Redirect public DNS to the local resolver

This example catches LAN clients that send plaintext DNS directly to well-known public resolver names and redirects only TCP/UDP port 53 to the router's local resolver. DoH and DoT ports are not touched.

The complete, validated YAML is in examples/example-local-dns-redirect.yaml.

Topology

Diagram map

No.	Meaning	Main resources
[1]	Client that tries to query public DNS directly.	External client
[2]	LAN interface where prerouting redirect rules match.	LocalServiceRedirect/lan-local-services.spec.interface
[3]	Local resolver that receives redirected port 53 traffic.	DNSResolver/lan-resolver
[4]	Exact FQDNs resolved into reusable nftables sets.	IPAddressSet/public-dns
[5]	Real upstream resolvers used by the local resolver.	DNSForwarder, DNSUpstream

What this manages

Area	routerd resources
Local DNS	DNSResolver/lan-resolver, DNSZone/home
DHCP advertisement	DHCPv4Server/lan-dhcpv4
FQDN-backed destination set	IPAddressSet/public-dns
Local redirect	LocalServiceRedirect/lan-local-services

Key config

# [4] Resolve exact public DNS names into an IPAddressSet.
- apiVersion: net.routerd.net/v1alpha1
  kind: IPAddressSet
  metadata:
    name: public-dns
  spec:
    names:
      - dns.google
      - one.one.one.one
    refreshInterval: 10m

# [2] -> [3] Redirect only plaintext DNS port 53 to the local resolver.
# This matches LAN-client prerouting traffic only. Router-origin TCP/443
# HealthCheck probes are not redirected, so they can use the same public target
# address when policy routing selects the path explicitly.
- apiVersion: firewall.routerd.net/v1alpha1
  kind: LocalServiceRedirect
  metadata:
    name: lan-local-services
  spec:
    interface: lan
    rules:
      - name: public-dns
        protocols: [tcp, udp]
        destinationSetRef: IPAddressSet/public-dns
        destinationPort: 53
        redirectPort: 53

IPAddressSet.spec.names are exact names. dns.google does not include subdomains. Use explicit names for every destination whose resolved addresses you want to match.

Checks

routerd validate --config examples/example-local-dns-redirect.yaml
routerd apply --config examples/example-local-dns-redirect.yaml --once --dry-run
routerctl describe IPAddressSet/public-dns
nft list table ip routerd_nat

From a LAN client:

dig @8.8.8.8 router.home.example
dig @1.1.1.1 router.home.example