Re: [lwip-users] PolarSSL and mbedTLS

[Jan Menzel]

Hi Noam!
        I've designed a system with almost the same setup which works well
since a few years incl. firmware updates of a ~200kb.
        Did you checked the memory consumption of the ip stack and the ssl max
content length setting? The default max content length setting is IIRC
16kb, which means that data is hashed and encrypted in chunks of up to
16kb and can only be verified and decrypted once the entire chunk has
been received. The firmware update on my system only works if the max
content length is reduced. With the default setting I faced memory
issues on LPC1768 (which has just a fraction of your F4xx).
        I also had to fiddle around a little bit with errno in the interface
between mbedtls and lwip. One last advice: carefully check your stack
usage. mbedtls uses lots of function pointers which Keils static call
graph analysis can not see and does not warn about.

        Jan

On 01.03.2017 14:01, Noam Weissman wrote:
> Hi,
> 
>  
> 
> I have a client, single task using the socket API using and also
> PolarSSL for SSL support.
> 
>  
> 
> The client is WebSocket client and all seems to work ok.
> 
>  
> 
> When I try to send small messages from the server to my client all is
> working ok but when I try to push a large
> 
> message 6K and up my ssl_read function fails with a read error?.
> 
>  
> 
> The ssl_read is actually calling lwip_read internally.
> 
>  
> 
> For some reason the SSL code is trying to read a large buffer 8-16K
> bytes and the read function fails.
> 
>  
> 
> Normally when we read from a socket more than is available the return
> value should be the number
> 
> of bytes actually read and not an error ?.
> 
>  
> 
> The processor is STM32F427 using CCM for heap and Keil IDE
> 
>  
> 
> My main project uses Lwip 1.41, FreeRTOS 8.0.1 and PolarSSL 1.0.0
> 
>  
> 
> I have created two almost identical projects to the one I use. The first
> uses:
> 
> Lwip 2.01, FreeRTOS 9.0
> 
>  
> 
> The second project is the same as the one with Lwip 2.01 but instead of
> PolaSSL I switched to mbedTLS 2.4.0
> 
>  
> 
> In none secure mode everything works as expected and have no problems
> getting a large message (600K)
> 
> In secured mode I get a read fail on the first packet ??
> 
>  
> 
> Anyone has an idea what I am doing wrong or what setting are not correct ??
> 
>  
> 
> A second question for Simon or anyone that can assist. I tried to set
> LWIP_DEBUG to 1 and my total used RAM (compiler) dropped
> 
> about 30K ?? Why is that ?... I understood that debug should take more
> RAM not Less ?
> 
>  
> 
> Thanks,
> 
> Noam.
> 
>  
> 
> cid:image001.jpg@01D26A92.68494F10
> 
>       
> 
> Noam Weissman
> 
> Software Engineer
> 
> SILORA R&D
> 
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> 
>       
> 
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> 
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