netdev - Re: [PATCH net-next] fq_codel: add memory limitation per queue

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Message-ID: <CAM_iQpURNs3vVVN1cceRLh2ptvsMno3bPubc9wwfQvcWe8je8g@mail.gmail.com>
Date:	Mon, 9 May 2016 21:34:50 -0700
From:	Cong Wang <xiyou.wangcong@...il.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	David Miller <davem@...emloft.net>,
	Jesper Dangaard Brouer <brouer@...hat.com>,
	Dave Täht <dave.taht@...il.com>,
	netdev <netdev@...r.kernel.org>, moeller0 <moeller0@....de>
Subject: Re: [PATCH net-next] fq_codel: add memory limitation per queue

On Mon, May 9, 2016 at 7:26 AM, Eric Dumazet <eric.dumazet@...il.com> wrote:
> On Sun, 2016-05-08 at 22:07 -0700, Cong Wang wrote:
>> On Sun, May 8, 2016 at 9:31 PM, Eric Dumazet <eric.dumazet@...il.com> wrote:
>> > On Sun, 2016-05-08 at 21:14 -0700, Cong Wang wrote:
>> >
>> >> So when the packet is dropped due to memory over limit, should
>> >> we return failure for this case? Or I miss anything?
>> >
>> > Same behavior than before.
>> >
>> > If we dropped some packets of this flow, we return NET_XMIT_CN
>>
>> I think for the limited memory case, the upper layer is supposed
>> to stop sending more packets when hitting the limit.
>
> They doe. NET_XMIT_CN for example aborts IP fragmentation.
>
> TCP flows will also instantly react.

But not for the NET_XMIT_SUCCESS case:

        return ret == idx ? NET_XMIT_CN : NET_XMIT_SUCCESS;