/#http-sec-purpose
+    success =
+        httpChannel->SetRequestHeader("Sec-Purpose"_ns, "prefetch"_ns, false);
+    MOZ_ASSERT(NS_SUCCEEDED(success));
+  }
+
+  // Reduce the priority of prefetch network requests.
+  nsCOMPtr<nsISupportsPriority> priorityChannel = do_QueryInterface(mChannel);
+  if (priorityChannel) {
+    priorityChannel->AdjustPriority(nsISupportsPriority::PRIORITY_LOWEST);
+  }
+
+  rv = mChannel->AsyncOpen(this);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    // Drop the ref to the channel, because we don't want to end up with
+    // cycles through it.
+    mChannel = nullptr;
+  }
+  return rv;
+}
+
+nsresult nsPrefetchNode::CancelChannel(nsresult error) {
+  mChannel->Cancel(error);
+  mChannel = nullptr;
+
+  return NS_OK;
+}
+
+//-----------------------------------------------------------------------------
+// nsPrefetchNode::nsISupports
+//-----------------------------------------------------------------------------
+
+NS_IMPL_ISUPPORTS(nsPrefetchNode, nsIRequestObserver, nsIStreamListener,
+                  nsIInterfaceRequestor, nsIChannelEventSink,
+                  nsIRedirectResultListener)
+
+//-----------------------------------------------------------------------------
+// nsPrefetchNode::nsIStreamListener
+//-----------------------------------------------------------------------------
+
+NS_IMETHODIMP
+nsPrefetchNode::OnStartRequest(nsIRequest* aRequest) {
+  nsresult rv;
+
+  nsCOMPtr<nsIHttpChannel> httpChannel = do_QueryInterface(aRequest, &rv);
+  if (NS_FAILED(rv)) return rv;
+
+  // if the load is cross origin without CORS, or the CORS access is rejected,
+  // always fire load event to avoid leaking site information.
+  nsCOMPtr<nsILoadInfo> loadInfo = httpChannel->LoadInfo();
+  mShouldFireLoadEvent =
+      loadInfo->GetTainting() == LoadTainting::Opaque ||
+      (loadInfo->GetTainting() == LoadTainting::CORS &&
+       (NS_FAILED(httpChannel->GetStatus(&rv)) || NS_FAILED(rv)));
+
+  // no need to prefetch http error page
+  bool requestSucceeded;
+  if (NS_FAILED(httpChannel->GetRequestSucceeded(&requestSucceeded)) ||
+      !requestSucceeded) {
+    return NS_BINDING_ABORTED;
+  }
+
+  nsCOMPtr<nsICacheInfoChannel> cacheInfoChannel =
+      do_QueryInterface(aRequest, &rv);
+  if (NS_FAILED(rv)) return rv;
+
+  // no need to prefetch a document that is already in the cache
+  bool fromCache;
+  if (NS_SUCCEEDED(cacheInfoChannel->IsFromCache(&fromCache)) && fromCache) {
+    LOG(("document is already in the cache; canceling prefetch\n"));
+    // although it's canceled we still want to fire load event
+    mShouldFireLoadEvent = true;
+    return NS_BINDING_ABORTED;
+  }
+
+  //
+  // no need to prefetch a document that must be requested fresh each
+  // and every time.
+  //
+  uint32_t expTime;
+  if (NS_SUCCEEDED(cacheInfoChannel->GetCacheTokenExpirationTime(&expTime))) {
+    if (mozilla::net::NowInSeconds() >= expTime) {
+      LOG(
+          ("document cannot be reused from cache; "
+           "canceling prefetch\n"));
+      return NS_BINDING_ABORTED;
+    }
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsPrefetchNode::OnDataAvailable(nsIRequest* aRequest, nsIInputStream* aStream,
+                                uint64_t aOffset, uint32_t aCount) {
+  uint32_t bytesRead = 0;
+  aStream->ReadSegments(NS_DiscardSegment, nullptr, aCount, &bytesRead);
+  mBytesRead += bytesRead;
+  LOG(("prefetched %u bytes [offset=%" PRIu64 "]\n", bytesRead, aOffset));
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsPrefetchNode::OnStopRequest(nsIRequest* aRequest, nsresult aStatus) {
+  LOG(("done prefetching [status=%" PRIx32 "]\n",
+       static_cast<uint32_t>(aStatus)));
+
+  if (mBytesRead == 0 && aStatus == NS_OK && mChannel) {
+    // we didn't need to read (because LOAD_ONLY_IF_MODIFIED was
+    // specified), but the object should report loadedSize as if it
+    // did.
