Recalculate pcap ipv4 header checksum

fixcsum.py

#!/usr/bin/env python3

import sys
from scapy.all import *

def fix(infile, outfile):
    i = 0
    # packets = rdpcap(infile)
    fp = PcapWriter(outfile, append=True, sync=True)
    for p in PcapReader(infile):
        i += 1
        if (i % 100 == 0):
            print(i)
        if p.haslayer(IP):
            del (p.chksum)
            npacket = p.__class__(bytes(p))
            fp.write(npacket)


if __name__ == '__main__':
    if len(sys.argv) != 3:
        print("Bad number of args, put infile and outfile")
        sys.exit(1)

    in_file=sys.argv[1]
    out_file=sys.argv[2]
    fix(in_file, out_file)