/*
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* Copyright (C) 2018 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef _DNS_DNSTLSQUERYMAP_H
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#define _DNS_DNSTLSQUERYMAP_H
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#include <future>
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#include <map>
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#include <mutex>
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#include <vector>
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#include <android-base/thread_annotations.h>
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#include <netdutils/Slice.h>
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#include "DnsTlsServer.h"
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namespace android {
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namespace net {
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// Keeps track of queries and responses. This class matches responses with queries.
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// All methods are thread-safe and non-blocking.
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class DnsTlsQueryMap {
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public:
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struct Query {
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// The new ID number assigned to this query.
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uint16_t newId;
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// A query that has been passed to recordQuery(), with its original ID number.
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const netdutils::Slice query;
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};
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typedef DnsTlsServer::Response Response;
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typedef DnsTlsServer::Result Result;
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struct QueryFuture {
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QueryFuture(Query query, std::future<Result> result)
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: query(query), result(std::move(result)) {}
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Query query;
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// A future which will resolve to the result of this query.
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std::future<Result> result;
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};
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// Returns an object containing everything needed to complete processing of
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// this query, or null if the query could not be recorded.
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std::unique_ptr<QueryFuture> recordQuery(const netdutils::Slice query);
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// Process a response, including a new ID. If the response
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// is not recognized as matching any query, it will be ignored.
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void onResponse(std::vector<uint8_t> response);
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// Clear all map contents. This causes all pending queries to resolve with failure.
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void clear();
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// Get all pending queries. This returns a shallow copy, mostly for thread-safety.
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std::vector<Query> getAll();
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// Mark a query has having been retried. If the query hits the retry limit, it will
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// be expired at the next call to cleanup.
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void markTried(uint16_t newId);
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void cleanup();
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// Returns true if there are no pending queries.
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bool empty();
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private:
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std::mutex mLock;
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struct QueryPromise {
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QueryPromise(Query query) : query(query) {}
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Query query;
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// Number of times the query has been tried. Limited to kMaxTries.
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int tries = 0;
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// A promise whose future is returned by recordQuery()
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// It is fulfilled by onResponse().
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std::promise<Result> result;
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};
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// The maximum number of times we will send a query before abandoning it.
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static constexpr int kMaxTries = 3;
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// Outstanding queries by newId.
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std::map<uint16_t, QueryPromise> mQueries GUARDED_BY(mLock);
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// Get a "newId" number that is not currently in use. Returns -1 if there are none.
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int32_t getFreeId() REQUIRES(mLock);
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// Fulfill the result with an error code.
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static void expire(QueryPromise* _Nonnull p);
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};
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} // end of namespace net
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} // end of namespace android
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#endif // _DNS_DNSTLSQUERYMAP_H
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