+    mChannel->GetContentLength(&mBytesRead);
+  }
+
+  mService->NotifyLoadCompleted(this);
+  mService->DispatchEvent(this, mShouldFireLoadEvent || NS_SUCCEEDED(aStatus));
+  mService->RemoveNodeAndMaybeStartNextPrefetchURI(this);
+  return NS_OK;
+}
+
+//-----------------------------------------------------------------------------
+// nsPrefetchNode::nsIInterfaceRequestor
+//-----------------------------------------------------------------------------
+
+NS_IMETHODIMP
+nsPrefetchNode::GetInterface(const nsIID& aIID, void** aResult) {
+  if (aIID.Equals(NS_GET_IID(nsIChannelEventSink))) {
+    NS_ADDREF_THIS();
+    *aResult = static_cast<nsIChannelEventSink*>(this);
+    return NS_OK;
+  }
+
+  if (aIID.Equals(NS_GET_IID(nsIRedirectResultListener))) {
+    NS_ADDREF_THIS();
+    *aResult = static_cast<nsIRedirectResultListener*>(this);
+    return NS_OK;
+  }
+
+  return NS_ERROR_NO_INTERFACE;
+}
+
+//-----------------------------------------------------------------------------
+// nsPrefetchNode::nsIChannelEventSink
+//-----------------------------------------------------------------------------
+
+NS_IMETHODIMP
+nsPrefetchNode::AsyncOnChannelRedirect(
+    nsIChannel* aOldChannel, nsIChannel* aNewChannel, uint32_t aFlags,
+    nsIAsyncVerifyRedirectCallback* callback) {
+  nsCOMPtr<nsIURI> newURI;
+  nsresult rv = aNewChannel->GetURI(getter_AddRefs(newURI));
+  if (NS_FAILED(rv)) return rv;
+
+  if (!newURI->SchemeIs("http") && !newURI->SchemeIs("https")) {
+    LOG(("rejected: URL is not of type http/https\n"));
+    return NS_ERROR_ABORT;
+  }
+
+  // HTTP request headers are not automatically forwarded to the new channel.
+  nsCOMPtr<nsIHttpChannel> httpChannel = do_QueryInterface(aNewChannel);
+  NS_ENSURE_STATE(httpChannel);
+
+  // https://fetch.spec.whatwg.org/#http-sec-purpose
+  rv = httpChannel->SetRequestHeader("Sec-Purpose"_ns, "prefetch"_ns, false);
+  MOZ_ASSERT(NS_SUCCEEDED(rv));
+
+  // Assign to mChannel after we get notification about success of the
+  // redirect in OnRedirectResult.
+  mRedirectChannel = aNewChannel;
+
+  callback->OnRedirectVerifyCallback(NS_OK);
+  return NS_OK;
+}
+
+//-----------------------------------------------------------------------------
+// nsPrefetchNode::nsIRedirectResultListener
+//-----------------------------------------------------------------------------
+
+NS_IMETHODIMP
+nsPrefetchNode::OnRedirectResult(nsresult status) {
+  if (NS_SUCCEEDED(status) && mRedirectChannel) mChannel = mRedirectChannel;
+
+  mRedirectChannel = nullptr;
+
+  return NS_OK;
+}
+
+//-----------------------------------------------------------------------------
+// nsPrefetchService <public>
+//-----------------------------------------------------------------------------
+
+nsPrefetchService::nsPrefetchService()
+    : mMaxParallelism(6),
+      mStopCount(0),
+      mHaveProcessed(false),
+      mPrefetchDisabled(true),
+      mAggressive(false) {}
+
+nsPrefetchService::~nsPrefetchService() {
+  Preferences::RemoveObserver(this, PREFETCH_PREF);
+  Preferences::RemoveObserver(this, PARALLELISM_PREF);
+  Preferences::RemoveObserver(this, AGGRESSIVE_PREF);
+  // cannot reach destructor if prefetch in progress (listener owns reference
+  // to this service)
+  EmptyPrefetchQueue();
+}
+
+nsresult nsPrefetchService::Init() {
+  nsresult rv;
+
+  // read prefs and hook up pref observer
+  mPrefetchDisabled = !Preferences::GetBool(PREFETCH_PREF, !mPrefetchDisabled);
+  Preferences::AddWeakObserver(this, PREFETCH_PREF);
+
+  mMaxParallelism = Preferences::GetInt(PARALLELISM_PREF, mMaxParallelism);
+  if (mMaxParallelism < 1) {
+    mMaxParallelism = 1;
+  }
+  Preferences::AddWeakObserver(this, PARALLELISM_PREF);
+
+  mAggressive = Preferences::GetBool(AGGRESSIVE_PREF, false);
+  Preferences::AddWeakObserver(this, AGGRESSIVE_PREF);
+
+  // Observe xpcom-shutdown event
+  nsCOMPtr<nsIObserverService> observerService =
+      mozilla::services::GetObserverService();
+  if (!observerService) return NS_ERROR_FAILURE;
+
+  rv = observerService->AddObserver(this, NS_XPCOM_SHUTDOWN_OBSERVER_ID, true);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  if (!mPrefetchDisabled) {
+    AddProgressListener();
+  }
+
+  return NS_OK;
+}
+
+void nsPrefetchService::RemoveNodeAndMaybeStartNextPrefetchURI(
+    nsPrefetchNode* aFinished) {
+  if (aFinished) {
+    mCurrentNodes.RemoveElement(aFinished);
+  }
+
+  if ((!mStopCount && mHaveProcessed) || mAggressive) {
+    ProcessNextPrefetchURI();
+  }
+}
+
+void nsPrefetchService::ProcessNextPrefetchURI() {
+  if (mCurrentNodes.Length() >= static_cast<uint32_t>(mMaxParallelism)) {
+    // We already have enough prefetches going on, so hold off
+    // for now.
