netdev - Re: Default qdisc not correctly initialized with custom MTU

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Message-ID: <928db740-b80d-02d5-5846-5d34ea709579@applied-asynchrony.com>
Date:   Tue, 10 Sep 2019 19:45:37 +0200
From:   Holger Hoffstätte <holger@...lied-asynchrony.com>
To:     Cong Wang <xiyou.wangcong@...il.com>
Cc:     Netdev <netdev@...r.kernel.org>
Subject: Re: Default qdisc not correctly initialized with custom MTU

On 9/10/19 6:56 PM, Cong Wang wrote:
> It is _not_ created when sysctl is configured, it is either created via tc
> command, or implicitly created by kernel when you bring up eth0.
> sysctl only tells kernel what to create by default, but never commits it.

Ok, thank you - that's good to know, because it means there is something
wrong with how my interface is initially brought up. And indeed I found
the problem: my startup scripts apparently bring up the interface twice -
once to "pre-start" (load/verify modules etc.) and then again after
applying mtu/route/etc. settings. Obviously without MTU bringing up the
interface will pull in the default qdisc in the interface's default config,
and that's what I saw after boot. Weird but what can I say.

Anyway, thanks for trying to help. :)

Holger