feat(cilium): export Plex's pre-SNAT client address via Hubble, scoped to tcp/32400

The requirement is log visibility only -- which address connected to Plex.

Plex's own log cannot show it. Every LoadBalancer Service here is
externalTrafficPolicy: Cluster, so the node holding the VIP's L2 lease SNATs
the client before forwarding to the backend pod. Measured: Plex had logged
3,214 requests from 10.0.1.x (lease holder k3s-prod-3's own address, Cilium
identity 1 = reserved:host) and ZERO from any 192.168.x address, ever. No
X-Forwarded-For either -- it serves raw tcp/32400, not HTTP via the Gateway.
Nothing on the router does this; there is no hairpin NAT. It is Cilium.

The address is not lost, only unrecorded. Cilium observes the flow at ingress,
BEFORE its own translation, so Hubble already has it:

  192.168.2.133 -> 10.0.0.135   real LAN client -> the Plex pod
  10.0.1.78     -> 10.0.0.135   same traffic post-SNAT, what Plex sees

What was missing is RETENTION: 4095/4095 flows at ~303/s is about thirteen
seconds of history, metrics disabled, no exporter configured.

So enable the static exporter, port-scoped, to the agent's stdout -- Alloy
already tails every pod into Loki, so this needs no new mount, no rotation
handling and no Alloy change.

  {namespace="kube-system", app="cilium"} |= "32400"

Scoped BY PORT, not namespace, on evidence: --to-namespace plex returned only
the post-SNAT flows; the record carrying the real client address did not match
it. A namespace filter would drop exactly what this exists to capture.

Rejected, with reasons: eTP:Local is incompatible with cilium 1.20's L2
announcer per upstream docs for this version ("may cause service IPs to be
announced on nodes without pods causing traffic drops") -- and the VIP is on
prod-3 while the pod is on prod-1, so it would black-hole 32400 immediately;
making it safe costs Plex its ability to reschedule. DSR: routing-mode is
vxlan, not native/geneve, and DSR returns bypass the ingress node, breaking
the router's stateful NAT on the remote path.

Also corrects the repo's own record: 2026-10-03 says the SNAT lands in
192.168.0.0/16 (the node's LAN address). It is 10.0.1.x, the cilium_host
inside the pod CIDR -- which is why LanNetworksBandwidth can never separate
local from remote while eTP is Cluster.

UNVERIFIED and stated in the handoff: nothing is reconciled; `filePath: stdout`
is taken from a verbatim upstream sentence but not confirmed against 1.20.1
source (a wrong notation is a silent no-op, with the file+Alloy fallback
documented); the port FlowFilter has no upstream example; and this change
ROLLS CILIUM -- prod-3 announces the Gateway, PiHole DNS and Plex VIPs, so a
lease move during the rollout could briefly interrupt LAN DNS.

