netdev - Re: [PATCH net-next] net-core: add InMacErrors counter

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Date:   Mon, 24 Jan 2022 09:13:12 -0800
From:   Brian Vazquez <brianvv@...gle.com>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     Jeffrey Ji <jeffreyjilinux@...il.com>,
        Eric Dumazet <edumazet@...gle.com>,
        "David S . Miller" <davem@...emloft.net>,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        jeffreyji <jeffreyji@...gle.com>
Subject: Re: [PATCH net-next] net-core: add InMacErrors counter

On Fri, Jan 21, 2022 at 7:41 PM Jakub Kicinski <kuba@...nel.org> wrote:
>
> On Sat, 22 Jan 2022 00:03:01 +0000 Jeffrey Ji wrote:
> > From: jeffreyji <jeffreyji@...gle.com>
> >
> > Increment InMacErrors counter when packet dropped due to incorrect dest
> > MAC addr.
> >
> > example output from nstat:
> > \~# nstat -z "*InMac*"
> > \#kernel
> > Ip6InMacErrors                  0                  0.0
> > IpExtInMacErrors                1                  0.0
> >
> > Tested: Created 2 netns, sent 1 packet using trafgen from 1 to the other
> > with "{eth(daddr=$INCORRECT_MAC...}", verified that nstat showed the
> > counter was incremented.
> >
> > Signed-off-by: jeffreyji <jeffreyji@...gle.com>
>
> How about we use the new kfree_skb_reason() instead to avoid allocating
> per-netns memory the stats?

I'm not too familiar with the new kfree_skb_reason , but my
understanding is that it needs either the drop_monitor  or ebpf to get
the reason from the tracepoint, right? This is not too different from
using perf tool to find where the pkt is being dropped.

The idea here was to have a high level metric that is easier to find
for users that have less expertise on using more advance tools.