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

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Date: Thu, 4 May 2023 21:10:43 -0600
From: David Ahern <dsahern@...nel.org>
To: Stephen Hemminger <stephen@...workplumber.org>
Cc: Aleksey Shumnik <ashumnik9@...il.com>, 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 03, 2023 at 11:35:28AM -0700, Stephen Hemminger 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. The route cache has been completely removed from
> the kernel for a long time.

These are exceptions (fib_nh_exception), not the legacy routing cache.