content/browser/preloading/prefetch/prefetch_params.cc

// 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.

#include "content/browser/preloading/prefetch/prefetch_params.h"

#include "base/command_line.h"
#include "base/metrics/field_trial_params.h"
#include "base/rand_util.h"
#include "content/browser/preloading/prefetch/prefetch_features.h"
#include "content/public/browser/prefetch_service_delegate.h"
#include "third_party/blink/public/mojom/speculation_rules/speculation_rules.mojom.h"

namespace content {

bool PrefetchContentRefactorIsEnabled() {
  return base::FeatureList::IsEnabled(features::kPrefetchUseContentRefactor);
}

GURL PrefetchProxyHost(const GURL& default_proxy_url) {
  // Command line overrides take priority.
  std::string cmd_line_value =
      base::CommandLine::ForCurrentProcess()->GetSwitchValueASCII(
          "isolated-prerender-tunnel-proxy");
  if (!cmd_line_value.empty()) {
    GURL cmd_line_url(cmd_line_value);
    if (cmd_line_url.is_valid()) {
      return cmd_line_url;
    }
    LOG(ERROR) << "--isolated-prerender-tunnel-proxy value is invalid";
  }

  GURL url(base::GetFieldTrialParamValueByFeature(
      features::kPrefetchUseContentRefactor, "proxy_host"));
  if (url.is_valid() && url.SchemeIs(url::kHttpsScheme)) {
    return url;
  }

  return default_proxy_url;
}

std::string PrefetchProxyHeaderKey() {
  std::string header = base::GetFieldTrialParamValueByFeature(
      features::kPrefetchUseContentRefactor, "proxy_header_key");
  if (!header.empty()) {
    return header;
  }
  return "chrome-tunnel";
}

std::string PrefetchProxyServerExperimentGroup() {
  return base::GetFieldTrialParamValueByFeature(
      features::kPrefetchUseContentRefactor, "server_experiment_group");
}

bool PrefetchAllowAllDomains() {
  return base::GetFieldTrialParamByFeatureAsBool(
             features::kPrefetchUseContentRefactor, "allow_all_domains",
             false) ||
         base::CommandLine::ForCurrentProcess()->HasSwitch(
             "isolated-prerender-allow-all-domains");
}

bool PrefetchAllowAllDomainsForExtendedPreloading() {
  return base::GetFieldTrialParamByFeatureAsBool(
      features::kPrefetchUseContentRefactor,
      "allow_all_domains_for_extended_preloading", true);
}

size_t PrefetchServiceMaximumNumberOfConcurrentPrefetches() {
  return base::GetFieldTrialParamByFeatureAsInt(
      features::kPrefetchUseContentRefactor, "max_concurrent_prefetches", 1);
}

absl::optional<int> PrefetchServiceMaximumNumberOfPrefetchesPerPage() {
  if (base::CommandLine::ForCurrentProcess()->HasSwitch(
          "isolated-prerender-unlimited-prefetches")) {
    return absl::nullopt;
  }

  int max = base::GetFieldTrialParamByFeatureAsInt(
      features::kPrefetchUseContentRefactor, "max_srp_prefetches", 5);
  if (max < 0) {
    return absl::nullopt;
  }
  return max;
}

bool PrefetchServiceSendDecoyRequestForIneligblePrefetch(
    bool disabled_based_on_user_settings) {
  if (base::CommandLine::ForCurrentProcess()->HasSwitch(
          "prefetch-proxy-never-send-decoy-requests-for-testing")) {
    return false;
  }
  if (base::CommandLine::ForCurrentProcess()->HasSwitch(
          "prefetch-proxy-always-send-decoy-requests-for-testing")) {
    return true;
  }

  if (base::GetFieldTrialParamByFeatureAsBool(
          features::kPrefetchUseContentRefactor,
          "disable_decoys_based_on_user_settings", true) &&
      disabled_based_on_user_settings) {
    return false;
  }

  double probability = base::GetFieldTrialParamByFeatureAsDouble(
      features::kPrefetchUseContentRefactor,
      "ineligible_decoy_request_probability", 1.0);

  // Clamp to [0.0, 1.0].
  probability = std::max(0.0, probability);
  probability = std::min(1.0, probability);

