我正在尝试使用 BS 项目的 VpnService 为 Android 实现一个简单的防火墙。我选择 VpnService 因为它将在非 root 设备上运行。它将记录连接并让您过滤连接。 （基于IP）
有一个应用程序可以做到这一点，因此这是可能的。
谷歌应用商店 https://play.google.com/store/apps/details?id=com.netspark.firewall
我做了一些研究，发现 VpnService 创建了一个 Tun 接口。而已。 （没有 VPN 实现，只是一个隧道）它允许您为此接口提供地址并添加路由。它返回一个文件描述符。您可以读取传出包并写入传入包。
我创建了一个 VpnService 派生类并开始提供服务。我可以配置tun0与 VpnService.Builder 类。当我看着mobiwol's连接与adb shell netcfg它创造了一个tun0地址为 10.2.3.4/32 的接口。它将所有包路由到该专用网络并发送到互联网。我也在尝试同样的事情。创建了一个地址为 10.0.0.2/32 的接口。使用 addRoute 函数添加了一条路线。 0.0.0.0/0 所以据我所知，我可以捕获来自所有网络的所有包。 （我对这个主题还很陌生，仍在学习。我在互联网上找到了一些东西，所以我不太确定。如果我错了，请纠正我。）
我创建了 2 个正在服务的线程。使用受保护的套接字从文件描述符读取并将其写入 127.0.0.1。 （我不太确定是否应该读/写 127.0.0.1。也许这就是问题所在。）
我分析了从文件描述符中读取的数据包。例如：
01000101 byte:69 //ipv4 20byte header
00000000 byte:0 //TOS
00000000 byte:0 //Total Length
00111100 byte:60 //Total Length
11111100 byte:-4 //ID
11011011 byte:-37 //ID
01000000 byte:64 //fragment
00000000 byte:0 //"
01000000 byte:64 //TTL
00000110 byte:6 //Protocol 6 -> TCP
01011110 byte:94 //Header checksum
11001111 byte:-49 //Header checksum
00001010 byte:10 //10.0.0.2
00000000 byte:0
00000000 byte:0
00000010 byte:2
10101101 byte:-83 //173.194.39.78 //google
00111110 byte:-62
00100111 byte:39
******** byte:78
10110100 byte:-76 // IP option
01100101 byte:101
00000001 byte:1
10111011 byte:-69
//20byte IP haeder
01101101 byte:109
. . //40byte data (i couldnt parse TCP header,
I think its not needed when I route this in IP layer)
. .
. .
00000110 byte:6
我在其余数据中没有找到任何其他 IP 标头。我认为 10.0.0.2 网络到本地网络（192.168.2.1）和互联网之间应该有一个封装。我不知道。
我真正的问题是我陷入了传入包线程。我什么都读不了。没有反应。正如您在屏幕截图中看到的，没有传入数据：
截屏 https://i.stack.imgur.com/1EvZ7.jpg
我正在尝试从与受保护套接字写入 127.0.0.1 时使用的同一连接进行读取。
Android Tun 接口 (tun0) 互联网连接
所有包 10.0.0.2 127.0.0.1？ 192.168.2.1 互联网？
我找不到任何有关 VpnService 的有用信息。 （ToyVPN 示例毫无用处）我阅读了有关 Linux Tun/Tap 的文档，但它是关于主机和远程之间的隧道。我希望主机和遥控器位于同一设备上。不像隧道。
我怎样才能做到这一点？
编辑：请求代码。目前还处于非常早期的阶段。正如我之前提到的，它是一个 VpnService 派生类。在服务线程中创建 2 个线程（读取和写入）。
package com.git.firewall;
public class GITVpnService extends VpnService implements Handler.Callback, Runnable {
private static final String TAG = "GITVpnService";
private String mServerAddress = "127.0.0.1";
private int mServerPort = 55555;
private PendingIntent mConfigureIntent;
private Handler mHandler;
private Thread mThread;
private ParcelFileDescriptor mInterface;
@Override
public int onStartCommand(Intent intent, int flags, int startId) {
// The handler is only used to show messages.
if (mHandler == null) {
mHandler = new Handler(this);
}
// Stop the previous session by interrupting the thread.
if (mThread != null) {
mThread.interrupt();
}
// Start a new session by creating a new thread.
mThread = new Thread(this, "VpnThread");
mThread.start();
return START_STICKY;
}
@Override
public void onDestroy() {
if (mThread != null) {
mThread.interrupt();
}
}
@Override
public boolean handleMessage(Message message) {
if (message != null) {
Toast.makeText(this, (String)message.obj, Toast.LENGTH_SHORT).show();
}
return true;
}
@Override
public synchronized void run() {
try {
Log.i(TAG, "Starting");
InetSocketAddress server = new InetSocketAddress(
mServerAddress, mServerPort);
run(server);
} catch (Exception e) {
Log.e(TAG, "Got " + e.toString());
try {
mInterface.close();
} catch (Exception e2) {
// ignore
}
Message msgObj = mHandler.obtainMessage();
msgObj.obj = "Disconnected";
mHandler.sendMessage(msgObj);
} finally {
}
}
DatagramChannel mTunnel = null;
private boolean run(InetSocketAddress server) throws Exception {
boolean connected = false;
android.os.Debug.waitForDebugger();
// Create a DatagramChannel as the VPN tunnel.
