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// Copyright 2021 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "net/dns/dns_config_service_android.h"
#include <sys/system_properties.h>
#include <memory>
#include <string>
#include <utility>
#include "base/android/build_info.h"
#include "base/files/file_path.h"
#include "base/functional/bind.h"
#include "base/logging.h"
#include "base/memory/raw_ptr.h"
#include "base/sequence_checker.h"
#include "base/time/time.h"
#include "net/android/network_library.h"
#include "net/base/address_tracker_linux.h"
#include "net/base/ip_address.h"
#include "net/base/ip_endpoint.h"
#include "net/base/network_interfaces.h"
#include "net/dns/dns_config.h"
#include "net/dns/dns_config_service.h"
#include "net/dns/public/dns_protocol.h"
#include "net/dns/serial_worker.h"
#include "third_party/abseil-cpp/absl/types/optional.h"
namespace net {
namespace internal {
namespace {
constexpr base::FilePath::CharType kFilePathHosts[] =
FILE_PATH_LITERAL("/system/etc/hosts");
bool IsVpnPresent() {
NetworkInterfaceList networks;
if (!GetNetworkList(&networks, INCLUDE_HOST_SCOPE_VIRTUAL_INTERFACES))
return false;
for (NetworkInterface network : networks) {
if (AddressTrackerLinux::IsTunnelInterfaceName(network.name.c_str()))
return true;
}
return false;
}
} // namespace
// static
constexpr base::TimeDelta DnsConfigServiceAndroid::kConfigChangeDelay;
class DnsConfigServiceAndroid::ConfigReader : public SerialWorker {
public:
explicit ConfigReader(DnsConfigServiceAndroid& service,
android::DnsServerGetter dns_server_getter)
: dns_server_getter_(std::move(dns_server_getter)), service_(&service) {}
~ConfigReader() override = default;
ConfigReader(const ConfigReader&) = delete;
ConfigReader& operator=(const ConfigReader&) = delete;
std::unique_ptr<SerialWorker::WorkItem> CreateWorkItem() override {
return std::make_unique<WorkItem>(dns_server_getter_);
}
bool OnWorkFinished(std::unique_ptr<SerialWorker::WorkItem>
serial_worker_work_item) override {
DCHECK(serial_worker_work_item);
DCHECK(!IsCancelled());
WorkItem* work_item = static_cast<WorkItem*>(serial_worker_work_item.get());
if (work_item->dns_config_.has_value()) {
service_->OnConfigRead(std::move(work_item->dns_config_).value());
return true;
} else {
LOG(WARNING) << "Failed to read DnsConfig.";
return false;
}
}
private:
class WorkItem : public SerialWorker::WorkItem {
public:
explicit WorkItem(android::DnsServerGetter dns_server_getter)
: dns_server_getter_(std::move(dns_server_getter)) {}
void DoWork() override {
dns_config_.emplace();
dns_config_->unhandled_options = false;
if (base::android::BuildInfo::GetInstance()->sdk_int() >=
base::android::SDK_VERSION_MARSHMALLOW) {
if (!dns_server_getter_.Run(
&dns_config_->nameservers, &dns_config_->dns_over_tls_active,
&dns_config_->dns_over_tls_hostname, &dns_config_->search)) {
dns_config_.reset();
}
return;
}
if (IsVpnPresent()) {
dns_config_->unhandled_options = true;
}
// NOTE(pauljensen): __system_property_get and the net.dns1/2 properties
// are not supported APIs, but they're only read on pre-Marshmallow
// Android which was released years ago and isn't changing.
char property_value[PROP_VALUE_MAX];
__system_property_get("net.dns1", property_value);
std::string dns1_string = property_value;
__system_property_get("net.dns2", property_value);
std::string dns2_string = property_value;
if (dns1_string.empty() && dns2_string.empty()) {
dns_config_.reset();
return;
}
IPAddress dns1_address;
IPAddress dns2_address;
bool parsed1 = dns1_address.AssignFromIPLiteral(dns1_string);
bool parsed2 = dns2_address.AssignFromIPLiteral(dns2_string);
if (!parsed1 && !parsed2) {
dns_config_.reset();
return;
}
if (parsed1) {
IPEndPoint dns1(dns1_address, dns_protocol::kDefaultPort);
dns_config_->nameservers.push_back(dns1);
}
if (parsed2) {
IPEndPoint dns2(dns2_address, dns_protocol::kDefaultPort);
dns_config_->nameservers.push_back(dns2);
}
}
private:
friend class ConfigReader;
android::DnsServerGetter dns_server_getter_;
absl::optional<DnsConfig> dns_config_;
};
android::DnsServerGetter dns_server_getter_;
// Raw pointer to owning DnsConfigService.
const raw_ptr<DnsConfigServiceAndroid> service_;
};
DnsConfigServiceAndroid::DnsConfigServiceAndroid()
: DnsConfigService(kFilePathHosts, kConfigChangeDelay) {
// Allow constructing on one thread and living on another.
DETACH_FROM_SEQUENCE(sequence_checker_);
dns_server_getter_ = base::BindRepeating(&android::GetCurrentDnsServers);
}
DnsConfigServiceAndroid::~DnsConfigServiceAndroid() {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
if (is_watching_network_change_) {
NetworkChangeNotifier::RemoveNetworkChangeObserver(this);
}
if (config_reader_)
config_reader_->Cancel();
}
void DnsConfigServiceAndroid::ReadConfigNow() {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
if (!config_reader_) {
DCHECK(dns_server_getter_);
config_reader_ =
std::make_unique<ConfigReader>(*this, std::move(dns_server_getter_));
}
config_reader_->WorkNow();
}
bool DnsConfigServiceAndroid::StartWatching() {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
CHECK(!is_watching_network_change_);
is_watching_network_change_ = true;
// On Android, assume DNS config may have changed on every network change.
NetworkChangeNotifier::AddNetworkChangeObserver(this);
// Hosts file should never change on Android (and watching it is
// problematic; see http://crbug.com/600442), so don't watch it.
return true;
}
void DnsConfigServiceAndroid::OnNetworkChanged(
NetworkChangeNotifier::ConnectionType type) {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
if (type != NetworkChangeNotifier::CONNECTION_NONE) {
OnConfigChanged(/*succeeded=*/true);
}
}
} // namespace internal
// static
std::unique_ptr<DnsConfigService> DnsConfigService::CreateSystemService() {
return std::make_unique<internal::DnsConfigServiceAndroid>();
}
} // namespace net
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