Add middleware.NextOrFailure (#462)

This checks if the next middleware to be called is nil, and if so returns
ServerFailure and an error. This makes the next calling more robust and
saves some lines of code.

Also prefix the error with the name of the middleware to aid in
debugging.

1 files changed, 3 insertions, 6 deletions

diff --git a/middleware/kubernetes/handler.go b/middleware/kubernetes/handler.go
index e21ea6d58..f35792881 100644
--- a/middleware/kubernetes/handler.go
+++ b/middleware/kubernetes/handler.go
@@ -1,7 +1,7 @@
 package kubernetes
 
 import (
-	"fmt"
+	"errors"
 
 	"github.com/miekg/coredns/middleware"
 	"github.com/miekg/coredns/middleware/pkg/dnsutil"
@@ -15,7 +15,7 @@ import (
 func (k Kubernetes) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error) {
 	state := request.Request{W: w, Req: r}
 	if state.QClass() != dns.ClassINET {
-		return dns.RcodeServerFailure, fmt.Errorf("can only deal with ClassINET")
+		return dns.RcodeServerFailure, middleware.Error(k.Name(), errors.New("can only deal with ClassINET"))
 	}
 
 	m := new(dns.Msg)
@@ -26,10 +26,7 @@ func (k Kubernetes) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.M
 	// otherwise delegate to the next in the pipeline.
 	zone := middleware.Zones(k.Zones).Matches(state.Name())
 	if zone == "" {
-		if k.Next == nil {
-			return dns.RcodeServerFailure, nil
-		}
-		return k.Next.ServeDNS(ctx, w, r)
+		return middleware.NextOrFailure(k.Name(), k.Next, ctx, w, r)
 	}
 
 	var (