Using LwIP on the STM32H7

[Joel Sherrill]

On Mon, Feb 1, 2021 at 4:54 PM Mr. Andrei Chichak <groups at chichak.ca> wrote:

> Oh, crap, I’m off by 3 orders of magnitude, I’ve got 512KB.
>

That's an LWIP candidate. :)

But Sebastian did a driver for libbsd for the H7 series. If you have more
memory
or can attach external RAM, that's an option.


> Bother, I need a nap already.
>
> A
>
> On 2021-February-01, at 15:35, Joel Sherrill <joel at rtems.org> wrote:
>
>
>
> On Mon, Feb 1, 2021 at 4:25 PM Andrei Chichak <andrei at chichak.ca> wrote:
>
>> any guidance choosing between “Legacy Stack” and libbsd?
>>
>
> This one is easy. Please please please please do NOT choose the legacy
> stack. :)
>
> The legacy stack should only be used on projects that are using it and
> those
> are encouraged to move along to libbsd or lwip or new hardware.  We have no
> plans to eliminate the legacy stack from the world. But as Gedare said, we
> want
> to move it to a separate repository. If someone cares, then it gets a
> build system
> and can be used with a strong discouragement.
>
> It is 20+ years old now and IPV4 only. Do the math. :)
>
>
>>
>> I’ve got a 512MB of RAM processor, so I expect that I’ll have lots left
>> over. But that is TBD.
>>
>
> 512MB is still huge in RTEMS terms. That won't be a problem for libbsd at
> all.  It is when you
> start considering targets with < 16MB that we have concerns. I suspect
> that number is <4MB
> but the original BSP for the legacy stack only had 1MB for code and data
> space. It is clear
> some boards that could run the legacy stack will not be capable of running
> libbsd but we
> don't have a hard cutoff yet.
>
> --joel
>
>>
>> A
>>
>> On 2021-February-01, at 15:21, Joel Sherrill <joel at rtems.org> wrote:
>>
>>
>>
>> On Mon, Feb 1, 2021 at 4:03 PM Gedare Bloom <gedare at rtems.org> wrote:
>>
>>>
>>>
>>> On Mon, Feb 1, 2021 at 2:42 PM Chris Johns <chrisj at rtems.org> wrote:
>>>
>>>> On 2/2/21 8:32 am, Mr. Andrei Chichak wrote:
>>>> > Is there any advantage to using bsd networking over LWiP, or vice
>>>> versa?
>>>>
>>>> They are different stacks with different feature sets and different
>>>> hardware
>>>> resource demands. I am not familiar with the features of LwIP so I am
>>>> not the
>>>> best person to compare them.
>>>>
>>>> The BSD stack has most of the features you get with FreeBSD. It has
>>>> IPv4, IPv6,
>>>> IPsec, VLAN, bridging, dhcp, openssl, lots of routing alternatives,
>>>> packet
>>>> filtering and more. It has a range of useful commands including tcpdump.
>>>>
>>>> The BSD based system provides a solid base to solve a range of
>>>> networking issues
>>>> your RTEMS device may encounter at the system level and not at the low
>>>> level
>>>> programming level.
>>>>
>>>> The BSD stack uses a lot more resources to do all this and LwIP may be
>>>> a prefect
>>>> fit. I welcome RTEMS being able to support a range of networking
>>>> solutions.
>>>>
>>>>
>>> I have a student (Vijay) working on refactoring libnetworking out of
>>> RTEMS, and will be testing ability to compile legacy vs libbsd. If the lwip
>>> build is demonstrated and clear, I can have him also look at bringing that
>>> into the fold. This is in line with https://devel.rtems.org/ticket/3850
>>>
>>
>> One thing to be aware of is that all the POSIX networking header files
>> for RTEMS are in newlib and always present. I had to address this and lwip
>> when we did Deos+RTEMS. Deos uses lwip as their native stack running in a
>> partition and other partitions use a client to get to it. The lwip
>> constants had values that were not the same as the RTEMS BSD headers for
>> POSIX defines. There were also some places where the structure definitions
>> did not align. I had to write a bit of mapping in the client. When lwip
>> works at all, it would be awesome to have a way for it to ignore their own
>> minimal POSIX API files and build against ours.
>>
>> This would be similar to how the newlib headers define a very complete
>> POSIX API set but each target OS may only support a subset of it.
>>
>> As it is, I wonder if there is a conflict between the RTEMS newlib
>> network .h files and those provided by lwip which could cause issues.
>>
>>
>>>
>>> We have no certain timeline yet, but it is now work-in-progress. We will
>>> bring to devel when progress is made. If we do lwIP too, we will aim to do
>>> a performance analysis with real hardware, so that we can hopefully provide
>>> evidence to help these kind of questions.
>>>
>>> -Gedare
>>>
>>> Chris
>>>>
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>>
>>
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>>
>>
>>
>>
>>
>>
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