mTunnel = DatagramChannel.open();
// Protect the tunnel before connecting to avoid loopback.
if (!protect(mTunnel.socket())) {
throw new IllegalStateException("Cannot protect the tunnel");
}
// Connect to the server.
mTunnel.connect(server);
// For simplicity, we use the same thread for both reading and
// writing. Here we put the tunnel into non-blocking mode.
mTunnel.configureBlocking(false);
// Authenticate and configure the virtual network interface.
handshake();
// Now we are connected. Set the flag and show the message.
connected = true;
Message msgObj = mHandler.obtainMessage();
msgObj.obj = "Connected";
mHandler.sendMessage(msgObj);
new Thread ()
{
public void run ()
{
// Packets to be sent are queued in this input stream.
FileInputStream in = new FileInputStream(mInterface.getFileDescriptor());
// Allocate the buffer for a single packet.
ByteBuffer packet = ByteBuffer.allocate(32767);
int length;
try
{
while (true)
{
while ((length = in.read(packet.array())) > 0) {
// Write the outgoing packet to the tunnel.
packet.limit(length);
debugPacket(packet); // Packet size, Protocol, source, destination
mTunnel.write(packet);
packet.clear();
}
}
}
catch (IOException e)
{
e.printStackTrace();
}
}
}.start();
new Thread ()
{
public void run ()
{
DatagramChannel tunnel = mTunnel;
// Allocate the buffer for a single packet.
ByteBuffer packet = ByteBuffer.allocate(8096);
// Packets received need to be written to this output stream.
FileOutputStream out = new FileOutputStream(mInterface.getFileDescriptor());
while (true)
{
try
{
// Read the incoming packet from the tunnel.
int length;
while ((length = tunnel.read(packet)) > 0)
{
// Write the incoming packet to the output stream.
out.write(packet.array(), 0, length);
packet.clear();
}
}
catch (IOException ioe)
{
ioe.printStackTrace();
}
}
}
}.start();
return connected;
}
private void handshake() throws Exception {
if (mInterface == null)
{
Builder builder = new Builder();
builder.setMtu(1500);
builder.addAddress("10.0.0.2",32);
builder.addRoute("0.0.0.0", 0);
//builder.addRoute("192.168.2.0",24);
//builder.addDnsServer("8.8.8.8");
// Close the old interface since the parameters have been changed.
try {
mInterface.close();
} catch (Exception e) {
// ignore
}
// Create a new interface using the builder and save the parameters.
mInterface = builder.setSession("GIT VPN")
.setConfigureIntent(mConfigureIntent)
.establish();
}
}
private void debugPacket(ByteBuffer packet)
{
/*
for(int i = 0; i < length; ++i)
{
byte buffer = packet.get();
Log.d(TAG, "byte:"+buffer);
}*/
int buffer = packet.get();
int version;
int headerlength;
version = buffer >> 4;
headerlength = buffer & 0x0F;
headerlength *= 4;
Log.d(TAG, "IP Version:"+version);
Log.d(TAG, "Header Length:"+headerlength);
String status = "";
status += "Header Length:"+headerlength;
buffer = packet.get(); //DSCP + EN
buffer = packet.getChar(); //Total Length
Log.d(TAG, "Total Length:"+buffer);
buffer = packet.getChar(); //Identification
buffer = packet.getChar(); //Flags + Fragment Offset
buffer = packet.get(); //Time to Live
buffer = packet.get(); //Protocol
Log.d(TAG, "Protocol:"+buffer);
status += " Protocol:"+buffer;
buffer = packet.getChar(); //Header checksum
String sourceIP = "";
buffer = packet.get(); //Source IP 1st Octet
sourceIP += buffer;
sourceIP += ".";
buffer = packet.get(); //Source IP 2nd Octet
sourceIP += buffer;
sourceIP += ".";
buffer = packet.get(); //Source IP 3rd Octet
sourceIP += buffer;
sourceIP += ".";
buffer = packet.get(); //Source IP 4th Octet
sourceIP += buffer;
Log.d(TAG, "Source IP:"+sourceIP);
status += " Source IP:"+sourceIP;
String destIP = "";
buffer = packet.get(); //Destination IP 1st Octet
destIP += buffer;
destIP += ".";
buffer = packet.get(); //Destination IP 2nd Octet
destIP += buffer;
destIP += ".";
buffer = packet.get(); //Destination IP 3rd Octet
destIP += buffer;
destIP += ".";
buffer = packet.get(); //Destination IP 4th Octet
destIP += buffer;
Log.d(TAG, "Destination IP:"+destIP);
status += " Destination IP:"+destIP;
/*
msgObj = mHandler.obtainMessage();
msgObj.obj = status;
mHandler.sendMessage(msgObj);
*/
//Log.d(TAG, "version:"+packet.getInt());
//Log.d(TAG, "version:"+packet.getInt());
//Log.d(TAG, "version:"+packet.getInt());
}
}
