Hi, On Thu, Apr 14, 2016 at 10:53:02AM +0200, Peter Kietzmann wrote: > Hi, > > thanks for giving this topic some informational background! As it was me > triggering that discussion, I just wanted to give my linux-network-newie > opinion back to you. > > IMO "avoiding invalid fragments" has higher priority than "avoiding latency" > for the reason that dropping one fragment means dropping all fragments of an > IPv6 packet. Processing 1280B IPv6 packets leads to 14 6LoWPAN fragments > which we'd have processed for nothing when dropping one of them fragments. > Therefore I like Alex's proposal about queuing 6Lowpan fragments and > checking space in the actual xmit queue. However, I currently don't know > much about IPv6 fragmentation but probably one thing to be careful about is > interaction between 6lo and IPv6 fragmentation and possible amplification > effects which could affect the needed txqueue size. > I think for dealing with the fragments right inside the queue we need to use "skb_shinfo(skb)->frag_list". A kfree_skb will then care about for releasing all other skb's which are use for the fragment and I hope this will deal with every others skb's which are inside the tx queue. I need to dig more into that if using frag_list really fix this issue. In case of IPv6 fragmentation for the wpan interface queue (lowpan interface doesn't have any tx queue, dev_queue_xmit will direct call xmit of lowpan interface) it's another issue and not easy because we have a fragmentation (IPv6) over fragmentation(6LoWPAN) there and notify dropped fragments from wpan-interface to the correct ipv6 fragments (in case of ipv6 fragmentation) sounds more complicated. I would try to fix at first the fragmentation for 6LoWPAN fragmentation, which is more likely than doing IPv6 fragmentation over 6LoWPAN. - Alex -- To unsubscribe from this list: send the line "unsubscribe linux-wpan" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
