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#!/usr/bin/env python3
import socket
import struct
def parse_udp(packet):
header_length = 8
header = packet[:header_length]
data = packet[header_length:]
(source_port, dest_port, data_length, checksum) = struct.unpack(
"!HHHH", header)
return source_port, dest_port, data_length, data, checksum
def parse_ip(packet):
header_length_in_bytes = (packet[0] & 0x0f) * 4
header = packet[:20]
data = packet[header_length_in_bytes:]
length, protocol, src, dst = struct.unpack(
"!xxHxxxxxBxx4s4s", header)
header = {'length': length,
'protocol': protocol,
'source': src,
'destination': dst}
return header_length_in_bytes, header, data
def format_ip(addr):
return '.'.join('%d'%i for i in addr)
def main():
s = socket.socket(socket.AF_INET, socket.SOCK_RAW, socket.IPPROTO_UDP)
while True:
raw, address = s.recvfrom(2 ** 16 - 1)
ip_header_len, ip_header, ip_payload = parse_ip(raw)
src_port, dst_port, udp_len, udp_data, udp_crc = parse_udp(ip_payload)
print("{}:{} --> {}:{}\nData length: {}\nChecksum: {}\n{}\n".format(
format_ip(ip_header['source']), src_port,
format_ip(ip_header['destination']), dst_port,
udp_len, udp_crc, udp_data))
if __name__ == "__main__":
main()
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