libp2p-test-plans/hole-punch-interop/router/README.md

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 process¹.

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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. ↩︎