* Daniel Phillips <[EMAIL PROTECTED]> 2006-08-08 22:47 > David Miller wrote: > >From: Daniel Phillips <[EMAIL PROTECTED]> > >>Can you please characterize the conditions under which skb->dev changes > >>after the alloc? Are there writings on this subtlety? > > > >The packet scheduler and classifier can redirect packets to different > >devices, and can the netfilter layer. > > > >The setting of skb->dev is wholly transient and you cannot rely upon > >it to be the same as when you set it on allocation. > > > >Even simple things like the bonding device change skb->dev on every > >receive. > > Thankyou, this is easily fixed.
It's not that simple, in order to just fix the most obvious case being packet forwarding when skb->dev changes its meaning from device the packet is coming from to device the packet will be leaving on is difficult. You can't unreserve at that point so you need to keep the original skb->dev. Since the packet is mostly likely queued before freeing you will lose the refcnt on the original skb->dev. Keeping a refcnt just for this memalloc stuff is out of question. Even keeping the ifindex on a best effort basis is unlikely an option, sk_buff is way overweight already. - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
