#!/usr/bin/env python3
# drop_icmp_v4.py
# Requirements: NetfilterQueue, scapy

import sys
from netfilterqueue import NetfilterQueue
from scapy.all import IP

def on_packet(pkt):
    data = pkt.get_payload()
    try:
        ip = IP(data)
        # IPv4 ICMP protocol number == 1
        if ip.proto == 1:
            pkt.drop()
            return
    except Exception:
        # parsing error -> accept (conservative choice)
        pass
    pkt.accept()

def main():
    if len(sys.argv) < 2:
        print("Usage: drop_icmp_v4.py <QUEUE_NUM>", file=sys.stderr)
        sys.exit(1)
    qnum = int(sys.argv[1])
    nfq = NetfilterQueue()
    nfq.bind(qnum, on_packet)
    try:
        nfq.run()
    except KeyboardInterrupt:
        pass
    finally:
        nfq.unbind()

if __name__ == "__main__":
    main()