Co-Authored-By: Claude Opus 5 (1M context) <[email protected]>

decisions/2026-10-04-hubble-flow-export-plex.md

@@ -0,0 +1,157 @@
+---
+date: 2026-10-04
+branch: feat/hubble-flow-export-plex
+title: Record the pre-SNAT client address for Plex via Hubble static flow export, instead of breaking externalTrafficPolicy to get it
+---
+
+## What changed
+
+Operator requirement, narrowed explicitly: **this is 100% about log visibility** — knowing which
+address connected to Plex. Not bandwidth metering, which does not matter here.
+
+**The problem, measured.** Plex's own log cannot show it. Every LoadBalancer Service in this cluster
+is `externalTrafficPolicy: Cluster`, so the node holding the L2 lease for the VIP SNATs the client
+before forwarding to the backend pod:
+
+| Measured 2026-10-04 | Value |
+|---|---|
+| Node announcing `192.168.2.24` | `k3s-prod-3` (also holds `.20` Gateway, `.23` pihole-dns) |
+| Node running the Plex pod | `k3s-prod-1` (`10.0.0.135`) |
+| Sources in Plex's log | **3,214 × `10.0.1.x`**, 105 × `10.0.2.x`, 120 × loopback |
+| `192.168.x` sources in Plex's log, ever | **0** |
+| `X-Forwarded-For` in Plex's log | **0** (it serves raw tcp/32400, not HTTP via the Gateway) |
+| `10.0.1.78` identity (`cilium-dbg bpf ipcache`) | `identity=1` → `reserved:host` = prod-3 itself |
+
+**Nothing on the router is involved** — the operator correctly pointed out there is no hairpin NAT
+here. The rewrite is entirely in-cluster, done by Cilium's BPF load-balancer on the lease holder,
+because the backend pod is on a different node.
+
+**The address is not lost, only unrecorded.** Cilium observes the flow at ingress, *before* its own
+translation, so Hubble already holds the true source:
+
+    192.168.2.133 -> 10.0.0.135    (real LAN client -> the Plex pod)
+    10.0.1.78     -> 10.0.0.135    (the same traffic post-SNAT — what Plex sees)
+
+What was missing is **retention**: the ring buffer was **4095/4095 flows at ~303 flows/s — about
+thirteen seconds of history** — with hubble metrics disabled and no exporter configured.
+
+So: enable the static flow exporter, scoped to Plex's port, writing to the agent's stdout.
+
+- **`platform/cilium/helmrelease.yaml`** (authoritative): `hubble.export.static.enabled: true`,
+  `filePath: stdout`, `allowList` of `{"destination_port":["32400"]}` and
+  `{"source_port":["32400"]}`.
+- **`platform/cilium/values.yaml`** (reference mirror) and
+  **`infra/ansible/roles/cilium/templates/cilium-values.yaml.j2`** (the `[parity]` source of truth):
+  the same block, so a bootstrap render does not differ from what Flux reconciles — a mismatch would
+  be a permanent Helm diff and an avoidable agent rollout.
+
+**`filePath: stdout`, not a file,** because Grafana Alloy already runs as a DaemonSet tailing every
+pod's logs into Loki (`platform/monitoring/alloy.yaml`). stdout therefore reaches Loki with **no new
+hostPath mount, no file-rotation handling, and no Alloy change at all**. Upstream documents the
+value: *"To get Hubble flows directly exported to the logs instead of written to a rotated file,
+`stdout` can be defined as `hubble-export-file-path`."* Query:
+
+    {namespace="kube-system", app="cilium"} |= "32400"
+
+**SCOPED BY PORT, NOT BY NAMESPACE — a measured decision, not a preference.** A
+`--to-namespace plex` query returned **only the post-SNAT flows**; the flow carrying the real client
+address did not match it, because at the point of observation the destination identity is not yet
+resolved to the plex pod. A namespace filter would have dropped exactly the record this change
+exists to capture.
+
+**WHY NOT FIX THE SNAT INSTEAD — both alternatives rejected on evidence.**
