Struct Client

tailcat.go:1399–1435

Client connects to a [Server] over a WireGuard tunnel relayed through DERP. Populate Server (the only required field, or use the [NewClient] shorthand), then just dial: [Client.Dial], [Client.DialTCPPort], and [Client.DialTCP] lazily establish the tunnel on first use, picking defaults for any unset

// and is useful to test connectivity first or to measure the relay
// round-trip time.
type Client struct {
	// Server is the token identifying the server to connect to.
	// It is required and must be set before the client's first use.
	Server ConnBlob

	// Key is the client's node identity, which servers can allowlist.
	// If zero, a new ephemeral key is generated at first use.
	// If set, it must be set before the client's first use.
	Key key.NodePrivate

	// Logf is the logger used for debug messages. If nil, log.Printf
	// is used. If set, it must be set before the client's first use.
	Logf logger.Logf

	// DERPMapURL, if non-empty, is an alternate URL to fetch the DERP
	// map from when the token doesn't embed the relay details.
	// If empty, [DefaultDERPMapURL] is used. If set, it must be set
	// before the client's first use.
	DERPMapURL string

	// DERPMapCache, if non-nil, caches fetched DERP maps. If nil, a
	// process-wide in-memory cache is used. If set, it must be set
	// before the client's first use.
	DERPMapCache DERPMapCache

	lb       *locoBackend
	ci       ConnInfo      // of server
	meowWait chan struct{} // closed on first meowed message from server

	serverAddr netip.Addr

	startMu sync.Mutex      // guards key, started, and the one-time startup work
	key     key.NodePrivate // the effective node identity; Key or generated
	started bool

	upDone atomic.Bool // whether the server has meowed us at least once
}

// nodeKeyLocked returns the client's effective node private key,
// resolving it from the Key field (or generating a fresh one) on