IP6 exception has no attribute

I am programming in python and I have a problem, indeed when I throw my script, it ends a few seconds after the IP6 packet is detected. Apparently I have to filter packets and only accept IP4 packet to avoid this problem, and I would like to know how I can use it with the dpkt library, if possible when I started. I tried something but I am a beginner and it doesn't work as you can see in this line:

#Select Ipv4 packets because of problem with the .p in Ipv6
            if ip.p == dpkt.ip6:
                return`

      

        
        
        
      

    

The error encountered says "AttributeError: 'IP6' has no attribute 'p'." This is the traceback:

This is my code if you want to take a look :) Thanks for your time :)

import pcapy
import dpkt
from threading import Thread
import re
import binascii

liste=[]
listip=[]
piece_request_handshake = re.compile('13426974546f7272656e742070726f746f636f6c(?P<reserved>\w{8})(?P<info_hash>\w{20})(?P<peer_id>\w{20})')
piece_request_tcpclose = re.compile('(?P<start>\w{12})5011')


class PieceRequestSniffer(Thread):
    def __init__(self, dev='eth0'):
        Thread.__init__(self)

        self.expr = 'udp or tcp'

        self.maxlen = 65535  # max size of packet to capture
        self.promiscuous = 1  # promiscuous mode?
        self.read_timeout = 100  # in milliseconds
        self.max_pkts = -1  # number of packets to capture; -1 => no limit

        self.active = True
        self.p = pcapy.open_live(dev, self.maxlen, self.promiscuous, self.read_timeout)
        self.p.setfilter(self.expr)

    @staticmethod
    def cb(hdr, data):

        eth = dpkt.ethernet.Ethernet(str(data))
        ip = eth.data

        #Select only TCP protocols
        if ip.p == dpkt.ip.IP_PROTO_TCP:
            tcp = ip.data

            #Select Ipv4 packets because of problem with the .p in Ipv6
            if ip.p == dpkt.ip6:
                return
            else:
                try:
                    #Return hexadecimal representation
                    hex_data = binascii.hexlify(tcp.data)
                except:
                    return                

                handshake = piece_request_handshake.findall(hex_data)
                if handshake:
                    print "-----------handsheck filtered-------------"
                    liste.append(handshake)
                    print "\n"
                    #for element in zip(liste,"123456789abcdefghijklmnopqrstuvwxyz"):
                    #    print(element)



    def stop(self):
        self.active = False

    def run(self):
        while self.active:
            self.p.dispatch(0, PieceRequestSniffer.cb)


sniffer = PieceRequestSniffer()
sniffer.start()