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      1 /*
      2  * Copyright (C) 2017 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 NETD_SERVER_IPTABLES_RESTORE_CONTROLLER_H
     18 #define NETD_SERVER_IPTABLES_RESTORE_CONTROLLER_H
     19 
     20 #include <memory>
     21 #include <mutex>
     22 #include <sys/types.h>
     23 
     24 #include "NetdConstants.h"
     25 
     26 class IptablesProcess;
     27 
     28 class IptablesRestoreInterface {
     29   public:
     30     virtual ~IptablesRestoreInterface() = default;
     31 
     32     // Execute |commands| on the given |target|, and populate |output| with stdout.
     33     virtual int execute(const IptablesTarget target, const std::string& commands,
     34                         std::string* output) = 0;
     35 };
     36 
     37 class IptablesRestoreController final : public IptablesRestoreInterface {
     38   public:
     39     // Not for general use. Use gCtls->iptablesRestoreCtrl
     40     // to get an instance of this class.
     41     IptablesRestoreController();
     42 
     43     ~IptablesRestoreController() override;
     44 
     45     int execute(const IptablesTarget target, const std::string& commands,
     46                 std::string* output) override;
     47 
     48     enum IptablesProcessType {
     49         IPTABLES_PROCESS,
     50         IP6TABLES_PROCESS,
     51         INVALID_PROCESS = -1,
     52     };
     53 
     54     // Called by the SIGCHLD signal handler when it detects that one
     55     // of the forked iptables[6]-restore process has died.
     56     IptablesProcessType notifyChildTermination(pid_t pid);
     57 
     58 protected:
     59     friend class IptablesRestoreControllerTest;
     60     pid_t getIpRestorePid(const IptablesProcessType type);
     61 
     62     // The maximum number of times we poll(2) for a response on our set of polled
     63     // fds. Chosen so that the overall timeout is 5s. The timeout is so high because
     64     // our version of iptables still polls every second in xtables_lock.
     65     static int MAX_RETRIES;
     66 
     67     // The timeout (in millis) for each call to poll. The maximum wait is
     68     // |POLL_TIMEOUT_MS * MAX_RETRIES|. Chosen so that the overall timeout is 1s.
     69     static int POLL_TIMEOUT_MS;
     70 
     71     void Init();
     72 
     73 private:
     74     static IptablesProcess* forkAndExec(const IptablesProcessType type);
     75 
     76     int sendCommand(const IptablesProcessType type, const std::string& command,
     77                     std::string *output);
     78 
     79     static bool drainAndWaitForAck(const std::unique_ptr<IptablesProcess> &process,
     80                                    const std::string& command,
     81                                    std::string *output);
     82 
     83     static void maybeLogStderr(const std::unique_ptr<IptablesProcess> &process,
     84                                const std::string& command);
     85 
     86     // Guards calls to execute().
     87     std::mutex mLock;
     88 
     89     std::unique_ptr<IptablesProcess> mIpRestore;
     90     std::unique_ptr<IptablesProcess> mIp6Restore;
     91 };
     92 
     93 #endif  // NETD_SERVER_IPTABLES_RESTORE_CONTROLLER_H
     94