Netkit, which is what this is built on, is pretty neat. For transmitting packets from one container/VM to another, the conventional solution is to give each its own veth device. When you do that, the kernel network stack, at like the broad logic level, is sort of oblivious to the fact that the devices aren't real ethernet devices and don't have to go through the ethernet motions to transact.

Netkit replaces that logic with a simple pairing of sending and receiving eBPF programs; it's an eBPF cut-through for packet-level networking between networks that share a host kernel. It's faster, and it's simpler to reason about; the netkit.c code is pretty easy to read straight through.