+    return;
+  }
+
+  nsresult rv;
+
+  do {
+    if (mPrefetchQueue.empty()) {
+      break;
+    }
+    RefPtr<nsPrefetchNode> node = std::move(mPrefetchQueue.front());
+    mPrefetchQueue.pop_front();
+
+    if (LOG_ENABLED()) {
+      LOG(("ProcessNextPrefetchURI [%s]\n",
+           node->mURI->GetSpecOrDefault().get()));
+    }
+
+    //
+    // if opening the channel fails (e.g. security check returns an error),
+    // send an error event and then just skip to the next uri
+    //
+    rv = node->OpenChannel();
+    if (NS_SUCCEEDED(rv)) {
+      mCurrentNodes.AppendElement(node);
+    } else {
+      DispatchEvent(node, false);
+    }
+  } while (NS_FAILED(rv));
+}
+
+void nsPrefetchService::NotifyLoadRequested(nsPrefetchNode* node) {
+  nsCOMPtr<nsIObserverService> observerService =
+      mozilla::services::GetObserverService();
+  if (!observerService) return;
+
+  observerService->NotifyObservers(
+      static_cast<nsIStreamListener*>(node),
+      (node->mPreload) ? "preload-load-requested" : "prefetch-load-requested",
+      nullptr);
+}
+
+void nsPrefetchService::NotifyLoadCompleted(nsPrefetchNode* node) {
+  nsCOMPtr<nsIObserverService> observerService =
+      mozilla::services::GetObserverService();
+  if (!observerService) return;
+
+  observerService->NotifyObservers(
+      static_cast<nsIStreamListener*>(node),
+      (node->mPreload) ? "preload-load-completed" : "prefetch-load-completed",
+      nullptr);
+}
+
+void nsPrefetchService::DispatchEvent(nsPrefetchNode* node, bool aSuccess) {
+  for (uint32_t i = 0; i < node->mSources.Length(); i++) {
+    nsCOMPtr<nsINode> domNode = do_QueryReferent(node->mSources.ElementAt(i));
+    if (domNode && domNode->IsInComposedDoc()) {
+      // We don't dispatch synchronously since |node| might be in a DocGroup
+      // that we're not allowed to touch. (Our network request happens in the
+      // DocGroup of one of the mSources nodes--not necessarily this one).
