PrivateDnsConfiguration.cpp - platform/packages/modules/DnsResolver - Git at Google

 /*
  * Copyright (C) 2018 The Android Open Source Project
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *      http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */

 #define LOG_TAG "resolv"

 #include "PrivateDnsConfiguration.h"

 #include <android-base/format.h>
 #include <android-base/logging.h>
 #include <android-base/stringprintf.h>
 #include <netdutils/ThreadUtil.h>
 #include <sys/socket.h>

 #include "DnsTlsTransport.h"
 #include "ResolverEventReporter.h"
 #include "netd_resolv/resolv.h"
 #include "netdutils/BackoffSequence.h"
 #include "util.h"

 using aidl::android::net::resolv::aidl::IDnsResolverUnsolicitedEventListener;
 using aidl::android::net::resolv::aidl::PrivateDnsValidationEventParcel;
 using android::base::StringPrintf;
 using android::netdutils::setThreadName;
 using std::chrono::milliseconds;

 namespace android {
 namespace net {

 bool parseServer(const char* server, sockaddr_storage* parsed) {
     addrinfo hints = {
             .ai_flags = AI_NUMERICHOST | AI_NUMERICSERV,
             .ai_family = AF_UNSPEC,
     };
     addrinfo* res;

     int err = getaddrinfo(server, "853", &hints, &res);
     if (err != 0) {
         LOG(WARNING) << "Failed to parse server address (" << server << "): " << gai_strerror(err);
         return false;
     }

     memcpy(parsed, res->ai_addr, res->ai_addrlen);
     freeaddrinfo(res);
     return true;
 }

 int PrivateDnsConfiguration::set(int32_t netId, uint32_t mark,
                                  const std::vector<std::string>& servers, const std::string& name,
                                  const std::string& caCert) {
     LOG(DEBUG) << "PrivateDnsConfiguration::set(" << netId << ", 0x" << std::hex << mark << std::dec
                << ", " << servers.size() << ", " << name << ")";

     // Parse the list of servers that has been passed in
     PrivateDnsTracker tmp;
     for (const auto& s : servers) {
         sockaddr_storage parsed;
         if (!parseServer(s.c_str(), &parsed)) {
             return -EINVAL;
         }
         DnsTlsServer server(parsed);
         server.name = name;
         server.certificate = caCert;
         server.mark = mark;
         tmp[ServerIdentity(server)] = server;
     }

     std::lock_guard guard(mPrivateDnsLock);
     if (!name.empty()) {
         mPrivateDnsModes[netId] = PrivateDnsMode::STRICT;
     } else if (!tmp.empty()) {
         mPrivateDnsModes[netId] = PrivateDnsMode::OPPORTUNISTIC;
     } else {
         mPrivateDnsModes[netId] = PrivateDnsMode::OFF;
         mPrivateDnsTransports.erase(netId);
         // TODO: signal validation threads to stop.
         return 0;
     }

     // Create the tracker if it was not present
     auto& tracker = mPrivateDnsTransports[netId];

     // Add the servers if not contained in tracker.
     for (const auto& [identity, server] : tmp) {
         if (tracker.find(identity) == tracker.end()) {
             tracker[identity] = server;
         }
     }

     for (auto& [identity, server] : tracker) {
         const bool active = tmp.find(identity) != tmp.end();
         server.setActive(active);

         // For simplicity, deem the validation result of inactive servers as unreliable.
         if (!server.active() && server.validationState() == Validation::success) {
             updateServerState(identity, Validation::success_but_expired, netId);
         }

         if (needsValidation(server)) {
             updateServerState(identity, Validation::in_process, netId);
             startValidation(server, netId);
         }
     }

     return 0;
 }

 PrivateDnsStatus PrivateDnsConfiguration::getStatus(unsigned netId) {
     PrivateDnsStatus status{PrivateDnsMode::OFF, {}};
     std::lock_guard guard(mPrivateDnsLock);

     const auto mode = mPrivateDnsModes.find(netId);
     if (mode == mPrivateDnsModes.end()) return status;
     status.mode = mode->second;

