Seeing RST being sent from Avi to client, which is causing connection drops

Products

• VMware Avi Load Balancer

Issue/Introduction

Clients cannot access backend server via ALB.

Avi sent RST to client after finished TCP three-way handshake with client.

 

Cause

The client is advertising a window size of 512 bytes. We do not let any connections from client offering a receive window size less than 1K. This is done to handle cases where the attackers may cause a build up of buffers on the Service Engines. 

> show virtualservice xxx dosstat
| small_window_stress              | 5800           |

Resolution

Ask customer to check if these are legit clients and if so why they are advertising such small windows.