feat: one pod routing table, decided by longest prefix (#576)

The rule stack grew a carve-out layer because table 47 held nothing but a default route: it matched everything, so every cluster-internal destination had to be excluded by a rule naming its prefix. Those exclusions were wrong twice over — too broad, since fd00::/8 and 10.0.0.0/8 also caught every LAN client and sent its reply back over mgmt0, and unnecessary, since the networks in question are directly attached and a connected route already beats a default.

So the table gets the connected routes and decides on its own. bird's direct protocol generates them from the interfaces rather than from a list, alongside the peers' pod CIDRs it already learns and the egress default it now originates. One rule per family remains, on the pod source prefix; 980/981, 990/991 and table 48 are gone.

bird owns the table outright, including the default. That is what keeps the failure benign: if the daemon stops the table empties, the rule finds nothing and falls through to main, so pod traffic returns to VLAN 40 unseparated rather than misrouted. A default declared in the Talos config would have outlived the specific routes and sent pod traffic to the UDM.

The ingress gateway moves from a route in each node patch to one node annotation in the site patch, which is now the only place it is stated.

Verified: bird -p parses the rendered config inside the image, exit 0; the templates render GW6 fd02:47::1 and GW4 10.2.47.1 from the live k8s-1 object; kubectl kustomize builds.

Refs #576

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

ci/images/bird/Containerfile

@@ -9,14 +9,14 @@ 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.
 #
-# curl and jq are for the init container, which renders the per-node peer list
-# from the Kubernetes API. busybox wget cannot verify against the API server's
-# CA bundle, and the query must not run unverified.
-RUN apk add --no-cache bird2 curl jq
+# 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 a binary or its path is wrong.
 RUN /usr/sbin/bird --version \
- && curl --version > /dev/null \
- && jq --version > /dev/null
+ && kubectl version --client > /dev/null
 
 ENTRYPOINT ["/usr/sbin/bird", "-f", "-c", "/etc/bird/bird.conf"]

kubernetes/infrastructure/bird/bird.conf

@@ -0,0 +1,107 @@
+# 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; }
+
+# Everything a pod may need to reach, in one table, resolved by longest prefix:
+# the node's attached networks, the peers' pod CIDRs, and a default for the
+# rest. No rule has to carve out exceptions, because the specific routes win on
+# their own.
+#
+# The table is BIRD's alone. If this daemon stops, it empties, the rule finds
+# nothing and falls through to main — pod traffic returns to VLAN 40,
+# unseparated rather than misrouted. That is why the default route lives here
+# and not in the Talos config: a default that outlived the specific routes
+# would send pod traffic to the UDM.
+
+# The node's attached networks, taken from the interfaces rather than written
+# down. The usual advice is not to export these to the kernel because it
+# maintains them itself — true of main, not of a table the kernel never fills.
+protocol direct attached {
+  interface "mgmt0", "ingress0", "pod0";
+  ipv4 { table master4; };
+  ipv6 { table master6; };
+}
+
+# Pod egress. GW4/GW6 are the UDM on the ingress segment, published as node
+# annotations beside the address that defines them.
+protocol static egress4 {
+  ipv4 { table master4; };
+  route 0.0.0.0/0 via GW4;
+}
+protocol static egress6 {
+  ipv6 { table master6; };
+  route ::/0 via GW6;
+}
+
+# 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".
+#
+# blackhole because it is only ever advertised — it is filtered out below.
+protocol static own4 {
+  ipv4 { table master4; };
+  route OWN_POD4 blackhole;
+}
+protocol static own6 {
+  ipv6 { table master6; };
+  route OWN_POD6 blackhole;
+}
+
+# Everything except this node's own CIDR, which cilium_host already serves in
+# main and which is a blackhole here.
+filter to_pod_table {
+  if source = RTS_STATIC && dest = RTD_BLACKHOLE then reject;
+  accept;
+}
+
+protocol kernel k4 {
+  kernel table 47;
+  metric 0;
+  ipv4 { table master4; import none; export filter to_pod_table; };
+}
+protocol kernel k6 {
+  kernel table 47;
+  metric 0;
+  ipv6 { table master6; import none; export filter to_pod_table; };
+}
+
+# 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.
+#
+# Only the node's own CIDR is offered: the export filter drops everything the
+# static protocols and the direct protocol produce.
+template bgp pod4 {
+  local as 64514;
+  source address MY4;
+  direct;
+  strict bind;
+  ipv4 {
+    next hop self;
+    import all;
+    export filter { if net = OWN_POD4 then accept; reject; };
+  };
+}
+template bgp pod6 {
+  local as 64514;
+  source address MY6;
+  direct;
+  strict bind;
+  ipv6 {
+    next hop self;
+    import all;
+    export filter { if net = OWN_POD6 then accept; reject; };
+  };
+}
+
+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 +1,9 @@
+define MY6 = {{ index .metadata.annotations "net.renner.uno/pod0-v6" }};
+define MY4 = {{ index .metadata.annotations "net.renner.uno/pod0-v4" }};
+define GW6 = {{ index .metadata.annotations "net.renner.uno/egress-gw-v6" }};
+define GW4 = {{ index .metadata.annotations "net.renner.uno/egress-gw-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
@@ -182,14 +188,13 @@ addresses:
 # network's clients selectively, so the client goes rather than the record.
 # DHCP is off on VLAN 47 for the same reason.
 #
-# Both defaults live in table 47, not in main, so only the pod-source rules in
-# site-homelab.yaml reach them. mgmt0 keeps main's default and with it every
-# reply the node sends from its own addresses.
+# No route here. Table 47 belongs to bird, which fills it with this node's
+# attached networks, the peers' pod CIDRs and the egress default, and empties it
+# if it stops — leaving the rule to fall through to main. A default declared
+# here would outlive the specific routes and send pod traffic to the UDM.
 #
-# The v6 gateway is the UDM's configured ULA on this segment, the same address
-# BGP peers with. The RA-learned link-local would be the alternative and is not
-# a value to write down. accept_ra_defrtr stays 0 for that reason: the RA
-# default would land in main, where it does not belong.
+# accept_ra_defrtr stays 0 on this link so the RA default does not land in main,
+# where mgmt0 owns it.
 apiVersion: v1alpha1
 kind: VLANConfig
 name: ingress0
@@ -198,11 +203,6 @@ parent: uplink
 up: true
 addresses:
   - address: 10.2.47.11/24
-routes:
-  - gateway: fd02:47::1
-    table: "47"
-  - gateway: 10.2.47.1
-    table: "47"
 ---
 # Dedicated Ceph cluster network on X710 port 1, VLAN 49, untagged on the
 # wire. OSD-to-OSD replication and nothing else. The udev rule in the machine

