mw/kubernetes: remove kService and kPod

Remove the intermediate step of gathering everyhing in a kPod and
kService and extracting the msg.Service from there. Now findPods and
findServices return []msg.Service.

This cuts down on the code and also removed the double looping of
finding the data we need, so it should be faster.

middleware/kubernetes/reverse.go

@@ -1,6 +1,8 @@
 package kubernetes
 
 import (
+	"strings"
+
 	"github.com/coredns/coredns/middleware"
 	"github.com/coredns/coredns/middleware/etcd/msg"
 	"github.com/coredns/coredns/middleware/pkg/dnsutil"
@@ -18,3 +20,36 @@ func (k *Kubernetes) Reverse(state request.Request, exact bool, opt middleware.O
 	records := k.serviceRecordForIP(ip, state.Name())
 	return records, nil, nil
 }
+
+// serviceRecordForIP gets a service record with a cluster ip matching the ip argument
+// If a service cluster ip does not match, it checks all endpoints
+func (k *Kubernetes) serviceRecordForIP(ip, name string) []msg.Service {
+	// First check services with cluster ips
+	svcList := k.APIConn.ServiceList()
+
+	for _, service := range svcList {
+		if (len(k.Namespaces) > 0) && !k.namespaceExposed(service.Namespace) {
+			continue
+		}
+		if service.Spec.ClusterIP == ip {
+			domain := strings.Join([]string{service.Name, service.Namespace, Svc, k.primaryZone()}, ".")
+			return []msg.Service{{Host: domain}}
+		}
+	}
+	// If no cluster ips match, search endpoints
+	epList := k.APIConn.EndpointsList()
+	for _, ep := range epList.Items {
+		if (len(k.Namespaces) > 0) && !k.namespaceExposed(ep.ObjectMeta.Namespace) {
+			continue
+		}
+		for _, eps := range ep.Subsets {
+			for _, addr := range eps.Addresses {
+				if addr.IP == ip {
+					domain := strings.Join([]string{endpointHostname(addr), ep.ObjectMeta.Name, ep.ObjectMeta.Namespace, Svc, k.primaryZone()}, ".")
+					return []msg.Service{{Host: domain}}
+				}
+			}
+		}
+	}
+	return nil
+}