getifaddrs fix

extra/getifaddrs_bridge/readme

@@ -0,0 +1,19 @@
+### 编译
+
+使用NDK编译getifaddrs_bridge_server.c:
+
+`aarch64-linux-android-clang getifaddrs_bridge_server.c -o getifaddrs_bridge_server`
+
+在小小电脑上编译getifaddrs_bridge_client_lib.c:
+
+`gcc getifaddrs_bridge_client_lib.c -o getifaddrs_bridge_client_lib.so -shared`
+
+### 使用
+
+在安卓端:
+
+`getifaddrs_bridge_server /path/to/container/tmp/.getifaddrs-bridge`
+
+在proot容器：
+
+`LD_PRELOAD=/path/to/getifaddrs_bridge_client_lib.so <your_program>`