[lwip-users] Re: [lwip] Intention of poll,tcp_output() in tcp_slowtmr() call.

[Chris Borrelli]

Michael,

I have noticed this as well.  I have been calling the tcp_output() 
function in my application - after a call to tcp_write().  But it would 
be nice if the PCB had a nodelay option, so that when enabled, 
tcp_output() would get called inside tcp_write()  (after the call to 
tcp_enqueue()).

 -Chris

Michael Portmann wrote:

>Hi all.
>
>  I think this is a bug, however...
>
>  Can someone (Adam?) explain the intention of the call poll,tcp_output() in 
> tcp_slowtmr().
>Both V0.5.3 and CVS call it at the rate of the pollinterval. What this means 
>is if you haven't filled up to MSS worth of data, the data won't be sent until 
>the poll call.
>
>  My understanding from documentation I've read, is the poll is for "watchdog" 
> type functionality.
>
>  What is the "normal" delay used for transmitting packets less than MSS ? I 
> feel this should be either changed such that tcp_output() is called at every 
> tcp_slowtmr() call (500ms) or that the documentation be changed to mention 
> that the poll() call has this effect.
>
>  Finally on this matter - I can't see where this pollinterval is initialised 
> except for by the tcp_poll() function (Not even bzero'ed.) Would it be 
> reasonable to say pollinterval should be initialised to zero in the tcp_input 
> function ?
>
>Regards,
>Michael Portmann
>
>HYDRA Electronic Design Solutions Pty Ltd
>140 Ashley Street, Underdale, SA 5032.
>Ph. +61 8 8234-0477
>Fx. +61 8 8234-1840
>
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