1 /* 2 * Copyright (C) 2018 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 #ifndef _DNS_DNSTLSQUERYMAP_H 18 #define _DNS_DNSTLSQUERYMAP_H 19 20 #include <future> 21 #include <map> 22 #include <mutex> 23 #include <vector> 24 25 #include <android-base/thread_annotations.h> 26 #include <netdutils/Slice.h> 27 28 #include "DnsTlsServer.h" 29 30 namespace android { 31 namespace net { 32 33 // Keeps track of queries and responses. This class matches responses with queries. 34 // All methods are thread-safe and non-blocking. 35 class DnsTlsQueryMap { 36 public: 37 struct Query { 38 // The new ID number assigned to this query. 39 uint16_t newId; 40 // A query that has been passed to recordQuery(), with its original ID number. 41 const netdutils::Slice query; 42 }; 43 44 typedef DnsTlsServer::Response Response; 45 typedef DnsTlsServer::Result Result; 46 47 struct QueryFuture { QueryFutureQueryFuture48 QueryFuture(Query query, std::future<Result> result) 49 : query(query), result(std::move(result)) {} 50 Query query; 51 // A future which will resolve to the result of this query. 52 std::future<Result> result; 53 }; 54 55 // Returns an object containing everything needed to complete processing of 56 // this query, or null if the query could not be recorded. 57 std::unique_ptr<QueryFuture> recordQuery(const netdutils::Slice query); 58 59 // Process a response, including a new ID. If the response 60 // is not recognized as matching any query, it will be ignored. 61 void onResponse(std::vector<uint8_t> response); 62 63 // Clear all map contents. This causes all pending queries to resolve with failure. 64 void clear(); 65 66 // Get all pending queries. This returns a shallow copy, mostly for thread-safety. 67 std::vector<Query> getAll(); 68 69 // Mark a query has having been retried. If the query hits the retry limit, it will 70 // be expired at the next call to cleanup. 71 void markTried(uint16_t newId); 72 void cleanup(); 73 74 // Returns true if there are no pending queries. 75 bool empty(); 76 77 private: 78 std::mutex mLock; 79 80 struct QueryPromise { QueryPromiseQueryPromise81 QueryPromise(Query query) : query(query) {} 82 Query query; 83 // Number of times the query has been tried. Limited to kMaxTries. 84 int tries = 0; 85 // A promise whose future is returned by recordQuery() 86 // It is fulfilled by onResponse(). 87 std::promise<Result> result; 88 }; 89 90 // The maximum number of times we will send a query before abandoning it. 91 static constexpr int kMaxTries = 3; 92 93 // Outstanding queries by newId. 94 std::map<uint16_t, QueryPromise> mQueries GUARDED_BY(mLock); 95 96 // Get a "newId" number that is not currently in use. Returns -1 if there are none. 97 int32_t getFreeId() REQUIRES(mLock); 98 99 // Fulfill the result with an error code. 100 static void expire(QueryPromise* _Nonnull p); 101 }; 102 103 } // end of namespace net 104 } // end of namespace android 105 106 #endif // _DNS_DNSTLSQUERYMAP_H 107