+      RefPtr<AsyncEventDispatcher> dispatcher = new AsyncEventDispatcher(
+          domNode, aSuccess ? u"load"_ns : u"error"_ns, CanBubble::eNo);
+      dispatcher->RequireNodeInDocument();
+      dispatcher->PostDOMEvent();
+    }
+  }
+}
+
+//-----------------------------------------------------------------------------
+// nsPrefetchService <private>
+//-----------------------------------------------------------------------------
+
+void nsPrefetchService::AddProgressListener() {
+  // Register as an observer for the document loader
+  nsCOMPtr<nsIWebProgress> progress = components::DocLoader::Service();
+  if (progress)
+    progress->AddProgressListener(this, nsIWebProgress::NOTIFY_STATE_DOCUMENT);
+}
+
+void nsPrefetchService::RemoveProgressListener() {
+  // Register as an observer for the document loader
+  nsCOMPtr<nsIWebProgress> progress = components::DocLoader::Service();
+  if (progress) progress->RemoveProgressListener(this);
+}
+
+nsresult nsPrefetchService::EnqueueURI(nsIURI* aURI,
+                                       nsIReferrerInfo* aReferrerInfo,
+                                       nsINode* aSource,
+                                       nsPrefetchNode** aNode) {
+  RefPtr<nsPrefetchNode> node = new nsPrefetchNode(
+      this, aURI, aReferrerInfo, aSource, nsIContentPolicy::TYPE_OTHER, false);
+  mPrefetchQueue.push_back(node);
+  node.forget(aNode);
+  return NS_OK;
+}
+
+void nsPrefetchService::EmptyPrefetchQueue() {
+  while (!mPrefetchQueue.empty()) {
+    mPrefetchQueue.pop_back();
+  }
+}
+
+void nsPrefetchService::StartPrefetching() {
+  //
+  // at initialization time we might miss the first DOCUMENT START
+  // notification, so we have to be careful to avoid letting our
+  // stop count go negative.
+  //
+  if (mStopCount > 0) mStopCount--;
+
+  LOG(("StartPrefetching [stopcount=%d]\n", mStopCount));
+
+  // only start prefetching after we've received enough DOCUMENT
+  // STOP notifications.  we do this inorder to defer prefetching
+  // until after all sub-frames have finished loading.
+  if (!mStopCount) {
+    mHaveProcessed = true;
+    while (!mPrefetchQueue.empty() &&
+           mCurrentNodes.Length() < static_cast<uint32_t>(mMaxParallelism)) {
+      ProcessNextPrefetchURI();
+    }
+  }
+}
+
+void nsPrefetchService::StopPrefetching() {
+  mStopCount++;
+
+  LOG(("StopPrefetching [stopcount=%d]\n", mStopCount));
+
+  // When we start a load, we need to stop all prefetches that has been
+  // added by the old load, therefore call StopAll only at the moment we
+  // switch to a new page load (i.e. mStopCount == 1).
+  // TODO: do not stop prefetches that are relevant for the new load.
+  if (mStopCount == 1) {
+    StopAll();
+  }
+}
+
+void nsPrefetchService::StopCurrentPrefetchsPreloads(bool aPreload) {
+  for (int32_t i = mCurrentNodes.Length() - 1; i >= 0; --i) {
+    if (mCurrentNodes[i]->mPreload == aPreload) {
+      mCurrentNodes[i]->CancelChannel(NS_BINDING_ABORTED);
+      mCurrentNodes.RemoveElementAt(i);
+    }
+  }
+
+  if (!aPreload) {
+    EmptyPrefetchQueue();
+  }
+}
+
+void nsPrefetchService::StopAll() {
+  for (uint32_t i = 0; i < mCurrentNodes.Length(); ++i) {
+    mCurrentNodes[i]->CancelChannel(NS_BINDING_ABORTED);
+  }
+  mCurrentNodes.Clear();
+  EmptyPrefetchQueue();
+}
+
+nsresult nsPrefetchService::CheckURIScheme(nsIURI* aURI,
+                                           nsIReferrerInfo* aReferrerInfo) {
+  //
+  // XXX we should really be asking the protocol handler if it supports
+  // caching, so we can determine if there is any value to prefetching.
+  // for now, we'll only prefetch http and https links since we know that's
+  // the most common case.
