Method Start

tailcat.go:356–491

Start connects to the DERP relay and begins accepting clients, first picking defaults for any unset configuration fields: a new ephemeral key, log.Printf for logging, and the nearest region of the default DERP map.

()

// ephemeral key, log.Printf for logging, and the nearest region of
// the default DERP map.
func (s *Server) Start() error {
	if s.lb != nil {
		return errors.New("tailcat: Server.Start called twice")
	}
	logf := s.Logf
	if logf == nil {
		logf = log.Printf
	}
	priv := s.Key
	if priv.IsZero() {
		priv = key.NewNode()
	}
	reg := s.Region
	if reg == nil {
		ci := &ConnInfo{RegionID: cmp.Or(s.RegionID, -1)}
		opts := []any{ExpandForServer}
		if s.DERPMapURL != "" {
			opts = append(opts, DERPMapURL(s.DERPMapURL))
		}
		if s.DERPMapCache != nil {
			opts = append(opts, s.DERPMapCache)
		}
		if err := ci.Expand(context.Background(), opts...); err != nil {
			return err
		}
		reg = ci.Region[0]
	}
	if reg.RegionID == 0 {
		return fmt.Errorf("missing RegionID in %v", logger.AsJSON(reg))
	}

	lb := newLocoBackend(priv)
	lb.logf = logf
	lb.dm = &tailcfg.DERPMap{}
	mak.Set(&lb.dm.Regions, reg.RegionID, reg)
	for _, k := range s.AllowedClients {
		mak.Set(&lb.allowedClients, k, true)
	}

	sys := &lb.sys
	bus := eventbus.New()
	sys.Set(bus)
	sys.Set(health.NewTracker(bus))

	netMon, err := netmon.New(bus, func(format string, args ...any) {
		logf(format, args...)
	})
	if err != nil {
		lb.Close() // closes the subsystems started so far
		return fmt.Errorf("netmon.New: %w", err)
	}
	sys.Set(netMon)

	dialer := &tsdial.Dialer{Logf: logf} // mutated below (before used)
	sys.Set(dialer)

	var store ipn.StateStore = new(mem.Store)
	sys.Set(store)