fix(bird): originate the node's own pod CIDR instead of learning it

IPv6 populated table 48 on all three nodes; IPv4 was empty. The daemon log gives the reason: KRT: Received route 10.244.0.0/24 with strange next-hop 10.244.0.195. Cilium's IPv4 pod route points at a next hop inside the prefix it describes, which BIRD's kernel protocol refuses. The IPv6 route is a device route with no next hop, so it passed — the asymmetry, not a filter, is why one family worked.

Reading the route back made BIRD's view depend on the shape Cilium happens to install. The prefix is already in the Node object, so a static protocol originates it directly: blackhole, because the route exists only to be advertised, and the sole kernel protocol exporting from these tables takes BGP routes.

That removes the kernel-learning tables, the pipes and the own-CIDR filters entirely — with them the dependence on learn all, on ifname, and on the maximum-length exclusion.

Verified: the templates render OWN_POD4 10.244.0.0/24 and OWN_POD6 fd10:244::/64 from the live k8s-1 object, and bird -p parses the result inside the image with exit 0.

Refs #576

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

ci/images/bird/Containerfile

@@ -8,9 +8,15 @@ FROM alpine:3.22@sha256:14358309a308569c32bdc37e2e0e9694be33a9d99e68afb0f5ff33cc
 #
 # Config is read from /etc/bird/bird.conf, not the package default
 # /etc/bird.conf, so the mount cannot shadow what the package ships.
-RUN apk add --no-cache bird2
+#
+# kubectl renders the init container's per-node config: go-template-file for
+# the templating, a field selector for excluding the node itself, in-cluster
+# config for the auth. From the distro, so there is no version literal to drift
+# and no download to trust. It is only ever used to read core/v1 Nodes.
+RUN apk add --no-cache bird2 kubectl
 
-# Fails the build rather than the first pod if the binary or its path is wrong.
-RUN /usr/sbin/bird --version
+# Fails the build rather than the first pod if a binary or its path is wrong.
+RUN /usr/sbin/bird --version \
+ && kubectl version --client > /dev/null
 
 ENTRYPOINT ["/usr/sbin/bird", "-f", "-c", "/etc/bird/bird.conf"]

kubernetes/infrastructure/bird/bird.conf

@@ -0,0 +1,67 @@
+# Identical on every node and free of addresses. defines.conf and peers.conf
+# are rendered per node by the init container; the first is included above the
+# templates that reference it, the second below them.
+include "/etc/bird/defines.conf";
+
+router id from "pod0";
+log stderr all;
+
+protocol device { scan time 10; }
+
+# This node's own pod CIDR, originated rather than read back out of the kernel.
+# Reading it back made BIRD's view depend on the shape of Cilium's route, and
+# the IPv4 one is rejected outright: its next hop sits inside the prefix it
+# describes, which KRT refuses with "strange next-hop". The prefix comes from
+# the Node object either way, so there is nothing to learn.
+#
+# blackhole because this route is only ever advertised. Nothing installs it:
+# the only kernel protocol exporting from these tables takes BGP routes.
+protocol static own4 {
+  ipv4 { table master4; };
+  route OWN_POD4 blackhole;
+}
+protocol static own6 {
+  ipv6 { table master6; };
+  route OWN_POD6 blackhole;
+}
+
+# Only BGP-learned routes reach table 48 — not the static above, and not
+# anything else that may end up in the master tables.
+filter to_t48 {
+  if source != RTS_BGP then reject;
+  accept;
+}
+
+protocol kernel k48v4 {
+  kernel table 48;
+  metric 0;
+  ipv4 { table master4; import none; export filter to_t48; };
+}
+protocol kernel k48v6 {
+  kernel table 48;
+  metric 0;
+  ipv6 { table master6; import none; export filter to_t48; };
+}
+
+# iBGP over pod0. 64514 keeps clear of Cilium's 64513, which peers with the UDM
+# from ingress0 and is unrelated.
+#
+# direct is explicit because iBGP defaults to multihop, which makes the gateway
+# recursive — BIRD would try to resolve the peer in the pod RIB. strict bind
+# keeps the listener off mgmt0 and ingress0.
+template bgp pod4 {
+  local as 64514;
+  source address MY4;
+  direct;
+  strict bind;
+  ipv4 { next hop self; import all; export all; };
+}
+template bgp pod6 {
+  local as 64514;
+  source address MY6;
+  direct;
+  strict bind;
+  ipv6 { next hop self; import all; export all; };
+}
+
+include "/etc/bird/peers.conf";

