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Re: [lwip-users] lwIP malloc fail

From: Simon Goldschmidt
Subject: Re: [lwip-users] lwIP malloc fail
Date: Wed, 14 Apr 2010 07:38:57 +0200

"Navcon - Pedro Paulo Santos" wrote:
> The main mistake I did was that I tried to send all the data in the recv 
> callback function. As I realized, lwIP received the ACK, but didn't freed 
> the memory because it does so in other handler (unknown for me) different 
> from recv.

Which memory isn't freed? The pbufs queued for sending/retransmission should be 
freed *before* your receive callback is called, so this shouldn't be a problem. 
However, you can only send as much data as fits into the buffers when you are 
in the recv callback. If you have more data than that, the *sent* callback gets 
called if an ACK is received and you can send more data from there.

The HTTP server in CVS contrib has no problems doing it this way.

> The latency can be improve for really small tranfers by sending
> in the recv function, but I would not suggest this.

That's not true, there should be no problems sending from the recv callback 
(i.e. calling tcp_write from that callback).

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