Author: Alex Rousskov <rousskov@measurement-factory.com>

Author: Alex Rousskov <rousskov@measurement-factory.com>
Break forwarding loops for "transparent" or "intercept" http_ports.

Squid detected forwarding loops in most configurations, but broke
them (using a customizable HTTP_FORBIDDEN response) only when working as
an accelerator. Squid now breaks loops when working as a transparent
proxy as well.

A persistent loop is going to be broken anyway, when the Via and
X-Forwarded-For headers exceed header size limit, but that wastes a lot of
resources and may also crash misconfigured Squids.

TODO: Consider breaking all loops, regardless of the http_port options.

TODO: Consider adding a specific and/or configurable error page for this case
instead of using hard-coded ACCESS_DENIED.