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:
@@ -128,11 +132,6 @@ parent: uplink
 up: true
 addresses:
   - address: 10.2.47.12/24
-routes:
-  - gateway: fd02:47::1
-    table: "47"
-  - gateway: 10.2.47.1
-    table: "47"
 ---
 # Dedicated Ceph cluster network on X710 port 1, VLAN 49, untagged on the
 # wire. OSD-to-OSD replication only, not routed off its own segment.

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:
@@ -115,11 +119,6 @@ parent: uplink
 up: true
 addresses:
   - address: 10.2.47.13/24
-routes:
-  - gateway: fd02:47::1
-    table: "47"
-  - gateway: 10.2.47.1
-    table: "47"
 ---
 # Dedicated Ceph cluster network — see k8s-1.yaml. The node holds NO address
 # here on purpose; the link is handed whole to the OSD pod (host-device).

kubernetes/talos/patches/site-homelab.yaml

@@ -20,41 +20,32 @@ machine:
       validSubnets:
         - 10.2.40.0/24
         - fd40::/64
+  # The UDM on the ingress segment. Published here rather than as a route
+  # because bird owns table 47 and originates the default from it; this is the
+  # one place the address is stated.
+  nodeAnnotations:
+    net.renner.uno/egress-gw-v6: fd02:47::1
+    net.renner.uno/egress-gw-v4: 10.2.47.1
 ---
-# Pod egress leaves over ingress0. Matching on the pod source prefix is what
-# keeps the node's own traffic out of it: the node IP, the API VIP and apid all
-# answer on mgmt0, and a reply that left over ingress0 would carry an mgmt0
-# source onto VLAN 47.
+# All pod traffic goes to table 47, and the table decides — longest prefix
+# match, no exceptions to carve out. bird fills it with the node's attached
+# networks, the peers' pod CIDRs and the egress default, so a packet to a node
+# on the mgmt segment takes the connected route, a packet to a pod on another
+# node takes pod0, and anything else takes the default over ingress0.
 #
-# The routing decision runs before Cilium's masquerade hook, so the rule sees
-# the pod address and the masquerade then rewrites it to ingress0's.
+# Matching the source is what keeps the node's own traffic out: it answers on
+# mgmt0, and a reply leaving over ingress0 would carry an mgmt0 source onto
+# VLAN 47. The routing decision runs before Cilium's masquerade hook, so the
+# rule sees the pod address and the masquerade then rewrites it.
 #
-# Table 47 holds nothing but the two default routes, so the destination rules
-# below have to run first: without them a pod's packet to a service or to a pod
-# on another node also matches the source rule, finds only the default, and
-# leaves for the UDM. Measured — in-cluster DNS stopped resolving.
-#
-# They send everything inside the cluster and the local networks back to main.
-# The prefixes are Cilium's ipv4/ipv6NativeRoutingCIDR, which already mark what
-# is not foreign traffic.
+# If bird stops, table 47 empties, the lookup misses and the rule falls through
+# to main — pod traffic returns to VLAN 40, unseparated rather than misrouted.
 #
 # Priorities are below main (32766) and clear of the rule Cilium installs at 9.
 # The two families are separate rule tables, so the priorities need not match;
 # the document name is the priority and must be unique.
 apiVersion: v1alpha1
 kind: RoutingRuleConfig
-name: "990"
-dst: fd00::/8
-table: main
----
-apiVersion: v1alpha1
-kind: RoutingRuleConfig
-name: "991"
-dst: 10.0.0.0/8
-table: main
----
-apiVersion: v1alpha1
-kind: RoutingRuleConfig
 name: "1000"
 src: fd10:244::/48
 table: "47"