Add DERP service

service/derp/stun.go

@@ -0,0 +1,89 @@
+package derp
+
+import (
+	"context"
+	"net"
+	"net/netip"
+	"time"
+
+	"github.com/sagernet/sing-box/adapter"
+	boxService "github.com/sagernet/sing-box/adapter/service"
+	"github.com/sagernet/sing-box/common/listener"
+	C "github.com/sagernet/sing-box/constant"
+	"github.com/sagernet/sing-box/log"
+	"github.com/sagernet/sing-box/option"
+	E "github.com/sagernet/sing/common/exceptions"
+	"github.com/sagernet/sing/common/logger"
+	N "github.com/sagernet/sing/common/network"
+	"github.com/sagernet/tailscale/net/stun"
+)
+
+func RegisterSTUN(registry *boxService.Registry) {
+	boxService.Register[option.DERPSTUNServiceOptions](registry, C.TypeDERPSTUN, NewSTUNService)
+}
+
+type STUNService struct {
+	boxService.Adapter
+	ctx      context.Context
+	logger   logger.ContextLogger
+	listener *listener.Listener
+}
+
+func NewSTUNService(ctx context.Context, logger log.ContextLogger, tag string, options option.DERPSTUNServiceOptions) (adapter.Service, error) {
+	return &STUNService{
+		Adapter: boxService.NewAdapter(C.TypeDERPSTUN, tag),
+		ctx:     ctx,
+		logger:  logger,
+		listener: listener.New(listener.Options{
+			Context: ctx,
+			Logger:  logger,
+			Network: []string{N.NetworkUDP},
+			Listen:  options.ListenOptions,
+		}),
+	}, nil
+}
+
+func (d *STUNService) Start(stage adapter.StartStage) error {
+	if stage != adapter.StartStateStart {
+		return nil
+	}
+	packetConn, err := d.listener.ListenUDP()
+	if err != nil {
+		return err
+	}
+	go d.loopPacket(packetConn.(*net.UDPConn))
+	return nil
+}
+
+func (d *STUNService) Close() error {
+	return d.listener.Close()
+}
+
+func (d *STUNService) loopPacket(packetConn *net.UDPConn) {
+	buffer := make([]byte, 65535)
+	oob := make([]byte, 1024)
+	var (
+		n        int
+		oobN     int
+		addrPort netip.AddrPort
+		err      error
+	)
+	for {
+		n, oobN, _, addrPort, err = packetConn.ReadMsgUDPAddrPort(buffer, oob)
+		if err != nil {
+			if E.IsClosedOrCanceled(err) {
+				return
+			}
+			time.Sleep(time.Second)
+			continue
+		}
+		if !stun.Is(buffer[:n]) {
+			continue
+		}
+		txid, err := stun.ParseBindingRequest(buffer[:n])
+		if err != nil {
+			continue
+		}
+		packetConn.WriteMsgUDPAddrPort(stun.Response(txid, addrPort), oob[:oobN], addrPort)
+	}
+}