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// Copyright 2022 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifdef UNSAFE_BUFFERS_BUILD
// TODO(crbug.com/341324165): Fix and remove.
#pragma allow_unsafe_buffers
#endif
#include "content/browser/preloading/prerenderer_impl.h"
#include <algorithm>
#include <vector>
#include "base/feature_list.h"
#include "base/strings/stringprintf.h"
#include "content/browser/preloading/prefetch/no_vary_search_helper.h"
#include "content/browser/preloading/prefetch/prefetch_document_manager.h"
#include "content/browser/preloading/preloading.h"
#include "content/browser/preloading/preloading_attempt_impl.h"
#include "content/browser/preloading/preloading_data_impl.h"
#include "content/browser/preloading/preloading_trigger_type_impl.h"
#include "content/browser/preloading/prerender/prerender_attributes.h"
#include "content/browser/preloading/prerender/prerender_features.h"
#include "content/browser/preloading/prerender/prerender_final_status.h"
#include "content/browser/preloading/prerender/prerender_host_registry.h"
#include "content/browser/preloading/prerender/prerender_metrics.h"
#include "content/browser/preloading/prerender/prerender_navigation_utils.h"
#include "content/browser/preloading/prerender/prerender_new_tab_handle.h"
#include "content/browser/renderer_host/render_frame_host_delegate.h"
#include "content/public/browser/preloading_trigger_type.h"
#include "content/public/browser/web_contents.h"
#include "third_party/blink/public/common/features.h"
namespace content {
struct PrerendererImpl::PrerenderInfo {
blink::mojom::SpeculationInjectionType injection_type;
blink::mojom::SpeculationEagerness eagerness;
bool is_target_blank;
FrameTreeNodeId prerender_host_id;
GURL url;
PrerenderInfo() = default;
explicit PrerenderInfo(
const blink::mojom::SpeculationCandidatePtr& candidate);
static bool PrerenderInfoComparator(const PrerenderInfo& p1,
const PrerenderInfo& p2);
bool operator<(const PrerenderInfo& p) const {
return PrerenderInfoComparator(*this, p);
}
bool operator==(const PrerenderInfo& p) const {
return !PrerenderInfoComparator(*this, p) &&
!PrerenderInfoComparator(p, *this);
}
};
bool PrerendererImpl::PrerenderInfo::PrerenderInfoComparator(
const PrerenderInfo& p1,
const PrerenderInfo& p2) {
if (p1.url != p2.url) {
return p1.url < p2.url;
}
return p1.is_target_blank < p2.is_target_blank;
}
// `prerender_host_id` is not provided by `SpeculationCandidatePtr`, so
// FrameTreeNodeId() is assigned instead. The value should be updated once it is
// available.
PrerendererImpl::PrerenderInfo::PrerenderInfo(
const blink::mojom::SpeculationCandidatePtr& candidate)
: injection_type(candidate->injection_type),
eagerness(candidate->eagerness),
is_target_blank(candidate->target_browsing_context_name_hint ==
blink::mojom::SpeculationTargetHint::kBlank),
url(candidate->url) {}
PrerendererImpl::PrerendererImpl(RenderFrameHost& render_frame_host)
: WebContentsObserver(WebContents::FromRenderFrameHost(&render_frame_host)),
render_frame_host_(render_frame_host) {
DCHECK_CURRENTLY_ON(BrowserThread::UI);
auto& rfhi = static_cast<RenderFrameHostImpl&>(render_frame_host);
registry_ = rfhi.delegate()->GetPrerenderHostRegistry()->GetWeakPtr();
if (registry_) {
observation_.Observe(registry_.get());
}
ResetReceivedPrerendersCountForMetrics();
if (base::FeatureList::IsEnabled(
blink::features::kLCPTimingPredictorPrerender2)) {
blocked_ = true;
}
}
PrerendererImpl::~PrerendererImpl() {
DCHECK_CURRENTLY_ON(BrowserThread::UI);
CancelStartedPrerenders();
RecordReceivedPrerendersCountToMetrics();
ResetReceivedPrerendersCountForMetrics();
}
void PrerendererImpl::PrimaryPageChanged(Page& page) {
// Listen to the change of the primary page. Since only the primary page can
// trigger speculationrules, the change of the primary page indicates that the
// trigger associated with this host is destroyed, so the browser should
// cancel the prerenders that are initiated by it.
