netpfil tests: improve pft_ping.py
4c3c6c9271c0
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Description

netpfil tests: improve pft_ping.py

Multiple improvements to pft_ping.py:

Automatically use IPv6 when IPv6 addresses are used, --ip6 is not needed.
Building of ping requests and parsing of ping replies is done layer by layer. This way most arguments are available both for IPv6 and IPv4, for ICMP and TCP.
Use argument groups for improved readability.
Change ToS and TTL argument name to TC and HL to reflect the modern IPv6 nomenclature. The argument still set related IPv4 header fields properly.
Instead of sniffing for the very specific case of duplicated packets, allow for sniffing on multiple interfaces.
Report which sniffer has failed by setting bits of error code.
Raise meaningful exceptions when irrecoverable errors happen.
Make IPv4 fragmentation flags configurable.
Make IPv6 HL / IPv4 TTL configurable.
Make TCP MSS configurable.
Make TCP sequence number configurable.
Make ICMP payload size configurable.
Add debug output.
Move command line argument parsing out of network functions.
Make the code somehow PEP-8 compliant.