Snap for 7000466 from 47aa2b61792c757d986ec8e2a69d1e3d259b69ac to sc-release (cb0429ca) · Commits · e / os / android_packages_modules_DnsResolver

Android.bp

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		@@ -259,6 +259,7 @@ cc_test {
		"DnsQueryLogTest.cpp",
		"DnsStatsTest.cpp",
		"ExperimentsTest.cpp",
		"OperationLimiterTest.cpp",
		"PrivateDnsConfigurationTest.cpp",
		],
		shared_libs: [

DnsProxyListener.cpp

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		@@ -39,7 +39,6 @@
		#include <cutils/misc.h> // FIRST_APPLICATION_UID
		#include <cutils/multiuser.h>
		#include <netdutils/InternetAddresses.h>
		#include <netdutils/OperationLimiter.h>
		#include <netdutils/ResponseCode.h>
		#include <netdutils/Slice.h>
		#include <netdutils/Stopwatch.h>
		@@ -50,6 +49,7 @@

		#include "DnsResolver.h"
		#include "NetdPermissions.h"
		#include "OperationLimiter.h"
		#include "PrivateDnsConfiguration.h"
		#include "ResolverEventReporter.h"
		#include "dnsproxyd_protocol/DnsProxydProtocol.h" // NETID_USE_LOCAL_NAMESERVERS

OperationLimiter.h

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		/*
		* 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.
		*/

		#ifndef NETUTILS_OPERATIONLIMITER_H
		#define NETUTILS_OPERATIONLIMITER_H

		#include <mutex>
		#include <unordered_map>

		#include <android-base/logging.h>
		#include <android-base/thread_annotations.h>

		namespace android {
		namespace netdutils {

		// Tracks the number of operations in progress on behalf of a particular key or
		// ID, rejecting further attempts to start new operations after a configurable
		// limit has been reached.
		//
		// The intended usage pattern is:
		// OperationLimiter<UserId> connections_per_user;
		// ...
		// // Before opening a new connection
		// if (!limiter.start(user)) {
		// return error;
		// } else {
		// // open the connection
		// // ...do some work...
		// // close the connection
		// limiter.finish(user);
		// }
		//
		// This class is thread-safe.
		template <typename KeyType>
		class OperationLimiter {
		public:
		explicit OperationLimiter(int limit) : mLimitPerKey(limit) {}

		~OperationLimiter() {
		DCHECK(mCounters.empty()) << "Destroying OperationLimiter with active operations";
		}

		// Returns false if \|key\| has reached the maximum number of concurrent
		// operations, otherwise increments the counter and returns true.
		//
		// Note: each successful start(key) must be matched by exactly one call to
		// finish(key).
		bool start(KeyType key) EXCLUDES(mMutex) {
		std::lock_guard lock(mMutex);
		auto& cnt = mCounters[key]; // operator[] creates new entries as needed.
		if (cnt >= mLimitPerKey) {
		// Oh, no!
		return false;
		}
		++cnt;
		return true;
		}

		// Decrements the number of operations in progress accounted to \|key\|.
		// See usage notes on start().
		void finish(KeyType key) EXCLUDES(mMutex) {
		std::lock_guard lock(mMutex);
		auto it = mCounters.find(key);
		if (it == mCounters.end()) {
		LOG(FATAL_WITHOUT_ABORT) << "Decremented non-existent counter for key=" << key;
		return;
		}
		auto& cnt = it->second;
		--cnt;
		if (cnt <= 0) {
		// Cleanup counters once they drop down to zero.
		mCounters.erase(it);
		}
		}

		private:
		// Protects access to the map below.
		std::mutex mMutex;

		// Tracks the number of outstanding queries by key.
		std::unordered_map<KeyType, int> mCounters GUARDED_BY(mMutex);

		// Maximum number of outstanding queries from a single key.
		const int mLimitPerKey;
		};

		} // namespace netdutils
		} // namespace android

		#endif // NETUTILS_OPERATIONLIMITER_H

OperationLimiterTest.cpp

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		/*
		* 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.
		*/

		#include "OperationLimiter.h"

		#include <gtest/gtest-spi.h>

		namespace android {
		namespace netdutils {

		TEST(OperationLimiter, limits) {
		OperationLimiter<int> limiter(3);

		EXPECT_TRUE(limiter.start(42));
		EXPECT_TRUE(limiter.start(42));
		EXPECT_TRUE(limiter.start(42));

		// Limit reached... calling any number of times should have no effect.
		EXPECT_FALSE(limiter.start(42));
		EXPECT_FALSE(limiter.start(42));
		EXPECT_FALSE(limiter.start(42));

		// Finishing a single operations is enough for starting a new one...
		limiter.finish(42);
		EXPECT_TRUE(limiter.start(42));

		// ...but not two!
		EXPECT_FALSE(limiter.start(42));

		// Different ids should still have quota...
		EXPECT_TRUE(limiter.start(666));
		limiter.finish(666);

		// Finish all pending operations
		limiter.finish(42);
		limiter.finish(42);
		limiter.finish(42);
		}

		TEST(OperationLimiter, finishWithoutStart) {
		OperationLimiter<int> limiter(1);

		// Will output a LOG(FATAL_WITHOUT_ABORT), but we have no way to probe this.
		limiter.finish(42);

		// This will ensure that the finish() above didn't set a negative value.
		EXPECT_TRUE(limiter.start(42));
		EXPECT_FALSE(limiter.start(42));
		}

		TEST(OperationLimiter, destroyWithActiveOperations) {
		// The death message doesn't seem to be captured on Android.
		EXPECT_DEBUG_DEATH(
		{
		OperationLimiter<int> limiter(3);
		limiter.start(42);
		},
		"" /* "active operations */);
		}

		} // namespace netdutils
		} // namespace android