plugin/k8s_external: fix external nsAddrs when CoreDNS Service has no External IPs (#4891)

fix external nsAddrs; add tests;

Signed-off-by: Chris O'Haver <cohaver@infoblox.com>

1 files changed, 6 insertions, 4 deletions

diff --git a/plugin/kubernetes/ns.go b/plugin/kubernetes/ns.go
index 84f4e344b..3e6a30586 100644
--- a/plugin/kubernetes/ns.go
+++ b/plugin/kubernetes/ns.go
@@ -15,8 +15,9 @@ func isDefaultNS(name, zone string) bool {
 // it returns a record for the local address of the machine we're running on.
 func (k *Kubernetes) nsAddrs(external bool, zone string) []dns.RR {
 	var (
-		svcNames []string
-		svcIPs   []net.IP
+		svcNames      []string
+		svcIPs        []net.IP
+		foundEndpoint bool
 	)
 
 	// Find the CoreDNS Endpoints
@@ -25,6 +26,7 @@ func (k *Kubernetes) nsAddrs(external bool, zone string) []dns.RR {
 
 		// Collect IPs for all Services of the Endpoints
 		for _, endpoint := range endpoints {
+			foundEndpoint = true
 			svcs := k.APIConn.SvcIndex(endpoint.Index)
 			for _, svc := range svcs {
 				if external {
@@ -54,8 +56,8 @@ func (k *Kubernetes) nsAddrs(external bool, zone string) []dns.RR {
 		}
 	}
 
-	// If no local IPs matched any endpoints, use the localIPs directly
-	if len(svcIPs) == 0 {
+	// If no CoreDNS endpoints were found, use the localIPs directly
+	if !foundEndpoint {
 		svcIPs = make([]net.IP, len(k.localIPs))
 		svcNames = make([]string, len(k.localIPs))
 		for i, localIP := range k.localIPs {