Publish metadata from kubernetes plugin (#2829)

* Publish metadata from kubernetes plugin

* stickler fix

* Add a couple tests

* Add metadata section to README

* Update plugin/kubernetes/README.md

Co-Authored-By: Chris O'Haver <cohaver@infoblox.com>

* Address nit

plugin/kubernetes/README.md

@@ -225,3 +225,17 @@ or the word "any"), then that label will match all values.  The labels that acce
 *.service.default.svc.cluster.local. 5	IN A	192.168.25.15
 ```
  This response can be randomized using the `loadbalance` plugin
+
+## Metadata
+
+The kubernetes plugin will publish the following metadata, if the _metadata_
+plugin is also enabled:
+
+ * kubernetes/endpoint: the endpoint name in the query
+ * kubernetes/kind: the resource kind (pod or svc) in the query
+ * kubernetes/namespace: the namespace in the query
+ * kubernetes/port-name: the port name in an SRV query
+ * kubernetes/protocol: the protocol in an SRV query
+ * kubernetes/service: the service name in the query
+ * kubernetes/client-namespace: the client pod's namespace, if `pods verified` mode is enabled
+ * kubernetes/client-pod-name: the client pod's name, if `pods verified` mode is enabled

plugin/kubernetes/handler_test.go

@@ -495,9 +495,12 @@ func (APIConnServeTest) EpIndexReverse(string) []*object.Endpoints { return nil
 func (APIConnServeTest) SvcIndexReverse(string) []*object.Service  { return nil }
 func (APIConnServeTest) Modified() int64                           { return time.Now().Unix() }
 
-func (APIConnServeTest) PodIndex(string) []*object.Pod {
+func (APIConnServeTest) PodIndex(ip string) []*object.Pod {
+	if ip != "10.240.0.1" {
+		return []*object.Pod{}
+	}
 	a := []*object.Pod{
-		{Namespace: "podns", PodIP: "10.240.0.1"}, // Remote IP set in test.ResponseWriter
+		{Namespace: "podns", Name: "foo", PodIP: "10.240.0.1"}, // Remote IP set in test.ResponseWriter
 	}
 	return a
 }

plugin/kubernetes/metadata.go

@@ -0,0 +1,59 @@
+package kubernetes
+
+import (
+	"context"
+
+	"github.com/coredns/coredns/plugin/metadata"
+	"github.com/coredns/coredns/request"
+)
+
+// Metadata implements the metadata.Provider interface.
+func (k *Kubernetes) Metadata(ctx context.Context, state request.Request) context.Context {
+	// possible optimization: cache r so it doesn't need to be calculated again in ServeDNS
+	r, err := parseRequest(state)
+	if err != nil {
+		metadata.SetValueFunc(ctx, "kubernetes/parse-error", func() string {
+			return err.Error()
+		})
+		return ctx
+	}
+
+	metadata.SetValueFunc(ctx, "kubernetes/port-name", func() string {
+		return r.port
+	})
+
+	metadata.SetValueFunc(ctx, "kubernetes/protocol", func() string {
+		return r.protocol
+	})
+
+	metadata.SetValueFunc(ctx, "kubernetes/endpoint", func() string {
+		return r.endpoint
+	})
+
+	metadata.SetValueFunc(ctx, "kubernetes/service", func() string {
+		return r.service
+	})
+
+	metadata.SetValueFunc(ctx, "kubernetes/namespace", func() string {
+		return r.namespace
+	})
+
+	metadata.SetValueFunc(ctx, "kubernetes/kind", func() string {
+		return r.podOrSvc
+	})
+
+	pod := k.podWithIP(state.IP())
+	if pod == nil {
+		return ctx
+	}
+
+	metadata.SetValueFunc(ctx, "kubernetes/client-namespace", func() string {
+		return pod.Namespace
+	})
+
+	metadata.SetValueFunc(ctx, "kubernetes/client-pod-name", func() string {
+		return pod.Name
+	})
+
+	return ctx
+}

plugin/kubernetes/metadata_test.go

@@ -0,0 +1,126 @@
+package kubernetes
+
+import (
+	"context"
+	"testing"
+
+	"github.com/coredns/coredns/plugin/metadata"
+	"github.com/coredns/coredns/plugin/test"
+	"github.com/coredns/coredns/request"
+
+	"github.com/miekg/dns"
+)
+
+var metadataCases = []struct {
+	Qname    string
+	Qtype    uint16
+	RemoteIP string
+	Md       map[string]string
+}{
+	{
+		Qname: "foo.bar.notapod.cluster.local.", Qtype: dns.TypeA,
+		Md: map[string]string{
+			"kubernetes/parse-error": "invalid query name",
+		},
+	},
+	{
+		Qname: "10-240-0-1.podns.pod.cluster.local.", Qtype: dns.TypeA,
+		Md: map[string]string{
+			"kubernetes/endpoint":         "",
+			"kubernetes/kind":             "pod",
+			"kubernetes/namespace":        "podns",
+			"kubernetes/port-name":        "*",
+			"kubernetes/protocol":         "*",