     const auto netPair = mPrivateDnsTransports.find(netId);
     if (netPair != mPrivateDnsTransports.end()) {
         for (const auto& [_, server] : netPair->second) {
             if (server.active()) {
                 status.serversMap.emplace(server, server.validationState());
             }
         }
     }

     return status;
 }

 void PrivateDnsConfiguration::clear(unsigned netId) {
     LOG(DEBUG) << "PrivateDnsConfiguration::clear(" << netId << ")";
     std::lock_guard guard(mPrivateDnsLock);
     mPrivateDnsModes.erase(netId);
     mPrivateDnsTransports.erase(netId);
 }

 bool PrivateDnsConfiguration::requestValidation(unsigned netId, const DnsTlsServer& server,
                                                 uint32_t mark) {
     std::lock_guard guard(mPrivateDnsLock);
     auto netPair = mPrivateDnsTransports.find(netId);
     if (netPair == mPrivateDnsTransports.end()) {
         return false;
     }

     auto& tracker = netPair->second;
     const ServerIdentity identity = ServerIdentity(server);
     auto it = tracker.find(identity);
     if (it == tracker.end()) {
         return false;
     }

     const DnsTlsServer& target = it->second;

     if (!target.active()) return false;

     if (target.validationState() != Validation::success) return false;

     // Don't run the validation if |mark| (from android_net_context.dns_mark) is different.
     // This is to protect validation from running on unexpected marks.
     // Validation should be associated with a mark gotten by system permission.
     if (target.mark != mark) return false;

     updateServerState(identity, Validation::in_process, netId);
     startValidation(target, netId);
     return true;
 }

 void PrivateDnsConfiguration::startValidation(const DnsTlsServer& server, unsigned netId)
         REQUIRES(mPrivateDnsLock) {
     // Note that capturing |server| and |netId| in this lambda create copies.
     std::thread validate_thread([this, server, netId] {
         setThreadName(StringPrintf("TlsVerify_%u", netId).c_str());

         // cat /proc/sys/net/ipv4/tcp_syn_retries yields "6".
         //
         // Start with a 1 minute delay and backoff to once per hour.
         //
         // Assumptions:
         //     [1] Each TLS validation is ~10KB of certs+handshake+payload.
         //     [2] Network typically provision clients with <=4 nameservers.
         //     [3] Average month has 30 days.
         //
         // Each validation pass in a given hour is ~1.2MB of data. And 24
         // such validation passes per day is about ~30MB per month, in the
         // worst case. Otherwise, this will cost ~600 SYNs per month
         // (6 SYNs per ip, 4 ips per validation pass, 24 passes per day).
         auto backoff = netdutils::BackoffSequence<>::Builder()
                                .withInitialRetransmissionTime(std::chrono::seconds(60))
                                .withMaximumRetransmissionTime(std::chrono::seconds(3600))
                                .build();

         while (true) {
             // ::validate() is a blocking call that performs network operations.
             // It can take milliseconds to minutes, up to the SYN retry limit.
             LOG(WARNING) << "Validating DnsTlsServer " << server.toIpString() << " with mark 0x"
                          << std::hex << server.mark;
             const bool success = DnsTlsTransport::validate(server, server.mark);
             LOG(WARNING) << "validateDnsTlsServer returned " << success << " for "
                          << server.toIpString();

             const bool needs_reeval = this->recordPrivateDnsValidation(server, netId, success);
             if (!needs_reeval) {
                 break;
             }

             if (backoff.hasNextTimeout()) {
                 // TODO: make the thread able to receive signals to shutdown early.
                 std::this_thread::sleep_for(backoff.getNextTimeout());
             } else {
                 break;
             }
         }
     });
     validate_thread.detach();
 }

 void PrivateDnsConfiguration::sendPrivateDnsValidationEvent(const DnsTlsServer& server,
                                                             unsigned netId, bool success) {
     LOG(DEBUG) << "Sending validation " << (success ? "success" : "failure") << " event on netId "
                << netId << " for " << server.toIpString() << " with hostname {" << server.name
                << "}";
     // Send a validation event to NetdEventListenerService.
     const auto& listeners = ResolverEventReporter::getInstance().getListeners();
     if (listeners.empty()) {
         LOG(ERROR)
                 << "Validation event not sent since no INetdEventListener receiver is available.";
     }
     for (const auto& it : listeners) {
         it->onPrivateDnsValidationEvent(netId, server.toIpString(), server.name, success);
     }

