WIP -- single binary -- works, replies to DNS, but need to check what got broken

coredns_plugin/coredns_plugin.go

@@ -185,6 +185,10 @@ func setupPlugin(c *caddy.Controller) (*plug, error) {
 		})
 	}
 
+	onceHook.Do(func() {
+		caddy.RegisterEventHook("dnsfilter-reload", hook)
+	})
+
 	p.upstream, err = upstream.New(nil)
 	if err != nil {
 		return nil, err
@@ -573,4 +577,5 @@ func (p *plug) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (
 // Name returns name of the plugin as seen in Corefile and plugin.cfg
 func (p *plug) Name() string { return "dnsfilter" }
 
+var onceHook sync.Once
 var onceQueryLog sync.Once

coredns_plugin/reload.go

@@ -0,0 +1,39 @@
+package dnsfilter
+
+import (
+	"log"
+
+	"github.com/mholt/caddy"
+)
+
+var Reload = make(chan bool)
+
+func hook(event caddy.EventName, info interface{}) error {
+	if event != caddy.InstanceStartupEvent {
+		return nil
+	}
+
+	// this should be an instance. ok to panic if not
+	instance := info.(*caddy.Instance)
+
+	go func() {
+		trace("Will wait for Reload channel")
+
+		for range Reload {
+			trace("Got message on Reload, restarting coredns")
+			corefile, err := caddy.LoadCaddyfile(instance.Caddyfile().ServerType())
+			if err != nil {
+				continue
+			}
+			_, err = instance.Restart(corefile)
+			if err != nil {
+				log.Printf("Corefile changed but reload failed: %s", err)
+				continue
+			}
+			// hook will be called again from new instance
+			return
+		}
+	}()
+
+	return nil
+}