+			"kubernetes/service":          "10-240-0-1",
+			"kubernetes/client-namespace": "podns",
+			"kubernetes/client-pod-name":  "foo",
+		},
+	},
+	{
+		Qname: "s.ns.svc.cluster.local.", Qtype: dns.TypeA,
+		Md: map[string]string{
+			"kubernetes/endpoint":         "",
+			"kubernetes/kind":             "svc",
+			"kubernetes/namespace":        "ns",
+			"kubernetes/port-name":        "*",
+			"kubernetes/protocol":         "*",
+			"kubernetes/service":          "s",
+			"kubernetes/client-namespace": "podns",
+			"kubernetes/client-pod-name":  "foo",
+		},
+	},
+	{
+		Qname: "s.ns.svc.cluster.local.", Qtype: dns.TypeA,
+		RemoteIP: "10.10.10.10",
+		Md: map[string]string{
+			"kubernetes/endpoint":  "",
+			"kubernetes/kind":      "svc",
+			"kubernetes/namespace": "ns",
+			"kubernetes/port-name": "*",
+			"kubernetes/protocol":  "*",
+			"kubernetes/service":   "s",
+		},
+	},
+	{
+		Qname: "_http._tcp.s.ns.svc.cluster.local.", Qtype: dns.TypeSRV,
+		RemoteIP: "10.10.10.10",
+		Md: map[string]string{
+			"kubernetes/endpoint":  "",
+			"kubernetes/kind":      "svc",
+			"kubernetes/namespace": "ns",
+			"kubernetes/port-name": "http",
+			"kubernetes/protocol":  "tcp",
+			"kubernetes/service":   "s",
+		},
+	},
+	{
+		Qname: "ep.s.ns.svc.cluster.local.", Qtype: dns.TypeA,
+		RemoteIP: "10.10.10.10",
+		Md: map[string]string{
+			"kubernetes/endpoint":  "ep",
+			"kubernetes/kind":      "svc",
+			"kubernetes/namespace": "ns",
+			"kubernetes/port-name": "*",
+			"kubernetes/protocol":  "*",
+			"kubernetes/service":   "s",
+		},
+	},
+}
+
+func mapsDiffer(a, b map[string]string) bool {
+	if len(a) != len(b) {
+		return true
+	}
+
+	for k, va := range a {
+		vb, ok := b[k]
+		if !ok || va != vb {
+			return true
+		}
+	}
+	return false
+}
+
+func TestMetadata(t *testing.T) {
+	k := New([]string{"cluster.local."})
+	k.APIConn = &APIConnServeTest{}
+
+	for i, tc := range metadataCases {
+		ctx := metadata.ContextWithMetadata(context.Background())
+		state := request.Request{
+			Req:  &dns.Msg{Question: []dns.Question{{Name: tc.Qname, Qtype: tc.Qtype}}},
+			Zone: "cluster.local.",
+			W:    &test.ResponseWriter{RemoteIP: tc.RemoteIP},
+		}
+
+		k.Metadata(ctx, state)
+
+		md := make(map[string]string)
+		for _, l := range metadata.Labels(ctx) {
+			md[l] = metadata.ValueFunc(ctx, l)()
+		}
+		if mapsDiffer(tc.Md, md) {
+			t.Errorf("case %d expected metadata %v and got %v", i, tc.Md, md)
+		}
+	}
+}

plugin/metadata/metadata.go

@@ -20,10 +20,15 @@ type Metadata struct {
 // Name implements the Handler interface.
 func (m *Metadata) Name() string { return "metadata" }
 
+// ContextWithMetadata is exported for use by provider tests
+func ContextWithMetadata(ctx context.Context) context.Context {
+	return context.WithValue(ctx, key{}, md{})
+}
+
 // ServeDNS implements the plugin.Handler interface.
 func (m *Metadata) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error) {
 
-	ctx = context.WithValue(ctx, key{}, md{})
+	ctx = ContextWithMetadata(ctx)
 
 	state := request.Request{W: w, Req: r}
 	if plugin.Zones(m.Zones).Matches(state.Name()) != "" {

plugin/test/responsewriter.go

@@ -10,7 +10,8 @@ import (
 // remote will always be 10.240.0.1 and port 40212. The local address is always 127.0.0.1 and
 // port 53.
 type ResponseWriter struct {
-	TCP bool // if TCP is true we return an TCP connection instead of an UDP one.
+	TCP      bool // if TCP is true we return an TCP connection instead of an UDP one.
+	RemoteIP string
 }
 
 // LocalAddr returns the local address, 127.0.0.1:53 (UDP, TCP if t.TCP is true).
@@ -23,9 +24,13 @@ func (t *ResponseWriter) LocalAddr() net.Addr {
 	return &net.UDPAddr{IP: ip, Port: port, Zone: ""}
 }
 
-// RemoteAddr returns the remote address, always 10.240.0.1:40212 (UDP, TCP is t.TCP is true).
+// RemoteAddr returns the remote address, defaults to 10.240.0.1:40212 (UDP, TCP is t.TCP is true).
 func (t *ResponseWriter) RemoteAddr() net.Addr {
-	ip := net.ParseIP("10.240.0.1")
+	remoteIP := "10.240.0.1"
+	if t.RemoteIP != "" {
+		remoteIP = t.RemoteIP
+	}
+	ip := net.ParseIP(remoteIP)
 	port := 40212
 	if t.TCP {
 		return &net.TCPAddr{IP: ip, Port: port, Zone: ""}