proxy

Running the Transparent UDP Proxy

This guide walks you through building and running the Symphony proxy locally, configuring iptables for transparent redirection, and debugging the setup.

1. Build and Run the Proxy

Build the proxy binary and run it under a dedicated user (e.g., proxyuser) to prevent redirect loops.

go build -trimpath -o myproxy
sudo -u proxyuser ./myproxy

💡 Create the proxyuser account if it doesn't exist:

sudo useradd -r -s /sbin/nologin proxyuser

2. Set Up iptables Rules

These rules transparently intercept both outbound and inbound UDP traffic:

sudo bash apply_symphony_iptables_local.sh

3. Confirm Rules Are Active

Check whether the iptables rules are installed and processing packets:

sudo iptables -t nat -L -n -v
sudo iptables -t mangle -L -n -v

Look for non-zero pkts and bytes columns on relevant rules after generating traffic.

4. Reset Rules (Cleanup)

To flush all rules in the nat and mangle tables:

sudo iptables -t nat -F
sudo iptables -t mangle -F

Debugging Tips

Dump conntrack entries (look for marks):

sudo conntrack -L -p udp

Monitor proxy ports (to verify redirection):

sudo tcpdump -n -i any udp port 15002 or port 15006