ISIS replay tool - sniffer stage

Since my last post, I have modified the code from the python routing toolkit to use the python-pypcap library, in order to catch all the ISIS packets (both outgoing and incoming ISIS packets on a given physical interface).

That means that at this stage, the tool can both capture the ISIS packets, interpret all the necessary fields from the ISIS headers and the containing TLVs, similar to how tcpdump and wireshark intepret packets for common protocols. Also, these packets can be stored now in two formats, both the toolkit's specific format and as a simple libpcap capture. Both these formats can be used in both ways - to write the dump and to read it, and interpret it from there.

Also, I have tested this on the GSoC testbed, with the below topology.

Below I have attached printscreens with hello packets and CSNP packets:

And CSNP packets, with the pyrt format on the upper side and the tcpdump equivalent below: