BackendService: add Reverse method (#381)

Add a Reverse method to BackendService because different backends want
to to do diff. things. This allows etc/k8s to share even more code and
we can unify the PTR handling.

middleware/backend.go

@@ -9,10 +9,14 @@ import (
 
 // ServiceBackend defines a (dynamic) backend that returns a slice of service definitions.
 type ServiceBackend interface {
-	// Services communitates with the backend to retrieve the service defintion. Exact indicates
+	// Services communicates with the backend to retrieve the service defintion. Exact indicates
 	// on exact much are that we are allowed to recurs.
 	Services(state request.Request, exact bool, opt Options) ([]msg.Service, []msg.Service, error)
 
+	// Reverse communicates with the backend to retrieve service definition based on a IP address
+	// instead of a name. I.e. a reverse DNS lookup.
+	Reverse(state request.Request, exact bool, opt Options) ([]msg.Service, []msg.Service, error)
+
 	// Lookup is used to find records else where.
 	Lookup(state request.Request, name string, typ uint16) (*dns.Msg, error)
 

middleware/backend_lookup.go

@@ -330,9 +330,8 @@ func TXT(b ServiceBackend, zone string, state request.Request, opt Options) (rec
 }
 
 // PTR returns the PTR records from the backend, only services that have a domain name as host are included.
-// TODO(miek|infoblox): move k8s to this as well.
 func PTR(b ServiceBackend, zone string, state request.Request, opt Options) (records []dns.RR, debug []msg.Service, err error) {
-	services, debug, err := b.Services(state, true, opt)
+	services, debug, err := b.Reverse(state, true, opt)
 	if err != nil {
 		return nil, debug, err
 	}

middleware/etcd/etcd.go

@@ -46,6 +46,11 @@ func (e *Etcd) Services(state request.Request, exact bool, opt middleware.Option
 	return
 }
 
+// Reverse implements the ServiceBackend interface.
+func (e *Etcd) Reverse(state request.Request, exact bool, opt middleware.Options) (services, debug []msg.Service, err error) {
+	return e.Services(state, exact, opt)
+}
+
 // Lookup implements the ServiceBackend interface.
 func (e *Etcd) Lookup(state request.Request, name string, typ uint16) (*dns.Msg, error) {
 	return e.Proxy.Lookup(state, name, typ)

middleware/kubernetes/controller.go

@@ -5,13 +5,13 @@ import (
 	"sync"
 	"time"
 
+	"k8s.io/client-go/1.5/kubernetes"
 	"k8s.io/client-go/1.5/pkg/api"
 	"k8s.io/client-go/1.5/pkg/api/v1"
-	"k8s.io/client-go/1.5/tools/cache"
-	"k8s.io/client-go/1.5/kubernetes"
 	"k8s.io/client-go/1.5/pkg/labels"
 	"k8s.io/client-go/1.5/pkg/runtime"
 	"k8s.io/client-go/1.5/pkg/watch"
+	"k8s.io/client-go/1.5/tools/cache"
 )
 
 var (

middleware/kubernetes/handler.go

@@ -22,24 +22,6 @@ func (k Kubernetes) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.M
 	m.SetReply(r)
 	m.Authoritative, m.RecursionAvailable, m.Compress = true, true, true
 
-	// TODO: find an alternative to this block
-	// TODO(miek): Why is this even here, why does the path Etcd takes not work?
-	// Should be a "case PTR" below. I would also like to use middleware.PTR for this.
-	ip := dnsutil.ExtractAddressFromReverse(state.Name())
-	if ip != "" {
-		records := k.getServiceRecordForIP(ip, state.Name())
-		if len(records) > 0 {
-			srvPTR := &records[0]
-			m.Answer = append(m.Answer, srvPTR.NewPTR(state.QName(), ip))
-
-			m = dnsutil.Dedup(m)
-			state.SizeAndDo(m)
-			m, _ = state.Scrub(m)
-			w.WriteMsg(m)
-			return dns.RcodeSuccess, nil
-		}
-	}
-
 	// Check that query matches one of the zones served by this middleware,
 	// otherwise delegate to the next in the pipeline.
 	zone := middleware.Zones(k.Zones).Matches(state.Name())
@@ -63,6 +45,8 @@ func (k Kubernetes) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.M
 		records, _, err = middleware.TXT(&k, zone, state, middleware.Options{})
 	case "CNAME":
 		records, _, err = middleware.CNAME(&k, zone, state, middleware.Options{})
+	case "PTR":
+		records, _, err = middleware.PTR(&k, zone, state, middleware.Options{})
 	case "MX":
 		records, extra, _, err = middleware.MX(&k, zone, state, middleware.Options{})
 	case "SRV":

middleware/kubernetes/kubernetes.go

@@ -18,13 +18,13 @@ import (
 	"github.com/miekg/coredns/request"
 
 	"github.com/miekg/dns"
+	"k8s.io/client-go/1.5/kubernetes"
 	"k8s.io/client-go/1.5/pkg/api"
 	unversionedapi "k8s.io/client-go/1.5/pkg/api/unversioned"
-	"k8s.io/client-go/1.5/kubernetes"
+	"k8s.io/client-go/1.5/pkg/labels"
 	"k8s.io/client-go/1.5/rest"
 	"k8s.io/client-go/1.5/tools/clientcmd"
 	clientcmdapi "k8s.io/client-go/1.5/tools/clientcmd/api"
-	"k8s.io/client-go/1.5/pkg/labels"
 )
 
 // Kubernetes implements a middleware that connects to a Kubernetes cluster.
@@ -50,6 +50,17 @@ func (k *Kubernetes) Services(state request.Request, exact bool, opt middleware.
 	return s, nil, e // Haven't implemented debug queries yet.
 }
 
+// Reverse implements the ServiceBackend interface.
+func (k *Kubernetes) Reverse(state request.Request, exact bool, opt middleware.Options) ([]msg.Service, []msg.Service, error) {
+	ip := dnsutil.ExtractAddressFromReverse(state.Name())
+	if ip == "" {
+		return nil, nil, nil
+	}
+
+	records := k.getServiceRecordForIP(ip, state.Name())
+	return records, nil, nil
+}
+
 // Lookup implements the ServiceBackend interface.
 func (k *Kubernetes) Lookup(state request.Request, name string, typ uint16) (*dns.Msg, error) {
 	return k.Proxy.Lookup(state, name, typ)
@@ -156,13 +167,6 @@ func (k *Kubernetes) getZoneForName(name string) (string, []string) {
 // just this name. This is used when find matches when completing SRV lookups
 // for instance.
 func (k *Kubernetes) Records(name string, exact bool) ([]msg.Service, error) {
-	// TODO: refactor this.
-	// Right now NamespaceFromSegmentArray do not supports PRE queries
-	ip := dnsutil.ExtractAddressFromReverse(name)
-	if ip != "" {
-		records := k.getServiceRecordForIP(ip, name)
-		return records, nil
-	}
 	var (
 		serviceName string
 		namespace   string