netdev - Re: [PATCH] hv_netvsc: Mark VF as slave before exposing it to user-mode

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Date: Thu, 26 Oct 2023 09:48:41 -0700
From: Stephen Hemminger <stephen@...workplumber.org>
To: longli@...uxonhyperv.com
Cc: "K. Y. Srinivasan" <kys@...rosoft.com>, Haiyang Zhang
 <haiyangz@...rosoft.com>, Wei Liu <wei.liu@...nel.org>, Dexuan Cui
 <decui@...rosoft.com>, "David S. Miller" <davem@...emloft.net>, Eric
 Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo
 Abeni <pabeni@...hat.com>, linux-hyperv@...r.kernel.org,
 netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-rdma@...r.kernel.org, Long Li <longli@...rosoft.com>
Subject: Re: [PATCH] hv_netvsc: Mark VF as slave before exposing it to
 user-mode

On Wed, 25 Oct 2023 15:50:50 -0700
longli@...uxonhyperv.com wrote:

> @@ -2347,6 +2342,12 @@ static int netvsc_register_vf(struct net_device *vf_netdev)
>  	if (!ndev)
>  		return NOTIFY_DONE;
>  
> +	if (event == NETDEV_POST_INIT) {
> +		/* set slave flag before open to prevent IPv6 addrconf */
> +		vf_netdev->flags |= IFF_SLAVE;
> +		return NOTIFY_DONE;
> +	}
> +
>  	net_device_ctx = netdev_priv(ndev);
>  	netvsc_dev = rtnl_dereference(net_device_ctx->nvdev);
>  	if (!netvsc_dev || rtnl_dereference(net_device_ctx->vf_netdev))
> @@ -2753,8 +2754,9 @@ static int netvsc_netdev_event(struct notifier_block *this,
>  		return NOTIFY_DONE;
>  
>  	switch (event) {
> +	case NETDEV_POST_INIT:
>  	case NETDEV_REGISTER:
> -		return netvsc_register_vf(event_dev);
> +		return netvsc_register_vf(event_dev, event);

Although correct, this is an awkward way to write this.
There are two events which call register_vf() but the post init
one short circuits and doesn't really register the VF.

The code is clearer if flag is set in switch statement.

@@ -2206,9 +2206,6 @@ static int netvsc_vf_join(struct net_device *vf_netdev,
 		goto upper_link_failed;
 	}

-	/* set slave flag before open to prevent IPv6 addrconf */
-	vf_netdev->flags |= IFF_SLAVE;
-
 	schedule_delayed_work(&ndev_ctx->vf_takeover, VF_TAKEOVER_INT);

 	call_netdevice_notifiers(NETDEV_JOIN, vf_netdev);
@@ -2753,6 +2750,10 @@ static int netvsc_netdev_event(struct notifier_block *this,
 		return NOTIFY_DONE;

 	switch (event) {
+	case NETDEV_POST_INIT:
+		/* set slave flag before open to prevent IPv6 addrconf */
+		vf_netdev->flags |= IFF_SLAVE;
+		return NOTIFY_DONE;
 	case NETDEV_REGISTER:
 		return netvsc_register_vf(event_dev);
 	case NETDEV_UNREGISTER: