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

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Message-ID: <ZOw7VIMulJLyU0QL@Laptop-X1>
Date: Mon, 28 Aug 2023 14:14:44 +0800
From: Hangbin Liu <liuhangbin@...il.com>
To: Thomas Haller <thaller@...hat.com>
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>,
	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 Thomas,

Any comments?

Thanks
Hangbin
On Tue, Aug 15, 2023 at 08:55:35PM +0800, Hangbin Liu wrote:
> On Thu, Aug 10, 2023 at 06:08:28PM +0300, Ido Schimmel wrote:
> > On Wed, Aug 09, 2023 at 10:02:34PM +0800, Hangbin Liu wrote:
> > > After deleting an interface address in fib_del_ifaddr(), the function
> > > scans the fib_info list for stray entries and calls fib_flush() and
> > > fib_table_flush(). Then the stray entries will be deleted silently and no
> > > RTM_DELROUTE notification will be sent.
> > > 
> > > This lack of notification can make routing daemons like NetworkManager,
> > > miss the routing changes. e.g.
> > 
> > [...]
> > 
> > > To fix this issue, let's add a new bit in "struct fib_info" to track the
> > > deleted prefer source address routes, and only send notify for them.
> > 
> > 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 Thomas ,do you have any comments?
> 
> Thanks
> Hangbin