netdev - Re: [PATCH v2] net: core: SIOCADDMULTI/SIOCDELMULTI distinguish between uc and mc

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Date:   Mon, 17 Aug 2020 15:08:03 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     dzagorui@...co.com
Cc:     kuba@...nel.org, netdev@...r.kernel.org,
        "ikhoronz@...co.com--cc=xe-linux-external"@cisco.com,
        xiyou.wangcong@...il.com, ap420073@...il.com,
        richardcochran@...il.com, f.fainelli@...il.com, andrew@...n.ch,
        mkubecek@...e.cz, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] net: core: SIOCADDMULTI/SIOCDELMULTI distinguish
 between uc and mc

From: Denys Zagorui <dzagorui@...co.com>
Date: Mon, 17 Aug 2020 10:52:24 -0700

> SIOCADDMULTI API allows adding multicast/unicast mac addresses but
> doesn't deferentiate them so if someone tries to add secondary
> unicast mac addr it will be added to multicast netdev list which is
> confusing. There is at least one user that allows adding secondary
> unicast through this API.
> (2f41f3358672 i40e/i40evf: fix unicast mac address add)

This doesn't seem appropriate at all.  If anything UC addresses
should be blocked and the Intel driver change reverted.  We have
a well defined way to add secondary UC addresses and the MC interfaces
are not it.

Furthermore, even if this was appropriate, "fixing" this only for
ethernet is definitely not appropriate.  The fix would need to be able
to handle any address type.  Having a generic interface work
inconsistently for one link type vs. another is a non-starter.

Thanks.