     // Send a validation event to unsolicited event listeners.
     const auto& unsolEventListeners = ResolverEventReporter::getInstance().getUnsolEventListeners();
     const PrivateDnsValidationEventParcel validationEvent = {
             .netId = static_cast<int32_t>(netId),
             .ipAddress = server.toIpString(),
             .hostname = server.name,
             .validation = success ? IDnsResolverUnsolicitedEventListener::VALIDATION_RESULT_SUCCESS
                                   : IDnsResolverUnsolicitedEventListener::VALIDATION_RESULT_FAILURE,
     };
     for (const auto& it : unsolEventListeners) {
         it->onPrivateDnsValidationEvent(validationEvent);
     }
 }

 bool PrivateDnsConfiguration::recordPrivateDnsValidation(const DnsTlsServer& server, unsigned netId,
                                                          bool success) {
     constexpr bool NEEDS_REEVALUATION = true;
     constexpr bool DONT_REEVALUATE = false;
     const ServerIdentity identity = ServerIdentity(server);

     std::lock_guard guard(mPrivateDnsLock);

     auto netPair = mPrivateDnsTransports.find(netId);
     if (netPair == mPrivateDnsTransports.end()) {
         LOG(WARNING) << "netId " << netId << " was erased during private DNS validation";
         notifyValidationStateUpdate(identity.ip.toString(), Validation::fail, netId);
         return DONT_REEVALUATE;
     }

     const auto mode = mPrivateDnsModes.find(netId);
     if (mode == mPrivateDnsModes.end()) {
         LOG(WARNING) << "netId " << netId << " has no private DNS validation mode";
         notifyValidationStateUpdate(identity.ip.toString(), Validation::fail, netId);
         return DONT_REEVALUATE;
     }
     const bool modeDoesReevaluation = (mode->second == PrivateDnsMode::STRICT);

     bool reevaluationStatus =
             (success || !modeDoesReevaluation) ? DONT_REEVALUATE : NEEDS_REEVALUATION;

     auto& tracker = netPair->second;
     auto serverPair = tracker.find(identity);
     if (serverPair == tracker.end()) {
         LOG(WARNING) << "Server " << server.toIpString()
                      << " was removed during private DNS validation";
         success = false;
         reevaluationStatus = DONT_REEVALUATE;
     } else if (!(serverPair->second == server)) {
         // TODO: It doesn't seem correct to overwrite the tracker entry for
         // |server| down below in this circumstance... Fix this.
         LOG(WARNING) << "Server " << server.toIpString()
                      << " was changed during private DNS validation";
         success = false;
         reevaluationStatus = DONT_REEVALUATE;
     } else if (!serverPair->second.active()) {
         LOG(WARNING) << "Server " << server.toIpString() << " was removed from the configuration";
         success = false;
         reevaluationStatus = DONT_REEVALUATE;
     }

     // Send private dns validation result to listeners.
     sendPrivateDnsValidationEvent(server, netId, success);

     if (success) {
         updateServerState(identity, Validation::success, netId);
     } else {
         // Validation failure is expected if a user is on a captive portal.
         // TODO: Trigger a second validation attempt after captive portal login
         // succeeds.
         const auto result = (reevaluationStatus == NEEDS_REEVALUATION) ? Validation::in_process
                                                                        : Validation::fail;
         updateServerState(identity, result, netId);
     }
     LOG(WARNING) << "Validation " << (success ? "success" : "failed");

     return reevaluationStatus;
 }

 void PrivateDnsConfiguration::updateServerState(const ServerIdentity& identity, Validation state,
                                                 uint32_t netId) {
     auto netPair = mPrivateDnsTransports.find(netId);
     if (netPair == mPrivateDnsTransports.end()) {
         notifyValidationStateUpdate(identity.ip.toString(), Validation::fail, netId);
         return;
     }

     auto& tracker = netPair->second;
     if (tracker.find(identity) == tracker.end()) {
         notifyValidationStateUpdate(identity.ip.toString(), Validation::fail, netId);
         return;
     }

     tracker[identity].setValidationState(state);
     notifyValidationStateUpdate(identity.ip.toString(), state, netId);

