From mboxrd@z Thu Jan  1 00:00:00 1970
From: Andi Kleen <ak@suse.de>
Subject: Re: Linux 2.4.22 loopback question
Date: Thu, 6 May 2004 08:35:47 +0200
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To: Cheng Jin <chengjin@cs.caltech.edu>
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On Wed, May 05, 2004 at 02:53:41PM -0700, Cheng Jin wrote:
> I have instrumented the code in net/core/dev.c, and it seems that indeed
> the corresponding ack would sometimes be generated by the receiver, 
> received and timestamped by netif_rx before tcp_transmit_skb returns.

Most likely because the network softirq runs in parallel in interrupt
context and picks up all the already queued packets. e.g. this
can be triggered when you receive a packet from ethernet.

-Adni