// We cannot do it in the destructor only, because DocumentService can be
// deleted asynchronously, but we want to make sure to cancel prerendering
// before the next primary page swaps in so that the next page can trigger a
// new prerender without hitting the max number of running prerenders.
DCHECK_CURRENTLY_ON(BrowserThread::UI);
CancelStartedPrerenders();
RecordReceivedPrerendersCountToMetrics();
ResetReceivedPrerendersCountForMetrics();
}
// TODO(isaboori) Part of the logic in |ProcessCandidatesForPrerender| method is
// about making preloading decisions and could be moved to PreloadingDecider
// class.
void PrerendererImpl::ProcessCandidatesForPrerender(
const std::vector<blink::mojom::SpeculationCandidatePtr>& candidates) {
if (!registry_)
return;
// Extract only the candidates which apply to prerender, and sort them by URL
// so we can efficiently compare them to `started_prerenders_`.
std::vector<std::pair<size_t, blink::mojom::SpeculationCandidatePtr>>
prerender_candidates;
for (const auto& candidate : candidates) {
if (candidate->action == blink::mojom::SpeculationAction::kPrerender) {
prerender_candidates.emplace_back(prerender_candidates.size(),
candidate.Clone());
}
}
std::ranges::stable_sort(
prerender_candidates, std::less<>(),
[](const auto& p) { return PrerenderInfo(p.second); });
std::vector<std::pair<size_t, blink::mojom::SpeculationCandidatePtr>>
candidates_to_start;
// Collects the host ids corresponding to the URLs that are removed from the
// speculation rules. These hosts are cancelled later.
std::vector<FrameTreeNodeId> removed_prerender_rules;
// Compare the sorted candidate and started prerender lists to one another.
// Since they are sorted, we process the lexicographically earlier of the two
// PrerenderInfos pointed at by the iterators, and compare the range of
// entries in each that match that PrerenderInfo.
//
// PrerenderInfos which are present in the prerender list but not the
// candidate list can no longer proceed and are cancelled.
//
// PrerenderInfos which are present in the candidate list but not the
// prerender list could be started and are gathered in `candidates_to_start`.
auto candidate_it = prerender_candidates.begin();
auto started_it = started_prerenders_.begin();
while (candidate_it != prerender_candidates.end() ||
started_it != started_prerenders_.end()) {
// Select the lesser of the two PrerenderInfos to diff.
PrerenderInfo prerender_info;
if (started_it == started_prerenders_.end()) {
prerender_info = PrerenderInfo(candidate_it->second);
} else if (candidate_it == prerender_candidates.end()) {
prerender_info = *started_it;
} else {
prerender_info =
std::min(PrerenderInfo(candidate_it->second), *started_it);
}
// Select the ranges from both that match the PrerenderInfo in question.
auto equal_prerender_end = std::ranges::find_if(
started_it, started_prerenders_.end(),
[&](const auto& started) { return started != prerender_info; });
base::span<PrerenderInfo> matching_prerenders(started_it,
equal_prerender_end);
auto equal_candidate_end = std::ranges::find_if(
candidate_it, prerender_candidates.end(), [&](const auto& candidate) {
return PrerenderInfo(candidate.second) != prerender_info;
});
base::span<std::pair<size_t, blink::mojom::SpeculationCandidatePtr>>
matching_candidates(candidate_it, equal_candidate_end);
// Decide what started prerenders to cancel.
for (PrerenderInfo& prerender : matching_prerenders) {
if (prerender.prerender_host_id.is_null()) {
continue;
}
// TODO(jbroman): This doesn't currently care about other aspects, like
// the referrer. This doesn't presently matter, but in the future we might
// want to cancel if there are candidates which match by PrerenderInfo but
// none of which permit this prerender.
if (matching_candidates.empty()) {
removed_prerender_rules.push_back(prerender.prerender_host_id);
}
}
// Decide what new candidates to start.
