netdev - Re: [RFC PATCH net] net: ipv4/ipv6 addrconf: call igmp{,6}_group

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Message-ID: <20230410100958.4o3ub7yy7gxnzzpy@skbuf>
Date:   Mon, 10 Apr 2023 13:09:58 +0300
From:   Vladimir Oltean <vladimir.oltean@....com>
To:     Ido Schimmel <idosch@...dia.com>
Cc:     David Ahern <dsahern@...nel.org>, netdev@...r.kernel.org,
        Jakub Kicinski <kuba@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>
Subject: Re: [RFC PATCH net] net: ipv4/ipv6 addrconf: call
 igmp{,6}_group_dropped() while dev is still up

Hi Ido,

On Mon, Apr 10, 2023 at 10:55:02AM +0300, Ido Schimmel wrote:
> > > The proposal is to respond to that slightly earlier notifier with the
> > > IGMP address deletion, so that the ndo_set_rx_mode() of the device does
> > > actually get called. I am not familiar with the details of these layers,
> > > but it appeared to me that NETDEV_DOWN needed to be replaced everywhere
> > > with NETDEV_GOING_DOWN, so I blindly did that and it worked.
> 
> I think there is a confusion here between the netdev notifier and
> inetaddr notifiers. They all use "NETDEV_DOWN", but in the inetaddr
> notifiers it means that an address is being deleted. Changing the event
> to "NETDEV_GOING_DOWN" is going to break a lot of users since none of
> the inetaddr listeners respond to "NETDEV_GOING_DOWN".
> 
> IOW, I believe you only need this change for IPv4 (and similarly for
> IPv6):
> 
> diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
> index 5deac0517ef7..679c9819f25b 100644
> --- a/net/ipv4/devinet.c
> +++ b/net/ipv4/devinet.c
> @@ -1588,7 +1588,7 @@ static int inetdev_event(struct notifier_block *this, unsigned long event,
>  		/* Send gratuitous ARP to notify of link change */
>  		inetdev_send_gratuitous_arp(dev, in_dev);
>  		break;
> -	case NETDEV_DOWN:
> +	case NETDEV_GOING_DOWN:
>  		ip_mc_down(in_dev);
>  		break;
>  	case NETDEV_PRE_TYPE_CHANGE:

You are correct, only that portion is needed for IPv4. When I open my
eyes, I see it too :)

Although it would have been a lot less confusing for someone looking at
the code for the first time if the inetaddr and inet6addr notifiers did
not use events from the same NETDEV_ namespace as the netdev notifiers...

So, how do you think I should proceed with this? One patch or two
(for IPv4 and IPv6)? Is the Fixes: tag ok?