feat: derive the DIAL discovery grace from the advertised max-age#54
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A Discovery listener's eviction grace was a fixed 60s; a device's advertisement actually states its validity in CACHE-CONTROL max-age, so honor it. ParseCacheControlMaxAge (ssdp_message) reads the first max-age directive of the first CACHE-CONTROL field -- bare integer only, like the MX parse. Whitespace around '=' is tolerated: HTTP's cache-directive grammar has none, but UDA's own header templates and examples write "max-age = 1800" and devices copy them. The proxy stores a per-endpoint grace: each advertisement re-states it (absent/unparseable -> the 30-minute UDA-recommended default), clamped to 2 hours since the value is attacker-controlled and pins a scarce proxy slot. Rest listeners keep their fixed activity-refreshed grace (they are minted from description responses, which carry no max-age); a promoted endpoint keeps its advertised validity. The rest-vs-discovery grace ordering inverts (300s vs the 30-minute default), so the role-grace eviction test swaps phases.
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Derive the DIAL Discovery listener's eviction grace from the advertisement's
CACHE-CONTROL: max-ageinstead of a fixed 60s.ParseCacheControlMaxAge(ssdp_message): first CACHE-CONTROL field, first max-age directive among its comma-separated directives, both case-insensitive. The value must be a bare integer fittinguint32_t(trailing OWS tolerated), like the MX parse. Whitespace around=is accepted: HTTP's cache-directive grammar has none, but UDA's own header templates and examples writemax-age = 1800and devices copy them. Longer tokens sharing the prefix (max-agenda=...) are skipped; a malformed max-age invalidates the field.DialProxy: endpoints carry a per-endpointgrace. Every advertisement re-states it — absent/unparseable falls toDEFAULT_DISCOVERY_GRACE(30 min, the UDA-recommended minimum device validity), and the value is clamped toMAX_DISCOVERY_GRACE(2 h) since it is attacker-controlled and sets a proxy-slot eviction deadline. Rest listeners keep their fixed activity-refreshed 300s grace (minted from description responses, which carry no max-age); a Discovery endpoint promoted to Rest keeps its advertised validity.Tests
13 new: 9 parser (incl. OWS-around-
=, longer-token disambiguation, garbage/overflow → default), 3 proxy-level (advertised grace honored, oversized clamp, re-advertisement replaces the grace in both directions), 1 reflector integration (max-age flows through the LOCATION rewrite: the listener outlives the default validity).Each behavior was verified to fail its test when the corresponding production line is removed (clamp, reuse-refresh, plumbing, advertised-sets-grace), then restored.
Verification