[$] The BPF-programmable network device

Containers and virtual machines on Linux communicate with the world via
virtual network devices. This arrangement makes the full power of the
Linux networking stack available, but it imposes the full overhead of that
stack as well. Often, the routing of this networking traffic can be
handled with relatively simple logic; the BPF-programmable network device,
which was merged for the 6.7 kernel release, makes it possible to avoid
expensive network processing, in at least some cases.