netdev - Re: [PATCH net v2] net: don't keep lonely packets forever in the gro hash

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Message-Id: <20181123.111943.147074718959730862.davem@davemloft.net>
Date:   Fri, 23 Nov 2018 11:19:43 -0800 (PST)
From:   David Miller <davem@...emloft.net>
To:     pabeni@...hat.com
Cc:     netdev@...r.kernel.org, willemdebruijn.kernel@...il.com,
        eric.dumazet@...il.com
Subject: Re: [PATCH net v2] net: don't keep lonely packets forever in the
 gro hash

From: Paolo Abeni <pabeni@...hat.com>
Date: Wed, 21 Nov 2018 18:21:35 +0100

> Eric noted that with UDP GRO and NAPI timeout, we could keep a single
> UDP packet inside the GRO hash forever, if the related NAPI instance
> calls napi_gro_complete() at an higher frequency than the NAPI timeout.
> Willem noted that even TCP packets could be trapped there, till the
> next retransmission.
> This patch tries to address the issue, flushing the old packets -
> those with a NAPI_GRO_CB age before the current jiffy - before scheduling
> the NAPI timeout. The rationale is that such a timeout should be
> well below a jiffy and we are not flushing packets eligible for sane GRO.
> 
> v1  -> v2:
>  - clarified the commit message and comment
> 
> RFC -> v1:
>  - added 'Fixes tags', cleaned-up the wording.
> 
> Reported-by: Eric Dumazet <eric.dumazet@...il.com>
> Fixes: 3b47d30396ba ("net: gro: add a per device gro flush timer")
> Signed-off-by: Paolo Abeni <pabeni@...hat.com>

Applied and queued up for -stable.