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feat(dns): real recursive forwarding with sinkhole fallback

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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.
This commit is contained in:
anti
2026-05-21 20:49:19 -04:00
parent 8f33f1b849
commit e5847b7e1e
3 changed files with 186 additions and 11 deletions
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21
decnet/services/dns.py
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@@ -18,7 +18,7 @@ class DNSService(BaseService):
type="enum",
enum=["auth", "recursive", "open"],
default="auth",
help="auth: authoritative only; recursive: RA flag set, NXDOMAIN for out-of-zone; open: responds to everything (amp bait)",
help="auth: authoritative only; recursive: forwards out-of-zone queries upstream (real_recursive=true) or sinkholes them; open: responds to everything (amp bait)",
),
ServiceConfigField(
key="domain",
@@ -50,6 +50,21 @@ class DNSService(BaseService):
placeholder="www A 10.0.0.5\nmail TXT v=spf1 ~all",
help="Additional zone records, one per line: <name> <TYPE> <value>",
),
ServiceConfigField(
key="real_recursive",
label="Real recursive forwarding",
type="bool",
default=False,
help="When zone_mode=recursive, forward out-of-zone queries to an upstream resolver instead of returning a sinkhole. Falls back to sinkhole on upstream timeout.",
),
ServiceConfigField(
key="upstream",
label="Upstream resolver",
type="string",
default="8.8.8.8:53",
placeholder="8.8.8.8:53",
help="Upstream DNS resolver used when real_recursive is enabled (host:port).",
),
]
def compose_fragment(
@@ -65,7 +80,9 @@ class DNSService(BaseService):
"DNS_DOMAIN": str(cfg.get("domain", "")),
"DNS_BIND_VERSION": str(cfg.get("bind_version", _DEFAULT_VERSION)),
"DNS_NSID": str(cfg.get("nsid", "")),
"DNS_EXTRA_RECORDS": str(cfg.get("extra_records", "")),
"DNS_EXTRA_RECORDS": str(cfg.get("extra_records", "")),
"DNS_REAL_RECURSIVE": "true" if cfg.get("real_recursive") else "false",
"DNS_UPSTREAM": str(cfg.get("upstream", "8.8.8.8:53")),
}
if log_target:
env["LOG_TARGET"] = log_target