On Thu, Jun 10, 2021 at 8:00 AM Shuyi Cheng <chengshuyi@xxxxxxxxxxxxxxxxx> wrote: > Thank you very much for your reply! > > Maybe it's not clear enough that I described it. The scenario where the > above problem occurs is precisely because the tcp server sets the size > of RCVBUFF to be smaller after the connection is established. Here is a > sample code that caused the problem. > > # default tcp_rmem is 87380 Except that this value is overridden at connection establishment. tcp_rmem[1] is only a floor value, say if you want a reasonable value even if MSS == 100 > tcpServerSocket= socket.socket(socket.AF_INET, socket.SOCK_STREAM) > tcpServerSocket.bind(server_addr) > tcpServerSocket.listen() > while True: > connection,client_addr = tcpServerSocket.accept() > # Shrink rmem > connection.setsockopt(socket.SOL_SOCKET, socket.SO_RCVBUF, 16*1024) > > Therefore, when the developer calls the sock_setsockopt function to > reset RCVBUF, we can use sock to determine the TCP state. When in the > connected state, it is not allowed to set RCVBUF smaller than mss. > Sure, but the application can _also_ set SO_RCVBUF before listen() or connect() We can not have assumptions about SO_RCVBUF values and socket states. Otherwise we would have to add some sk_rcvbuf adjustments every time the socket state is changed.
