Real root cause of the 2026-06-28 "Whisker UI empty" incident (the watchdog
added in 8d1d2fb9 was treating a symptom). The tigera operator's own `whisker`
NetworkPolicy is policyTypes:[Ingress,Egress]; its egress allows DNS only to the
kube-dns *pods* (podSelector k8s-app=kube-dns). But whisker-backend resolves
goldmane.calico-system.svc via the kube-dns *ClusterIP* (10.96.0.10), and Calico
drops UDP DNS to a ClusterIP under a podSelector-only egress rule.
Verified in an isolated repro: from the whisker pod's netns, ClusterIP DNS = 100%
timeout while direct kube-dns pod-IP DNS = OK; a pod with no egress policy
resolves fine; a test pod with the operator's podSelector-only egress rule
reproduces the failure, and adding an ipBlock(ClusterIP) egress rule flips it to
100% ok. whisker-backend resolves goldmane once in the brief startup window
before the policy programs, holds its long-lived gRPC stream, and only
re-resolves when that stream breaks (e.g. a node-reboot blip) — then the blocked
ClusterIP DNS wedges its Go resolver and the UI goes empty. The durable
aggregator (separate pod, unrestricted namespace) was never affected.
Fix: additive egress NetworkPolicy whisker-allow-dns-clusterip
(whisker -> 10.96.0.10/32 on 53 UDP+TCP); k8s egress policies are additive so
the operator NP is untouched. The whisker-watchdog CronJob is kept as a backstop
(repurposed comment). Applied + verified: ClusterIP DNS from the whisker netns
now 8/8 ok, whisker-backend 0 errors, flow API returns 828 flows / the namespace
list. Docs (runbook + CLAUDE.md) updated to the real root cause.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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