+- `externalTrafficPolicy: Local` would put the real address in Plex's own log, but cilium 1.20's L2
+  announcer is **explicitly incompatible** with it. Upstream docs for this exact version:
+  *"incompatible with the `externalTrafficPolicy: Local` on services as it may cause service IPs to
+  be announced on nodes without pods causing traffic drops"* and *"L2 announcements isn't currently
+  aware of this setting"*. Live proof it is not theoretical: the VIP is announced by prod-3 while the
+  pod runs on prod-1, so the flip would black-hole tcp/32400 **immediately**. Making it safe means
+  pinning both the pod and the announcement to one node and surrendering Plex's ability to
+  reschedule — a real availability loss to buy a log field. Same trap
+  `platform/crafty/service-l4.yaml` documents from an 8-day Minecraft outage.
+- **DSR** also preserves the client address, but `routing-mode` here is **vxlan**, not
+  native/geneve, and DSR returns bypass the ingress node, which breaks the SOHO router's stateful
+  NAT on the remote path. Cluster-wide blast radius across all eight LB Services for one service's
+  logging.
+
+**A correction to the repo's own record.** `decisions/2026-10-03-plex-remote-access-l4.md` states the
+SNAT puts the client inside `192.168.0.0/16` (the ingress node's LAN address), and I repeated that in
+the previous entry. **It is wrong**: measured, the SNAT source is `10.0.1.x` — the node's
+`cilium_host` inside the pod CIDR. This matters, because it means `LanNetworksBandwidth` can never
+discriminate local from remote while eTP is `Cluster`: `10.0.0.0/8` must be in the LAN set for the
+in-cluster consumers (Seerr) to count as local, and every external client arrives in that same range.
+PR #48's LAN definition therefore fixes the Remote badge by making *everything* local — acceptable
+only because metering is explicitly not a goal here.
+
+## What I verified
+
+Live prod, 2026-10-04, read-only.
+
+- **Every measurement in the table above**, including the VIP-lease-to-node map
+  (`cilium-dbg shell -- db/show l2-announce` on all three agents) and the pod's node.
+- **Hubble already carries the pre-SNAT source** — the single finding this whole approach rests on:
+  `hubble observe --port 32400` on the lease holder returned `192.168.2.133 -> 10.0.0.135` **and**
+  its return flow, alongside the post-SNAT `10.0.1.78 -> 10.0.0.135`.
+- **The retention gap is real:** `cilium-dbg status` reported `Hubble: Ok  Current/Max Flows:
+  4095/4095 (100.00%), Flows/s: 303.62  Metrics: Disabled`, and the `cilium-config` ConfigMap
+  contains no `hubble-export-*` key at all.
+- **The namespace-filter trap**, directly: `--to-namespace plex` returned only `10.0.1.78` and
+  `10.0.1.71`; the `192.168.2.133` flow was absent. This is why the allowList is port-scoped.
+- **All eight LoadBalancer Services are `eTP=Cluster`** (crafty ×2, gateway, pihole-dns ×2, plex,
+  unifi ×2) — so this is a cluster-wide pattern, not a Plex-specific choice.
+- **The eTP:Local incompatibility is upstream-documented for v1.20 specifically**, quoted above from
+  the docs for the running version — not inferred from the crafty incident.
+- **`routing-mode: tunnel`** and **`bpf-lb-mode-annotation: false`** in the live `cilium-config`,
+  which is what rules DSR out.
+- **The chart's value paths and defaults**, read from cilium v1.20.1's own `values.yaml`:
+  `hubble.export.static.{enabled,filePath,fieldMask,fieldAggregate,aggregationInterval,allowList,denyList,fileMaxSizeMb,fileMaxBackups,fileCompress}`,
+  with `filePath` defaulting to `/var/run/cilium/hubble/events.log`. The keys used here exist.
+- **Alloy's pipeline shape**, read from `platform/monitoring/alloy.yaml`: a DaemonSet with
