Using LwIP on the STM32H7

[Joel Sherrill]

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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