func (r *RawSocketServer) injectPacketFromDst(tcpLayer *layers.TCP, rawBytes []byte) error {
// Preparing ipLayer.
ipLayer := &layers.IPv4{
SrcIP: r.dst.ip,
DstIP: r.src.ip,
Version: 4,
TTL: 64,
Protocol: layers.IPProtocolTCP,
}
options := gopacket.SerializeOptions{
ComputeChecksums: true,
FixLengths: true,
}
tcpLayer.SrcPort = r.dst.port
tcpLayer.DstPort = r.src.port
tcpLayer.Window = r.window
tcpLayer.Ack = r.ack
tcpLayer.Seq = r.seq
tcpLayer.SetNetworkLayerForChecksum(ipLayer)
// And create the packet with the layers
buffer := gopacket.NewSerializeBuffer()
gopacket.SerializeLayers(buffer, options,
ipLayer,
tcpLayer,
gopacket.Payload(rawBytes),
)
outgoingPacket := buffer.Bytes()
p := tuntap.Packet{
Protocol: 0x800,
Truncated: false,
Packet: outgoingPacket,
}
return r.iface.WritePacket(&p)
}