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/etcd/handler.go b/middleware/etcd/handler.go
index b462d7c5b..331e57793 100644
--- a/middleware/etcd/handler.go
+++ b/middleware/etcd/handler.go
@@ -1,7 +1,7 @@
 package etcd
 
 import (
-	"fmt"
+	"errors"
 
 	"github.com/miekg/coredns/middleware"
 	"github.com/miekg/coredns/middleware/etcd/msg"
@@ -18,7 +18,7 @@ func (e *Etcd) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (
 	opt := middleware.Options{}
 	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(e.Name(), errors.New("can only deal with ClassINET"))
 	}
 	name := state.Name()
 	if e.Debugging {
@@ -43,13 +43,10 @@ func (e *Etcd) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (
 
 	zone := middleware.Zones(e.Zones).Matches(state.Name())
 	if zone == "" {
-		if e.Next == nil {
-			return dns.RcodeServerFailure, nil
-		}
 		if opt.Debug != "" {
 			r.Question[0].Name = opt.Debug
 		}
-		return e.Next.ServeDNS(ctx, w, r)
+		return middleware.NextOrFailure(e.Name(), e.Next, ctx, w, r)
 	}
 
 	var (