fix: quick reconnect after sleep or a network outage - the tunnel notices a dead connection, retries every 5 s at most, the WebSocket returns as soon as the server answers; version 0.1.1

internal/agent/tunnel.go

@@ -26,9 +26,7 @@ func (a *Agent) runTunnel(ctx context.Context, addr string) {
 			case <-ctx.Done():
 				return
 			}
-			if backoff < 15*time.Second {
-				backoff *= 2
-			}
+			backoff = min(backoff*2, retryCap)
 			continue
 		}
 		backoff = time.Second
@@ -96,8 +94,14 @@ func (t *tunClient) write(f tunnel.Frame) error {
 	return tunnel.WriteFrame(t.conn, f)
 }
 
+// tunnelSilence is how long the tunnel may say nothing before it is taken
+// for dead: the server pings every 20 s, so this is three missed pings - a
+// connection a NAT forgot while the machine slept, say.
+const tunnelSilence = 65 * time.Second
+
 func (t *tunClient) readLoop() error {
 	for {
+		_ = t.conn.SetReadDeadline(time.Now().Add(tunnelSilence))
 		f, err := tunnel.ReadFrame(t.conn)
 		if err != nil {
 			t.shutdown()
@@ -207,9 +211,7 @@ func (a *Agent) runUDP(ctx context.Context, addr string) {
 			case <-ctx.Done():
 				return
 			}
-			if backoff < 15*time.Second {
-				backoff *= 2
-			}
+			backoff = min(backoff*2, retryCap)
 			continue
 		}
 		backoff = time.Second