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Purpose

Make the data posted in https://wiki.recessim.com/view/Landis%2BGyr_GridStream_Protocol#Data_captures more readible, by enabling WireShark support for the protocol through a custom dissector written in LUA.

Please contribute!

  • This dissector is alpha quality, with fields definitions based upon descriptions in page above and my own additional reverse engineering.
  • PLEASE submit a pull request or create an issue if you discover new fields!

Example of a capture

Pre-requisites

  • WireShark - provides the user interface for packet navigation and analysis
  • tshark ("term shark") - provides command-line tools to create PCAP files, naive plugin testing.
  • a linux-like environment - provides and shell and GNU tools for capture processing

Use

Step 1: Create a capture (PCAP) from source text files (run once, already run)

  • See sample-cap/*-txt-to-hd-to-pcap.sh for examples of how text files from the link above were first converted to hex dumps, using awk, sed, etc., then converted into PCAP files.
  • The scripts flag the PCAP files with a custom protocol ID

Step 2: Copy the gridstream.lua plugin to the Wireshark plugin directory

  • See the file promote.sh for an example specific to WireShark portable on Windows 11.

Step 3: Start Wireshark

  • Load wireshark.
  • Open a pcap file from the sample-cap folder.
  • Wireshark should automatically detect the custom protocol in the PCAP file, select the matching custom dissector plugin, and display the dissected packets.

Step 4: Iterate!

  • Identify new patterns in the messages, and modify the dissector to decompose those fields.
  • Submit an issue or PR with your changes!