Adds DNS_FORWARD_BUDGET (default 50) and DNS_FORWARD_WINDOW (default 1.0s)
env vars. _can_forward() maintains a rolling deque of upstream call
timestamps; queries that exceed the budget within the window are answered
with the sinkhole (127.x) instead of being forwarded, making the honeypot
ineligible as a sustained amp vector even when real_recursive is enabled.
Rate limit is global (not per-source) so IP-spoofed amplification floods
hit the ceiling regardless of how many source addresses are rotated.
When DNS_REAL_RECURSIVE=true and DNS_ZONE_MODE=recursive, out-of-zone
queries are forwarded to DNS_UPSTREAM (default 8.8.8.8:53) via async
UDP. Upstream response is relayed as-is; on timeout or error the
already-computed sinkhole (127.x) is returned instead.
_handle() always runs first so logging, tunneling detection, flood
tracking, and recon-burst aggregation fire on every query regardless
of whether the response ultimately comes from upstream. _dispatch()
overlays forwarding on top of the sync handler.
Protocol handlers (UDP datagram_received, TCP session) are now async
via asyncio.ensure_future / await _dispatch(). Service class exposes
real_recursive (bool) and upstream (string) config fields.
Python asyncio DNS server on UDP+TCP/53 masquerading as BIND 9.x.
Emits four event_type values: query, fingerprint_probe (version.bind /
hostname.bind / id.server CHAOS), zone_transfer (AXFR/IXFR, always
REFUSED), amp_probe (qtype=ANY or EDNS udp_size>1232), and
tunneling_suspect (long high-entropy labels or rapid TXT burst).
Zone persona is generated per-decky from instance_seed (domain name,
SOA serial, NS, A, MX, TXT SPF); overridable via config_schema.
Three zone modes: auth (default), recursive, open (sinkhole).
