R: R: [lwip-users] ip_reass

[Ceresoli Luca]

Ed Sutter wrote:
>    2. pbuf_alloc() setting payload buffers up to be aligned 
> based on MEM_ALIGNMENT

"your driver must support it" means you have to:
- set ETH_PAD_SIZE to 2 in lwipopts.h
- allocate 2 extra bytes, eg
  pbuf_alloc(PBUF_RAW, your_current_size+ETH_PAD_SIZE, PBUF_RAM)
- take care of those few things that I quite forgot...

Luca


>    3. the increment of the payload pointer by 14 in ethernet_input()
> and...
>    4. the overlay of the "helper" structure in 
> ip_reass_chain_frag_into_datagram_and_validate()
> 
> will cause the misaligned access.  If the option you mention 
> fixes it for my
> situation on the BF537, that doesn't resolve it for other systems.
> Right?
> Ed
> 
> Ceresoli Luca wrote:
> > Ed Sutter wrote:
> >> I'm running LWIP 1.3.0 on a Blackfin, which is picky about 
> >> ...
> >> The ethernet_input() function then sees that it is IP, 
> >> increments the payload
> >> pointer by 14 (size of ethernet header) and passes the pbufs 
> >> to ip_input().
> >> Note that at this point, the payload pointer is no longer 
> >> aligned on a 4-byte
> >> boundary because the original 4-byte-aligned payload pointer 
> >> is incremented
> >> by 14.
> > 
> > Which Blackfin are you using?
> > Tha Ethernet MAC of Blackfin 536/7 can optionally add two 
> dummy bytes in front of incoming frames (setting bit RXDWA in 
> the EMAC_SYSCTL register). This makes all TCP/IP headers 
> 4-byte aligned.
> > 
> > Of course your driver must support it.
> > 
> > Luca
> > 
> > 
> > _______________________________________________
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> > 
> 
> 
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