def send_tcp_auto_reply(pkt, flag='PA'):
# p = IP()/TCP(flags=flag) # for further use - we can get char of the flags instead of hex
# [flags[x] for x in p.sprintf(flag)]
if flag == 'SA':
#handled 3 ways handshake
print("TCP 3 ways handshake send")
ip = IP()
tcp = TCP()
ip.src = pkt[IP].dst
ip.dst = pkt[IP].src
tcp.sport = pkt[TCP].dport
tcp.dport = pkt[TCP].sport
tcp.ack = pkt[TCP].seq + 1
tcp.seq = pkt[TCP].ack
tcp.flags = flag
send(ip / tcp)
else:
print("Send tcp reply")
ip = IP()
tcp = TCP()
ip.src = pkt[IP].dst
ip.dst = pkt[IP].src
tcp.ack = pkt[TCP].seq
tcp.seq = pkt[TCP].ack
tcp.sport = pkt[TCP].dport
tcp.dport = pkt[TCP].sport
tcp.flags = flag
data = pkt[TCP].payload
send(ip / tcp / data)