Fatal error when DNSEndpoint target is invalid

[vflaux]

What happened:

1. External-dns exit when a DNSEndpoint when an invalid target is provided.
2. It also exits with a DNSRecord of type AAAA and a hostname target and the AWS provider specific "alias" key.

What you expected to happen:

1. should log an error, not exit with a fatal log
2. DNRecord of types AAAA with a hostname target and the provider specific alias should be valid.

How to reproduce it (as minimally and precisely as possible):
args:

--source=crd

manifest:

apiVersion: externaldns.k8s.io/v1alpha1
kind: DNSEndpoint
metadata:
  name: alias
  namespace: default
spec:
  endpoints:
  - dnsName: alias.example.com
    recordType: AAAA
    targets:
    - target.example.com
    providerSpecific:
    - name: "alias"
      value: "true"

log:

{"level":"fatal","msg":"Failed to do run once: ParseAddr(\"target.example.com\"): unexpected character (at \"target.example.com\")","time":"xxx"}

Anything else we need to know?:

external-dns/source/wrappers/nat64source.go

Line 72 in b31afb4

ip, err := netip.ParseAddr(target)

Environment:

• External-DNS version (use external-dns --version): v0.19.0
• DNS provider: AWS
• Others:

[vflaux]

external-dns/source/wrappers/nat64source.go

Lines 72 to 75 in b31afb4

	ip, err := netip.ParseAddr(target)
	if err != nil {
	return nil, err
	}

Would it be ok to continue instead of returning an error in this case ?

			ip, err := netip.ParseAddr(target)
			if err != nil {
				continue
			}

This would simply ignore any non ip addresses targets

[ivankatliarchuk]

Hard to say. Another option is to

1. validate arguments and fail fast
2. Introduce an interface, pattern chain of responsibility

type Handler interface {
    execute()
    setNext(*Source, options...) error
    isEnabled() bool
}