relayd is a daemon to relay and dynamically redirect incoming connections
to a target host.  Its purposes is to run as a load-balancer.  The daemon
is able to monitor groups of hosts for availability, which is determined
by checking for a specific service common to a host group.  When availability
is confirmed, Layer 3 and/or layer 7 forwarding services are set up by relayd.

Layer 3 redirection happens at the packet level; to configure it, relayd
communicates with pf(4).

WWW: https://github.com/mmatuska/relayd