GeezerVison

Fixes #241.

h2() pools DoH connections for 3 minutes (IdleConnTimeout) with no HTTP/2 keep-alive health-check. Several resolvers close idle DoH connections far sooner — measured from a fixed network, same day, reusing a TLS connection after an idle period:

With Quad9 (or any resolver whose idle timeout is under 3 minutes), every DNS lull longer than the server's idle window leaves the pool full of dead connections. The next queries are written into them, hang ~8–10 s, and surface as Post "…": unexpected EOF or http-status: 502; maxEOFTries often just picks the next dead pooled connection, so bursts of parallel queries fail together. Downstream on Android this expires alg mappings (realips([])), killing established flows of allowed apps, and fails the OS connectivity probes routed through the tunnel.

Change

Two adjustments in h2():

1. IdleConnTimeout 3m → 10s — never keep a pooled connection longer than the shortest observed server-side idle window.
2. http2.ConfigureTransports + ReadIdleTimeout = 10s / PingTimeout = 5s — actively evict half-dead h2 connections via PING instead of losing a query to them.

golang.org/x/net is already a module dependency, so the only new import is golang.org/x/net/http2.

Testing

Built from source and run on-device (Android, v055x/v055y engines). Same device, same resolver (Quad9), driven with worst-case traffic — bursts of 10 parallel uncached queries after guaranteed > 30 s idle gaps, ~40 cycles over 33 min:

• Stock: query-failure bursts on nearly every cycle.
• Patched: zero idle-pool failures; the log instead shows the health-check discovering and evicting each server-closed connection (retrier: read … err: EOF with no query error following), roughly one per idle cycle.

One caveat: with the PING enabled I saw a single rare stream error: stream ID N; PROTOCOL_ERROR reset taking out one burst on one connection (once in ~40 cycles; recovered on redial). If that turns out to be an interaction with the custom dialer, the IdleConnTimeout reduction alone already removes the corpse-pool state and may be the safer minimal change.