Four places in the tree told the reader that the host nftables table is the
authoritative fail-closed backstop for egress-class=vpn pods: platform/vpn-egress
README, egress-steering.yaml, the role README, and the vpn-killswitch test's own
GIVEN/THEN prose. It is not, and cannot be — Cilium's eBPF egress-gateway
datapath bpf_redirect()s those skbs to the egress device without invoking
netfilter POSTROUTING. Corrected with the measurement in each place rather than
softened, because a guard the repo trusts and that does not fire is worse than no
guard.
What replaces the claim, everywhere: vpn-class fails closed because CILIUM drops
the traffic when it cannot use its cached egress interface, verified by tcpdump on
both the WAN and tun0 during a tunnel stop and a tunnel restart (0 packets out
either). The nft table keeps a narrower, now-proven job: node-originated traffic
sourced from a tunnel address (killswitch_drop moved 0 -> 3 packets on
k3s-prod-3 when such a packet was routed at the WAN).
Also recorded:
* egress-steering.yaml — `interface: tun0` is resolved ONCE and cached, and the
gateway node is what tells Cilium it changed (the egress-uplink node label). A
future reader's instinct will be to have the node write to that object; the
comment says not to, because it is Flux-managed, and points at the label and
`cilium-dbg bpf egress list` as the debugging entry points instead.
* egress-steering.yaml — why the new NFS media mounts are not affected by
pod-scoped steering: an NFS PV is mounted by the node kernel in the host netns,
so podSelector never matches it. The 192.168.0.0/16 exclusion covers the server
too, but that is the second reason, not the first.
* vpn-killswitch test — its recovery step depends on the re-steer path, and could
not have passed before it existed. Its no-leak assertion was always right; only
the explanation was wrong. Also states the prerequisite plainly: the test cannot
run at all without a labelled gateway node.
* platform README — prod is live on k3s-prod-3 with the before/after egress IPs,
and the note that prod's vpn-class pods had NO internet beforehand (CEGP with no
matching node -> `Gateway IP: Not Found` -> dropped), so arming the gateway
restored egress rather than moving it off the WAN.
* role README — the standing "add the shared fwmark to the interface contract"
escalation is closed as not implementable on Cilium OSS, rather than left open
for someone to attempt.
DECISIONS-LOG carries the full session entry, including the drafted ADR-0015 /
docs-03 amendment for the architect (specs are immutable to agents) and the five
things left for the operator — chief among them that a silent gateway outage still
has no alert, which is what let the dev gateway sit dead for 80 minutes.
Co-Authored-By: Claude Opus 5 <[email protected]>
jakman85andClaude Opus 5
04606d48b2