Operator reported DNS flapping between the cluster ingress and the router's
public IP. PiHole is not at fault -- both replicas answer 192.168.2.20
consistently (6/6 via the VIP, 8/8 from a client). The bug is an asymmetry in
CACHEABILITY that we created. Measured:
pihole 192.168.2.23 -> 192.168.2.20 TTL=0
public 1.1.1.1 -> wan.home.keithjackson.dev TTL=300
router 192.168.2.1 -> wan.... TTL=153 -> 148 -> 143 (decrementing = caching)
dnsmasq answers `address=` entries with TTL 0 unless told otherwise. The router
forwards LAN queries to PiHole and caches the result, so the CORRECT answer is
uncacheable -- re-queried on every lookup, maximum exposure to any gap -- while
the WRONG answer caches for 300s. The instant the router falls back to upstream
(standard forwarder behaviour when the target does not answer) it latches the
WAN address for the whole LAN for five minutes, then expires, re-queries PiHole,
gets TTL 0, and is immediately re-exposed.
So ONE sub-second PiHole gap -- pod restart, L2 lease move, ARP flap, kured
reboot -- becomes FIVE MINUTES of the house resolving to the WAN IP. That
asymmetry, not the gap, is why it reads as "flapping".
Fix: local-ttl=60 prepended to FTLCONF_misc_dnsmasq_lines. dnsmasq applies
local-ttl to replies made from configuration, so one directive covers all five
address= names. 60s rides out a pod restart and a lease re-election while a real
VIP change still propagates inside a minute; these VIPs are pinned and static.
apps/wave-0/pihole.yaml regenerated with the canonical render command
(--all catalog -o apps --wave-layout --no-image-automation, NOT --emit-waves);
exactly two files changed and the rendered diff is the single local-ttl prefix.
UNAPPLIED. Does NOT remove the trigger: .23 still has two independently-elected
L2 leases (as do crafty .22 and unifi .21), which the operator has parked. If
the TTL is still 0 after merge, suspect FTL silently rejecting the passthrough
line -- see the handoff.
Co-Authored-By: Claude Opus 5 (1M context) <[email protected]>
jakman85andClaude Opus 5