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# File: $Id: udp.py,v 1.4 2006/09/01 05:24:04 gnn Exp $
#
# Author: George V. Neville-Neil
#
# Description: A class which implements UDP v4 packets

import pcs
from pcs.packets.dns import *

class udp(pcs.Packet):
    """A UDP class."""

    layout = pcs.Layout()

    def __init__(self, bytes = None):
        """initialize a UDP packet"""
        sport = pcs.Field("sport", 16)
        dport = pcs.Field("dport", 16)
        length = pcs.Field("length", 16)
        checksum = pcs.Field("checksum", 16)
        pcs.Packet.__init__(self, [sport, dport, length, checksum],
                            bytes = bytes)
        self.description = "UDP"

        if (bytes != None):
            self.data = self.next(bytes[0:len(bytes)])
        else:
            self.data = None

    def next(self, bytes):
        """Decode some of the more well known services, such as DNS."""
        if ((self.dport == 53) or (self.sport ==53)):
            return dnsheader(bytes[8:len(bytes)])