Re: Headroom for bridging and wireless

On Friday 05 December 2003 07:44, Tom Marshall wrote:
> The madwifi driver (for Atheros cards) uses sk_buff's directly in its xmit
> code.  When using WEP, a 4 byte header is prepended to the data using
> skb_push().  Since normal ethernet drivers don't anticipate the need for
> this, a call to skb_realloc_headroom() is needed for all packets crossing
> the bridge from ethernet to wireless.
>
> How hard would it be to add some logic in the bridge code to supply extra
> headroom in the sk_buff allocator?  I'm thinking it could query each
> network device in the system for its headroom requirements and use the max.
>  Or it could recognize which interfaces are in bridging mode and only ask
> them.  Or something even more intelligent.

That shouldn't be too difficult, just put the hard_header_len of the bridge 
device to the max of the hard_header_len of the bridge ports, each time a 
port is added or deleted.

cheers,
Bart



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