kubernetes/infrastructure/bird/daemonset.yaml

@@ -0,0 +1,115 @@
+apiVersion: v1
+kind: ServiceAccount
+metadata:
+  name: bird
+  namespace: kube-system
+---
+apiVersion: rbac.authorization.k8s.io/v1
+kind: ClusterRole
+metadata:
+  name: bird
+rules:
+  # The peer list is read from the nodes' pod0 annotations, so no address is
+  # written into this repo twice.
+  - apiGroups: [""]
+    resources: ["nodes"]
+    verbs: ["get", "list"]
+---
+apiVersion: rbac.authorization.k8s.io/v1
+kind: ClusterRoleBinding
+metadata:
+  name: bird
+roleRef:
+  apiGroup: rbac.authorization.k8s.io
+  kind: ClusterRole
+  name: bird
+subjects:
+  - kind: ServiceAccount
+    name: bird
+    namespace: kube-system
+---
+apiVersion: apps/v1
+kind: DaemonSet
+metadata:
+  name: bird
+  namespace: kube-system
+  labels:
+    tier: node
+    app: bird
+spec:
+  selector:
+    matchLabels:
+      app: bird
+  updateStrategy:
+    type: RollingUpdate
+  template:
+    metadata:
+      labels:
+        tier: node
+        app: bird
+    spec:
+      # Carries pod east-west once the routing rules land. Without it table 48
+      # stays empty and the rules fall through to main, i.e. back to VLAN 40.
+      priorityClassName: system-node-critical
+      # Writes host routes and peers on host addresses.
+      hostNetwork: true
+      serviceAccountName: bird
+      # Every node here is a control plane node, so this is not optional.
+      tolerations:
+        - operator: Exists
+          effect: NoSchedule
+      initContainers:
+        - name: render-config
+          # By digest, not by the dated tag: the tag is rebuilt within the day
+          # it names, and the cluster's image path keeps resolving it to the
+          # first build of that day — imagePullPolicy: Always does not help,
+          # because the tag itself resolves stale. Update this when the image
+          # is rebuilt.
+          image: gitea.renner.uno/gitea_admin/bird@sha256:3bc8500613eeb45b2d8858b5445198bae3990ecf64f6d891aa94797f5a09dc1d
+          command: ["/bin/sh", "-c"]
+          args:
+            - |
+              set -eu
+              cp /config/bird.conf /etc/bird/bird.conf
+              kubectl get node "$NODE_NAME" \
+                -o go-template-file=/config/defines.tmpl > /etc/bird/defines.conf
+              kubectl get nodes --field-selector "metadata.name!=$NODE_NAME" \
+                -o go-template-file=/config/peers.tmpl > /etc/bird/peers.conf
+              # BIRD's own parser is the check: a node whose annotation is
+              # missing renders as <no value> and fails here rather than
+              # crashlooping the daemon or forming a mesh with a hole.
+              bird -p -c /etc/bird/bird.conf
+          env:
+            - name: NODE_NAME
+              valueFrom:
+                fieldRef:
+                  fieldPath: spec.nodeName
+          volumeMounts:
+            - name: config
+              mountPath: /config
+            - name: etc-bird
+              mountPath: /etc/bird
+      containers:
+        - name: bird
+          image: gitea.renner.uno/gitea_admin/bird@sha256:3bc8500613eeb45b2d8858b5445198bae3990ecf64f6d891aa94797f5a09dc1d
+          resources:
+            requests:
+              cpu: "50m"
+              memory: "32Mi"
+            limits:
+              cpu: "200m"
+              memory: "128Mi"
+          securityContext:
+            capabilities:
+              drop: ["ALL"]
+              # NET_ADMIN writes the routes; NET_BIND_SERVICE binds 179.
+              add: ["NET_ADMIN", "NET_BIND_SERVICE"]
+          volumeMounts:
+            - name: etc-bird
+              mountPath: /etc/bird
+      volumes:
+        - name: config
+          configMap:
+            name: bird-config
+        - name: etc-bird
+          emptyDir: {}

