On Wed, 2006-08-09 at 15:19 +0200, Thomas Graf wrote: > * 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.
I think Daniel was thinking of adding struct net_device * sk_buff::alloc_dev, I know I was after reading the first few mails. However if adding a field there is strict no-no.... /me takes a look at struct sk_buff Hmm, what does sk_buff::input_dev do? That seems to store the initial device? - 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