netdev - Re: [PATCH v2 net-next 1/2] Documentation: sysfs-class-net-statistics: Clarify rx_bytes and tx

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Date:   Thu, 25 May 2017 12:43:05 -0400 (EDT)
From:   David Miller <davem@...emloft.net>
To:     andrew@...n.ch
Cc:     f.fainelli@...il.com, hayeswang@...ltek.com, netdev@...r.kernel.org
Subject: Re: [PATCH v2 net-next 1/2] Documentation:
 sysfs-class-net-statistics: Clarify rx_bytes and tx_bytes

From: Andrew Lunn <andrew@...n.ch>
Date: Tue, 23 May 2017 23:10:57 +0200

> Document what is expected for the rx_bytes and tx_bytes statistics in
> /sys/class/net/<device>/statistics. The FCS should be included in the
> statistics. However, since this has been unclear until now, it is
> expected a number of drivers don't. But maybe with time they will.
> 
> Signed-off-by: Andrew Lunn <andrew@...n.ch>

Precedence has not been very kind to us here.

Also, we really I want drivers doing the simplest thing possible,
which on transmit is:

	tx_bytes += skb->len;

Not:

	tx_bytes += skb->len + ETH_FCS_LEN;

I understand the problem you're trying to tackle, but software stats
should be for software state, and that state is emphatically skb->len

So if we are to strive for software statistic "consistency" it should
be against the software part of the packet, not the software part
"plus X and Y link layer stuff no visible in the software packet".

Thanks.