Re: [LARTC] Is negative offset possible in u32 ?

[Stephane Ouellette <ouellettes@videotron.ca>]

Eric Leblond wrote:

>Has somebody realyy manage to use the examples given when using negative
>offset in u32 ?
>
>I look at the kernel code, I'm almost a real beginner here so I could
>wrote stupid things :
>
>I saw that in the file cls_u32.c we work with skb and use only 
>skb->nh.raw. That's the network header, so we don't have any information
>about Ethernet header (it's in skb->mac.raw that we have the ethernet
>header and that the protocol is given).
>Furthermore (maybe i'm wrong cause of inverted stockage in memory) in
>the skbuf struct the ethernet header union follow the network header
>union so we should read something else.
>Thus we can at least say that negative offset in u32 are really "tricky"
>and really non clean and as seems to show experiment that they don't
>work (?)
>
>  
>
Eric,

  the following offsets are from a mail previously posted on this list.
I hope it helps.

Stephane Ouellette.


Decimal Ofs	Description
-----------------------------------
-14:		DST MAC, 6 bytes
-8:		SRC MAC, 6 bytes
-2:		Eth PROTO, 2 bytes, eg. ETH_P_IP
0:		Protocol header (IP Header)





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