tcp-in-a-weekend

Implementation of the following in Go:

• ping utility
• UDP protocol
• TCP protocol

Setup

From a Linux VM (eg. OrbStack - ubuntu)

1. Install dependencies

   # Install tools
   $ sudo apt install -y iptables lsof
   
   # Install Go
   $ wget -O /tmp/go.tar.gz $LINK_TO_GO_BINARY (https://go.dev/dl)
   
   # Untar, add to path
   $ tar -C /usr/local -xzf /tmp/go.tar.gz
   $ export PATH=$PATH:/usr/local/go/bin
   
   # Confirm installation successful
   $ go version
   

2. Run a local server at: 192.0.2.1:8080

   $ python3 -m http.server --bind 192.0.2.1 8080

3. Run setup script to create a network tunnel (tun0) and set up NAT

   bash setup.sh

Usage

Ping

go run cmd/ping/main.go 192.0.2.1

go run cmd/ping/main.go -c 3 192.0.2.1

UDP

go run cmd/udp/main.go 8.8.8.8

TCP

go run cmd/tcp/main.go 192.0.2.1

Linux VM options

• Lima: some potential network issues?
• Colima
• OrbStack: free for personal use, subscription otherwise.
• UTM

Debugging

1. tcpdump

   sudo tcpdump -ni tun0
   
   sudo tcpdump -ni tun0 host 192.0.2.1

2. tshark (terminal Wireshark)

   sudo tshark -f "tcp port 12345" -i tun0 -w dump.pcap

   Open dump.pcap in Wireshark.

3. nc

   nc -l 192.0.2.1 8080