> ## Documentation Index
> Fetch the complete documentation index at: https://docs.kguardian.dev/llms.txt
> Use this file to discover all available pages before exploring further.

# CoreDNS (cluster DNS)

> Generated NetworkPolicy and seccomp profile for the kube-system CoreDNS deployment

<Warning>
  **Hand-authored illustration.** The YAML on this page illustrates the shape of the policies kguardian generates for this workload — it is not captured generator output. Exact metadata, rule grouping, and selectors produced by `kubectl kguardian gen` will differ. Regeneration of this gallery from a live cluster is planned.
</Warning>

<Note>
  CoreDNS lives in `kube-system`, which is excluded from monitoring by default — to capture this profile you must remove `kube-system` from `controller.excludedNamespaces` in the Helm values, or scope generation manually.
</Note>

## Workload

The cluster's CoreDNS deployment in `kube-system` (label `k8s-app: kube-dns`). It accepts DNS queries on UDP/53 and TCP/53 from every pod in the cluster, forwards external queries to the node-local upstream resolver (typically `169.254.169.254` on cloud VMs or the host's `/etc/resolv.conf`), and exposes a metrics endpoint on TCP/9153 scraped by Prometheus.

## Generated NetworkPolicy

```yaml theme={null}
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: coredns
  namespace: kube-system
  labels:
    kguardian.dev/managed-by: kguardian
    kguardian.dev/version: v1.0.0
spec:
  podSelector:
    matchLabels:
      k8s-app: kube-dns
  policyTypes:
    - Ingress
    - Egress
  ingress:
    - from:
        - namespaceSelector: {}
      ports:
        - protocol: UDP
          port: 53
        - protocol: TCP
          port: 53
    - from:
        - namespaceSelector:
            matchLabels:
              kubernetes.io/metadata.name: monitoring
          podSelector:
            matchLabels:
              app.kubernetes.io/name: prometheus
      ports:
        - protocol: TCP
          port: 9153
  egress:
    - to:
        - ipBlock:
            cidr: 169.254.169.254/32
      ports:
        - protocol: UDP
          port: 53
        - protocol: TCP
          port: 53
    - ports:
        - protocol: TCP
          port: 6443
      to:
        - ipBlock:
            cidr: 10.96.0.1/32
```

## Generated CiliumNetworkPolicy

```yaml theme={null}
apiVersion: cilium.io/v2
kind: CiliumNetworkPolicy
metadata:
  name: coredns
  namespace: kube-system
  labels:
    kguardian.dev/managed-by: kguardian
    kguardian.dev/version: v1.0.0
spec:
  endpointSelector:
    matchLabels:
      k8s-app: kube-dns
  ingress:
    - fromEndpoints:
        - {}
      toPorts:
        - ports:
            - port: "53"
              protocol: UDP
            - port: "53"
              protocol: TCP
    - fromEndpoints:
        - matchLabels:
            app.kubernetes.io/name: prometheus
            io.kubernetes.pod.namespace: monitoring
      toPorts:
        - ports:
            - port: "9153"
              protocol: TCP
  egress:
    - toCIDR:
        - 169.254.169.254/32
      toPorts:
        - ports:
            - port: "53"
              protocol: ANY
    - toEntities:
        - kube-apiserver
      toPorts:
        - ports:
            - port: "6443"
              protocol: TCP
```

## Generated seccomp profile (excerpt)

Full profile contains **78 syscall names**. Representative excerpt:

```json theme={null}
{
  "defaultAction": "SCMP_ACT_ERRNO",
  "architectures": ["SCMP_ARCH_X86_64"],
  "syscalls": [
    {
      "names": [
        "accept4", "bind", "close", "connect", "epoll_create1",
        "epoll_ctl", "epoll_pwait", "futex", "getsockname",
        "listen", "openat", "read", "recvfrom", "recvmsg",
        "sendmsg", "sendto", "setsockopt", "socket", "write"
      ],
      "action": "SCMP_ACT_ALLOW"
    }
  ]
}
```

## What kguardian observed

CoreDNS receives requests from every namespace in the cluster. The single `namespaceSelector: {}` ingress rule shown above is a hand-idealization — the generator emits one rule per observed peer, with pod and namespace selectors for in-cluster sources. Egress splits into two distinct destinations: node-local resolver IP for upstream lookups, and the Kubernetes API service ClusterIP (`10.96.0.1`) for the in-cluster zone plugin. The syscall set is small because CoreDNS is a single-purpose Go binary — heavy `recvmsg`/`sendmsg` for UDP, `epoll` for TCP, and minimal file I/O. Prometheus scrape ingress on TCP/9153 was captured separately because it originated from a single, identifiable pod.