Christian Glombek
9bb06d5cd6
dns_cache_lookup() computes each answer item's expiry ('until', also the
basis of the SD_RESOLVED_CLAMP_TTL TTL patch) as "30s from now" whenever
the caller did not pass SD_RESOLVED_NO_STALE — keyed on the lookup mode,
not on whether the entry being returned is actually stale. That misfires
in both directions:
* A fresh entry hit by a serve-stale retry (second transaction attempt
with StaleRetentionSec= set) has its TTL reported as 30s instead of
its real remaining TTL.
* A lookup that passes neither SD_RESOLVED_NO_STALE nor
SD_RESOLVED_CLAMP_TTL — as the mDNS browse path does for clients
that set no flags — leaves 'current' at 0, so every answer item's
expiry becomes the constant absolute time 30s after boot,
permanently in the past. The RFC 6762 section 5.2 cache maintenance
schedule that resolved-dns-browse-services.c derives from
item->until then degenerates to its already-expired fallback.
Key the rewrite on the entry's actual staleness instead: an entry whose
TTL has lapsed keeps reporting "30s from now", so clients don't hold on
to stale data for long, and a fresh entry reports its real expiry. For
lookups with SD_RESOLVED_NO_STALE set nothing changes: a stale entry
already makes the whole chain miss, so every item returned in that mode
is fresh.
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