Re: [lwip-devel] Problem with LWIP_ERROR in pbuf_header(..)

[address@hidden]

Justs an additional explanation: the ASSERT can (or should) only fail 
due to wrong configuration options (i.e. PBUF_POOL data size is too 
small to hold all the headers). We could discuss whether this should 
assert or not, but if not these problems would be harder to detect (you 
would have to debug why packets that are correct are rejected).

Simon


address@hidden wrote:
> Fredrik Hederstierna wrote:
>   
> > > In the case you mention, shouldn't the first clause in the if statement
> > > "if (p->tot_len < (IPH_HL(iphdr) * 4 + UDP_HLEN)"  protect us from the
> > > assertion?  I.e. if the packet is short it should do that clause, but
> > > then not the pbuf_header() call.
> > >       
> > But is it true that always  (p->tot_len == p->len)  here ?
> > Maybe due to almost full memory  p->tot_len  is  larger than  p->len ?
> > The ERROR is checking  p->len,  but if-statement checks  p->tot_len.
> >     
>
> I think you are right: if the first pbuf is smaller than the headers, 
> the assert may fail. We should check p->len: the lwIP code definively 
> can't cope with headers spreaded over multiple pbufs.
>
> Simon
>
>
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