Urs Thuermann wrote: > Patrick McHardy <[EMAIL PROTECTED]> writes: > >>And it allows you have both loopback and non-loopback devices >>in case that would be useful. > > > That sounds very promising. I also was unhappy with the fixed number > of vcan devices at module load time and have thought about ioctl's to > add/delete devices and to change the loopback flag. A more general > approach like the one you seem to be working on is preferable of > course.
I got a bit delayed, but I hope to have the patches in postable state tommorrow. >>Qdiscs might change skb->cb. Maybe use skb->sk? > > > When we decided to use skb->cb it seemed the only possible option. > We need a field that we can set to zero to indicate we don't want the > driver to loop back the packet and the value in that field must > survive the path > > can_send() > dev_queue_xmit() > ... > dev->hard_start_xmit() > > netif_rx() > can_rcv() > > I think I misread the comment > > * @cb: Control buffer. Free for use by every layer. Put private vars > here > > to mean I can use it for this purpose and since it worked as intended > we felt ok with this. Now I see, it states exactly the opposite that > I can't count on the value being preserved across layers. Yes, that comment is a bit misleading. > skb->sk can't be used since we shouldn't set it to zero before > dev_queue_xmit() as Oliver already pointed out. IIRC, skb->sk > couldn't also be used in rx half of that path, since it was set to > null somewhere in netif_rx() but now, reading the src, I can't see > where this would happen. Maybe this has changed or my memory has some > bit errors. I'll look at it again. Even if it turns out skb->sk can > be used in rx path, the need remains to pass down a flag from > can_send() to dev->hard_start_xmit() indicating whether to loop back > or not. That flag is a socket flag acording to Oliver, so you can use the flag itself. You could keep skb->sk for the RX path (don't call skb_orphan in your hard_start_xmit function), if that doesn't work worst case would be to use a flag in the skb (we still have 2 unused bits) until you've figured out a better way. - 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
