Messages in this thread |  | | Date | Sun, 14 Oct 2001 16:05:11 +0200 | From | Andi Kleen <> | Subject | Re: TCP acking too fast |
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On Sun, Oct 14, 2001 at 01:49:25PM +0200, Mika Liljeberg wrote: > Andi Kleen wrote: > > The only special case for PSH in RX left I can is in rcv_mss estimation, > > where is assumes that a packet with PSH set is not full sized. > > A packet without PSH should be full size. Assuming the sender implemets > SWS avoidance correctly, this should be a safe enough assumption.
It's not guaranteed by any spec; just common behaviour from BSD derived stacks. SWS avoidance does not say anything about PSH flags.
> > > On further > > look the 2.4 tcp_measure_rcv_mss will never update rcv_mss for packets > > which do have PSH set and in this case cause random ack behaviour depending > > on the initial rcv_mss guess. > > Not very nice; definitely violates the "be conservative what you accept" > > rule. I'm not sure how to fix it, adding a fallback to every-two-packet-add > > would pollute the fast path a bit. > > You're right. As far as I can see, it's not necessary to set the > TCP_ACK_PUSHED flag at all (except maybe for SYN-ACK). I'm just writing > a patch to clean this up.
Setting it for packets >= rcv_mss looks useful to me to catch mistakes. Better too many acks than to few.
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