// For now, start one candidate per target hint for a URL only if there are
// no matching prerenders. We could be cleverer in the future.
if (matching_prerenders.empty()) {
CHECK(!matching_candidates.empty());
std::set<PrerenderInfo> processed_prerender_info;
for (auto& matching_candidate : matching_candidates) {
PrerenderInfo matching_candidate_prerender_info =
PrerenderInfo(matching_candidate.second);
if (processed_prerender_info
.insert(std::move(matching_candidate_prerender_info))
.second) {
candidates_to_start.push_back(std::move(matching_candidate));
}
}
}
// Advance the iterators past all matching entries.
candidate_it = equal_candidate_end;
started_it = equal_prerender_end;
}
std::vector<GURL> urls;
for (auto ftn_id : removed_prerender_rules) {
if (PrerenderHost* prerender_host =
registry_->FindNonReservedHostById(ftn_id)) {
urls.push_back(prerender_host->GetInitialUrl());
}
}
std::set<FrameTreeNodeId> canceled_prerender_rules_set =
registry_->CancelHosts(
removed_prerender_rules,
PrerenderCancellationReason(
PrerenderFinalStatus::kSpeculationRuleRemoved));
if (base::FeatureList::IsEnabled(
features::kPrerender2FallbackPrefetchSpecRules)) {
WebContents* web_contents =
WebContents::FromRenderFrameHost(&render_frame_host_.get());
auto* prefetch_document_manager =
content::PrefetchDocumentManager::GetOrCreateForCurrentDocument(
web_contents->GetPrimaryMainFrame());
for (const auto& url : urls) {
prefetch_document_manager->ResetPrefetchAheadOfPrerenderIfExist(url);
}
}
// Canceled prerenders by kSpeculationRuleRemoved should have already been
// removed from `started_prerenders_` via `OnCancel`.
CHECK(std::find_if(started_prerenders_.begin(), started_prerenders_.end(),
[&](const PrerenderInfo& x) {
return base::Contains(canceled_prerender_rules_set,
x.prerender_host_id);
}) == started_prerenders_.end());
// Actually start the candidates in their original order once the diffing is
// done.
std::ranges::sort(candidates_to_start, std::less<>(),
[](const auto& p) { return p.first; });
for (const auto& [_, candidate] : candidates_to_start) {
PreloadingTriggerType trigger_type =
PreloadingTriggerTypeFromSpeculationInjectionType(
candidate->injection_type);
// Immediate candidates are enacted by the same predictor that creates them.
PreloadingPredictor enacting_predictor =
GetPredictorForPreloadingTriggerType(trigger_type);
MaybePrerender(candidate, enacting_predictor, PreloadingConfidence{100});
}
}
void PrerendererImpl::OnLCPPredicted() {
blocked_ = false;
for (auto& [candidate, enacting_predictor, confidence] :
std::move(blocked_candidates_)) {
MaybePrerender(candidate, enacting_predictor, confidence);
}
}
bool PrerendererImpl::MaybePrerender(
const blink::mojom::SpeculationCandidatePtr& candidate,
const PreloadingPredictor& enacting_predictor,
PreloadingConfidence confidence) {
CHECK_EQ(candidate->action, blink::mojom::SpeculationAction::kPrerender);
// Prerendering is not allowed in fenced frames.
