from scapy.all import *
from scapy.layers.inet import IP, UDP, TCP
from scapy.layers.l2 import Ether


def cut_packet(pkt):
    data = raw(pkt)
    if len(pkt) < 100:
        pad_len = 100 - len(pkt)
        pad = Padding()
        pad.load = '\x00' * pad_len
        pkt = pkt/pad
    if len(pkt) > 100:
        return Raw(data[:100])
    return pkt


def process():
    pkts = rdpcap('vpn_aim_chat1a.pcap')
    i = 0
    for pkt in pkts:
        # 只保留pair
        # target_pair = None
        # if UDP in pkt:
        #     target_pair = UDP
        # if TCP in pkt:
        #     target_pair = TCP
        # raw_data = pkt[target_pair].payload
        # pkt = IP(raw(raw_data))
        # print(pkt.summary())

        # 这个文件内的数据包没有数据链路层
        # pkt[Ether].src = '00:00:00:00:00:00'  # 将源MAC地址改为0x00
        # pkt[Ether].dst = '00:00:00:00:00:00'  # 将目标MAC地址改为0x00
        pkt[IP].src = '0.0.0.0'  # 将源IP地址改为0x00
        pkt[IP].dst = '0.0.0.0'  # 将目标IP地址改为0x00

        if UDP in pkt:
            layer_after = pkt[UDP].payload.copy()
            pad = Padding()
            pad.load = '\x00' * 12
            layer_before = pkt.copy()
            layer_before[UDP].remove_payload()
            pkt = layer_before / raw(pad) / layer_after

        pkt = cut_packet(pkt)

        wrpcap('output/packet_{0}.pcap'.format(i), [pkt])
        i = i + 1


def read_pkt(filename: str):
    pkts = rdpcap(filename)
    print(pkts)


# read_pkt("output/packet_1.pcap")
process()