66 lines
2.2 KiB
Python
66 lines
2.2 KiB
Python
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"""Hostname resolver: zeroconf when available, stdlib multicast fallback.
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Public API:
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resolve(host, family="v4"|"v6", timeout=1.0, retries=2, use_cache=True)
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-> str | None
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"""
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from . import cache
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from . import _stdlib_resolve as _std
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from ._pick import pick_best
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def _try_zeroconf(host: str, family: str, timeout: float) -> tuple[str, int] | None:
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try:
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from zeroconf import Zeroconf, AddressResolver, IPVersion
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except ImportError:
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return None
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hostname = host if host.endswith(".") else host + "."
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ver = IPVersion.V6Only if family == "v6" else IPVersion.V4Only
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zc = Zeroconf(ip_version=IPVersion.All)
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try:
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r = AddressResolver(hostname)
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# request() blocks up to `timeout` milliseconds
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if not r.request(zc, int(timeout * 1000)):
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return None
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addrs = r.parsed_addresses(ver)
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best = pick_best(addrs, family=family)
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if not best:
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return None
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return best, 120
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except Exception:
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return None
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finally:
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try:
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zc.close()
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except Exception:
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pass
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def resolve(host: str, family: str = "v4", timeout: float = 1.0,
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retries: int = 2, use_cache: bool = True) -> str | None:
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hostname = host if host.endswith(".local") else f"{host}.local"
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if use_cache:
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hit = cache.get(hostname, family)
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if hit:
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return hit
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per_try = max(0.3, timeout / max(1, retries))
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# IPv4: try stdlib first (fast, no zeroconf startup cost).
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if family == "v4":
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for _ in range(max(1, retries)):
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recs = _std.query_all(hostname, per_try)
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if recs:
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best = pick_best([ip for ip, _ in recs], family="v4")
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ttl = next((t for ip, t in recs if ip == best), 120)
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cache.put(hostname, best, family=family, ttl=ttl or 120)
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return best
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# IPv6 or IPv4-stdlib-miss: try zeroconf (heavier but RFC-complete).
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for _ in range(max(1, retries)):
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res = _try_zeroconf(hostname, family, per_try)
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if res:
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ip, ttl = res
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cache.put(hostname, ip, family=family, ttl=ttl)
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return ip
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return None
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