[Codel] [PATCH net-next] fq_codel: report congestion notification at enqueue time

[David Miller]

From: Eric Dumazet <eric.dumazet at gmail.com>
Date: Fri, 29 Jun 2012 07:24:08 +0200

> By the way, I am not sure NET_XMIT_CN is correctly used in RED.
> 
> Or maybe my understanding of NET_XMIT_CN is wrong.
> 
> If a the packet is dropped in enqueue(), why use NET_XMIT_CN instead of 
> NET_XMIT_DROP ?
> 
> This seems to mean : I dropped _this_ packet, but dont worry too much, I
> might accept other packets, so please go on...

I am pretty sure the behavior in RED is intentional.

It's a soft push back on TCP.

We're taking this path when we are unable to sucessfully ECN mark a
packet.  But our intention was to do so.