Interface counter inaccurate

[Daniel Ponte]

On Tue, Feb 16, 2021 at 10:39:28AM +0100, Kristof Provost wrote:
[...]
> Even stranger, in that you appear to only have the issue on one of your igb0
> interfaces.
> My initial guess was that there was a driver bug causing it to double count
> the packets.
> 
> That machine has 4 ethernet ports, does it have 4 igbX interfaces as well?
> Are there any vlans configured? (My current thinking is still that it’s a
> driver issue, manifesting only on one of the interfaces because of a
> configuration difference.)
> 
> It may also be useful to try capturing packets on igb0 and correlating the
> number of captured packets with the counters.
> 
> I’m not all that familiar with the igb driver code, so I don’t know if I’ll
> be able to help much.
> 
> Best regards,
> Kristof

It indeed has 4x igb interfaces.

I have been able to further correlate this. The issue is with incoming
packet counters on either interface. When the flow reverses (upload
speedtest vs download speedtest), the inside interface's ingress counter
starts counting double instead.

There is a single, seldom-used vlan, but it is only on the inside
interface. Destroying it made no difference.

Dan