add loss.go (#168)

tcp/conn.go

@@ -76,6 +76,16 @@ type ConnConfig struct {
 	// Logger sets the [Conn] logger.
 	// Lower level logging available at [Handler.SetLoggers] via [Conn.InternalHandler].
 	Logger *slog.Logger
+	// LossRecovery is the optional packet-loss recovery algorithm (RTO,
+	// congestion control, ...) for the connection. If set, Nanotime must also be
+	// set (else Configure returns an error). Leaving it nil disables loss
+	// recovery. See [LossRecovery].
+	LossRecovery LossRecovery
+	// Nanotime is the monotonic time source in nanoseconds (the func() int64
+	// convention used across lneto) that drives LossRecovery. It is required when
+	// LossRecovery is set and unused otherwise. The tcp package reads it only to
+	// stamp the loss-recovery hooks; it holds no clock itself.
+	Nanotime func() int64
 }
 
 // Configure should be called on any newly created connection before usage. See [ConnConfig].
@@ -83,6 +93,10 @@ func (conn *Conn) Configure(config ConnConfig) (err error) {
 	if config.RWBackoff == nil {
 		return lneto.ErrMissingHALConfig
 	}
+	if config.LossRecovery != nil && config.Nanotime == nil {
+		// The tcp package holds no clock: a loss-recovery algorithm cannot run without it.
+		return lneto.ErrInvalidConfig
+	}
 	conn.mu.Lock()
 	defer conn.mu.Unlock()
 	err = conn.h.SetBuffers(config.TxBuf, config.RxBuf, config.TxPacketQueueSize)
@@ -91,6 +105,7 @@ func (conn *Conn) Configure(config ConnConfig) (err error) {
 	}
 	conn._backoff = config.RWBackoff
 	conn.logger.log = config.Logger
+	conn.h.SetLossRecovery(config.LossRecovery, config.Nanotime)
 	return nil
 }