netdev - Re: [PATCHv2 net-next 2/2] ipv4/fib: send notify when delete source address routes

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Date: Tue, 12 Sep 2023 10:30:11 +0800
From: Hangbin Liu <liuhangbin@...il.com>
To: Ido Schimmel <idosch@...sch.org>
Cc: netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Ido Schimmel <idosch@...dia.com>, David Ahern <dsahern@...nel.org>,
	Benjamin Poirier <bpoirier@...dia.com>,
	Thomas Haller <thaller@...hat.com>,
	Stephen Hemminger <stephen@...workplumber.org>,
	Eric Dumazet <edumazet@...gle.com>
Subject: Re: [PATCHv2 net-next 2/2] ipv4/fib: send notify when delete source
 address routes

Hi Ido,

Do you think if I should modify the patch description and re-post it?

Thanks
Hangbin
On Mon, Sep 11, 2023 at 11:35:05AM +0200, Thomas Haller wrote:
> On Mon, 2023-08-28 at 14:14 +0800, Hangbin Liu wrote:
> > > > 
> > > > In the other thread Thomas mentioned that NM already requests a
> > > > route
> > > > dump following address deletion [1]. If so, can Thomas or you
> > > > please
> > > > explain how this patch is going to help NM? Is the intention to
> > > > optimize
> > > > things and avoid the dump request (which can only work on new
> > > > kernels)?
> > > > 
> > > > [1]
> > > > https://lore.kernel.org/netdev/07fcfd504148b3c721fda716ad0a549662708407.camel@redhat.com/
> > > 
> > > In my understanding, After deleting an address, deal with the
> > > delete notify is
> > > more efficient to maintain the route cache than dump all the
> > > routes.
> 
> 
> Hi,
> 
> 
> NetworkManager does so out of necessity, as there is no notification.
> Overall, it seems a pretty bad thing to do, because it's expensive if
> you have many routes/addresses.
> 
> Unfortunately, it's hard to ever drop a workaround, because we never
> know when the workaround can be dropped.
> 
> Also, it's simply a notification missing, and not tied to
> NetworkManager or to maintaining a cache. If you run `ip route
> monitor`, you also don't see the notification that kernel drops a
> route? The effort that NetworkManager takes to maintain correct
> information is not something that most programs would do.
> 
> 
> Thomas
>