where {{.Port}} is the port that alpaca is listening on and {{.PAC}} is the PAC file that alpaca has fetched and is using.
This can be served on /alpaca.pac by alpaca.
This allows you to configure your system to use http://localhost:3128/alpaca.pac as the PAC file and know what URLs should be not proxied (DIRECT). All others are sent to alpaca which runs the unwrapped PAC file to proxy the request to the right place.
If you were to direct all HTTP(s) requests to alpaca in the system proxy settings, the system would use the proxy protocol always, even if alpaca is just going to go DIRECT itself. Some programs don't seem to like that they go through a proxy, so this feature would allow them to continue to go direct to their URL target.
On a Mac, one specific use case that this feature resolves is Citrix remote desktop not working when you proxy all connections via alpaca, but does work when having the system use a PAC file that does the wrapping I've provided above.
This would also allow other features (to be raised as separate issues if desired) such as serving the raw pac file itself (on /proxy.pac) that alpaca is using and allowing custom wrapping of PAC files by supplying templates similar to above by users who wish to customise the PAC routing (on /wrapped.pac).
Serve a "copy" of the PAC file that alapca is using that is wrapped with:
where
{{.Port}}is the port that alpaca is listening on and{{.PAC}}is the PAC file that alpaca has fetched and is using.This can be served on
/alpaca.pacby alpaca.This allows you to configure your system to use
http://localhost:3128/alpaca.pacas the PAC file and know what URLs should be not proxied (DIRECT). All others are sent to alpaca which runs the unwrapped PAC file to proxy the request to the right place.If you were to direct all HTTP(s) requests to alpaca in the system proxy settings, the system would use the proxy protocol always, even if alpaca is just going to go DIRECT itself. Some programs don't seem to like that they go through a proxy, so this feature would allow them to continue to go direct to their URL target.
On a Mac, one specific use case that this feature resolves is Citrix remote desktop not working when you proxy all connections via alpaca, but does work when having the system use a PAC file that does the wrapping I've provided above.
Serving files and proxy requests on the same HTTP port is possible because proxy requests all use the absolute-form (https://tools.ietf.org/html/rfc7230#section-5.3.2) and resource requests to an origin server use the origin-form (https://tools.ietf.org/html/rfc7230#section-5.3.1). alpaca can differentiate between a proxy request that it should forward and a request for a resource it serves by looking at the request-target (https://tools.ietf.org/html/rfc7230#section-5.3) and determining the form.
This would also allow other features (to be raised as separate issues if desired) such as serving the raw pac file itself (on
/proxy.pac) that alpaca is using and allowing custom wrapping of PAC files by supplying templates similar to above by users who wish to customise the PAC routing (on/wrapped.pac).