RE: [PATCH net-next v3 3/3] net: icmp: add reasons of the skb drops to icmp protocol

[David Laight <David.Laight@ACULAB.COM>]

From: David Ahern
> Sent: 17 March 2022 14:49
> 
> On 3/16/22 10:05 PM, Jakub Kicinski wrote:
> > On Wed, 16 Mar 2022 21:35:47 -0600 David Ahern wrote:
> >> On 3/16/22 9:18 PM, Jakub Kicinski wrote:
> >>>
> >>> I guess this set raises the follow up question to Dave if adding
> >>> drop reasons to places with MIB exception stats means improving
> >>> the granularity or one MIB stat == one reason?
> >>
> >> There are a few examples where multiple MIB stats are bumped on a drop,
> >> but the reason code should always be set based on first failure. Did you
> >> mean something else with your question?
> >
> > I meant whether we want to differentiate between TYPE, and BROADCAST or
> > whatever other possible invalid protocol cases we can get here or just
> > dump them all into a single protocol error code.
> 
> I think a single one is a good starting point.

I remember looking at (I think) the packet drop stats a while back.
Two machines on the same LAN were reporting rather different values.
Basically 0 v quite a few.

It turned out that passing the packets to dhcp was deemed enough
to stop them being reported as 'dropped'.
And I think that version of dhcp fed every packed into its BPF? filter.
(I never did decide whether that caused every skb to be duplicated.)

	David

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