     RecordEntry record(netId, identity, state);
     mPrivateDnsLog.push(std::move(record));
 }

 bool PrivateDnsConfiguration::needsValidation(const DnsTlsServer& server) {
     // The server is not expected to be used on the network.
     if (!server.active()) return false;

     // The server is newly added.
     if (server.validationState() == Validation::unknown_server) return true;

     // The server has failed at least one validation attempt. Give it another try.
     if (server.validationState() == Validation::fail) return true;

     // The previous validation result might be unreliable.
     if (server.validationState() == Validation::success_but_expired) return true;

     return false;
 }

 void PrivateDnsConfiguration::setObserver(PrivateDnsValidationObserver* observer) {
     std::lock_guard guard(mPrivateDnsLock);
     mObserver = observer;
 }

 void PrivateDnsConfiguration::notifyValidationStateUpdate(const std::string& serverIp,
                                                           Validation validation,
                                                           uint32_t netId) const {
     if (mObserver) {
         mObserver->onValidationStateUpdate(serverIp, validation, netId);
     }
 }

 void PrivateDnsConfiguration::dump(netdutils::DumpWriter& dw) const {
     dw.println("PrivateDnsLog:");
     netdutils::ScopedIndent indentStats(dw);

     for (const auto& record : mPrivateDnsLog.copy()) {
         dw.println(fmt::format("{} - netId={} PrivateDns={{{}/{}}} state={}",
                                timestampToString(record.timestamp), record.netId,
                                record.serverIdentity.ip.toString(), record.serverIdentity.name,
                                validationStatusToString(record.state)));
     }
     dw.blankline();
 }

 }  // namespace net
 }  // namespace android
	/*
	* Copyright (C) 2018 The Android Open Source Project
	*
	* Licensed under the Apache License, Version 2.0 (the "License");
	* you may not use this file except in compliance with the License.
	* You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/

	#define LOG_TAG "resolv"

	#include "PrivateDnsConfiguration.h"

	#include <android-base/format.h>
	#include <android-base/logging.h>
	#include <android-base/stringprintf.h>
	#include <netdutils/ThreadUtil.h>
	#include <sys/socket.h>

	#include "DnsTlsTransport.h"
	#include "ResolverEventReporter.h"
	#include "netd_resolv/resolv.h"
	#include "netdutils/BackoffSequence.h"
	#include "util.h"

	using aidl::android::net::resolv::aidl::IDnsResolverUnsolicitedEventListener;
	using aidl::android::net::resolv::aidl::PrivateDnsValidationEventParcel;
	using android::base::StringPrintf;
	using android::netdutils::setThreadName;
	using std::chrono::milliseconds;

	namespace android {
	namespace net {

	bool parseServer(const char* server, sockaddr_storage* parsed) {
	addrinfo hints = {
	.ai_flags = AI_NUMERICHOST \| AI_NUMERICSERV,
	.ai_family = AF_UNSPEC,
	};
	addrinfo* res;

	int err = getaddrinfo(server, "853", &hints, &res);
	if (err != 0) {
	LOG(WARNING) << "Failed to parse server address (" << server << "): " << gai_strerror(err);
	return false;
	}

	memcpy(parsed, res->ai_addr, res->ai_addrlen);
	freeaddrinfo(res);
	return true;
	}

	int PrivateDnsConfiguration::set(int32_t netId, uint32_t mark,
	const std::vector<std::string>& servers, const std::string& name,
	const std::string& caCert) {
	LOG(DEBUG) << "PrivateDnsConfiguration::set(" << netId << ", 0x" << std::hex << mark << std::dec
	<< ", " << servers.size() << ", " << name << ")";

