cleaner startup/shutdown of the link writer's worker

src/yggdrasil/link.go

@@ -136,6 +136,7 @@ func (l *link) create(msgIO linkInterfaceMsgIO, name, linkType, local, remote st
 		force:    force,
 	}
 	intf.writer.intf = &intf
+	intf.writer.worker = make(chan [][]byte, 1)
 	intf.reader.intf = &intf
 	intf.reader.err = make(chan error)
 	return &intf, nil
@@ -151,6 +152,15 @@ func (l *link) stop() error {
 
 func (intf *linkInterface) handler() error {
 	// TODO split some of this into shorter functions, so it's easier to read, and for the FIXME duplicate peer issue mentioned later
+	go func() {
+		for bss := range intf.writer.worker {
+			intf.msgIO.writeMsgs(bss)
+		}
+	}()
+	defer intf.writer.Act(nil, func() {
+		intf.writer.closed = true
+		close(intf.writer.worker)
+	})
 	myLinkPub, myLinkPriv := crypto.NewBoxKeys()
 	meta := version_getBaseMetadata()
 	meta.box = intf.link.core.boxPub
@@ -256,11 +266,6 @@ func (intf *linkInterface) handler() error {
 		intf.link.core.log.Infof("Disconnected %s: %s, source %s",
 			strings.ToUpper(intf.info.linkType), themString, intf.info.local)
 	}
-	intf.writer.Act(nil, func() {
-		if intf.writer.worker != nil {
-			close(intf.writer.worker)
-		}
-	})
 	return err
 }
 
@@ -435,27 +440,20 @@ type linkWriter struct {
 	phony.Inbox
 	intf   *linkInterface
 	worker chan [][]byte
+	closed bool
 }
 
 func (w *linkWriter) sendFrom(from phony.Actor, bss [][]byte, isLinkTraffic bool) {
 	w.Act(from, func() {
+		if w.closed {
+			return
+		}
 		var size int
 		for _, bs := range bss {
 			size += len(bs)
 		}
-		if w.worker == nil {
-			w.worker = make(chan [][]byte, 1)
-			go func() {
-				for bss := range w.worker {
-					w.intf.msgIO.writeMsgs(bss)
-				}
-			}()
-		}
 		w.intf.notifySending(size, isLinkTraffic)
-		func() {
+		w.worker <- bss
-			defer func() { recover() }()
-			w.worker <- bss
-		}()
 		w.intf.notifySent(size, isLinkTraffic)
 	})
 }