Add new plugin: external - resolve k8s ingress and LB address with external names (#2379)

* Add new plugin: external

This plugin works in conjunction with the kubernetes plugin and exports
ingress and LB addresses as DNS records. It bypasses backend.go and
backend_lookup.go flow because it is not needed.

README, tests are implemented. The tests only exercise the unit tests,
this has not been tested in any ci.

Signed-off-by: Miek Gieben <miek@miek.nl>

* Rename to k8s_external

Signed-off-by: Miek Gieben <miek@miek.nl>

* go gen

Signed-off-by: Miek Gieben <miek@miek.nl>

1 files changed, 139 insertions, 0 deletions

diff --git a/plugin/kubernetes/external_test.go b/plugin/kubernetes/external_test.go
new file mode 100644
index 000000000..7fb5469e1
--- /dev/null
+++ b/plugin/kubernetes/external_test.go
@@ -0,0 +1,139 @@
+package kubernetes
+
+import (
+	"testing"
+
+	"github.com/coredns/coredns/plugin/etcd/msg"
+	"github.com/coredns/coredns/plugin/kubernetes/object"
+	"github.com/coredns/coredns/plugin/pkg/watch"
+	"github.com/coredns/coredns/plugin/test"
+	"github.com/coredns/coredns/request"
+
+	"github.com/miekg/dns"
+	api "k8s.io/api/core/v1"
+	meta "k8s.io/apimachinery/pkg/apis/meta/v1"
+)
+
+var extCases = []struct {
+	Qname string
+	Qtype uint16
+	Msg   []msg.Service
+	Rcode int
+}{
+	{
+		Qname: "svc1.testns.example.org.", Rcode: dns.RcodeSuccess,
+		Msg: []msg.Service{
+			msg.Service{Host: "1.2.3.4", Port: 80, TTL: 5, Key: "/c/org/example/testns/svc1"},
+		},
+	},
+	{
+		Qname: "svc6.testns.example.org.", Rcode: dns.RcodeSuccess,
+		Msg: []msg.Service{
+			msg.Service{Host: "1:2::5", Port: 80, TTL: 5, Key: "/c/org/example/testns/svc1"},
+		},
+	},
+	{
+		Qname: "*._not-udp-or-tcp.svc1.testns.example.com.", Rcode: dns.RcodeSuccess,
+	},
+	{
+		Qname: "_http._tcp.svc1.testns.example.com.", Rcode: dns.RcodeSuccess,
+		Msg: []msg.Service{
+			msg.Service{Host: "1.2.3.4", Port: 80, TTL: 5, Key: "/c/org/example/testns/svc1"},
+		},
+	},
+	{
+		Qname: "svc0.testns.example.com.", Rcode: dns.RcodeNameError,
+	},
+	{
+		Qname: "svc0.svc-nons.example.com.", Rcode: dns.RcodeNameError,
+	},
+}
+
+func TestExternal(t *testing.T) {
+	k := New([]string{"cluster.local."})
+	k.APIConn = &external{}
+	k.Next = test.NextHandler(dns.RcodeSuccess, nil)
+	k.Namespaces = map[string]struct{}{"testns": struct{}{}}
+
+	for i, tc := range extCases {
+		state := testRequest(tc.Qname)
+
+		svc, rcode := k.External(state)
+
+		if x := tc.Rcode; x != rcode {
+			t.Errorf("Test %d, expected rcode %d, got %d\n", i, x, rcode)
+		}
+
+		if len(svc) != len(tc.Msg) {
+			t.Errorf("Test %d, expected %d for messages, got %d\n", i, len(tc.Msg), len(svc))
+		}
+
+		for j, s := range svc {
+			if x := tc.Msg[j].Key; x != s.Key {
+				t.Errorf("Test %d, expected key %s, got %s\n", i, x, s.Key)
+			}
+			return
+		}
+	}
+}
+
+type external struct{}
+
+func (external) HasSynced() bool                              { return true }
+func (external) Run()                                         { return }
+func (external) Stop() error                                  { return nil }
+func (external) EpIndexReverse(string) []*object.Endpoints    { return nil }
+func (external) SvcIndexReverse(string) []*object.Service     { return nil }
+func (external) Modified() int64                              { return 0 }
+func (external) SetWatchChan(watch.Chan)                      {}
+func (external) Watch(string) error                           { return nil }
+func (external) StopWatching(string)                          {}
+func (external) EpIndex(s string) []*object.Endpoints         { return nil }
+func (external) EndpointsList() []*object.Endpoints           { return nil }
+func (external) GetNodeByName(name string) (*api.Node, error) { return nil, nil }
+func (external) SvcIndex(s string) []*object.Service          { return svcIndexExternal[s] }
+func (external) PodIndex(string) []*object.Pod                { return nil }
+
+func (external) GetNamespaceByName(name string) (*api.Namespace, error) {
+	return &api.Namespace{
+		ObjectMeta: meta.ObjectMeta{
+			Name: name,
+		},
+	}, nil
+}
+
+var svcIndexExternal = map[string][]*object.Service{
+	"svc1.testns": {
+		{
+			Name:        "svc1",
+			Namespace:   "testns",
+			Type:        api.ServiceTypeClusterIP,
+			ClusterIP:   "10.0.0.1",
+			ExternalIPs: []string{"1.2.3.4"},
+			Ports:       []api.ServicePort{{Name: "http", Protocol: "tcp", Port: 80}},
+		},
+	},
+	"svc6.testns": {
+		{
+			Name:        "svc6",
+			Namespace:   "testns",
+			Type:        api.ServiceTypeClusterIP,
+			ClusterIP:   "10.0.0.3",
+			ExternalIPs: []string{"1:2::5"},
+			Ports:       []api.ServicePort{{Name: "http", Protocol: "tcp", Port: 80}},
+		},
+	},
+}
+
+func (external) ServiceList() []*object.Service {
+	var svcs []*object.Service
+	for _, svc := range svcIndexExternal {
+		svcs = append(svcs, svc...)
+	}
+	return svcs
+}
+
+func testRequest(name string) request.Request {
+	m := new(dns.Msg).SetQuestion(name, dns.TypeA)
+	return request.Request{W: &test.ResponseWriter{}, Req: m, Zone: "example.org."}
+}