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Date: Mon, 06 Jun 2016 07:37:25 -0700
From: Eric Dumazet <eric.dumazet@...il.com>
To: Florian Westphal <fw@...len.de>
Cc: Jamal Hadi Salim <jhs@...atatu.com>,
Cong Wang <xiyou.wangcong@...il.com>,
David Miller <davem@...emloft.net>,
netdev <netdev@...r.kernel.org>,
Stas Nichiporovich <stasn77@...il.com>
Subject: Re: [PATCH v2 net] fq_codel: fix NET_XMIT_CN behavior
On Mon, 2016-06-06 at 13:42 +0200, Florian Westphal wrote:
> Jamal Hadi Salim <jhs@...atatu.com> wrote:
> > BTW, returning NET_XMIT_CN could be confusing to tcp;
> > it does not mean that the packet that we are getting return
> > code for was dropped; it could mean _another_ packet in
> > the queue was dropped.
>
> Yes, but we currently conceal NET_XMIT_CN from upper layer (tcp)
> via the net_xmit_* macros:
>
> #define net_xmit_eval(e) ((e) == NET_XMIT_CN ? 0 : (e))
> #define net_xmit_errno(e) ((e) != NET_XMIT_CN ? -ENOBUFS : 0)
>
> Might be worth changing this so tcp reduces cwnd in _CN case too.
It always had been the case.
tcp_transmit_skb() calls tcp_enter_cwr(), unless someone broke this.
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