WIP: udp backend

backend_udp.go

@@ -16,6 +16,8 @@ type udpRel struct {
 	backend    net.PacketConn
 	clientAddr string
 	expiry     time.Time
+	ctx        context.Context
+	ctxCancel  context.CancelFunc
 }
 
 type backendUDP struct {
@@ -32,6 +34,14 @@ type udpMessage struct {
 	buf  *bytes.Buffer
 }
 
+func (r udpRel) Network() string {
+	return "udp"
+}
+
+func (r udpRel) String() string {
+	return r.clientAddr
+}
+
 func initUDP(wg *sync.WaitGroup, ctx context.Context, cfg abstract.UDPConnectionConfig, client net.PacketConn) *backendUDP {
 	backend := &backendUDP{
 		relations: make(map[string]udpRel),
@@ -56,7 +66,7 @@ func initUDP(wg *sync.WaitGroup, ctx context.Context, cfg abstract.UDPConnection
 			case <-ctx.Done():
 				break readIncoming
 			case m := <-incoming:
-				backend.handle(m)
+				backend.handle(wg, ctx, m)
 			}
 		}
 	}(wg, ctx, cfg, backend)
@@ -70,6 +80,11 @@ func (b *backendUDP) findRel(clientAddr string) (udpRel, bool) {
 
 	rel, ok := b.relations[clientAddr]
 	if ok && rel.expiry.Before(time.Now()) {
+		if rel.ctxCancel != nil {
+			rel.ctxCancel()
+		}
+
+		_ = rel.backend.Close()
 		delete(b.relations, clientAddr)
 		return rel, false
 	}
@@ -77,7 +92,7 @@ func (b *backendUDP) findRel(clientAddr string) (udpRel, bool) {
 	return rel, ok
 }
 
-func (b *backendUDP) addRel(clientAddr string, rel udpRel) {
+func (b *backendUDP) addUpdateRel(clientAddr string, rel udpRel) {
 	b.relMtx.Lock()
 	defer b.relMtx.Unlock()
 
@@ -115,7 +130,7 @@ func (b *backendUDP) createRelSend(clientAddr string, buf []byte) (udpRel, error
 	return rel, nil
 }
 
-func (b *backendUDP) handle(msg udpMessage) {
+func (b *backendUDP) handle(wg *sync.WaitGroup, ctx context.Context, msg udpMessage) {
 	var (
 		rel udpRel
 		ok  bool
@@ -127,14 +142,16 @@ func (b *backendUDP) handle(msg udpMessage) {
 			log.Error().Err(err).Str(DIRECTION, CLIENT_TO_BACKEND).Msg("establish relation with udp backend")
 		}
 
-		b.addRel(msg.addr, rel)
+		rel.ctx, rel.ctxCancel = context.WithCancel(ctx)
+		b.addUpdateRel(msg.addr, rel)
+
+		wg.Add(1)
+		go b.udpBackend2Client(wg, rel)
 		return
 	}
 
 	_ = rel
-	// if rel.expiry.Before(time.Now()) {
-	// 	//TODO: handle expiry
-	// }
+	//TODO: handle existing valid client
 
 }
 
@@ -166,3 +183,52 @@ func (b *backendUDP) Send(ctx context.Context, addr string, p []byte) error {
 
 	return nil
 }
+
+func (b *backendUDP) udpBackend2Client(wg *sync.WaitGroup, rel udpRel) {
+	defer wg.Done()
+
+	var (
+		n, wn      int
+		err        error
+		ok         bool
+		clientAddr string
+	)
+
+	buf := make([]byte, BUF_SIZE)
+
+udpBackendLoop:
+	for {
+		if n, _, err = rel.backend.ReadFrom(buf); err != nil {
+			//TODO: error handling
+		}
+
+		clientAddr = rel.clientAddr
+		if rel, ok = b.findRel(clientAddr); !ok {
+			log.Error().Msg("relation not found")
+			return
+		}
+
+		select {
+		case <-rel.ctx.Done():
+			break udpBackendLoop
+		default:
+		}
+
+		if wn, err = b.client.WriteTo(buf[:n], rel); err != nil {
+			//TODO: error handling
+		}
+
+		if wn != n {
+			//TODO: error when mismatch length
+		}
+
+		rel.expiry = time.Now().Add(b.cfg.Timeout())
+		b.addUpdateRel(clientAddr, rel)
+
+		select {
+		case <-rel.ctx.Done():
+			break udpBackendLoop
+		default:
+		}
+	}
+}