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// Copyright 2020 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "chrome/browser/ash/net/network_diagnostics/dns_latency_routine.h"
#include <iterator>
#include <map>
#include <optional>
#include <string>
#include <utility>
#include <vector>
#include "base/functional/bind.h"
#include "base/rand_util.h"
#include "base/time/default_tick_clock.h"
#include "chrome/browser/ash/net/network_diagnostics/network_diagnostics_util.h"
#include "chrome/browser/ash/profiles/profile_helper.h"
#include "chrome/browser/profiles/profile_manager.h"
#include "components/session_manager/core/session_manager.h"
#include "content/public/browser/storage_partition.h"
#include "net/base/host_port_pair.h"
#include "net/base/net_errors.h"
#include "net/base/network_anonymization_key.h"
#include "services/network/public/cpp/simple_host_resolver.h"
namespace base {
class TimeTicks;
}
namespace ash::network_diagnostics {
namespace {
namespace mojom = ::chromeos::network_diagnostics::mojom;
constexpr int kHttpPort = 80;
constexpr int kTotalHostsToQuery = 3;
// The length of a random eight letter prefix obtained by the characters from
// |kPossibleChars|.
constexpr int kHostPrefixLength = 8;
constexpr base::TimeDelta kBadLatencyMs =
base::Milliseconds(util::kDnsPotentialProblemLatencyMs);
constexpr base::TimeDelta kVeryBadLatencyMs =
base::Milliseconds(util::kDnsProblemLatencyMs);
constexpr char kHostSuffix[] = "-ccd-testing-v4.metric.gstatic.com";
const std::string GetRandomString(int length) {
std::string prefix;
for (int i = 0; i < length; i++) {
prefix += ('a' + base::RandInt(0, 25));
}
return prefix;
}
// Use GetRandomString() to retrieve a random prefix. This random prefix is
// prepended to the |kHostSuffix|, resulting in a complete hostname. By
// including a random prefix, we ensure with a very high probability that the
// DNS queries are done on unique hosts.
std::vector<std::string> GetRandomHostnamesToQuery() {
std::vector<std::string> hostnames_to_query;
for (int i = 0; i < kTotalHostsToQuery; i++) {
hostnames_to_query.emplace_back(GetRandomString(kHostPrefixLength) +
kHostSuffix);
}
return hostnames_to_query;
}
Profile* GetUserProfile() {
// Use sign-in profile if user has not logged in
if (session_manager::SessionManager::Get()->IsUserSessionBlocked()) {
return ProfileHelper::GetSigninProfile();
}
// Use primary profile if user is logged in
return ProfileManager::GetPrimaryUserProfile();
}
double AverageLatency(const std::vector<base::TimeDelta>& latencies) {
double total_latency = 0.0;
for (base::TimeDelta latency : latencies) {
total_latency += latency.InMillisecondsF();
}
return total_latency / latencies.size();
}
} // namespace
DnsLatencyRoutine::DnsLatencyRoutine(mojom::RoutineCallSource source)
: NetworkDiagnosticsRoutine(source),
tick_clock_(base::DefaultTickClock::GetInstance()) {
profile_ = GetUserProfile();
network_context_ =
profile_->GetDefaultStoragePartition()->GetNetworkContext();
DCHECK(network_context_);
set_verdict(mojom::RoutineVerdict::kNotRun);
}
DnsLatencyRoutine::~DnsLatencyRoutine() = default;
mojom::RoutineType DnsLatencyRoutine::Type() {
return mojom::RoutineType::kDnsLatency;
}
void DnsLatencyRoutine::Run() {
CreateHostResolver();
hostnames_to_query_ = GetRandomHostnamesToQuery();
AttemptNextResolution();
}
void DnsLatencyRoutine::AnalyzeResultsAndExecuteCallback() {
double average_latency = AverageLatency(latencies_);
if (!successfully_resolved_all_addresses_ || average_latency == 0.0) {
set_verdict(mojom::RoutineVerdict::kProblem);
problems_.emplace_back(mojom::DnsLatencyProblem::kHostResolutionFailure);
} else if (average_latency > kBadLatencyMs.InMillisecondsF() &&
average_latency <= kVeryBadLatencyMs.InMillisecondsF()) {
set_verdict(mojom::RoutineVerdict::kProblem);
problems_.emplace_back(mojom::DnsLatencyProblem::kSlightlyAboveThreshold);
} else if (average_latency > kVeryBadLatencyMs.InMillisecondsF()) {
set_verdict(mojom::RoutineVerdict::kProblem);
problems_.emplace_back(
mojom::DnsLatencyProblem::kSignificantlyAboveThreshold);
} else {
set_verdict(mojom::RoutineVerdict::kNoProblem);
}
set_problems(mojom::RoutineProblems::NewDnsLatencyProblems(problems_));
ExecuteCallback();
}
void DnsLatencyRoutine::CreateHostResolver() {
CHECK(!host_resolver_);
host_resolver_ = network::SimpleHostResolver::Create(network_context());
}
void DnsLatencyRoutine::AttemptNextResolution() {
CHECK(host_resolver_);
std::string hostname = hostnames_to_query_.back();
hostnames_to_query_.pop_back();
// Resolver host parameter source must be unset or set to ANY in order for DNS
// queries with BuiltInDnsClientEnabled policy disabled to work (b/353448388).
network::mojom::ResolveHostParametersPtr parameters =
network::mojom::ResolveHostParameters::New();
parameters->dns_query_type = net::DnsQueryType::A;
parameters->cache_usage =
network::mojom::ResolveHostParameters::CacheUsage::DISALLOWED;
start_resolution_time_ = tick_clock_->NowTicks();
// Intentionally using a HostPortPair not to trigger ERR_DNS_NAME_HTTPS_ONLY
// error while resolving http:// scheme host when a HTTPS resource record
// exists.
// Unretained(this) is safe here because the callback is invoked directly by
// |host_resolver_| which is owned by |this|.
host_resolver_->ResolveHost(
network::mojom::HostResolverHost::NewHostPortPair(
net::HostPortPair(hostname, kHttpPort)),
net::NetworkAnonymizationKey::CreateTransient(), std::move(parameters),
base::BindOnce(&DnsLatencyRoutine::OnComplete, base::Unretained(this)));
}
void DnsLatencyRoutine::OnComplete(
int result,
const net::ResolveErrorInfo& resolve_error_info,
const std::optional<net::AddressList>& resolved_addresses,
const std::optional<net::HostResolverEndpointResults>&
endpoint_results_with_metadata) {
resolution_complete_time_ = tick_clock_->NowTicks();
const base::TimeDelta latency =
resolution_complete_time_ - start_resolution_time_;
if (result != net::OK) {
CHECK(!resolved_addresses);
// Failed to get resolved address of host
AnalyzeResultsAndExecuteCallback();
} else if (hostnames_to_query_.size() > 0) {
latencies_.emplace_back(latency);
AttemptNextResolution();
} else {
latencies_.emplace_back(latency);
successfully_resolved_all_addresses_ = true;
AnalyzeResultsAndExecuteCallback();
}
}
} // namespace ash::network_diagnostics
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