Messages in this thread | | | From | Eric Dumazet <> | Date | Thu, 3 Feb 2022 10:13:59 -0800 | Subject | Re: [PATCH v6 net-next] net-core: add InMacErrors counter |
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On Wed, Feb 2, 2022 at 8:59 PM Jakub Kicinski <kuba@kernel.org> wrote: > > On Tue, 1 Feb 2022 22:28:45 +0000 Jeffrey Ji wrote: > > From: jeffreyji <jeffreyji@google.com> > > > > Increment InMacErrors counter when packet dropped due to incorrect dest > > MAC addr. > > > > An example when this drop can occur is when manually crafting raw > > packets that will be consumed by a user space application via a tap > > device. For testing purposes local traffic was generated using trafgen > > for the client and netcat to start a server > > > > example output from nstat: > > \~# nstat -a | grep InMac > > Ip6InMacErrors 0 0.0 > > IpExtInMacErrors 1 0.0 > > I had another thing and this still doesn't sit completely well > with me :( > > Shouldn't we count those drops as skb->dev->rx_dropped? > Commonly NICs will do such filtering and if I got it right > in struct rtnl_link_stats64 kdoc - report them as rx_dropped. > It'd be inconsistent if on a physical interface we count > these as rx_dropped and on SW interface (or with promisc enabled > etc.) in the SNMP counters.
I like to see skb->dev->rx_dropped as a fallback-catch-all bucket for all cases we do not already have a more specific counter.
> Or we can add a new link stat that NICs can use as well.
Yes, this could be done, but we have to be careful about not hitting a single cache line, for the cases we receive floods of such messages on multiqueue NIC. (The single atomic in dev->rx_dropped) is suffering from this issue btw)
> > In fact I'm not sure this is really a IP AKA L3 statistic, > it's the L2 address that doesn't match. > > > If everyone disagrees - should we at least rename the MIB counter > similarly to the drop reason? Experience shows that users call for > help when they see counters with Error in their name, I'd vote for > IpExtInDropOtherhost or some such. The statistic should also be > documented in Documentation/networking/snmp_counter.rst
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