+  `loki.source.kubernetes "pods"` → `loki.process` → `loki.write` at
+  `http://loki.monitoring.svc.cluster.local:3100`. It already tails kube-system pods, which is why
+  stdout needs no Alloy change.
+- **All three value files agree** (one `destination_port` occurrence each) and both YAML files parse,
+  with `export.static` resolving to the intended object.
+- **Toolbox gate**: **rc 3**, with `spec-immutability`, `decisions-log`, `lint`, `l0`,
+  `render-golden`, `l1` and `approval-policy` all **pass**; rc 3 is the two known environmental skips
+  (`gitea-settings` — no local `SETTINGS_API_TOKEN`; `conformance` L2/L3 — `CLUSTER_AVAILABLE`
+  unset). **Not green. Reported as rc 3.**
+- **No sensitive paths touched** — `platform/cilium/**` and `infra/ansible/**` are not in
+  `infra/gitea/approval-policy.json`, so this needs no approval override, unlike PR #48.
+
+## What I did NOT verify
+
+- **THE OUTCOME. Nothing has been reconciled and no flow has ever been exported.** `cilium-config`
+  still has no `hubble-export-*` key. Every claim is about inputs.
+- **Whether `filePath: stdout` is accepted as written.** This is the single largest risk. The value
+  comes from a verbatim upstream doc sentence (*"`stdout` can be defined as
+  `hubble-export-file-path`"*), but I did not confirm the exact notation in cilium 1.20.1's source,
+  and the chart default is a real filesystem path. If the literal string is not special-cased, the
+  agent may create a FILE named `stdout` in its working directory and nothing reaches Loki — a
+  silent no-op, not a crash. **Fallback if so:** leave `filePath` at the chart default and add a
+  `local.file_match` + `loki.source.file` target to Alloy with a hostPath mount for
+  `/var/run/cilium/hubble`.
+- **Whether the FlowFilter JSON is accepted.** `{"destination_port":["32400"]}` follows the proto
+  (`destination_port` is a repeated string) and the documented shape (`'{"verdict":["DROPPED"]}'`),
+  but upstream gives **no port example** and I did not validate it against the running agent. A
+  malformed filter could be rejected — or, worse, be silently treated as "no match" and export
+  nothing.
+- **THIS CHANGE ROLLS CILIUM.** Editing the HelmRelease restarts the agent DaemonSet across all
+  three nodes. BPF maps are preserved so established traffic should survive, but prod-3 currently
+  announces the Gateway VIP, **PiHole's DNS VIP** and Plex's VIP, so a lease change during the
+  rollout could briefly interrupt LAN DNS for the whole house. Not measured, and worth doing at a
+  quiet moment.
+- **Log volume in practice.** Estimated "a few hundred to a few thousand lines a day" from the
+  observed request counts; never measured as flows. Both directions are exported and no `fieldMask`
+  is set, so each record is a full flow object. If it is noisy, narrow with `fieldMask` rather than
+  by dropping a filter.
+- **Loki's retention for this data**, and whether the `{namespace="kube-system", app="cilium"}` label
+  set actually matches (it depends on the cilium pods carrying
+  `app.kubernetes.io/name`, which Alloy maps to `app` — I did not confirm that label exists on the
+  cilium DaemonSet pods). The query in the comment may need adjusting to `pod=~"cilium-.*"`.
+- **That the exported flow actually contains the pre-SNAT address.** Hubble's *live* stream does
+  (measured). I am assuming the exporter sees the same flow objects; I did not confirm the exporter
+  is not fed a post-translation view.
+- **The parity convention has no automated check.** I kept all three files in sync by hand because
+  the comments demand it; nothing in `ci/` or `conformance/` verifies cilium Helm↔Ansible parity, so
+  a future edit can still drift them silently.

