Remove the word middleware (#1067)

* Rename middleware to plugin

first pass; mostly used 'sed', few spots where I manually changed
text.

This still builds a coredns binary.

* fmt error

* Rename AddMiddleware to AddPlugin

* Readd AddMiddleware to remain backwards compat

plugin/kubernetes/ns.go

@@ -0,0 +1,65 @@
+package kubernetes
+
+import (
+	"net"
+	"strings"
+
+	"github.com/miekg/dns"
+	"k8s.io/client-go/1.5/pkg/api"
+)
+
+func isDefaultNS(name, zone string) bool {
+	return strings.Index(name, defaultNSName) == 0 && strings.Index(name, zone) == len(defaultNSName)
+}
+
+func (k *Kubernetes) nsAddr() *dns.A {
+	var (
+		svcName      string
+		svcNamespace string
+	)
+
+	rr := new(dns.A)
+	localIP := k.interfaceAddrsFunc()
+	endpointsList := k.APIConn.EndpointsList()
+
+	rr.A = localIP
+
+FindEndpoint:
+	for _, ep := range endpointsList.Items {
+		for _, eps := range ep.Subsets {
+			for _, addr := range eps.Addresses {
+				if localIP.Equal(net.ParseIP(addr.IP)) {
+					svcNamespace = ep.ObjectMeta.Namespace
+					svcName = ep.ObjectMeta.Name
+					break FindEndpoint
+				}
+			}
+		}
+	}
+
+	if len(svcName) == 0 {
+		rr.Hdr.Name = defaultNSName
+		rr.A = localIP
+		return rr
+	}
+	// Find service to get ClusterIP
+	serviceList := k.APIConn.ServiceList()
+
+FindService:
+	for _, svc := range serviceList {
+		if svcName == svc.Name && svcNamespace == svc.Namespace {
+			if svc.Spec.ClusterIP == api.ClusterIPNone {
+				rr.A = localIP
+			} else {
+				rr.A = net.ParseIP(svc.Spec.ClusterIP)
+			}
+			break FindService
+		}
+	}
+
+	rr.Hdr.Name = strings.Join([]string{svcName, svcNamespace, "svc."}, ".")
+
+	return rr
+}
+
+const defaultNSName = "ns.dns."