# Router

This directory contains a Debian-based router implemented on top of nftables.

It expects to be run with two network interfaces:

- `eth0`: The "external" interface.
- `eth1`: The "internal" interface.

The order of these is important.
The router cannot possibly know which one is which and thus assumes that `eth0` is the external one and `eth1` the internal one.
The firewall is set up to take incoming traffic on `eth1` and forward + masquerade it to `eth0`.

It also expects an env variable `DELAY_MS` to be set and will apply this delay as part of the routing process[^1].

[^1]: This is done via `tc qdisc` which only works for egress traffic. To ensure the delay applies in both directions, we divide it by 2 and apply it on both interfaces.