Re: [lwip-users] p->payload == iphdr failed...

[Ed Sutter]

Jonathan Larmour wrote:
> Ed Sutter wrote:
> > Jonathan Larmour wrote:
> > > Ah I see in the implementation of pbuf_header, that it can't expand
> > > PBUF_REFs to the front. That will be your problem.
> > >
> > > I think the only reason it doesn't do it is because there's no way to
> > > sanity check that it's a valid thing to do.
> >
> > Hmmmm...
> > If I can't use PBUF_RAW/PBUF_REF to allocate the pbuf, then does that
> > mean I have no choice but to do the loop of memcpy's like this...
> [snip]
> > Or is there some other way to avoid that copy loop?
>
> I think the better answer for you would be to adjust the PBUF_REF case 
> in pbuf_header() to allow PBUF_REF pbufs to be expanded to the front.
>
> I'm undecided whether that would be a good change to have in the master 
> code base.

Ok, I see what you're talking about in pbuf_header().  I don't know the history
of the code to comment on whether or not the change should be in the master
code base; but it would seem to me that if this is forcing a driver to use
the memcpy loop to build the pbuf chain, then it would be a good improvement.

Anyway, if there is no other better way to do this I suppose I'll just stick
with it (don't have time to look into pbuf_header() at the moment).  I guess
this must be what everyone does (otherwise they would be running into the same
problem I'm running into), right?
Thanks much,
Ed