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      1 /*
      2  * Copyright (C) 2014 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 #ifdef LIBC_STATIC
     18 #error NetdClient.cpp should NOT be included in static libc builds.
     19 #endif
     20 
     21 #include <async_safe/log.h>
     22 
     23 #include "private/NetdClientDispatch.h"
     24 
     25 #include <dlfcn.h>
     26 #include <pthread.h>
     27 
     28 template <typename FunctionType>
     29 static void netdClientInitFunction(void* handle, const char* symbol, FunctionType* function) {
     30     typedef void (*InitFunctionType)(FunctionType*);
     31     InitFunctionType initFunction = reinterpret_cast<InitFunctionType>(dlsym(handle, symbol));
     32     if (initFunction != NULL) {
     33         initFunction(function);
     34     }
     35 }
     36 
     37 static void netdClientInitImpl() {
     38     void* netdClientHandle = dlopen("libnetd_client.so", RTLD_NOW);
     39     if (netdClientHandle == NULL) {
     40         // If the library is not available, it's not an error. We'll just use
     41         // default implementations of functions that it would've overridden.
     42         return;
     43     }
     44     netdClientInitFunction(netdClientHandle, "netdClientInitAccept4",
     45                            &__netdClientDispatch.accept4);
     46     netdClientInitFunction(netdClientHandle, "netdClientInitConnect",
     47                            &__netdClientDispatch.connect);
     48     netdClientInitFunction(netdClientHandle, "netdClientInitNetIdForResolv",
     49                            &__netdClientDispatch.netIdForResolv);
     50     netdClientInitFunction(netdClientHandle, "netdClientInitSocket", &__netdClientDispatch.socket);
     51 }
     52 
     53 static pthread_once_t netdClientInitOnce = PTHREAD_ONCE_INIT;
     54 
     55 extern "C" __LIBC_HIDDEN__ void netdClientInit() {
     56     if (pthread_once(&netdClientInitOnce, netdClientInitImpl)) {
     57         async_safe_format_log(ANDROID_LOG_ERROR, "netdClient", "Failed to initialize netd_client");
     58     }
     59 }
     60