| /* |
| * Copyright (C) 2016 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 requied 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 DNS_RESPONDER_H |
| #define DNS_RESPONDER_H |
| |
| #include <arpa/nameser.h> |
| |
| #include <atomic> |
| #include <mutex> |
| #include <string> |
| #include <thread> |
| #include <unordered_map> |
| #include <vector> |
| |
| #include <android-base/thread_annotations.h> |
| |
| namespace test { |
| |
| struct DNSHeader; |
| struct DNSQuestion; |
| struct DNSRecord; |
| |
| /* |
| * Simple DNS responder, which replies to queries with the registered response |
| * for that type. Class is assumed to be IN. If no response is registered, the |
| * default error response code is returned. |
| */ |
| class DNSResponder { |
| public: |
| DNSResponder(const char* listen_address, const char* listen_service, |
| int poll_timeout_ms, uint16_t error_rcode, |
| double response_probability); |
| ~DNSResponder(); |
| void addMapping(const char* name, ns_type type, const char* addr); |
| void removeMapping(const char* name, ns_type type); |
| void setResponseProbability(double response_probability); |
| bool running() const; |
| bool startServer(); |
| bool stopServer(); |
| std::vector<std::pair<std::string, ns_type>> queries() const; |
| void clearQueries(); |
| |
| private: |
| // Key used for accessing mappings. |
| struct QueryKey { |
| std::string name; |
| unsigned type; |
| QueryKey(std::string n, unsigned t) : name(n), type(t) {} |
| bool operator == (const QueryKey& o) const { |
| return name == o.name && type == o.type; |
| } |
| bool operator < (const QueryKey& o) const { |
| if (name < o.name) return true; |
| if (name > o.name) return false; |
| return type < o.type; |
| } |
| }; |
| |
| struct QueryKeyHash { |
| size_t operator() (const QueryKey& key) const { |
| return std::hash<std::string>()(key.name) + |
| static_cast<size_t>(key.type); |
| } |
| }; |
| |
| // DNS request handler. |
| void requestHandler(); |
| |
| // Parses and generates a response message for incoming DNS requests. |
| // Returns false on parsing errors. |
| bool handleDNSRequest(const char* buffer, ssize_t buffer_len, |
| char* response, size_t* response_len) const; |
| |
| bool addAnswerRecords(const DNSQuestion& question, |
| std::vector<DNSRecord>* answers) const; |
| |
| bool generateErrorResponse(DNSHeader* header, ns_rcode rcode, |
| char* response, size_t* response_len) const; |
| bool makeErrorResponse(DNSHeader* header, ns_rcode rcode, char* response, |
| size_t* response_len) const; |
| |
| |
| // Address and service to listen on, currently limited to UDP. |
| const std::string listen_address_; |
| const std::string listen_service_; |
| // epoll_wait() timeout in ms. |
| const int poll_timeout_ms_; |
| // Error code to return for requests for an unknown name. |
| const uint16_t error_rcode_; |
| // Probability that a valid response is being sent instead of being sent |
| // instead of returning error_rcode_. |
| std::atomic<double> response_probability_; |
| |
| // Mappings from (name, type) to registered response and the |
| // mutex protecting them. |
| std::unordered_map<QueryKey, std::string, QueryKeyHash> mappings_ |
| GUARDED_BY(mappings_mutex_); |
| // TODO(imaipi): enable GUARDED_BY(mappings_mutex_); |
| std::mutex mappings_mutex_; |
| // Query names received so far and the corresponding mutex. |
| mutable std::vector<std::pair<std::string, ns_type>> queries_ |
| GUARDED_BY(queries_mutex_); |
| mutable std::mutex queries_mutex_; |
| // Socket on which the server is listening. |
| int socket_; |
| // File descriptor for epoll. |
| int epoll_fd_; |
| // Signal for request handler termination. |
| std::atomic<bool> terminate_ GUARDED_BY(update_mutex_); |
| // Thread for handling incoming threads. |
| std::thread handler_thread_ GUARDED_BY(update_mutex_); |
| std::mutex update_mutex_; |
| }; |
| |
| } // namespace test |
| |
| #endif // DNS_RESPONDER_H |