Design Overview

This part describes the design of the CSjark to help all the future developers to understand what is under the hood.

Textual description

CSjark starts with the csjark module. It takes as input command line arguments, including file and folder names for C header files and configuration files. It replaces folder names with the file names of the files inside the folders, and checks that all the files exists, then it gives the names of the configuration files to the config module.

The config module parses configuration files and stores them in suitable config data structures in memory. It takes as input file names, and it opens those files to read their content.

Csjark module then gives file names of C header files to the cpp module. The cpp module gives the file names and some other arguments to an external program, the C preprocessor (cpp.exe on Windows). This external program opens the header files, and when it encounters #include directives it searches for the right file and opens it as well. The output of this external program is just a long string of C code, which cpp module returns to the csjark module.

The csjark module then gives the C code string to cparser module, which forwards the string to pycparser. Pycparser parse the C code to generate an abstract syntax tree, which it returns to cparser which returns it to csjark.

Csjark module then tells cparser to find all struct definitions in the abstract syntax tree, which it does by traversing the tree. Each time it finds a struct, it asks dissector module to create a protocol for it. Afterwards cparser holds a list of all the created protocols.

Csjark then gets the list of protocols from cparser, and for each one asks dissector module to generate lua code for Wireshark dissectors. It writes these dissectors to files, and finishes with a status message informing the user how it all went.

The new field module is simply to move class Fields and its sub-classes into their own module to make dissector module smaller and less complex.

Summary

csjark module writes Lua files, config module opens and reads YAML files, cpp module starts an external program which reads C header files. The structure as well as the associations among the classes are shown on following module and class diagrams.

Module diagram

CSjark: module diagram

Class diagram

CSjark: class diagram