Oliver Hartkopp wrote: > Patrick McHardy wrote: > >>Urs Thuermann wrote: >> >> >>>+ /* tx socket reference pointer: Loopback required if not NULL */ >>>+ loop = *(struct sock **)skb->cb != NULL; >>> >> >> >>Qdiscs might change skb->cb. Maybe use skb->sk? >> >> > > due to current projects Urs and me had only a short time today to > discuss the use of other skbuff-elements to implement the needed > loopback functionality. Urs remembered that the value of skb->sk was not > 'stable' in the whole loopback and therefore the use of skb->cb was a > reasonable approach - and it was indeed working. Btw. triggered by your > remark, we're looking for alternatives.
Yes, its working, but only in certain combinations and you're breaking the rules for skb->cb, making it impossible for other layers to use. skb->sk is "stable" at the output path, the regular loopback device orphans the skb in hard_start_xmit. So you can at least use it there. > Another thing is, that i would like to know, if Qdiscs would ever touch > skb's containing CAN-frames?!? > The MTU is 16 bytes (sizeof(struct can_frame)) and each skb contains > exact one CAN-frame. > What would a packet scheduler do with these skb's? IMO there is nothing > that could be optimized and linked together like in IPv4 / IPv6 data. Qdiscs don't care about the content. If a user attaches one to your device, it will get used. > Would therefore skb->cb left unchanged in my skb's? Or is there any flag > that can be set in the skb to keep the packet scheduler's hands off? No, and I don't think we want a flag to signal that something is violating the rules for skb->cb, there are other users of this besides qdiscs. - 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
