netdev - Re: [BUG] Dependence of routing cache entries on the ignore-df flag

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Message-ID: <CAJGXZLgC-D9owgVdkE2nybEvLme_VsVGMdb6dKuGK0a2+5Vq+A@mail.gmail.com>
Date: Thu, 4 May 2023 02:39:29 +0300
From: Aleksey Shumnik <ashumnik9@...il.com>
To: stephen@...workplumber.org
Cc: netdev@...r.kernel.org, waltje@...lt.nl.mugnet.org, 
	Jakub Kicinski <kuba@...nel.org>, gw4pts@...pts.ampr.org, kuznet@....inr.ac.ru, 
	"willemdebruijn.kernel@...il.com" <willemdebruijn.kernel@...il.com>, gnault@...hat.com
Subject: Re: [BUG] Dependence of routing cache entries on the ignore-df flag

On Wed, May 3, 2023 at 9:35 PM Stephen Hemminger
<stephen@...workplumber.org> wrote:
>
> On Wed, 3 May 2023 18:01:03 +0300
> Aleksey Shumnik <ashumnik9@...il.com> wrote:
>
> > Might you answer the questions:
> > 1. How the ignore-df flag and adding entries to the routing cache is
> > connected? In which kernel files may I look to find this connection?
> > 2. Is this behavior wrong?
> > 3. Is there any way to completely disable the use of the routing
> > cache? (as far as I understand, it used to be possible to set the
> > rhash_entries parameter to 0, but now there is no such parameter)
> > 4. Why is an entry added to the routing cache if a suitable entry was
> > eventually found in the arp table (it is added directly, without being
> > temporarily added to the routing table)?
>
> What kernel version.

Sorry, I didn't specify the kernel version.
I'm using kernel version 6.1.15

> The route cache has been completely removed from the kernel for a long time.

Yes, I even found a commit in which this was done
89aef8921bfbac22f00e04f8450f6e447db13e42.
This is my question, it is strange that the routing cache is still
used in version 6 of the kernel. In my first letter I wrote how to
reproduce such behavior, which seems to be erroneous.
I also ask you to pay attention to the fact that this error is
reproduced if the ignore-df flag is set on the interface.