+  //
+  if (!aURI->SchemeIs("http") && !aURI->SchemeIs("https")) {
+    LOG(("rejected: URL is not of type http/https\n"));
+    return NS_ERROR_ABORT;
+  }
+
+  //
+  // the referrer URI must be http:
+  //
+  nsCOMPtr<nsIURI> referrer = aReferrerInfo->GetOriginalReferrer();
+  if (!referrer) {
+    return NS_ERROR_ABORT;
+  }
+
+  if (!referrer->SchemeIs("http") && !referrer->SchemeIs("https")) {
+    LOG(("rejected: referrer URL is neither http nor https\n"));
+    return NS_ERROR_ABORT;
+  }
+
+  return NS_OK;
+}
+
+//-----------------------------------------------------------------------------
+// nsPrefetchService::nsISupports
+//-----------------------------------------------------------------------------
+
+NS_IMPL_ISUPPORTS(nsPrefetchService, nsIPrefetchService, nsIWebProgressListener,
+                  nsIObserver, nsISupportsWeakReference)
+
+//-----------------------------------------------------------------------------
+// nsPrefetchService::nsIPrefetchService
+//-----------------------------------------------------------------------------
+
+nsresult nsPrefetchService::Preload(nsIURI* aURI,
+                                    nsIReferrerInfo* aReferrerInfo,
+                                    nsINode* aSource,
+                                    nsContentPolicyType aPolicyType) {
+  NS_ENSURE_ARG_POINTER(aURI);
+  NS_ENSURE_ARG_POINTER(aReferrerInfo);
+  if (LOG_ENABLED()) {
+    LOG(("PreloadURI [%s]\n", aURI->GetSpecOrDefault().get()));
+  }
+
+  LOG(("rejected: preload service is deprecated\n"));
+  return NS_ERROR_ABORT;
+}
+
+nsresult nsPrefetchService::Prefetch(nsIURI* aURI,
+                                     nsIReferrerInfo* aReferrerInfo,
+                                     nsINode* aSource, bool aExplicit) {
+  NS_ENSURE_ARG_POINTER(aURI);
+  NS_ENSURE_ARG_POINTER(aReferrerInfo);
+
+  if (LOG_ENABLED()) {
+    LOG(("PrefetchURI [%s]\n", aURI->GetSpecOrDefault().get()));
+  }
+
+  if (mPrefetchDisabled) {
+    LOG(("rejected: prefetch service is disabled\n"));
+    return NS_ERROR_ABORT;
+  }
+
+  nsresult rv = CheckURIScheme(aURI, aReferrerInfo);
+  if (NS_FAILED(rv)) {
+    return rv;
+  }
+
+  // XXX we might want to either leverage nsIProtocolHandler::protocolFlags
+  // or possibly nsIRequest::loadFlags to determine if this URI should be
+  // prefetched.
+  //
+
+  // skip URLs that contain query strings, except URLs for which prefetching
+  // has been explicitly requested.
+  if (!aExplicit) {
+    nsCOMPtr<nsIURL> url(do_QueryInterface(aURI, &rv));
+    if (NS_FAILED(rv)) return rv;
+    nsAutoCString query;
+    rv = url->GetQuery(query);
+    if (NS_FAILED(rv) || !query.IsEmpty()) {
+      LOG(("rejected: URL has a query string\n"));
+      return NS_ERROR_ABORT;
+    }
+  }
+
+  //
+  // Check whether it is being prefetched.
+  //
+  for (uint32_t i = 0; i < mCurrentNodes.Length(); ++i) {
+    bool equals;
+    if (NS_SUCCEEDED(mCurrentNodes[i]->mURI->Equals(aURI, &equals)) && equals) {
+      nsWeakPtr source = do_GetWeakReference(aSource);
+      if (mCurrentNodes[i]->mSources.IndexOf(source) ==
+          mCurrentNodes[i]->mSources.NoIndex) {
+        LOG(
+            ("URL is already being prefetched, add a new reference "
+             "document\n"));
+        mCurrentNodes[i]->mSources.AppendElement(source);
+        return NS_OK;
+      } else {
+        LOG(("URL is already being prefetched by this document"));
+        return NS_ERROR_ABORT;
+      }
+    }
+  }
+
+  //
+  // Check whether it is on the prefetch queue.
+  //
+  for (std::deque<RefPtr<nsPrefetchNode>>::iterator nodeIt =
+           mPrefetchQueue.begin();
+       nodeIt != mPrefetchQueue.end(); nodeIt++) {
+    bool equals;
+    RefPtr<nsPrefetchNode> node = nodeIt->get();
+    if (NS_SUCCEEDED(node->mURI->Equals(aURI, &equals)) && equals) {
+      nsWeakPtr source = do_GetWeakReference(aSource);
+      if (node->mSources.IndexOf(source) == node->mSources.NoIndex) {
+        LOG(
+            ("URL is already being prefetched, add a new reference "
+             "document\n"));
+        node->mSources.AppendElement(do_GetWeakReference(aSource));
