netdev - Re: [PATCH net 2/2] tcp: fix reordering SNMP under-counting

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Date:   Wed, 05 Apr 2017 18:42:01 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     ycheng@...gle.com
Cc:     netdev@...r.kernel.org, ncardwell@...gle.com, edumazet@...gle.com,
        soheil@...gle.com
Subject: Re: [PATCH net 2/2] tcp: fix reordering SNMP under-counting

From: Yuchung Cheng <ycheng@...gle.com>
Date: Tue,  4 Apr 2017 14:15:40 -0700

> Currently the reordering SNMP counters only increase if a connection
> sees a higher degree then it has previously seen. It ignores if the
> reordering degree is not greater than the default system threshold.
> This significantly under-counts the number of reordering events
> and falsely convey that reordering is rare on the network.
> 
> This patch properly and faithfully records the number of reordering
> events detected by the TCP stack, just like the comment says "this
> exciting event is worth to be remembered". Note that even so TCP
> still under-estimate the actual reordering events because TCP
> requires TS options or certain packet sequences to detect reordering
> (i.e. ACKing never-retransmitted sequence in recovery or disordered
>  state).
> 
> Signed-off-by: Yuchung Cheng <ycheng@...gle.com>
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Signed-off-by: Neal Cardwell <ncardwell@...gle.com>
> Signed-off-by: Soheil Hassas Yeganeh <soheil@...gle.com>

Applied.