From 77f42642ef7917cffd74360b5f51ab8c0f191ccc Mon Sep 17 00:00:00 2001
From: Aaron Henshaw <aaron@bisontrails.co>
Date: Mon, 24 Jun 2019 12:21:59 -0400
Subject: [PATCH] Add use-external-host-ip as annotation to use ExternalIP of
 Node for headless services

---
 source/service.go | 26 +++++++++++++++++++++++---
 source/source.go  |  7 +++++++
 2 files changed, 30 insertions(+), 3 deletions(-)

diff --git a/source/service.go b/source/service.go
index 1fba3d624b..85a7ca0225 100644
--- a/source/service.go
+++ b/source/service.go
@@ -211,7 +211,7 @@ func (sc *serviceSource) Endpoints() ([]*endpoint.Endpoint, error) {
 	return endpoints, nil
 }
 
-func (sc *serviceSource) extractHeadlessEndpoints(svc *v1.Service, hostname string, ttl endpoint.TTL) []*endpoint.Endpoint {
+func (sc *serviceSource) extractHeadlessEndpoints(svc *v1.Service, hostname string, ttl endpoint.TTL, externalIp bool) []*endpoint.Endpoint {
 	var endpoints []*endpoint.Endpoint
 
 	labelSelector, err := metav1.ParseToLabelSelector(labels.Set(svc.Spec.Selector).AsSelectorPreValidated().String())
@@ -237,7 +237,22 @@ func (sc *serviceSource) extractHeadlessEndpoints(svc *v1.Service, hostname stri
 			headlessDomains = append(headlessDomains, fmt.Sprintf("%s.%s", v.Spec.Hostname, hostname))
 		}
 		for _, headlessDomain := range headlessDomains {
-			if sc.publishHostIP == true {
+			if sc.publishHostIP && externalIp {
+				node, err := sc.nodeInformer.Lister().Get(v.Spec.NodeName)
+				if err != nil {
+					return nil
+				}
+				if v.Status.Phase == v1.PodRunning {
+					for _, x := range node.Status.Addresses {
+						if x.Type == v1.NodeExternalIP {
+							log.Debugf("Generating matching endpoint %s with External %s", headlessDomain, v.Status.HostIP)
+							targetsByHeadlessDomain[headlessDomain] = append(targetsByHeadlessDomain[headlessDomain], x.Address)
+						}
+					}
+				} else {
+					log.Debugf("Pod %s is not in running phase", v.Spec.Hostname)
+				}
+			} else if sc.publishHostIP == true {
 				log.Debugf("Generating matching endpoint %s with HostIP %s", headlessDomain, v.Status.HostIP)
 				// To reduce traffice on the DNS API only add record for running Pods. Good Idea?
 				if v.Status.Phase == v1.PodRunning {
@@ -365,6 +380,11 @@ func (sc *serviceSource) generateEndpoints(svc *v1.Service, hostname string, pro
 		log.Warn(err)
 	}
 
+	externalIp := getExternalIpFromAnnotations(svc.Annotations)
+	if err != nil {
+		log.Warn(err)
+	}
+
 	epA := &endpoint.Endpoint{
 		RecordTTL:        ttl,
 		RecordType:       endpoint.RecordTypeA,
@@ -394,7 +414,7 @@ func (sc *serviceSource) generateEndpoints(svc *v1.Service, hostname string, pro
 			targets = append(targets, extractServiceIps(svc)...)
 		}
 		if svc.Spec.ClusterIP == v1.ClusterIPNone {
-			endpoints = append(endpoints, sc.extractHeadlessEndpoints(svc, hostname, ttl)...)
+			endpoints = append(endpoints, sc.extractHeadlessEndpoints(svc, hostname, ttl, externalIp)...)
 		}
 	case v1.ServiceTypeNodePort:
 		// add the nodeTargets and extract an SRV endpoint
diff --git a/source/source.go b/source/source.go
index 83fc846917..e45e464f29 100644
--- a/source/source.go
+++ b/source/source.go
@@ -37,6 +37,8 @@ const (
 	ttlAnnotationKey = "external-dns.alpha.kubernetes.io/ttl"
 	// The annotation used for switching to the alias record types e. g. AWS Alias records instead of a normal CNAME
 	aliasAnnotationKey = "external-dns.alpha.kubernetes.io/alias"
+	// The annotation used for having publishHostIP use the ExternalIP of the Host Node
+	externalIPAnnotationKey = "external-dns.alpha.kubernetes.io/use-external-host-ip"
 	// The value of the controller annotation so that we feel responsible
 	controllerAnnotationValue = "dns-controller"
 )
@@ -86,6 +88,11 @@ func getAliasFromAnnotations(annotations map[string]string) bool {
 	return exists && aliasAnnotation == "true"
 }
 
+func getExternalIpFromAnnotations(annotations map[string]string) bool {
+	aliasAnnotation, exists := annotations[externalIPAnnotationKey]
+	return exists && aliasAnnotation == "true"
+}
+
 func getProviderSpecificAnnotations(annotations map[string]string) endpoint.ProviderSpecific {
 	providerSpecificAnnotations := endpoint.ProviderSpecific{}