About the TCp/ip stack in RTEMS

Ralf Corsepius ralf.corsepius at rtems.org
Fri Sep 12 03:04:45 UTC 2008

On Thu, 2008-09-11 at 15:11 -0400, Gene Smith wrote:
> Ralf Corsepius wrote:
> > On Wed, 2008-09-10 at 10:58 +0800, PowerMan wrote:
> >> I am doing a project which uses the NXP LPC2300.
> >> The NXP LPC2300 is based on arm7-tdmi & have a internal ethernet 
> >> controller. But the internal sdam is only 32KB.
> >> The FreeBSD tcp/ip stack in RTEMS seems too large for such kind of
> >> MCU ( with internal ethernet controller and small sram, another
> >> example is at91sam7x128) .
> >> Why not substitute lwip for it in the source tree?
> > 
> > First of all lwip would have to prove
> > 
> > a) functional equivalence to the BSD stack
> > Though the BSD stack in RTEMS is only a partial port of the original BSD
> > stack and gradually diverging from the BSD stack due to the fact it
> > receives too little attention, it should not be too difficult to add
> > further features, the original BSD-stack supports.
> I assume you are saying rtems port of BSD stack "receives too little 
> attention," not the free BSD stack itself?

FreeBSD's BSD stack (From which RTEMS BSD stack is derived from) has
moved on, while RTEMS BSD stack more or less stagnated with more or less
the state FreeBSD had when RTEMS BSD-stack had been forked off.

> > c) portability, standard conformance.
> > A non-portable "toy stack" not complying to any standard doesn't help
> > anybody.
> > 
> > That said, I don't see any reason to replace the BSD stack. If at all,
> > an alternative stack may be added in parallel to the BSD stack. Should
> > this stack once prove its viability, we could start discussing to
> > abandon the BSD stack.
> Yes, I agree, don't think RTEMS should "abandon" the FreeBSD stack. Just 
> provide hooks to use a more compact stack as an alternative for small 
> systems or systems needing better security or performance. I thought I 
> read something on the list about doing this possibly through a "Summer 
> of Code" project to include a lighter stack alternative.
I do not think security, performance or size are the real issues with
the RTEMS BSD-stack. I consider the fact the code in RTEMS is gradually
aging and it lacking modern and more advanced features, to be gradually
becoming a problem.

> It would be nice if one could link in any comm stack to RTEMS such as 
> the well maintained (according to marketing blurbs), also BSD derived 
> but non-free Interniche stack (Granted, source could not be distributed 
> and have rtems remain free).
Anything "non-free" is not an option to me :)


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