Firewall Configuration Manager
App Description:
This firewall configuration manager is a custom-built Linux-based client-server system that allows users to interactively and remotely manage firewall rules via terminal or socket connections. The server maintains a list of firewall rules and keeps a log of all connection queries, including matched IP-port pairs. Users can add, remove, and list firewall rules, validate connection requests, and view stored queries through a well-defined command interface.
I designed and implemented the entire system in C, focusing on concurrent socket-based communication, memory-safe request handling, and accurate parsing of firewall rules and IP/port validations. A Bash-based test suite was also developed to ensure protocol correctness and stability.
Why I built this:
The project was built to deepen my understanding of low-level systems programming, socket communication, and concurrent server architecture in C. I wanted to create a real-world tool that simulates the basic operation of a firewall controller similar to how real firewalls match incoming connections to allowlists or blocklists based on IP address and port rules.
How it was built:
Technologies used:
The system was implemented in C using POSIX sockets and multithreading for concurrent request handling. It supports both interactive and client-server modes. I wrote custom parsing and validation routines to enforce rule formatting and used dynamically managed memory structures to safely store active rules and request logs.
Functionality highlights:
- Add/delete firewall rules via command line
- Validate connections against stored rules
- Track which rules accepted which queries
- Full query logging with request listing
- Concurrency-safe multithreaded server
- Client program for remote interaction
Compiling and testing:
The application was compiled with GCC and tested using a university-provided Linux VM. I used valgrind to eliminate memory leaks and verified correct thread handling. A Bash script, test.sh, automated both interactive and network-based tests to validate rule correctness, command parsing, and multi-client handling.