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 "dns/DnsTlsServer.h" 29 30 namespace android { 31 namespace net { 32 33 using netdutils::Slice; 34 35 // Keeps track of queries and responses. This class matches responses with queries. 36 // All methods are thread-safe and non-blocking. 37 class DnsTlsQueryMap { 38 public: 39 struct Query { 40 // The new ID number assigned to this query. 41 uint16_t newId; 42 // A query that has been passed to recordQuery(), with its original ID number. 43 const Slice query; 44 }; 45 46 typedef DnsTlsServer::Response Response; 47 typedef DnsTlsServer::Result Result; 48 49 struct QueryFuture { QueryFutureQueryFuture50 QueryFuture(Query query, std::future<Result> result) : 51 query(query), result(std::move(result)) {} 52 Query query; 53 // A future which will resolve to the result of this query. 54 std::future<Result> result; 55 }; 56 57 // Returns an object containing everything needed to complete processing of 58 // this query, or null if the query could not be recorded. 59 std::unique_ptr<QueryFuture> recordQuery(const Slice query); 60 61 // Process a response, including a new ID. If the response 62 // is not recognized as matching any query, it will be ignored. 63 void onResponse(std::vector<uint8_t> response); 64 65 // Clear all map contents. This causes all pending queries to resolve with failure. 66 void clear(); 67 68 // Get all pending queries. This returns a shallow copy, mostly for thread-safety. 69 std::vector<Query> getAll(); 70 71 // Mark a query has having been retried. If the query hits the retry limit, it will 72 // be expired at the next call to cleanup. 73 void markTried(uint16_t newId); 74 void cleanup(); 75 76 // Returns true if there are no pending queries. 77 bool empty(); 78 79 private: 80 std::mutex mLock; 81 82 struct QueryPromise { QueryPromiseQueryPromise83 QueryPromise(Query query) : query(query) {} 84 Query query; 85 // Number of times the query has been tried. Limited to kMaxTries. 86 int tries = 0; 87 // A promise whose future is returned by recordQuery() 88 // It is fulfilled by onResponse(). 89 std::promise<Result> result; 90 }; 91 92 // The maximum number of times we will send a query before abandoning it. 93 static constexpr int kMaxTries = 3; 94 95 // Outstanding queries by newId. 96 std::map<uint16_t, QueryPromise> mQueries GUARDED_BY(mLock); 97 98 // Get a "newId" number that is not currently in use. Returns -1 if there are none. 99 int32_t getFreeId() REQUIRES(mLock); 100 101 // Fulfill the result with an error code. 102 static void expire(QueryPromise* _Nonnull p); 103 }; 104 105 } // end of namespace net 106 } // end of namespace android 107 108 #endif // _DNS_DNSTLSQUERYMAP_H 109