kubernetes/infrastructure/bird/defines.tmpl

@@ -0,0 +1,7 @@
+define MY6 = {{ index .metadata.annotations "net.renner.uno/pod0-v6" }};
+define MY4 = {{ index .metadata.annotations "net.renner.uno/pod0-v4" }};
+{{/* podCIDRs follows the cluster's podSubnets order, v4 first. A flip puts an
+     IPv6 prefix into an ipv4 protocol, which fails the parse in the init
+     container rather than passing silently. */}}
+define OWN_POD4 = {{ index .spec.podCIDRs 0 }};
+define OWN_POD6 = {{ index .spec.podCIDRs 1 }};

kubernetes/infrastructure/bird/kustomization.yaml

@@ -0,0 +1,12 @@
+apiVersion: kustomize.config.k8s.io/v1beta1
+kind: Kustomization
+resources:
+  - daemonset.yaml
+configMapGenerator:
+  # Hashed name, so editing any of these rolls the DaemonSet.
+  - name: bird-config
+    namespace: kube-system
+    files:
+      - bird.conf
+      - defines.tmpl
+      - peers.tmpl

kubernetes/infrastructure/bird/peers.tmpl

@@ -0,0 +1,7 @@
+{{- range $i, $n := .items -}}
+{{- $v6 := index $n.metadata.annotations "net.renner.uno/pod0-v6" -}}
+{{- $v4 := index $n.metadata.annotations "net.renner.uno/pod0-v4" -}}
+# {{ $n.metadata.name }}
+protocol bgp peer{{ $i }}_v6 from pod6 { neighbor {{ $v6 }} as 64514; }
+protocol bgp peer{{ $i }}_v4 from pod4 { neighbor {{ $v4 }} as 64514; }
+{{ end -}}

kubernetes/infrastructure/kustomization.yaml

@@ -7,6 +7,7 @@ resources:
   - cluster-settings/
   - cilium/
   - multus/
+  - bird/
   - cert-manager/
   - snapshot-controller/
   - metrics-server/

kubernetes/talos/patches/k8s-1.yaml

@@ -52,6 +52,12 @@ machine:
     # this label instead of listing hostnames, so which boxes carry storage is
     # stated once, here, by the machine that knows.
     storage.renner.uno/ceph-osd: "true"
+  # Publishes this node's pod0 addresses, declared below in its VLANConfig, so
+  # the bird DaemonSet reads its peers from the node list rather than from a
+  # copy. Annotations, not labels: a label value cannot contain a colon.
+  nodeAnnotations:
+    net.renner.uno/pod0-v6: fd02:48::11
+    net.renner.uno/pod0-v4: 10.2.48.11
   udev:
     # Renames every port this node uses to its role at boot, matched by
     # burned-in MAC — kernel names derive from PCI topology and shift when

kubernetes/talos/patches/k8s-2.yaml

@@ -33,6 +33,10 @@ machine:
     topology.kubernetes.io/zone: saturn
     # Holds a Ceph OSD drive — see k8s-1.yaml.
     storage.renner.uno/ceph-osd: "true"
+  # pod0 addresses for the bird peer list — see k8s-1.yaml.
+  nodeAnnotations:
+    net.renner.uno/pod0-v6: fd02:48::12
+    net.renner.uno/pod0-v4: 10.2.48.12
   udev:
     # Renames every port to its role at boot — see k8s-1.yaml.
     rules:

kubernetes/talos/patches/k8s-3.yaml

@@ -29,6 +29,10 @@ machine:
     topology.kubernetes.io/zone: neptune
     # Holds a Ceph OSD drive — see k8s-1.yaml.
     storage.renner.uno/ceph-osd: "true"
+  # pod0 addresses for the bird peer list — see k8s-1.yaml.
+  nodeAnnotations:
+    net.renner.uno/pod0-v6: fd02:48::13
+    net.renner.uno/pod0-v4: 10.2.48.13
   udev:
     # Renames every port to its role at boot — see k8s-1.yaml.
     rules: