How to pick up IP packets and inject on different VM and interface

Question

I have been trying to solve these 2 problems, but without success.

1. I wonder if it's possible to remove specific packets from an interface with Gopacket or is it just for listening on the wire? For example when I send a UDP packet to a wrong port and then with Gopacket I correct it, it will send 2 packets, 1 to the wrong port and 1 to the correct one. Is there a way to discard/drop the wrong packet with Gopacket?

2. What I am trying to do, is to pick up all packets that are sent by a client over IP and then encapsulate each packet as a payload in another protocol X and send to the remote host which will receive on protocol X, get the payload and send it on its interface to reach the server over IP again. (IP (Client) -> Protocol X (Sniffer 1) -> Protocol X (Sniffer 2) -> IP (Server))

I have verified that the packet which Sniffer 1 picks up from the Client's interface is the same which arrives at Sniffer 2, but the problem is when Sniffer 2 injects it on the Server's interface. I can't see that packet with tcpdump or any other tool. The packet is injected with this command:

if handle, err := pcap.OpenLive("enp0s8", 1600, true, 100); err != nil {
    panic(err)
} else {
   err = handle.WritePacketData(packet.Data())
}

If the Protocol X part is avoided, then the server will receive messages from client, but with Protocol X it is not possible.

Thanks in advance!

Answer 1

According to the Documentation

Package pcap allows users of gopacket to read packets off the wire or from pcap files.

To discard packages, you will need to be able to intercept them. Depending on how generic you want to solve this problem, you probably need to hook into the kernel. I recommend looking into iptables and netfilters.

I found some VPN that are written in go, maybe look into how they are built, as you want to do something similar (tunnelling of packets).