if (render_frame_host_->IsNestedWithinFencedFrame()) {
render_frame_host_->AddMessageToConsole(
blink::mojom::ConsoleMessageLevel::kWarning,
"The SpeculationRules API does not support prerendering in fenced "
"frames.");
return false;
}
WebContents* web_contents =
WebContents::FromRenderFrameHost(&render_frame_host_.get());
static_cast<PreloadingDataImpl*>(
PreloadingData::GetOrCreateForWebContents(web_contents))
->SetHasSpeculationRulesPrerender();
if (blocked_) {
blocked_candidates_.emplace_back(candidate->Clone(), enacting_predictor,
confidence);
return false;
}
// Prerendering frames should not trigger any prerender request.
CHECK(!render_frame_host_->IsInLifecycleState(
RenderFrameHost::LifecycleState::kPrerendering));
if (!registry_)
return false;
auto& rfhi = static_cast<RenderFrameHostImpl&>(render_frame_host_.get());
// `prerender_host_id` is not available yet.
PrerenderInfo prerender_info(candidate);
auto [begin, end] = std::ranges::equal_range(
started_prerenders_.begin(), started_prerenders_.end(), prerender_info,
PrerenderInfo::PrerenderInfoComparator);
// cannot currently start a second prerender with the same URL and target_hint
if (begin != end) {
return false;
}
GetContentClient()->browser()->LogWebFeatureForCurrentPage(
&rfhi, blink::mojom::WebFeature::kSpeculationRulesPrerender);
IncrementReceivedPrerendersCountForMetrics(
PreloadingTriggerTypeFromSpeculationInjectionType(
candidate->injection_type),
candidate->eagerness);
// TODO(crbug.com/40168192): Remove it after supporting cross-site
// prerender.
if (!prerender_navigation_utils::IsSameSite(candidate->url,
rfhi.GetLastCommittedOrigin())) {
rfhi.AddMessageToConsole(
blink::mojom::ConsoleMessageLevel::kWarning,
base::StringPrintf(
"The SpeculationRules API does not support cross-site prerender "
"yet (initiator origin: %s, prerender origin: %s). "
"https://crbug.com/1176054 tracks cross-site support.",
rfhi.GetLastCommittedOrigin().Serialize().c_str(),
url::Origin::Create(candidate->url).Serialize().c_str()));
}
std::optional<net::HttpNoVarySearchData> no_vary_search_hint;
if (candidate->no_vary_search_hint) {
no_vary_search_hint = no_vary_search::ParseHttpNoVarySearchDataFromMojom(
candidate->no_vary_search_hint);
}
const bool should_warm_up_compositor = [&] {
switch (candidate->eagerness) {
case blink::mojom::SpeculationEagerness::kImmediate:
return base::FeatureList::IsEnabled(
features::kPrerender2WarmUpCompositorForImmediate);
case blink::mojom::SpeculationEagerness::kModerate:
case blink::mojom::SpeculationEagerness::kConservative:
return base::FeatureList::IsEnabled(
features::kPrerender2WarmUpCompositorForNonImmediate);
}
}();
PrerenderAttributes attributes(
candidate->url,
PreloadingTriggerTypeFromSpeculationInjectionType(
candidate->injection_type),
/*embedder_histogram_suffix=*/"",
SpeculationRulesParams(candidate->target_browsing_context_name_hint,
candidate->eagerness,
SpeculationRulesTags(candidate->tags)),
Referrer{*candidate->referrer}, no_vary_search_hint, &rfhi,
web_contents->GetWeakPtr(), ui::PAGE_TRANSITION_LINK,
should_warm_up_compositor,
/*should_prepare_paint_tree=*/false,
/*url_match_predicate=*/{},
/*prerender_navigation_handle_callback=*/{},
PreloadPipelineInfoImpl::Create(
/*planned_max_preloading_type=*/PreloadingType::kPrerender));
PreloadingTriggerType trigger_type =
PreloadingTriggerTypeFromSpeculationInjectionType(
candidate->injection_type);
PreloadingPredictor creating_predictor =
GetPredictorForPreloadingTriggerType(trigger_type);
prerender_info.prerender_host_id = [&] {
// TODO(crbug.com/40235424): Handle the case where multiple speculation
// rules have the same URL but its `target_browsing_context_name_hint` is
// different. In the current implementation, only the first rule is
// triggered.
