Re: [lwip-users] Zero window and refused data problem

[Oleg Gladyshev]

> And since we don't want to create even more traffic in an overload situation, 
> we don't even send
> and ACK (with an old ACKNO), since there's nothing the remote host can improve: 
> we can't accept new
> segments! By doing that, we give the application time to overcome resource 
> shortage and only can
> hope the connection survives this.
Simon, let's look at the issue from another side. If the refused_data is 
full LwIP doesn't send any ACK for probe packet but if the receiving 
window is really zero it WILL ACK with previous ACKNO. From sender's 
point of view these two cases are identical! In both cases receiver 
announces zero window and sender "asks peer if it has a liitle more 
space". I think it is wrong when received under LwIP control has 
different behavior depending on it's internal state (real window size 
and refused_data variable). For sender both cases are exactly the same 
so receiver must ACK with old ACKNO if it can't receive more data no 
matter why it can't.

--
Best regards, Oleg