My understanding is that it started life as a fork(note: by same author) of openbsd's httpd. The author wanted to add reverse proxy capability to httpd and deci

My understanding is that it started life as a fork(note: by same author) of openbsd's httpd. The author wanted to add reverse proxy capability to httpd and decided that the problem domain was complex enough that it would hurt httpd's simplicity and warranted it's own program. So it's heart is a reverse http proxy. generalized to be a generic application layer proxy. and then integrated with the pf firewall to be a ip layer forwarder. note the distinction in the manual between redirections(ip forwarder) and relays(application proxy) According to the manual it has application specific relays for http and dns. for other than that you have to use the generic tcp relay. if you are redirecting, it does not look at the internals of the packet at all.