+        return NS_OK;
+      } else {
+        LOG(("URL is already being prefetched by this document"));
+        return NS_ERROR_ABORT;
+      }
+    }
+  }
+
+  RefPtr<nsPrefetchNode> enqueuedNode;
+  rv = EnqueueURI(aURI, aReferrerInfo, aSource, getter_AddRefs(enqueuedNode));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  NotifyLoadRequested(enqueuedNode);
+
+  // if there are no pages loading, kick off the request immediately
+  if ((!mStopCount && mHaveProcessed) || mAggressive) {
+    ProcessNextPrefetchURI();
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsPrefetchService::CancelPrefetchPreloadURI(nsIURI* aURI, nsINode* aSource) {
+  NS_ENSURE_ARG_POINTER(aURI);
+
+  if (LOG_ENABLED()) {
+    LOG(("CancelPrefetchURI [%s]\n", aURI->GetSpecOrDefault().get()));
+  }
+
+  //
+  // look in current prefetches
+  //
+  for (uint32_t i = 0; i < mCurrentNodes.Length(); ++i) {
+    bool equals;
+    if (NS_SUCCEEDED(mCurrentNodes[i]->mURI->Equals(aURI, &equals)) && equals) {
+      nsWeakPtr source = do_GetWeakReference(aSource);
+      if (mCurrentNodes[i]->mSources.IndexOf(source) !=
+          mCurrentNodes[i]->mSources.NoIndex) {
+        mCurrentNodes[i]->mSources.RemoveElement(source);
+        if (mCurrentNodes[i]->mSources.IsEmpty()) {
+          mCurrentNodes[i]->CancelChannel(NS_BINDING_ABORTED);
+          mCurrentNodes.RemoveElementAt(i);
+        }
+        return NS_OK;
+      }
+      return NS_ERROR_FAILURE;
+    }
+  }
+
+  //
+  // look into the prefetch queue
+  //
+  for (std::deque<RefPtr<nsPrefetchNode>>::iterator nodeIt =
+           mPrefetchQueue.begin();
+       nodeIt != mPrefetchQueue.end(); nodeIt++) {
+    bool equals;
+    RefPtr<nsPrefetchNode> node = nodeIt->get();
+    if (NS_SUCCEEDED(node->mURI->Equals(aURI, &equals)) && equals) {
+      nsWeakPtr source = do_GetWeakReference(aSource);
+      if (node->mSources.IndexOf(source) != node->mSources.NoIndex) {
+#ifdef DEBUG
+        int32_t inx = node->mSources.IndexOf(source);
+        nsCOMPtr<nsINode> domNode =
+            do_QueryReferent(node->mSources.ElementAt(inx));
+        MOZ_ASSERT(domNode);
+#endif
+
+        node->mSources.RemoveElement(source);
+        if (node->mSources.IsEmpty()) {
+          mPrefetchQueue.erase(nodeIt);
+        }
+        return NS_OK;
+      }
+      return NS_ERROR_FAILURE;
+    }
+  }
+
+  // not found!
+  return NS_ERROR_FAILURE;
+}
+
+NS_IMETHODIMP
+nsPrefetchService::PreloadURI(nsIURI* aURI, nsIReferrerInfo* aReferrerInfo,
+                              nsINode* aSource,
+                              nsContentPolicyType aPolicyType) {
+  return Preload(aURI, aReferrerInfo, aSource, aPolicyType);
+}
+
+NS_IMETHODIMP
+nsPrefetchService::PrefetchURI(nsIURI* aURI, nsIReferrerInfo* aReferrerInfo,
+                               nsINode* aSource, bool aExplicit) {
+  return Prefetch(aURI, aReferrerInfo, aSource, aExplicit);
+}
+
+NS_IMETHODIMP
+nsPrefetchService::HasMoreElements(bool* aHasMore) {
+  *aHasMore = (mCurrentNodes.Length() || !mPrefetchQueue.empty());
+  return NS_OK;
+}
+
+//-----------------------------------------------------------------------------
+// nsPrefetchService::nsIWebProgressListener
+//-----------------------------------------------------------------------------
+
+NS_IMETHODIMP
+nsPrefetchService::OnProgressChange(nsIWebProgress* aProgress,
+                                    nsIRequest* aRequest,
+                                    int32_t curSelfProgress,
+                                    int32_t maxSelfProgress,
+                                    int32_t curTotalProgress,
+                                    int32_t maxTotalProgress) {
+  MOZ_ASSERT_UNREACHABLE("notification excluded in AddProgressListener(...)");
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsPrefetchService::OnStateChange(nsIWebProgress* aWebProgress,
+                                 nsIRequest* aRequest,
+                                 uint32_t progressStateFlags,
+                                 nsresult aStatus) {
+  if (progressStateFlags & STATE_IS_DOCUMENT) {
+    if (progressStateFlags & STATE_STOP)
+      StartPrefetching();
