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To:     brambonne@google.com
Cc:     kuznet@ms2.inr.ac.ru, yoshfuji@linux-ipv6.org, kuba@kernel.org,
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Subject: Re: [RFC PATCH] ipv6: Use dev_addr in stable-privacy address
 generation
From:   David Miller <davem@davemloft.net>
In-Reply-To: <20200326094252.157914-1-brambonne@google.com>
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From: "Bram Bonné" <brambonne@google.com>
Date: Thu, 26 Mar 2020 10:42:52 +0100

> This patch extends the IN6_ADDR_GEN_MODE_STABLE_PRIVACY address
> generation mode to use the software-defined MAC address (dev_addr)
> rather than the permanent, hardware-defined MAC address (perm_addr) of
> the interface when generating IPv6 link-local addresses.
> 
> This ensures that the IPv6 link-local address changes in line with the
> MAC address when per-network MAC address randomization is used,
> providing the expected privacy guarantees.
> 
> When no MAC address randomization is used, dev_addr corresponds to
> perm_addr, and IN6_ADDR_GEN_MODE_STABLE_PRIVACY behaves as before.
> 
> When MAC address randomization is used, this makes the MAC address
> fulfill the role of both the Net_Iface and the (optional) Network_ID
> parameters in RFC7217.
> 
> Cc: Lorenzo Colitti <lorenzo@google.com>
> Cc: Jeffrey Vanderstoep <jeffv@google.com>
> Signed-off-by: Bram Bonné <brambonne@google.com>

I think the current behavior is intentional in that it's supposed to use
something that is unchanging even across arbitrary administrator changes
to the in-use MAC address.