i have code that receives pcap packates as bytes.
I decode the IP and UDP layer and later the proprietary app layer within (“UMS”).

I would like to check the IP header checksum and the UDP checksum prior continuing.
How to do this?

Here is my current code:

import io
import socket
from typing import Iterator
from dpkt import pcap, ip, udp


class DecodePcap:
    """
    Receives a pcap file as bytes to decode it with dpkt.
    """
    def __init__(self, pcap_bytes: bytes) -> None:
        self.pcap = pcap.Reader(io.BytesIO(pcap_bytes))
        """
        the reader is a iterator of tuples (timestamp, buf) where timestamp is a float and buf is a bytes object.
        """    


    def get_ums_packet_iterator(self) -> Iterator['UmsPacket']:
        """
        Returns a iterator of UmsPacket.
        """
        return map(UmsPacket, self.pcap)


class UmsPacket:
    """
    Data class to hold the fields of a packet from pcap.
    """
    def __init__(self, ums_tuple: tuple) -> None:
        self.timestamp: float = ums_tuple[0]
        ip_packet: ip.IP = ip.IP(ums_tuple[1])
        udp_packet: udp.UDP = ip_packet.data
        self.src_ip: str = socket.inet_ntoa(ip_packet.src)
        self.dst_ip: str = socket.inet_ntoa(ip_packet.dst)
        self.src_port: int = udp_packet.sport
        self.dst_port: int = udp_packet.dport
        self.data: bytes = udp_packet.data
        # check ip header checksum
        #?? assert ip_packet.sum 
        # check udp checksum
        #?? assert udp_packet.sum
        # 6th byte is the ICD version
        self.icd: int = self.data[6]