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/etcd/stub_test.go

@@ -0,0 +1,88 @@
+// +build etcd
+
+package etcd
+
+import (
+	"net"
+	"strconv"
+	"testing"
+
+	"github.com/coredns/coredns/plugin/etcd/msg"
+	"github.com/coredns/coredns/plugin/pkg/dnsrecorder"
+	"github.com/coredns/coredns/plugin/test"
+
+	"github.com/miekg/dns"
+)
+
+func fakeStubServerExampleNet(t *testing.T) (*dns.Server, string) {
+	server, addr, err := test.UDPServer("127.0.0.1:0")
+	if err != nil {
+		t.Fatalf("failed to create a UDP server: %s", err)
+	}
+	// add handler for example.net
+	dns.HandleFunc("example.net.", func(w dns.ResponseWriter, r *dns.Msg) {
+		m := new(dns.Msg)
+		m.SetReply(r)
+		m.Answer = []dns.RR{test.A("example.net.	86400	IN	A	93.184.216.34")}
+		w.WriteMsg(m)
+	})
+
+	return server, addr
+}
+
+func TestStubLookup(t *testing.T) {
+	server, addr := fakeStubServerExampleNet(t)
+	defer server.Shutdown()
+
+	host, p, _ := net.SplitHostPort(addr)
+	port, _ := strconv.Atoi(p)
+	exampleNetStub := &msg.Service{Host: host, Port: port, Key: "a.example.net.stub.dns.skydns.test."}
+	servicesStub = append(servicesStub, exampleNetStub)
+
+	etc := newEtcdMiddleware()
+
+	for _, serv := range servicesStub {
+		set(t, etc, serv.Key, 0, serv)
+		defer delete(t, etc, serv.Key)
+	}
+
+	etc.updateStubZones()
+
+	for _, tc := range dnsTestCasesStub {
+		m := tc.Msg()
+
+		rec := dnsrecorder.New(&test.ResponseWriter{})
+		_, err := etc.ServeDNS(ctxt, rec, m)
+		if err != nil && m.Question[0].Name == "example.org." {
+			// This is OK, we expect this backend to *not* work.
+			continue
+		}
+		if err != nil {
+			t.Errorf("expected no error, got %v for %s\n", err, m.Question[0].Name)
+		}
+		resp := rec.Msg
+		if resp == nil {
+			// etcd not running?
+			continue
+		}
+
+		test.SortAndCheck(t, resp, tc)
+	}
+}
+
+var servicesStub = []*msg.Service{
+	// Two tests, ask a question that should return servfail because remote it no accessible
+	// and one with edns0 option added, that should return refused.
+	{Host: "127.0.0.1", Port: 666, Key: "b.example.org.stub.dns.skydns.test."},
+}
+
+var dnsTestCasesStub = []test.Case{
+	{
+		Qname: "example.org.", Qtype: dns.TypeA, Rcode: dns.RcodeServerFailure,
+	},
+	{
+		Qname: "example.net.", Qtype: dns.TypeA,
+		Answer: []dns.RR{test.A("example.net.	86400	IN	A	93.184.216.34")},
+		Extra: []dns.RR{test.OPT(4096, false)}, // This will have an EDNS0 section, because *we* added our local stub forward to detect loops.
+	},
+}