Per-app DNS

[ignoramous]

It isn't really possible to know which app sent a DNS request, but what could be done is:

1. Learn from previous queries (names) and answers (IPs) and send the IPs that a particular app connects to, to a DNS server of user's choice.
2. Or, whenever the said app is in the foreground, change the DNS to use the one user has intended to.
3. Use technique similar to DNS64/NAT64 and then trap "placeholder-IP" (from 100.64.0.0/10) to forward to "actual-IP" as resolved just-in-time by app-specific upstream DNS instead.

Merits to both those approaches... Though, No. 2 requires access to accessibility-service. No. 3 will help support per-App proxies #229

See also #3 (ConnTrack)

[ignoramous]

Firestack changes are in: https://github.com/celzero/firestack/commit/b3c4b783cee5b25ec9a4e909f1edeab3388c0d7f

[ignoramous]

Kotlin / UI changes done too and released in v054.