plugin/log: remove ErrorFunc (#2716)

The server handles this case no need to also do it in the log plugin.

Means DefaultErrorFunc can be private to the dnsserver and is now
renamed to just errorFunc

Fixes: #2715

Signed-off-by: Miek Gieben <miek@miek.nl>

plugin/log/log.go

@@ -6,10 +6,8 @@ import (
 	"time"
 
 	"github.com/coredns/coredns/plugin"
-	"github.com/coredns/coredns/plugin/metrics/vars"
 	"github.com/coredns/coredns/plugin/pkg/dnstest"
 	clog "github.com/coredns/coredns/plugin/pkg/log"
-	"github.com/coredns/coredns/plugin/pkg/rcode"
 	"github.com/coredns/coredns/plugin/pkg/replacer"
 	"github.com/coredns/coredns/plugin/pkg/response"
 	"github.com/coredns/coredns/request"
@@ -19,9 +17,8 @@ import (
 
 // Logger is a basic request logging plugin.
 type Logger struct {
-	Next      plugin.Handler
-	Rules     []Rule
-	ErrorFunc func(context.Context, dns.ResponseWriter, *dns.Msg, int) // failover error handler
+	Next  plugin.Handler
+	Rules []Rule
 
 	repl replacer.Replacer
 }
@@ -37,22 +34,6 @@ func (l Logger) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg)
 		rrw := dnstest.NewRecorder(w)
 		rc, err := plugin.NextOrFailure(l.Name(), l.Next, ctx, rrw, r)
 
-		if rc > 0 {
-			// There was an error up the chain, but no response has been written yet.
-			// The error must be handled here so the log entry will record the response size.
-			if l.ErrorFunc != nil {
-				l.ErrorFunc(ctx, rrw, r, rc)
-			} else {
-				answer := new(dns.Msg)
-				answer.SetRcode(r, rc)
-
-				vars.Report(ctx, state, vars.Dropped, rcode.ToString(rc), answer.Len(), time.Now())
-
-				w.WriteMsg(answer)
-			}
-			rc = 0
-		}
-
 		tpe, _ := response.Typify(rrw.Msg, time.Now().UTC())
 		class := response.Classify(tpe)
 		// If we don't set up a class in config, the default "all" will be added