NetStack

Features

• Subnetting & CIDR calculator: Parses CIDR notation (192.168.1.0/24) by hand
• TCP/UDP socket layer: Dual-stack IPv4/IPv6 support (handles IPv4-mapped IPv6 addresses correctly). Working TCP echo server as the first working socket primitive.
• Hand-crafted DNS resolver: Constructs raw DNS query packets byte-by-byte per RFC 1035, no DNS library.
• TCP handshake internals: Raw-socket-level SYN/SYN-ACK/ACK construction and observation.
• Port scanner: CIDR-range expansion (built on the subnetting layer) to generate scan targets.
• Packet sniffer: Raw/promiscuous-mode socket capture. Manual Ethernet/IP/TCP header parsing off the wire.

Reason it’s made

I used a lot of enumeration tools while solving CTF challenges, but never truly understand the underlying mechanism. This project is mainly a learning exercise to understand how everything works under the hood, down to the networking concepts. I created it in Rust to push me to understand memory safety concepts.

Structure

• User selects one of the following commands:
  • echo-server: create tcp server with optional custom port number (DONE)
  • subnet: parse CIDR notation and compute network address, broadcast address, and usable host range
  • dig: hand-craft a raw DNS query packet, send it over UDP, and parse the response
  • scan: scan a target host for open ports across a given port range
  • sniff: raw packet capture

Images