hwfq contains userspace implementations of a few useful scheduling algorithms, as well as a datapath to run them in userspace via a TUN/TAP interface.
Schedulers implement the Scheduler trait, and can be used anywhere this trait is the right interface. This crate is currently opinionated about what a packet is, and specifically targets packets that parse as TCP/IP or UDP/IP.
The datapath module will capture packets on a TUN interface, apply rate limiting to simulate a link (bring your own delay emulation), apply scheduler implementations, and then forward packets out over a Unix pipe. The uds_out process can read from this pipe and send packets out via a second TUN interface.