Add NTP service

ntp/service.go

@@ -0,0 +1,99 @@
+package ntp
+
+import (
+	"context"
+	"time"
+
+	"github.com/sagernet/sing-box/adapter"
+	"github.com/sagernet/sing-box/common/dialer"
+	"github.com/sagernet/sing-box/option"
+	E "github.com/sagernet/sing/common/exceptions"
+	"github.com/sagernet/sing/common/logger"
+	M "github.com/sagernet/sing/common/metadata"
+	N "github.com/sagernet/sing/common/network"
+	"github.com/sagernet/sing/common/ntp"
+)
+
+const timeLayout = "2006-01-02 15:04:05 -0700"
+
+var _ adapter.TimeService = (*Service)(nil)
+
+type Service struct {
+	ctx    context.Context
+	cancel context.CancelFunc
+	server M.Socksaddr
+	dialer N.Dialer
+	logger logger.Logger
+
+	ticker      *time.Ticker
+	clockOffset time.Duration
+}
+
+func NewService(ctx context.Context, router adapter.Router, logger logger.Logger, options option.NTPOptions) *Service {
+	ctx, cancel := context.WithCancel(ctx)
+	server := options.ServerOptions.Build()
+	if server.Port == 0 {
+		server.Port = 123
+	}
+	var interval time.Duration
+	if options.Interval > 0 {
+		interval = time.Duration(options.Interval) * time.Second
+	} else {
+		interval = 30 * time.Minute
+	}
+	return &Service{
+		ctx:    ctx,
+		cancel: cancel,
+		server: server,
+		dialer: dialer.New(router, options.DialerOptions),
+		logger: logger,
+		ticker: time.NewTicker(interval),
+	}
+}
+
+func (s *Service) Start() error {
+	err := s.update()
+	if err != nil {
+		return E.Cause(err, "initialize time")
+	}
+	s.logger.Info("updated time: ", s.TimeFunc()().Local().Format(timeLayout))
+	go s.loopUpdate()
+	return nil
+}
+
+func (s *Service) Close() error {
+	s.ticker.Stop()
+	s.cancel()
+	return nil
+}
+
+func (s *Service) TimeFunc() func() time.Time {
+	return func() time.Time {
+		return time.Now().Add(s.clockOffset)
+	}
+}
+
+func (s *Service) loopUpdate() {
+	for {
+		select {
+		case <-s.ctx.Done():
+			return
+		case <-s.ticker.C:
+		}
+		err := s.update()
+		if err == nil {
+			s.logger.Debug("updated time: ", s.TimeFunc()().Local().Format(timeLayout))
+		} else {
+			s.logger.Warn("update time: ", err)
+		}
+	}
+}
+
+func (s *Service) update() error {
+	response, err := ntp.Exchange(s.ctx, s.dialer, s.server)
+	if err != nil {
+		return err
+	}
+	s.clockOffset = response.ClockOffset
+	return nil
+}