tcpdump traffic verification in robot framework

Question

Using these below command im verifying traffic flow on a interface.

tcpdump -i v100 -nnvXSs 0 -w /tmp/tr.pcap  
tcpdump -nnvXSs 0 -A -r /tmp/tr.pcap "src host ${client_ip}"
Result should contain  ${client_ip}

But how do I verify there is no packets in the .pcap file? And also how do I verify all traffic passes through?

Answer 1

I would write a python module tcpdump_util and use the python pyshark package.

def collect_capture(file='tr.pcap'):
    return pyshark.FileCapture(file)

def get_capture_length(capture):
    return len([packet for packet in capture])

That could give you the number of packets captured. As for verification... I am not sure. You might have to capture on both sides?