	// Parse the list of servers that has been passed in
	PrivateDnsTracker tmp;
	for (const auto& s : servers) {
	sockaddr_storage parsed;
	if (!parseServer(s.c_str(), &parsed)) {
	return -EINVAL;
	}
	DnsTlsServer server(parsed);
	server.name = name;
	server.certificate = caCert;
	server.mark = mark;
	tmp[ServerIdentity(server)] = server;
	}

	std::lock_guard guard(mPrivateDnsLock);
	if (!name.empty()) {
	mPrivateDnsModes[netId] = PrivateDnsMode::STRICT;
	} else if (!tmp.empty()) {
	mPrivateDnsModes[netId] = PrivateDnsMode::OPPORTUNISTIC;
	} else {
	mPrivateDnsModes[netId] = PrivateDnsMode::OFF;
	mPrivateDnsTransports.erase(netId);
	// TODO: signal validation threads to stop.
	return 0;
	}

	// Create the tracker if it was not present
	auto& tracker = mPrivateDnsTransports[netId];

	// Add the servers if not contained in tracker.
	for (const auto& [identity, server] : tmp) {
	if (tracker.find(identity) == tracker.end()) {
	tracker[identity] = server;
	}
	}

	for (auto& [identity, server] : tracker) {
	const bool active = tmp.find(identity) != tmp.end();
	server.setActive(active);

	// For simplicity, deem the validation result of inactive servers as unreliable.
	if (!server.active() && server.validationState() == Validation::success) {
	updateServerState(identity, Validation::success_but_expired, netId);
	}

	if (needsValidation(server)) {
	updateServerState(identity, Validation::in_process, netId);
	startValidation(server, netId);
	}
	}

	return 0;
	}

	PrivateDnsStatus PrivateDnsConfiguration::getStatus(unsigned netId) {
	PrivateDnsStatus status{PrivateDnsMode::OFF, {}};
	std::lock_guard guard(mPrivateDnsLock);

	const auto mode = mPrivateDnsModes.find(netId);
	if (mode == mPrivateDnsModes.end()) return status;
	status.mode = mode->second;

	const auto netPair = mPrivateDnsTransports.find(netId);
	if (netPair != mPrivateDnsTransports.end()) {
	for (const auto& [_, server] : netPair->second) {
	if (server.active()) {
	status.serversMap.emplace(server, server.validationState());
	}
	}
	}

	return status;
	}

	void PrivateDnsConfiguration::clear(unsigned netId) {
	LOG(DEBUG) << "PrivateDnsConfiguration::clear(" << netId << ")";
	std::lock_guard guard(mPrivateDnsLock);
	mPrivateDnsModes.erase(netId);
	mPrivateDnsTransports.erase(netId);
	}

	bool PrivateDnsConfiguration::requestValidation(unsigned netId, const DnsTlsServer& server,
	uint32_t mark) {
	std::lock_guard guard(mPrivateDnsLock);
	auto netPair = mPrivateDnsTransports.find(netId);
	if (netPair == mPrivateDnsTransports.end()) {
	return false;
	}

	auto& tracker = netPair->second;
	const ServerIdentity identity = ServerIdentity(server);
	auto it = tracker.find(identity);
	if (it == tracker.end()) {
	return false;
	}

	const DnsTlsServer& target = it->second;

	if (!target.active()) return false;

	if (target.validationState() != Validation::success) return false;

	// Don't run the validation if \|mark\| (from android_net_context.dns_mark) is different.
	// This is to protect validation from running on unexpected marks.
	// Validation should be associated with a mark gotten by system permission.
	if (target.mark != mark) return false;

	updateServerState(identity, Validation::in_process, netId);
	startValidation(target, netId);
	return true;
	}

	void PrivateDnsConfiguration::startValidation(const DnsTlsServer& server, unsigned netId)
	REQUIRES(mPrivateDnsLock) {
	// Note that capturing \|server\| and \|netId\| in this lambda create copies.
	std::thread validate_thread([this, server, netId] {
	setThreadName(StringPrintf("TlsVerify_%u", netId).c_str());

