linux-kernel - Re: [PATCH net-next v4] hv_netvsc: Mark VF as slave before exposing it to user-mode

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Date:   Wed, 8 Nov 2023 18:13:18 -0800
From:   Jakub Kicinski <kuba@...nel.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>,
        Paolo Abeni <pabeni@...hat.com>, linux-hyperv@...r.kernel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Long Li <longli@...rosoft.com>
Subject: Re: [PATCH net-next v4] hv_netvsc: Mark VF as slave before exposing
 it to user-mode

On Wed,  8 Nov 2023 14:56:52 -0800 longli@...uxonhyperv.com wrote:
> From: Long Li <longli@...rosoft.com>
> 
> When a VF is being exposed form the kernel, it should be marked as "slave"
> before exposing to the user-mode. The VF is not usable without netvsc running
> as master. The user-mode should never see a VF without the "slave" flag.
> 
> An example of a user-mode program depending on this flag is cloud-init
> (https://github.com/canonical/cloud-init/blob/19.3/cloudinit/net/__init__.py)

Quick grep for "flags", "priv" and "slave" doesn't show anything.
Can you point me to the line of code?

> When scanning interfaces, it checks on if this interface has a master to
> decide if it should be configured. There are other user-mode programs perform
> similar checks.
> 
> This commit moves the code of setting the slave flag to the time before VF is
> exposed to user-mode.

> Change since v3:
> Change target to net-next.

You don't consider this a fix? It seems like a race condition.

> -		if (ether_addr_equal(vf_netdev->perm_addr, ndev->perm_addr)) {
> -			netdev_notice(vf_netdev,
> -				      "falling back to mac addr based matching\n");
> +		if (ether_addr_equal(vf_netdev->perm_addr, ndev->perm_addr) ||
> +		    ether_addr_equal(vf_netdev->dev_addr, ndev->perm_addr))

This change doesn't seem to be described in the commit message.

Please note that we have a rule against reposting patches within 24h:

https://www.kernel.org/doc/html/next/process/maintainer-netdev.html#resending-after-review