infra/ansible/roles/cilium/templates/cilium-values.yaml.j2

@@ -45,6 +45,20 @@ hubble:
     enabled: true
   ui:
     enabled: true
+  # Static flow export -> cilium-agent stdout. Kept EQUAL to the Flux values
+  # (platform/cilium/helmrelease.yaml), which carry the full rationale: it records the PRE-SNAT
+  # client address for Plex's raw tcp/32400, which Plex itself cannot log because every
+  # LoadBalancer Service here is externalTrafficPolicy: Cluster and the VIP lease holder SNATs the
+  # client. Present here so a BOOTSTRAP render does not differ from what Flux reconciles -- a
+  # mismatch would show up as a permanent Helm diff and an avoidable agent rollout. Scoped by PORT,
+  # not namespace: the flow carrying the real client address does not match a namespace filter.
+  export:
+    static:
+      enabled: true
+      filePath: stdout
+      allowList:
+        - '{"destination_port":["32400"]}'
+        - '{"source_port":["32400"]}'
 
 # Ingress VIP announcement on the NAT LAN. IP pool / CiliumL2AnnouncementPolicy
 # (from the reserved 10.73.0.240-.250 range) is authored by WS-NET in Phase 2.

platform/cilium/helmrelease.yaml

@@ -101,6 +101,60 @@ spec:
         enabled: true
       ui:
         enabled: true   # exposure gated behind oauth2-proxy forward-auth later (ADR-0014)
+      # --- STATIC FLOW EXPORT: persist the PRE-SNAT client address for Plex (2026-10-04) ---
+      # [parity] MUST equal Ansible: hubble.export.static.{enabled,filePath,allowList}
+      #
+      # WHY THIS EXISTS. Plex's own log cannot show who connected. Every LoadBalancer Service in
+      # this cluster is `externalTrafficPolicy: Cluster`, so the node holding the L2 lease for the
+      # VIP SNATs the client before forwarding to the backend pod. Measured 2026-10-04: Plex had
+      # logged 3,214 requests from `10.0.1.x` (the lease holder k3s-prod-3's own address, Cilium
+      # identity 1 = reserved:host) and ZERO from any 192.168.x address, ever. No X-Forwarded-For
+      # either -- it serves raw tcp/32400, not HTTP through the Gateway.
+      #
+      # THE ADDRESS IS NOT LOST, ONLY UNRECORDED. Cilium observes the flow at ingress, BEFORE its
+      # own translation, so Hubble already has the true source. Measured on the lease holder:
+      #     192.168.2.133 -> 10.0.0.135   (real LAN client -> the Plex pod)
+      #     10.0.1.78     -> 10.0.0.135   (the same traffic, post-SNAT -- what Plex sees)
+      # What was missing is RETENTION: the ring buffer was 4095/4095 flows at ~303 flows/s, i.e.
+      # about THIRTEEN SECONDS of history, with hubble metrics disabled and no exporter configured.
+      #
+      # WHY NOT FIX THE SNAT INSTEAD. `externalTrafficPolicy: Local` would preserve the address in
+      # Plex's own log, but cilium 1.20's L2 announcer is explicitly incompatible with it -- upstream
+      # docs for this exact version: "incompatible with the externalTrafficPolicy: Local on services
+      # as it may cause service IPs to be announced on nodes without pods causing traffic drops",
+      # and "L2 announcements isn't currently aware of this setting". Live proof that this is not
+      # theoretical: the VIP is announced by k3s-prod-3 while the pod runs on k3s-prod-1, so the
+      # flip would black-hole tcp/32400 immediately. Making it safe would mean pinning BOTH the pod
+      # and the announcement to one node and giving up Plex's ability to reschedule -- a real
+      # availability loss to buy a log field. (It is the same trap platform/crafty/service-l4.yaml
+      # documents from an 8-day Minecraft outage.) DSR was also rejected: routing-mode here is
+      # vxlan, not native/geneve, and DSR returns bypass the ingress node, which breaks the SOHO
+      # router's stateful NAT on the remote path.
+      #
+      # `filePath: stdout` RATHER THAN A FILE, deliberately. Grafana Alloy already runs as a
+      # DaemonSet tailing every pod's logs into Loki (platform/monitoring/alloy.yaml), so stdout
+      # reaches Loki with NO new hostPath mount, no file-rotation handling and no Alloy change.
+      # Upstream documents it: "To get Hubble flows directly exported to the logs instead of written
+      # to a rotated file, `stdout` can be defined as `hubble-export-file-path`." fileMaxSizeMb /
+      # fileMaxBackups are therefore left at chart defaults and do not apply.
+      #   Query:  {namespace="kube-system", app="cilium"} |= "32400"
+      #
+      # SCOPED BY PORT, NOT BY NAMESPACE -- and that is a measured decision, not a preference. A
+      # `--to-namespace plex` query returned ONLY the post-SNAT flows; the flow carrying the real
+      # client address did NOT match it, because at the point of observation the destination
+      # identity is not yet resolved to the plex pod. Filtering by namespace would therefore drop
+      # exactly the record this change exists to capture. Port it is.
+      #
+      # Both directions are listed so the return path is captured too. Volume is small (a few
+      # hundred to a few thousand lines a day); if it ever becomes noisy, narrow it with
+      # `fieldMask` rather than by removing a filter.
+      export:
+        static:
+          enabled: true
+          filePath: stdout
+          allowList:
+            - '{"destination_port":["32400"]}'
+            - '{"source_port":["32400"]}'
     # --- L2 announcement for the ingress VIP on the flat LAN (docs/09, OQ-1 resolved) ---
     # [parity] MUST equal Ansible: l2announcements.enabled: true. IP pool +
     # CiliumL2AnnouncementPolicy (reserved 10.73.0.240-.250) authored by WS-NET in Phase 2.

platform/cilium/values.yaml

@@ -38,6 +38,18 @@ hubble:
     enabled: true
   ui:
     enabled: true
+  # [parity] static flow export -> cilium-agent stdout -> Alloy -> Loki. Records the PRE-SNAT
+  # client address for Plex's raw tcp/32400, which Plex's own log cannot show (every LB Service here
+  # is externalTrafficPolicy: Cluster, so the VIP lease holder SNATs the client). Scoped BY PORT,
+  # not namespace: the flow carrying the real client IP does not match a namespace filter. Full
+  # rationale, measurements and the rejected alternatives are in helmrelease.yaml.
+  export:
+    static:
+      enabled: true
+      filePath: stdout
+      allowList:
+        - '{"destination_port":["32400"]}'
+        - '{"source_port":["32400"]}'
 # [parity] ingress VIP announcement on the flat LAN (docs/09, OQ-1)
 l2announcements:
   enabled: true