	// cat /proc/sys/net/ipv4/tcp_syn_retries yields "6".
	//
	// Start with a 1 minute delay and backoff to once per hour.
	//
	// Assumptions:
	// [1] Each TLS validation is ~10KB of certs+handshake+payload.
	// [2] Network typically provision clients with <=4 nameservers.
	// [3] Average month has 30 days.
	//
	// Each validation pass in a given hour is ~1.2MB of data. And 24
	// such validation passes per day is about ~30MB per month, in the
	// worst case. Otherwise, this will cost ~600 SYNs per month
	// (6 SYNs per ip, 4 ips per validation pass, 24 passes per day).
	auto backoff = netdutils::BackoffSequence<>::Builder()
	.withInitialRetransmissionTime(std::chrono::seconds(60))
	.withMaximumRetransmissionTime(std::chrono::seconds(3600))
	.build();

	while (true) {
	// ::validate() is a blocking call that performs network operations.
	// It can take milliseconds to minutes, up to the SYN retry limit.
	LOG(WARNING) << "Validating DnsTlsServer " << server.toIpString() << " with mark 0x"
	<< std::hex << server.mark;
	const bool success = DnsTlsTransport::validate(server, server.mark);
	LOG(WARNING) << "validateDnsTlsServer returned " << success << " for "
	<< server.toIpString();

	const bool needs_reeval = this->recordPrivateDnsValidation(server, netId, success);
	if (!needs_reeval) {
	break;
	}

	if (backoff.hasNextTimeout()) {
	// TODO: make the thread able to receive signals to shutdown early.
	std::this_thread::sleep_for(backoff.getNextTimeout());
	} else {
	break;
	}
	}
	});
	validate_thread.detach();
	}

	void PrivateDnsConfiguration::sendPrivateDnsValidationEvent(const DnsTlsServer& server,
	unsigned netId, bool success) {
	LOG(DEBUG) << "Sending validation " << (success ? "success" : "failure") << " event on netId "
	<< netId << " for " << server.toIpString() << " with hostname {" << server.name
	<< "}";
	// Send a validation event to NetdEventListenerService.
	const auto& listeners = ResolverEventReporter::getInstance().getListeners();
	if (listeners.empty()) {
	LOG(ERROR)
	<< "Validation event not sent since no INetdEventListener receiver is available.";
	}
	for (const auto& it : listeners) {
	it->onPrivateDnsValidationEvent(netId, server.toIpString(), server.name, success);
	}

	// Send a validation event to unsolicited event listeners.
	const auto& unsolEventListeners = ResolverEventReporter::getInstance().getUnsolEventListeners();
	const PrivateDnsValidationEventParcel validationEvent = {
	.netId = static_cast<int32_t>(netId),
	.ipAddress = server.toIpString(),
	.hostname = server.name,
	.validation = success ? IDnsResolverUnsolicitedEventListener::VALIDATION_RESULT_SUCCESS
	: IDnsResolverUnsolicitedEventListener::VALIDATION_RESULT_FAILURE,
	};
	for (const auto& it : unsolEventListeners) {
	it->onPrivateDnsValidationEvent(validationEvent);
	}
	}

	bool PrivateDnsConfiguration::recordPrivateDnsValidation(const DnsTlsServer& server, unsigned netId,
	bool success) {
	constexpr bool NEEDS_REEVALUATION = true;
	constexpr bool DONT_REEVALUATE = false;
	const ServerIdentity identity = ServerIdentity(server);

	std::lock_guard guard(mPrivateDnsLock);

	auto netPair = mPrivateDnsTransports.find(netId);
	if (netPair == mPrivateDnsTransports.end()) {
	LOG(WARNING) << "netId " << netId << " was erased during private DNS validation";
	notifyValidationStateUpdate(identity.ip.toString(), Validation::fail, netId);
	return DONT_REEVALUATE;
	}

	const auto mode = mPrivateDnsModes.find(netId);
	if (mode == mPrivateDnsModes.end()) {
	LOG(WARNING) << "netId " << netId << " has no private DNS validation mode";
	notifyValidationStateUpdate(identity.ip.toString(), Validation::fail, netId);
	return DONT_REEVALUATE;
	}
	const bool modeDoesReevaluation = (mode->second == PrivateDnsMode::STRICT);