+    else if (progressStateFlags & STATE_START)
+      StopPrefetching();
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsPrefetchService::OnLocationChange(nsIWebProgress* aWebProgress,
+                                    nsIRequest* aRequest, nsIURI* location,
+                                    uint32_t aFlags) {
+  MOZ_ASSERT_UNREACHABLE("notification excluded in AddProgressListener(...)");
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsPrefetchService::OnStatusChange(nsIWebProgress* aWebProgress,
+                                  nsIRequest* aRequest, nsresult aStatus,
+                                  const char16_t* aMessage) {
+  MOZ_ASSERT_UNREACHABLE("notification excluded in AddProgressListener(...)");
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsPrefetchService::OnSecurityChange(nsIWebProgress* aWebProgress,
+                                    nsIRequest* aRequest, uint32_t aState) {
+  MOZ_ASSERT_UNREACHABLE("notification excluded in AddProgressListener(...)");
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsPrefetchService::OnContentBlockingEvent(nsIWebProgress* aWebProgress,
+                                          nsIRequest* aRequest,
+                                          uint32_t aEvent) {
+  MOZ_ASSERT_UNREACHABLE("notification excluded in AddProgressListener(...)");
+  return NS_OK;
+}
+
+//-----------------------------------------------------------------------------
+// nsPrefetchService::nsIObserver
+//-----------------------------------------------------------------------------
+
+NS_IMETHODIMP
+nsPrefetchService::Observe(nsISupports* aSubject, const char* aTopic,
+                           const char16_t* aData) {
+  LOG(("nsPrefetchService::Observe [topic=%s]\n", aTopic));
+
+  if (!strcmp(aTopic, NS_XPCOM_SHUTDOWN_OBSERVER_ID)) {
+    StopAll();
+    mPrefetchDisabled = true;
+  } else if (!strcmp(aTopic, NS_PREFBRANCH_PREFCHANGE_TOPIC_ID)) {
+    const nsCString converted = NS_ConvertUTF16toUTF8(aData);
+    const char* pref = converted.get();
+    if (!strcmp(pref, PREFETCH_PREF)) {
+      if (Preferences::GetBool(PREFETCH_PREF, false)) {
+        if (mPrefetchDisabled) {
+          LOG(("enabling prefetching\n"));
+          mPrefetchDisabled = false;
+          AddProgressListener();
+        }
+      } else {
+        if (!mPrefetchDisabled) {
+          LOG(("disabling prefetching\n"));
+          StopCurrentPrefetchsPreloads(false);
+          mPrefetchDisabled = true;
+          RemoveProgressListener();
+        }
+      }
+    } else if (!strcmp(pref, PARALLELISM_PREF)) {
+      mMaxParallelism = Preferences::GetInt(PARALLELISM_PREF, mMaxParallelism);
+      if (mMaxParallelism < 1) {
+        mMaxParallelism = 1;
+      }
+      // If our parallelism has increased, go ahead and kick off enough
+      // prefetches to fill up our allowance. If we're now over our
+      // allowance, we'll just silently let some of them finish to get
+      // back below our limit.
+      while (((!mStopCount && mHaveProcessed) || mAggressive) &&
+             !mPrefetchQueue.empty() &&
+             mCurrentNodes.Length() < static_cast<uint32_t>(mMaxParallelism)) {
+        ProcessNextPrefetchURI();
+      }
+    } else if (!strcmp(pref, AGGRESSIVE_PREF)) {
+      mAggressive = Preferences::GetBool(AGGRESSIVE_PREF, false);
+      // in aggressive mode, start prefetching immediately
+      if (mAggressive) {
+        while (mStopCount && !mPrefetchQueue.empty() &&
+               mCurrentNodes.Length() <
+                   static_cast<uint32_t>(mMaxParallelism)) {
+          ProcessNextPrefetchURI();
+        }
+      }
+    }
+  }
+
+  return NS_OK;
+}
+
+// vim: ts=4 sw=2 expandtab
diff --git a/uriloader/prefetch/nsPrefetchService.h b/uriloader/prefetch/nsPrefetchService.h
new file mode 100644
index 0000000000..7b931ba52c
--- /dev/null
+++ b/uriloader/prefetch/nsPrefetchService.h
@@ -0,0 +1,130 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef nsPrefetchService_h__
+#define nsPrefetchService_h__
+
+#include "nsIObserver.h"
+#include "nsIInterfaceRequestor.h"
+#include "nsIChannelEventSink.h"
+#include "nsIPrefetchService.h"