switch (candidate->target_browsing_context_name_hint) {
case blink::mojom::SpeculationTargetHint::kBlank: {
if (base::FeatureList::IsEnabled(
blink::features::kPrerender2InNewTab)) {
GetContentClient()->browser()->LogWebFeatureForCurrentPage(
&rfhi,
blink::mojom::WebFeature::kSpeculationRulesTargetHintBlank);
// For the prerender-in-new-tab, PreloadingAttempt will be managed by
// a prerender WebContents to be created later.
return registry_->CreateAndStartHostForNewTab(
attributes, creating_predictor, enacting_predictor, confidence);
}
// Handle the rule as kNoHint if the prerender-in-new-tab is not
// enabled.
[[fallthrough]];
}
case blink::mojom::SpeculationTargetHint::kNoHint:
case blink::mojom::SpeculationTargetHint::kSelf: {
if (base::FeatureList::IsEnabled(
features::kPrerender2FallbackPrefetchSpecRules)) {
auto* prefetch_document_manager =
content::PrefetchDocumentManager::GetOrCreateForCurrentDocument(
web_contents->GetPrimaryMainFrame());
prefetch_document_manager->PrefetchAheadOfPrerender(
attributes.preload_pipeline_info, candidate.Clone(),
enacting_predictor);
}
// Create new PreloadingAttempt and pass all the values corresponding to
// this prerendering attempt.
auto* preloading_data =
PreloadingDataImpl::GetOrCreateForWebContents(web_contents);
PreloadingURLMatchCallback same_url_matcher =
PreloadingData::GetSameURLMatcher(candidate->url);
auto* preloading_attempt = static_cast<PreloadingAttemptImpl*>(
preloading_data->AddPreloadingAttempt(
creating_predictor, enacting_predictor,
PreloadingType::kPrerender, std::move(same_url_matcher),
web_contents->GetPrimaryMainFrame()->GetPageUkmSourceId()));
preloading_attempt->SetSpeculationEagerness(candidate->eagerness);
return registry_->CreateAndStartHost(attributes, preloading_attempt);
}
}
}();
// An existing prerender may be canceled to start a new prerender, and
// `started_prerenders_` may be modified through this cancellation. Therefore,
// it is needed to re-calculate the right place here on `started_prerenders_`
// for new candidates.
end = std::ranges::upper_bound(started_prerenders_.begin(),
started_prerenders_.end(), prerender_info,
PrerenderInfo::PrerenderInfoComparator);
started_prerenders_.insert(end, std::move(prerender_info));
return true;
}
bool PrerendererImpl::ShouldWaitForPrerenderResult(const GURL& url) {
// This function is used to check whetehr a prerender is started to avoid
// starting prefetch in OnPointerDown, OnPointerHover or other heuristic
// methods which don't take target_hint into consideration. So unlike other
// functions in this file, this part uses `url` only instead of
// `PrerenderInfo` which consists of target_hint information.
auto [begin, end] = std::ranges::equal_range(
started_prerenders_.begin(), started_prerenders_.end(), url,
std::less<>(), &PrerenderInfo::url);
for (auto it = begin; it != end; ++it) {
if (it->prerender_host_id.is_null()) {
return false;
}
}
return begin != end;
}
void PrerendererImpl::OnCancel(FrameTreeNodeId host_frame_tree_node_id,
const PrerenderCancellationReason& reason) {
switch (reason.final_status()) {
// TODO(crbug.com/40275452): Support other final status cases.