	bool reevaluationStatus =
	(success \|\| !modeDoesReevaluation) ? DONT_REEVALUATE : NEEDS_REEVALUATION;

	auto& tracker = netPair->second;
	auto serverPair = tracker.find(identity);
	if (serverPair == tracker.end()) {
	LOG(WARNING) << "Server " << server.toIpString()
	<< " was removed during private DNS validation";
	success = false;
	reevaluationStatus = DONT_REEVALUATE;
	} else if (!(serverPair->second == server)) {
	// TODO: It doesn't seem correct to overwrite the tracker entry for
	// \|server\| down below in this circumstance... Fix this.
	LOG(WARNING) << "Server " << server.toIpString()
	<< " was changed during private DNS validation";
	success = false;
	reevaluationStatus = DONT_REEVALUATE;
	} else if (!serverPair->second.active()) {
	LOG(WARNING) << "Server " << server.toIpString() << " was removed from the configuration";
	success = false;
	reevaluationStatus = DONT_REEVALUATE;
	}

	// Send private dns validation result to listeners.
	sendPrivateDnsValidationEvent(server, netId, success);

	if (success) {
	updateServerState(identity, Validation::success, netId);
	} else {
	// Validation failure is expected if a user is on a captive portal.
	// TODO: Trigger a second validation attempt after captive portal login
	// succeeds.
	const auto result = (reevaluationStatus == NEEDS_REEVALUATION) ? Validation::in_process
	: Validation::fail;
	updateServerState(identity, result, netId);
	}
	LOG(WARNING) << "Validation " << (success ? "success" : "failed");

	return reevaluationStatus;
	}

	void PrivateDnsConfiguration::updateServerState(const ServerIdentity& identity, Validation state,
	uint32_t netId) {
	auto netPair = mPrivateDnsTransports.find(netId);
	if (netPair == mPrivateDnsTransports.end()) {
	notifyValidationStateUpdate(identity.ip.toString(), Validation::fail, netId);
	return;
	}

	auto& tracker = netPair->second;
	if (tracker.find(identity) == tracker.end()) {
	notifyValidationStateUpdate(identity.ip.toString(), Validation::fail, netId);
	return;
	}

	tracker[identity].setValidationState(state);
	notifyValidationStateUpdate(identity.ip.toString(), state, netId);

	RecordEntry record(netId, identity, state);
	mPrivateDnsLog.push(std::move(record));
	}

	bool PrivateDnsConfiguration::needsValidation(const DnsTlsServer& server) {
	// The server is not expected to be used on the network.
	if (!server.active()) return false;

	// The server is newly added.
	if (server.validationState() == Validation::unknown_server) return true;

	// The server has failed at least one validation attempt. Give it another try.
	if (server.validationState() == Validation::fail) return true;

	// The previous validation result might be unreliable.
	if (server.validationState() == Validation::success_but_expired) return true;

	return false;
	}

	void PrivateDnsConfiguration::setObserver(PrivateDnsValidationObserver* observer) {
	std::lock_guard guard(mPrivateDnsLock);
	mObserver = observer;
	}

	void PrivateDnsConfiguration::notifyValidationStateUpdate(const std::string& serverIp,
	Validation validation,
	uint32_t netId) const {
	if (mObserver) {
	mObserver->onValidationStateUpdate(serverIp, validation, netId);
	}
	}

	void PrivateDnsConfiguration::dump(netdutils::DumpWriter& dw) const {
	dw.println("PrivateDnsLog:");
	netdutils::ScopedIndent indentStats(dw);

	for (const auto& record : mPrivateDnsLog.copy()) {
	dw.println(fmt::format("{} - netId={} PrivateDns={{{}/{}}} state={}",
	timestampToString(record.timestamp), record.netId,
	record.serverIdentity.ip.toString(), record.serverIdentity.name,
	validationStatusToString(record.state)));
	}
	dw.blankline();
	}

	} // namespace net
	} // namespace android