  // RandDouble returns [0.0, 1.0) so don't use <= here since that may return
  // true when the probability is supposed to be 0 (i.e.: always false).
  return base::RandDouble() < probability;
}

base::TimeDelta PrefetchTimeoutDuration() {
  return base::Milliseconds(base::GetFieldTrialParamByFeatureAsInt(
      features::kPrefetchUseContentRefactor, "prefetch_timeout_ms",
      10 * 1000 /* 10 seconds */));
}

size_t PrefetchMainframeBodyLengthLimit() {
  return 1024 * base::GetFieldTrialParamByFeatureAsInt(
                    features::kPrefetchUseContentRefactor,
                    "max_mainframe_body_length_kb", 5 * 1024);
}

bool PrefetchCloseIdleSockets() {
  return base::GetFieldTrialParamByFeatureAsBool(
      features::kPrefetchUseContentRefactor, "close_idle_sockets", true);
}

bool PrefetchStartsSpareRenderer() {
  return base::CommandLine::ForCurrentProcess()->HasSwitch(
             "isolated-prerender-start-spare-renderer") ||
         base::GetFieldTrialParamByFeatureAsBool(
             features::kPrefetchUseContentRefactor, "start_spare_renderer",
             true);
}

base::TimeDelta PrefetchContainerLifetimeInPrefetchService() {
  // A value of 0 or less, indicates that |PrefetchService| should keep the
  // prefetch forever.
  return base::Seconds(base::GetFieldTrialParamByFeatureAsInt(
      features::kPrefetchUseContentRefactor, "prefetch_container_lifetime_s",
      10 * 60 /* 10 minutes */));
}

bool PrefetchServiceHTMLOnly() {
  return base::GetFieldTrialParamByFeatureAsBool(
      features::kPrefetchUseContentRefactor, "html_only", false);
}

absl::optional<std::string> PrefetchBypassProxyForHost() {
  absl::optional<std::string> value;
  auto val_str = base::CommandLine::ForCurrentProcess()->GetSwitchValueASCII(
      "bypass-prefetch-proxy-for-host");
  if (val_str.size())
    value = std::move(val_str);
  return value;
}

base::TimeDelta PrefetchCacheableDuration() {
  return base::Seconds(base::GetFieldTrialParamByFeatureAsInt(
      features::kPrefetchUseContentRefactor, "cacheable_duration", 300));
}

bool PrefetchProbingEnabled() {
  return base::GetFieldTrialParamByFeatureAsBool(
      features::kPrefetchUseContentRefactor, "must_probe_origin", true);
}

bool PrefetchCanaryCheckEnabled() {
  return base::GetFieldTrialParamByFeatureAsBool(
      features::kPrefetchUseContentRefactor, "do_canary", true);
}

bool PrefetchTLSCanaryCheckEnabled() {
  return base::GetFieldTrialParamByFeatureAsBool(
      features::kPrefetchUseContentRefactor, "do_tls_canary", false);
}

GURL PrefetchTLSCanaryCheckURL(const GURL& default_tls_canary_check_url) {
  GURL url(base::GetFieldTrialParamValueByFeature(
      features::kPrefetchUseContentRefactor, "tls_canary_url"));
  if (url.is_valid())
    return url;

  return default_tls_canary_check_url;
}

GURL PrefetchDNSCanaryCheckURL(const GURL& default_dns_canary_check_url) {
  GURL url(base::GetFieldTrialParamValueByFeature(
      features::kPrefetchUseContentRefactor, "dns_canary_url"));
  if (url.is_valid())
    return url;

  return default_dns_canary_check_url;
}

base::TimeDelta PrefetchCanaryCheckCacheLifetime() {
  return base::Hours(base::GetFieldTrialParamByFeatureAsInt(
      features::kPrefetchUseContentRefactor, "canary_cache_hours", 24));
}

base::TimeDelta PrefetchCanaryCheckTimeout() {
  return base::Milliseconds(base::GetFieldTrialParamByFeatureAsInt(
      features::kPrefetchUseContentRefactor, "canary_check_timeout_ms",
      5 * 1000 /* 5 seconds */));
}

int PrefetchCanaryCheckRetries() {
  return base::GetFieldTrialParamByFeatureAsInt(
      features::kPrefetchUseContentRefactor, "canary_check_retries", 1);
}

bool PrefetchUseStreamingURLLoader() {
  return base::GetFieldTrialParamByFeatureAsBool(
      features::kPrefetchUseContentRefactor, "use_streaming_url_loader", true);
}

bool PrefetchShouldBlockUntilHead(
    blink::mojom::SpeculationEagerness prefetch_eagerness) {
  switch (prefetch_eagerness) {
    case blink::mojom::SpeculationEagerness::kEager:
      return base::GetFieldTrialParamByFeatureAsBool(
          features::kPrefetchUseContentRefactor,
          "block_until_head_eager_prefetch", false);
    case blink::mojom::SpeculationEagerness::kDefault:
      return base::GetFieldTrialParamByFeatureAsBool(
          features::kPrefetchUseContentRefactor,
          "block_until_head_default_prefetch", true);
  }
}

bool IsContentPrefetchHoldback() {
  return base::GetFieldTrialParamByFeatureAsBool(
      features::kPrefetchUseContentRefactor, "prefetch_holdback", false);
}
}  // namespace content