Allow defining multiple proxies & switching per app

[ilonachan]

Is your feature request related to a problem? Please describe.
It is currently possible to define a SOCKS5 proxy which all traffic captured by TC will be routed through (if this is turned off, traffic is just sent out to the network normally). This is useful to, for example, chain TC with Orbot or another VPN (that supports running in proxy mode).

The problem is that this setting applies to all apps indiscriminately. There may be apps that are incompatible with the TOR/VPN that all other apps should use, and which must be exempted from the proxy; but the only way to do that is to "disable monitoring", which bypasses TC's filters completely. (See #142)

The more specific problem here is that only a single proxy can be defined. It may be useful to route some apps through a VPN, and others through TOR exclusively. Or perhaps some Apps' backend disallows one VPN, so another one needs to be used specifically for those apps. (The latter case is feasible if one of the VPNs already supports proxy mode.)

Describe the solution you'd like
The settings should allow the user to define a list of proxies to use. One entry in that list should always be "No proxy". One of these proxies should be selected there as default for all apps (potentially with an easier-access method, see #319). The default on app install is "No proxy".

In the per-app settings, that proxy choice can be overridden with any of the other entries in the list. This could be a dropdown, with the default selection being a "Use default" entry. If no proxy is defined in settings, this dropdown doesn't need to be present.

Optionally, this dropdown could contain an entry "Bypass TC", which replaces the current functionality of "Disable Monitoring" by letting that specific app connect to the internet directly. Said option would then only decide whether to apply filters or not, and if "Bypass" is active it would be force-selected. This is a proposed solution to the extended case of #142, which in my opinion improves clarity.

[kasnder]

Thanks for your suggestion!

[ilonachan]

Now that I've built master, I see you've already implemented part 3 of this suggestion. That's immediately super useful, and I really like the UX too! One point of improvement: when "Exclude from VPN" is active, all other options become meaningless and should probably be greyed out (that's already what happens when "Tracker Protection" is turned off, but that one should also be greyed out).

With this new UI in mind, instead of the original idea of "Bypass TC" being a special option, it probably makes more sense to put the off-state of "Internet Access" in there. In short: the "Internet Access" toggle turns into a dropdown, with the options "Direct Connection" and "Blocked" if no proxy is defined, and "Default (<default selection from settings>)", "Direct Connection", "Proxy 1", "Proxy 2",..., "Blocked" otherwise. Since "Blocked" is essentially a "dummy sink", I think grouping it together with the other possible sinks makes sense. What do you think?

[kasnder]

love it!

Now that I've built master, I see you've already implemented part 3 of this suggestion. That's immediately super useful, and I really like the UX too! One point of improvement: when "Exclude from VPN" is active, all other options become meaningless and should probably be greyed out (that's already what happens when "Tracker Protection" is turned off, but that one should also be greyed out).

With this new UI in mind, instead of the original idea of "Bypass TC" being a special option, it probably makes more sense to put the off-state of "Internet Access" in there. In short: the "Internet Access" toggle turns into a dropdown, with the options "Direct Connection" and "Blocked" if no proxy is defined, and "Default ()", "Direct Connection", "Proxy 1", "Proxy 2",..., "Blocked" otherwise. Since "Blocked" is essentially a "dummy sink", I think grouping it together with the other possible sinks makes sense. What do you think?