They handle the link-local addresses in a reasonable way: uses MAC address when there's a random MAC address, otherwise a stable privacy address. They were previously screwing up MAC address randomization by always using stable link-local privacy addresses on newer Linux kernels.
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We were disabling that feature downstream but now we no longer need to disable it since they fixed it to be conditional. There are still other issues though. The Linux kernel happily reuses the global privacy address across networks. State isn't always properly flushed for it.
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It's worse to have privacy addresses enabled right now if you're using MAC randomization than not having them enabled. In theory, they help due to rotation but in practice there are serious issues with them. Some network management tools reset more state and handle it better.
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There are other issues aside from the addresses. It's frustrating digging deeper into it and realizing how screwed up this stuff is in the Linux kernel. Shouldn't need to reboot between connecting to each network to avoid reusing identifiers, 'keys', counters, etc. for things.
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Agree, and we don't intend to disable privacy addresses, but it's frustrating that a privacy feature is making things worse than not using the feature. Not much point using privacy addresses for link-local addresses though, so the new status quo for that upstream is good.
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If you want to avoid correlation, why do you use stable addresses in the first place? Why not RFC8981 addressess only?
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FWIW, we explicitly removed the requirement to configure stable addresses with that in mind ;-)
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Associated MAC randomization is enabled by default in Android. It uses a persistent per-network random MAC address. When MAC randomization is enabled, they use a link-local IP address based on the MAC address. They only use the stable privacy address feature when MAC rand is off.
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Do you really want/need a stable address on an Android phone?
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If you explicitly disable MAC randomization their assumption is that you do want a stable IP address. It's not at all normal to disable MAC randomization.
Their default mode is persistent per-network randomization based on a keyed hash of the SSID so that MAC doesn't change.
They have support for cycling it when the DHCP lease expires. The disabled MAC randomization mode is only for people doing something weird. Their MAC randomization mode already works around the silly approach of authenticating users / giving them resources based on MAC address.
Yep.. Windows does something similar, IIRC -- kind of RFC7217 for the mac layer :-)