When numa is its own system DNS resolver (HAOS add-on, Pi-hole-style
container, /etc/resolv.conf → 127.0.0.1), every numa-originated HTTPS
connection — DoH upstream, ODoH relay/target, blocklist CDN — routed
its hostname through getaddrinfo() back to numa itself. Cold boot
deadlocked; steady state taxed every new TCP connection. 0.14.1's
retry-with-backoff masked the startup race but not the underlying
self-loop.
NumaResolver implements reqwest::dns::Resolve with two lanes:
- Per-host overrides (ODoH relay_ip/target_ip) short-circuit DNS
entirely, preserving ODoH's zero-plain-DNS-leak property.
- Otherwise: A+AAAA in parallel via UDP to IP-literal bootstrap
servers, with TCP fallback for UDP-hostile networks.
Bootstrap IPs come from upstream.fallback (IP-literal filtered,
hostnames skipped with a warning). Empty fallback yields the
hardcoded default [9.9.9.9, 1.1.1.1]; the chosen source is logged
at startup so the silent default is visible.
doh_keepalive_loop now fires its first tick immediately, and
keepalive_doh logs failures at WARN — bootstrap issues surface
within ~100ms of boot instead of on the first client query.
Distinct from UpstreamPool.fallback (client-query failover) which
stays untouched: client queries with no configured fallback still
SERVFAIL on primary failure rather than silently shadow-routing.
Reproducer: tests/docker/self-resolver-loop.sh. Before: 0 blocklist
domains, 3072ms SERVFAIL. After: 397k domains, 118ms NOERROR.
