plugin/secondary: serve catalog member zones (#8230)

Signed-off-by: houyuwushang <liuluoqianqiu@outlook.com>

plugin/secondary/zones.go

@@ -0,0 +1,46 @@
+package secondary
+
+import (
+	"github.com/coredns/coredns/plugin"
+	"github.com/coredns/coredns/plugin/file"
+)
+
+func (s *Secondary) lookupZone(qname string) (string, *file.Zone, bool) {
+	s.zoneMu.RLock()
+	defer s.zoneMu.RUnlock()
+
+	zone := plugin.Zones(s.Names).Matches(qname)
+	if zone == "" {
+		return "", nil, false
+	}
+	z, ok := s.Z[zone]
+	if !ok {
+		return zone, nil, true
+	}
+	return zone, z, true
+}
+
+func (s *Secondary) zoneName(z *file.Zone) string {
+	s.zoneMu.RLock()
+	defer s.zoneMu.RUnlock()
+
+	return s.zoneNames[z]
+}
+
+func (s *Secondary) stopDynamicZones() {
+	s.zoneMu.Lock()
+	defer s.zoneMu.Unlock()
+
+	for _, dyn := range s.dynamicZones {
+		dyn.stopOnce.Do(func() { close(dyn.shutdown) })
+	}
+}
+
+func removeZoneName(names []string, name string) []string {
+	for i, n := range names {
+		if n == name {
+			return append(names[:i], names[i+1:]...)
+		}
+	}
+	return names
+}