case PrerenderFinalStatus::kTimeoutBackgrounded:
case PrerenderFinalStatus::kMaxNumOfRunningNonImmediatePrerendersExceeded:
case PrerenderFinalStatus::kSpeculationRuleRemoved: {
auto erasing_prerender_it = std::find_if(
started_prerenders_.begin(), started_prerenders_.end(),
[&](const PrerenderInfo& prerender_info) {
return prerender_info.prerender_host_id == host_frame_tree_node_id;
});
if (erasing_prerender_it != started_prerenders_.end()) {
auto url = erasing_prerender_it->url;
started_prerenders_.erase(erasing_prerender_it);
// Notify PreloadingDecider.
prerender_cancellation_callback_.Run(url);
}
break;
}
default:
break;
}
}
void PrerendererImpl::OnRegistryDestroyed() {
observation_.Reset();
}
void PrerendererImpl::SetPrerenderCancellationCallback(
PrerenderCancellationCallback callback) {
prerender_cancellation_callback_ = std::move(callback);
}
void PrerendererImpl::CancelStartedPrerenders() {
if (registry_) {
std::vector<FrameTreeNodeId> started_prerender_ids;
for (auto& prerender_info : started_prerenders_) {
started_prerender_ids.push_back(prerender_info.prerender_host_id);
}
registry_->CancelHosts(
started_prerender_ids,
PrerenderCancellationReason(PrerenderFinalStatus::kTriggerDestroyed));
}
started_prerenders_.clear();
}
void PrerendererImpl::CancelStartedPrerendersForTesting() {
CancelStartedPrerenders();
}
void PrerendererImpl::ResetReceivedPrerendersCountForMetrics() {
for (auto trigger_type :
{PreloadingTriggerType::kSpeculationRule,
PreloadingTriggerType::kSpeculationRuleFromIsolatedWorld}) {
received_prerenders_by_eagerness_[trigger_type].fill({});
}
}
void PrerendererImpl::IncrementReceivedPrerendersCountForMetrics(
PreloadingTriggerType trigger_type,
blink::mojom::SpeculationEagerness eagerness) {
received_prerenders_by_eagerness_[trigger_type]
[static_cast<size_t>(eagerness)]++;
}
void PrerendererImpl::RecordReceivedPrerendersCountToMetrics() {
for (auto trigger_type :
{PreloadingTriggerType::kSpeculationRule,
PreloadingTriggerType::kSpeculationRuleFromIsolatedWorld}) {
int conservative =
received_prerenders_by_eagerness_[trigger_type][static_cast<size_t>(
blink::mojom::SpeculationEagerness::kConservative)];
int moderate =
received_prerenders_by_eagerness_[trigger_type][static_cast<size_t>(
blink::mojom::SpeculationEagerness::kModerate)];
int immediate =
received_prerenders_by_eagerness_[trigger_type][static_cast<size_t>(
blink::mojom::SpeculationEagerness::kImmediate)];
// This will record zero when
// 1) there are no started prerenders eventually. Also noted that if
// there is no rule set, PreloadingDecider won't be created (which means
// PrerenderImpl also won't be created), so it cannot be reached this
// code path at the first place.
// 2) when the corresponding RFH lives but is inactive (such as the case in
// BFCache) after once PrimaryPageChanged was called and the recorded
// number was reset (As long as PreloadingDecider (which has the same
// lifetime with a document) that owns this (PrerenderImpl) lives, this
// function will be called per PrimaryPageChanged).
//
// Avoids recording these cases uniformly.
if (conservative + moderate + immediate == 0) {
continue;
}
// Record per single eagerness.
RecordReceivedPrerendersPerPrimaryPageChangedCount(
conservative, trigger_type, "Conservative");
RecordReceivedPrerendersPerPrimaryPageChangedCount(moderate, trigger_type,
"Moderate");
RecordReceivedPrerendersPerPrimaryPageChangedCount(immediate, trigger_type,
"Immediate");
}
}
} // namespace content
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