Scapy sniff the packet multiple times?

Question

I am using Scapy to capture packets by using the following code

from scapy.all import *

def verify(p):
     p.display()

sniff(prn=verify, iface="lo")

The sniff function captures every packet multiple times. For example, if I have a DNS query packet, this packet will display two times. How can make The sniff function to capture each packet only single time?

Answer 1

This is expected behavior. Scapy sees the packets on the loopback interface both when they "leave" and when they "arrive." So everything is duplicated with no distinction, because loopback is a special interface. Perhaps you should yourself just skip every second packet.

It was reported as a bug once, but rejected: https://bitbucket.org/secdev/scapy/issues/887/sniff-sends-packets-twice