Hello! On 2015-06-21 18:50, Oliver Hartkopp wrote: > As reported by Manfred Schlaegl here > > http://marc.info/?l=linux-netdev&m=143482089824232&w=2 > > commit 514ac99c64b "can: fix multiple delivery of a single CAN frame for > overlapping CAN filters" requires the skb->tstamp to be set to check for > identical CAN skbs. > > As net timestamping is influenced by several players (netstamp_needed and > netdev_tstamp_prequeue) Manfred missed a proper timestamp which leads to > CAN frame loss. > > As skb timestamping became now mandatory for CAN related skbs this patch > makes sure that received CAN skbs always have a proper timestamp set. > Maybe there's a better solution in the future but this patch fixes the > CAN frame loss so far. >
I'm not sure, but maybe this patch (and also my original one) opens a new potential issue with timestamps. If the timestamp is set at allocation time, this cancels setting the timestamp at delivery (by net_timestamp_check in, for example, netif_receive_skb_internal.) -> So it changes the behavior of timestamping (http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/Documentation/networking/timestamping.txt?id=b953c0d234bc72e8489d3bf51a276c5c4ec85345) generally. Hypothetical example: If timestamping is enabled by the user and there is a significant delay between allocation and delivery of a skb (early allocation in driver or something) the timestamp does not reflect the reception time anymore. What do you thing about this? best regards, Manfred -- To unsubscribe from this list: send the line "unsubscribe netdev" in
