USB Gadget Configfs Library
Rust has built-in support to compile examples. You can build the HID + ECM example like so:
cargo build --example hidecm
A Vagrant box is available that pre-installs packages needed to compile a loopback dummy_hcd kernel module. Be aware that the provisioning step is a two-step process and requires a vagrant reload and execution of the script mentioned at the end of the first provision to build and install the kernel module.
Before running the shell scripts accompanying the examples, run sudo modprobe dummy_hcd to load the loopback.