In k3s how to whitelist specific namespaces to work with traefik?

Traefik Traefik v3 (latest)
1

In k3s how to whitelist specific namespaces to work with traefik? There is an allowCrossNamespace option for traefik, somewhere, helm or just in its plain setup, and I had to have enabled it because there was the UI for one of my services in a different namespace (longhorn), but I dont like the idea of it being open for all namespaces, also that might get messy with multiple ingresses for the future, so is there a way to whitelist specific namepsaces to work cross-namespace?

2

I will suggest you to look for k3s network policies. I found the next example code in the net:

apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: isolate-and-allow-db-system
  namespace: your-target-namespace
spec:
  podSelector: {} # Selects all pods in this namespace
  policyTypes:
    - Egress
  egress:
    # 1. Allow communication with kube-system (for CoreDNS, etc.)
    - to:
        - namespaceSelector:
            matchLabels:
              kubernetes.io/metadata.name: kube-system
    
    # 2. Allow DNS traffic (UDP/TCP Port 53) for kube-system (if CoreDNS runs there)
    - ports:
        - protocol: UDP
          port: 53
        - protocol: TCP
          port: 53

    # 3. Allow traffic to your External Database IP
    - to:
        - ipBlock:
            cidr: 203.0.113.50/32 # REPLACE with your actual external database IP/CIDR

Hope this helps