netdev - Re: [PATCH net 1/3] ipvlan: fix NETDEV_UP/NETDEV

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Message-ID: <Z_yy7WpZQWJiScJl@fedora>
Date: Mon, 14 Apr 2025 07:02:05 +0000
From: Hangbin Liu <liuhangbin@...il.com>
To: Sabrina Dubroca <sd@...asysnail.net>
Cc: netdev@...r.kernel.org, Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Simon Horman <horms@...nel.org>, Shuah Khan <shuah@...nel.org>,
	Xiao Liang <shaw.leon@...il.com>,
	Kuniyuki Iwashima <kuniyu@...zon.com>,
	Alexander Lobakin <aleksander.lobakin@...el.com>,
	Stanislav Fomichev <sdf@...ichev.me>,
	Venkat Venkatsubra <venkat.x.venkatsubra@...cle.com>,
	Etienne Champetier <champetier.etienne@...il.com>,
	Nikolay Aleksandrov <razor@...ckwall.org>,
	linux-kselftest@...r.kernel.org
Subject: Re: [PATCH net 1/3] ipvlan: fix NETDEV_UP/NETDEV_DOWN event handling

On Thu, Apr 03, 2025 at 05:00:14PM +0200, Sabrina Dubroca wrote:
> 2025-04-03, 13:09:02 +0000, Hangbin Liu wrote:
> > Hi Sabrina,
> > On Thu, Apr 03, 2025 at 12:28:54PM +0200, Sabrina Dubroca wrote:
> > > Hello Hangbin,
> > > 
> > > 2025-04-03, 08:58:55 +0000, Hangbin Liu wrote:
> > > > When setting the lower-layer link up/down, the ipvlan device synchronizes
> > > > its state via netif_stacked_transfer_operstate(), which only checks the
> > > > carrier state. However, setting the link down does not necessarily change
> > > > the carrier state for virtual interfaces like bonding. This causes the
> > > > ipvlan state to become out of sync with the lower-layer link state.
> > > > 
> > > > If the lower link and ipvlan are in the same namespace, this issue is
> > > > hidden because ip link show checks the link state in IFLA_LINK and has
> > > > a m_flag to control the state, displaying M-DOWN in the flags. However,
> > > > if the ipvlan and the lower link are in different namespaces, this
> > > > information is not available, and the ipvlan link state remains unchanged.
> > > 
> > > Is the issue with the actual behavior (sending/receiving packets,
> > > etc), or just in how it's displayed by iproute?
> > 
> > The upper link in netns up while lower link down will cause the traffic break
> > in the pod.
> 
> That seems like the correct behavior based on the actual (not
> displayed) state of the links.

Hmm, since this behavior is controversial, do you think if we should
drop this until some users request?

> 
> 
> I wonder if netif_stacked_transfer_operstate should consider the admin
> state of the lower device as well as link state:
> 
> @@ -10724,7 +10724,7 @@ void netif_stacked_transfer_operstate(const struct net_device *rootdev,
>  	else
>  		netif_testing_off(dev);
>  
> -	if (netif_carrier_ok(rootdev))
> +	if (netif_carrier_ok(rootdev) && rootdev->flags & IFF_UP)
>  		netif_carrier_on(dev);
>  	else
>  		netif_carrier_off(dev);
> 
> 
> but I haven't looked at all the consequences and possible side
> effects.

I'm not sure. Only sync link carrier seems reasonable too.

Thanks
Hangbin