add wildcard warnings (#5030)

Signed-off-by: Chris O'Haver <cohaver@infoblox.com>

plugin/kubernetes/handler.go

@@ -2,6 +2,8 @@ package kubernetes
 
 import (
 	"context"
+	"strings"
+	"sync/atomic"
 
 	"github.com/coredns/coredns/plugin"
 	"github.com/coredns/coredns/request"
@@ -27,6 +29,10 @@ func (k Kubernetes) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.M
 		err     error
 	)
 
+	if wildQuestion(state.Name()) {
+		atomic.AddUint64(&wildCount, 1)
+	}
+
 	switch state.QType() {
 	case dns.TypeA:
 		records, err = plugin.A(ctx, &k, zone, state, nil, plugin.Options{})
@@ -85,8 +91,13 @@ func (k Kubernetes) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.M
 	m.Answer = append(m.Answer, records...)
 	m.Extra = append(m.Extra, extra...)
 	w.WriteMsg(m)
+
 	return dns.RcodeSuccess, nil
 }
 
+func wildQuestion(name string) bool {
+	return strings.HasPrefix(name, "*.") || strings.HasPrefix(name, "any.") || strings.Contains(name, ".*.") || strings.Contains(name, ".any.")
+}
+
 // Name implements the Handler interface.
 func (k Kubernetes) Name() string { return "kubernetes" }