[lwip-users] Re: [lwip] struct packing

[Adam Dunkels]

Hi James!

On Wednesday 20 February 2002 00.26, you wrote:
>     1.  struct packing

Ok, so GCC needs an extra __attribute__ ((packed)) at the end of the structs. 
Another #define PACK_STRUCT_STRUCT should be added then, like this:

struct foo {
   PACK_STRUCT_FIELD(struct x bar);
} PACK_STRUCT_STRUCT;

>     2. more packing:
>
>         After I have added the extra attribute to the structs, the
> ethernet frame is recognized as an IP packet with correct version number
> etc.  I suspect that there are other structs to be packed.  lwIP sends
> continuous arp requests for the ip address on its own default interface.
>
>     Should I try to repack the ethernet frame from within the 8900a
> driver?  Would I have to re-pack differently for each ip or arp packet
> type, or can it be generalized to 2 cases?

The only structs that needs to be packed are those that define protocol 
headers. I'll add the packet attribute to all protocol header structs in the 
next lwIP version.

/adam
-- 
Adam Dunkels <address@hidden>
http://www.sics.se/~adam

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