On Fri, 2015-02-27 at 10:12 +0100, Bjørn Mork wrote:
> Ben Hutchings <ben.hutchings@xxxxxxxxxxxxxxx> writes:
>
> > cdc_ncm disagrees with usbnet about how much framing overhead should
> > be counted in the tx_bytes statistics, and tries 'fix' this by
> > decrementing tx_bytes on the transmit path. But statistics must never
> > be decremented except due to roll-over; this will thoroughly confuse
> > user-space. Also, tx_bytes is only incremented by usbnet in the
> > completion path.
> >
> > Fix this by requiring drivers that set FLAG_MULTI_FRAME to set a
> > tx_bytes delta along with the tx_packets count.
> >
> > Signed-off-by: Ben Hutchings <ben.hutchings@xxxxxxxxxxxxxxx>
> > ---
> > I noticed this bug while trying to fix the tx_packets statistic in asix.
> > It depends on the patch I just sent for that. I don't have any hardware
> > to test this with, or any need to make it work. If you want this fix,
> > please test and re-submit it yoursef.
>
> I tested this on an MBIM device, and it worked perfectly as-is. Please
> submit it without the RFC prefix. This fixes a real and reported
> problem with the cdc_ncm driver, so I'd claim it's "net" material along
> with a stable Cc and
>
> Fixes: beeecd42c3b4 ("net: cdc_ncm/cdc_mbim: adding NCM protocol statistics")
>
> But you and David decide that, of course...
>
>
> Fixing this was actually on my TODO-list after a recent report showing
> one of the problems with the previous hack: The decremented tx_bytes
> counter was never corrected if the URB transmission failed, possibly
> ending up with a negative (i.e. very large since it is unsigned)
> tx_bytes counter.
>
> Thanks a lot. I didn't know how to do this without introducing a new
> callback or something. Your solutions is very nice, and so obvious when
> I see it. Just brilliant :-)
>
> Tested-by: Bjørn Mork <bjorn@xxxxxxx>
>
> And you might also want (if this is OK for Sami):
>
> Reported-by: Sami Farin <hvtaifwkbgefbaei@xxxxxxxxx>
Acked-by: Oliver Neukum <oliver@xxxxxxxxxx>
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