Dns.join (#944)

* Add dnsutil.Join

* Create dnsutil.Join

Create Join helper function and move bits in the code over.

middleware/etcd/msg/path.go

@@ -4,6 +4,8 @@ import (
 	"path"
 	"strings"
 
+	"github.com/coredns/coredns/middleware/pkg/dnsutil"
+
 	"github.com/miekg/dns"
 )
 
@@ -24,7 +26,7 @@ func Domain(s string) string {
 	for i, j := 1, len(l)-1; i < j; i, j = i+1, j-1 {
 		l[i], l[j] = l[j], l[i]
 	}
-	return dns.Fqdn(strings.Join(l[1:len(l)-1], "."))
+	return dnsutil.Join(l[1 : len(l)-1])
 }
 
 // PathWithWildcard ascts as Path, but if a name contains wildcards (* or any), the name will be

middleware/etcd/stub.go

@@ -4,10 +4,10 @@ import (
 	"log"
 	"net"
 	"strconv"
-	"strings"
 	"time"
 
 	"github.com/coredns/coredns/middleware/etcd/msg"
+	"github.com/coredns/coredns/middleware/pkg/dnsutil"
 	"github.com/coredns/coredns/middleware/proxy"
 	"github.com/coredns/coredns/request"
 
@@ -62,7 +62,7 @@ Services:
 			// Chop of left most label, because that is used as the nameserver place holder
 			// and drop the right most labels that belong to zone.
 			// We must *also* chop of dns.stub. which means cutting two more labels.
-			domain = dns.Fqdn(strings.Join(labels[1:len(labels)-dns.CountLabel(z)-2], "."))
+			domain = dnsutil.Join(labels[1 : len(labels)-dns.CountLabel(z)-2])
 			if domain == z {
 				log.Printf("[WARNING] Skipping nameserver for domain we are authoritative for: %s", domain)
 				continue Services

middleware/federation/federation.go

@@ -14,8 +14,6 @@ Federation is only useful in conjunction with the kubernetes middleware, without
 package federation
 
 import (
-	"strings"
-
 	"github.com/coredns/coredns/middleware"
 	"github.com/coredns/coredns/middleware/etcd/msg"
 	"github.com/coredns/coredns/middleware/pkg/dnsutil"
@@ -133,7 +131,7 @@ func (f *Federation) isNameFederation(name, zone string) (string, string) {
 	fed := labels[ll-2]
 
 	if _, ok := f.f[fed]; ok {
-		without := strings.Join(labels[:ll-2], ".") + "." + labels[ll-1] + "." + zone
+		without := dnsutil.Join(labels[:ll-2]) + labels[ll-1] + "." + zone
 		return without, fed
 	}
 	return "", ""

middleware/file/dname.go

@@ -1,7 +1,7 @@
 package file
 
 import (
-	"strings"
+	"github.com/coredns/coredns/middleware/pkg/dnsutil"
 
 	"github.com/miekg/dns"
 )
@@ -14,7 +14,7 @@ func substituteDNAME(qname, owner, target string) string {
 		labels := dns.SplitDomainName(qname)
 		labels = append(labels[0:len(labels)-dns.CountLabel(owner)], dns.SplitDomainName(target)...)
 
-		return strings.Join(labels, ".") + "."
+		return dnsutil.Join(labels)
 	}
 
 	return ""

middleware/kubernetes/federation.go

@@ -1,9 +1,8 @@
 package kubernetes
 
 import (
-	"strings"
-
 	"github.com/coredns/coredns/middleware/etcd/msg"
+	"github.com/coredns/coredns/middleware/pkg/dnsutil"
 	"github.com/coredns/coredns/request"
 )
 
@@ -36,8 +35,8 @@ func (k *Kubernetes) Federations(state request.Request, fname, fzone string) (ms
 	lr := node.Labels[LabelRegion]
 
 	if r.endpoint == "" {
-		return msg.Service{Host: strings.Join([]string{r.service, r.namespace, fname, r.podOrSvc, lz, lr, fzone}, ".")}, nil
+		return msg.Service{Host: dnsutil.Join([]string{r.service, r.namespace, fname, r.podOrSvc, lz, lr, fzone})}, nil
 	}
 
-	return msg.Service{Host: strings.Join([]string{r.endpoint, r.service, r.namespace, fname, r.podOrSvc, lz, lr, fzone}, ".")}, nil
+	return msg.Service{Host: dnsutil.Join([]string{r.endpoint, r.service, r.namespace, fname, r.podOrSvc, lz, lr, fzone})}, nil
 }

middleware/kubernetes/kubernetes.go

@@ -508,7 +508,7 @@ func (k *Kubernetes) getServiceRecordForIP(ip, name string) []msg.Service {
 			continue
 		}
 		if service.Spec.ClusterIP == ip {
-			domain := strings.Join([]string{service.Name, service.Namespace, Svc, k.primaryZone()}, ".")
+			domain := dnsutil.Join([]string{service.Name, service.Namespace, Svc, k.primaryZone()})
 			return []msg.Service{{Host: domain}}
 		}
 	}
@@ -521,7 +521,7 @@ func (k *Kubernetes) getServiceRecordForIP(ip, name string) []msg.Service {
 		for _, eps := range ep.Subsets {
 			for _, addr := range eps.Addresses {
 				if addr.IP == ip {
-					domain := strings.Join([]string{endpointHostname(addr), ep.ObjectMeta.Name, ep.ObjectMeta.Namespace, Svc, k.primaryZone()}, ".")
+					domain := dnsutil.Join([]string{endpointHostname(addr), ep.ObjectMeta.Name, ep.ObjectMeta.Namespace, Svc, k.primaryZone()})
 					return []msg.Service{{Host: domain}}
 				}
 			}

middleware/pkg/dnsutil/join.go

@@ -0,0 +1,19 @@
+package dnsutil
+
+import (
+	"strings"
+
+	"github.com/miekg/dns"
+)
+
+// Join joins labels to form a fully qualified domain name. If the last label is
+// the root label it is ignored. Not other syntax checks are performed.
+func Join(labels []string) string {
+	ll := len(labels)
+	if labels[ll-1] == "." {
+		s := strings.Join(labels[:ll-1], ".")
+		return dns.Fqdn(s)
+	}
+	s := strings.Join(labels, ".")
+	return dns.Fqdn(s)
+}

middleware/pkg/dnsutil/join_test.go

@@ -0,0 +1,20 @@
+package dnsutil
+
+import "testing"
+
+func TestJoin(t *testing.T) {
+	tests := []struct {
+		in  []string
+		out string
+	}{
+		{[]string{"bla", "bliep", "example", "org"}, "bla.bliep.example.org."},
+		{[]string{"example", "."}, "example."},
+		{[]string{"."}, "."},
+	}
+
+	for i, tc := range tests {
+		if x := Join(tc.in); x != tc.out {
+			t.Errorf("Test %d, expected %s, got %s", i, tc.out, x)
+		}
+	}
+}