Re: [RFC davem] revert: net: Make skb->skb_iif always track skb->dev

[Oliver Hartkopp <socketcan@hartkopp.net>]

On 12.01.2013 22:36, David Miller wrote:

> As per your problem with CAN, that's also rediculous.  You have an SKB
> control block in skb->cb[] that you can put whatever values with
> whatever semantics you want.
> 
> Use it.


I'm not writing a RFC to you, when i'm not sure having checked several options
before.

In the tx path already net/sched is using cb[] for it's purposes.
Adding the information somewhere at the end of cb[] to not interfere with
sched becomes tricky. See users of qdisc_cb_private_validate().

So the 'incoming interface index' could be stored safely in the tx path in

- skb->data
- skb_shared_info
- skb_iif

skb_iif was the obvious choice then. And the question why a seven year old
if-statement in net/core/dev.c has been removed must be allowed.

Networking is not only IP networking.

Oliver