Where i can get packet information to make .pcap log ?

[Amattia]

@hexene could you explain to me how i can convert the packet data to the .pcap ?

In which part of code I can get the information (packages) that i must save to create a log ?

Please don't close this, i have some question.

Thanks so much

[hexene]

Please check the code in LocalVPNService. The device->network data would be available in the variable bufferToNetwork and network->device data in bufferFromNetwork.

[Amattia]

                        byte[] bytes = new byte[bufferCopy.remaining()];
                        bufferCopy.get(bytes);
                        String packet = new String(bytes);

                        FileOutputStream stream = new FileOutputStream(file);
                        stream.write(packet.getBytes());

bufferCopy is a copy of bufferFromNetwork, is it correct this ?

[hexene]

This is what you'll need:

bufferCopy = bufferToNetwork/FromNetwork.duplicate();
bufferCopy.flip(); // Assuming that bufferToNetwork/FromNetwork hasn't already been flipped
bufferSize = bufferCopy.limit();

Please refer to the documentation for ByteBuffer for more details.

[Amattia]

I apologize for the bad explanation , I wanted to know is:

Through these variables can obtain the information needed to create a file in .pcap format? This it would take to generate a .har and make the traffic test.

it is fair to say that the information that I need are in:
bufferToNetwork and in bufferFromNetwor ?

[hexene]

Yes.

[Amattia]

Is it correct this reasoning ?

               ByteBuffer bufferFromNetwork = networkToDeviceQueue.poll();
                if (bufferFromNetwork != null){
                    bufferFromNetwork.flip();

                  // Other copy of  bufferFromNetwork, necessary to write log

                    bufferCopy = bufferFromNetwork.duplicate();
                    bufferCopy.flip();
                    bufferSize = bufferCopy.limit();


                    while (bufferFromNetwork.hasRemaining()) {
                        vpnOutput.write(bufferFromNetwork);

                        // For each element in buffer i write a line in a file

                        byte[] bytes = new byte[bufferCopy.remaining()];
                        bufferCopy.get(bytes);
                        String packet = new String(bytes);

                        FileOutputStream stream = new FileOutputStream(file);
                        stream.write(packet.getBytes());
                    }
                       dataReceived = true;

I'm sorry for the many questions but I need to generate the log, and I find myself in difficulty in implementing this function.

Thanks to the availability

[hexene]

As I'd mentioned earlier, please familiarize yourself with how a ByteBuffer works, specifically how its limit and position are updated. Please also pay close attention to the code snipped I'd posted earlier.

In short, this is what you'll need:

FileOutputStream stream.....
....
ByteBuffer bufferFromNetwork = networkToDeviceQueue.poll();
if (bufferFromNetwork != null) {
  bufferFromNetwork.flip();

  ByteBuffer bufferCopy = bufferFromNetwork.duplicate();
  byte[] packetData = new byte[bufferCopy.limit()];
  bufferCopy.get(packetData);
  stream.write(packetData);
  ....
  while (bufferFromNetwork.hasRemaining())

Please note that this will only write the raw packet data to the file, you'll still have to convert it to the pcap format.

[hexene]

If all you need to do is to decode and print the packet data, you could do this instead:

Packet packet = new Packet(bufferCopy);
stream.write(packet.toString().getBytes());