+#include "nsIRedirectResultListener.h"
+#include "nsIWebProgressListener.h"
+#include "nsIStreamListener.h"
+#include "nsIChannel.h"
+#include "nsIURI.h"
+#include "nsWeakReference.h"
+#include "nsCOMPtr.h"
+#include "mozilla/Attributes.h"
+#include <deque>
+
+class nsPrefetchService;
+class nsPrefetchNode;
+class nsIReferrerInfo;
+
+//-----------------------------------------------------------------------------
+// nsPrefetchService
+//-----------------------------------------------------------------------------
+
+class nsPrefetchService final : public nsIPrefetchService,
+                                public nsIWebProgressListener,
+                                public nsIObserver,
+                                public nsSupportsWeakReference {
+ public:
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSIPREFETCHSERVICE
+  NS_DECL_NSIWEBPROGRESSLISTENER
+  NS_DECL_NSIOBSERVER
+
+  nsPrefetchService();
+
+  nsresult Init();
+  void RemoveNodeAndMaybeStartNextPrefetchURI(nsPrefetchNode* aFinished);
+  void ProcessNextPrefetchURI();
+
+  void NotifyLoadRequested(nsPrefetchNode* node);
+  void NotifyLoadCompleted(nsPrefetchNode* node);
+  void DispatchEvent(nsPrefetchNode* node, bool aSuccess);
+
+ private:
+  ~nsPrefetchService();
+
+  nsresult Prefetch(nsIURI* aURI, nsIReferrerInfo* aReferrerInfo,
+                    nsINode* aSource, bool aExplicit);
+
+  nsresult Preload(nsIURI* aURI, nsIReferrerInfo* aReferrerInfo,
+                   nsINode* aSource, nsContentPolicyType aPolicyType);
+
+  void AddProgressListener();
+  void RemoveProgressListener();
+  nsresult EnqueueURI(nsIURI* aURI, nsIReferrerInfo* aReferrerInfo,
+                      nsINode* aSource, nsPrefetchNode** node);
+  void EmptyPrefetchQueue();
+
+  void StartPrefetching();
+  void StopPrefetching();
+  void StopCurrentPrefetchsPreloads(bool aPreload);
+  void StopAll();
+  nsresult CheckURIScheme(nsIURI* aURI, nsIReferrerInfo* aReferrerInfo);
+
+  std::deque<RefPtr<nsPrefetchNode>> mPrefetchQueue;
+  nsTArray<RefPtr<nsPrefetchNode>> mCurrentNodes;
+  int32_t mMaxParallelism;
+  int32_t mStopCount;
+  bool mHaveProcessed;
+  bool mPrefetchDisabled;
+
+  // In usual case prefetch does not start until all normal loads are done.
+  // Aggressive mode ignores normal loads and just start prefetch ASAP.
+  // It's mainly for testing purpose and discoraged for normal use;
+  // see https://bugzilla.mozilla.org/show_bug.cgi?id=1281415 for details.
+  bool mAggressive;
+};
+
+//-----------------------------------------------------------------------------
+// nsPreFetchingNode
+//-----------------------------------------------------------------------------
+
+class nsPrefetchNode final : public nsIStreamListener,
+                             public nsIInterfaceRequestor,
+                             public nsIChannelEventSink,
+                             public nsIRedirectResultListener {
+ public:
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSIREQUESTOBSERVER
+  NS_DECL_NSISTREAMLISTENER
+  NS_DECL_NSIINTERFACEREQUESTOR
+  NS_DECL_NSICHANNELEVENTSINK
+  NS_DECL_NSIREDIRECTRESULTLISTENER
+
+  nsPrefetchNode(nsPrefetchService* aPrefetchService, nsIURI* aURI,
+                 nsIReferrerInfo* aReferrerInfo, nsINode* aSource,
+                 nsContentPolicyType aPolicyType, bool aPreload);
+
+  nsresult OpenChannel();
+  nsresult CancelChannel(nsresult error);
+
+  nsCOMPtr<nsIURI> mURI;
+  nsCOMPtr<nsIReferrerInfo> mReferrerInfo;
+  nsTArray<nsWeakPtr> mSources;
+
+  // The policy type to be used for fetching the resource.
+  nsContentPolicyType mPolicyType;
+  // nsPrefetchNode is used for prefetching and preloading resource.
+  // mPreload is true if a resource is preloaded. Preloads and
+  // prefetches are fetched in different phases (during load and
+  // after a page load), therefore we need to distinguish them.
+  bool mPreload;
+
+ private:
+  ~nsPrefetchNode() {}
+
+  RefPtr<nsPrefetchService> mService;
+  nsCOMPtr<nsIChannel> mChannel;
+  nsCOMPtr<nsIChannel> mRedirectChannel;
+  int64_t mBytesRead;
+  bool mShouldFireLoadEvent;
+};
+
+#endif  // !nsPrefetchService_h__