SSH multiplexing library, allowing you to write "jump host" style proxies.
Supports both transparent -oProxyJump=sshmux-server style jumps, as well as interactive session forwarding (with some limitations).
Look at sshmuxd instead, then: https://github.com/kennylevinsen/sshmuxd. For fleet management, look at https://github.com/kennylevinsen/sshfleet.