From: Denis Kenzior <denkenz@gmail.com>
To: Johannes Berg <johannes@sipsolutions.net>,
James Prestwood <prestwoj@gmail.com>,
linux-wireless@vger.kernel.org
Subject: Re: [RFC 0/1] Allow MAC change on up interface
Date: Mon, 19 Aug 2019 15:58:16 -0500 [thread overview]
Message-ID: <1d975fec-a480-f40b-ff98-90d0e4852758@gmail.com> (raw)
In-Reply-To: <4848c3a9d0b330fab4442436244387a2c127fa03.camel@sipsolutions.net>
Hi Johannes,
> TBH, I'm not really sure I see any point in this to start with, many
> devices will give the address to the firmware when the interface is
> brought up (even iwlwifi does - I'm not sure we'd want to take your
> patch for iwlwifi even if that works today, nothing says the firmware
> might not change its mind on that), and so it's quite likely only going
> to be supported in few devices.
Hmm... I sense a pattern of you not seeing a point in doing many
things... Do you actually use the stuff you maintain?
>
> You've also not really explained what exactly is troubling you with
> changing the MAC address, you just mentioned some sort of "race
> condition"?
Well, one possible use case might be, oh something like this:
https://source.android.com/devices/tech/connect/wifi-mac-randomization
>
> Now, one thing I can imagine would be that you'd want to optimize
>
> * ifdown
> - remove iface from fw/hw
> - stop fw/hw
> * change MAC
> * ifup
> - start fw/hw
> - add iface to fw/hw
>
> to just
>
> * ifdown
> - remove iface from fw/hw
> * change MAC
> * ifup
> - add iface to fw/hw
>
That would be a part of it...
> i.e. not restart the firmware (which takes time) for all this, but that
> seems much easier to solve by e.g. having a combined operation for all
> of this that gets handled in mac80211, or more generally by having a
> "please keep the firmware running" token that you can hold while you do
> the operation?
And also maybe a bunch of other optimizations like not flushing scan
results?
>
> Your changes are also a bit strange - you modified the "connect" path
> and iwlwifi, but the connect path is not usually (other than with iw or
> even iwconfig) taken for iwlwifi? And if you modify auth/assoc paths,
> you get into even weirder problems - what if you use different addresses
> for auth and assoc? What if the assoc (or even connect) really was a
> *re*assoc, and thus must have the same MAC address? To me, the whole
> thing seems like more of a problem than a solution.
>
Okay, so there are some obstacles. But can you get over the whole
"Don't hold it like this" part and actually offer up something constructive?
Regards,
-Denis
next prev parent reply other threads:[~2019-08-19 20:58 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-15 18:57 [RFC 0/1] Allow MAC change on up interface James Prestwood
2019-08-15 18:57 ` [RFC 1/1] RFC: allow mac address change on up iface James Prestwood
2019-08-15 20:48 ` [RFC 0/1] Allow MAC change on up interface Jeff Johnson
2019-08-16 9:56 ` Toke Høiland-Jørgensen
2019-08-19 10:14 ` Johannes Berg
2019-08-19 15:55 ` James Prestwood
2019-08-19 20:20 ` Johannes Berg
2019-08-19 20:58 ` Denis Kenzior [this message]
2019-08-20 8:59 ` Johannes Berg
2019-08-20 15:40 ` Denis Kenzior
2019-08-20 17:53 ` Dan Williams
2019-08-20 18:21 ` Denis Kenzior
2019-08-20 18:54 ` Toke Høiland-Jørgensen
2019-08-20 19:32 ` Johannes Berg
2019-08-20 19:46 ` Denis Kenzior
2019-08-20 20:01 ` Johannes Berg
2019-08-19 21:14 ` James Prestwood
2019-08-20 6:59 ` Johannes Berg
2019-08-20 19:22 ` Denis Kenzior
2019-08-20 19:43 ` Johannes Berg
2019-08-20 19:58 ` Denis Kenzior
2019-08-20 20:15 ` Johannes Berg
2019-08-20 20:37 ` Denis Kenzior
2019-08-20 21:18 ` Dan Williams
2019-08-20 21:52 ` Denis Kenzior
2019-08-21 7:21 ` Johannes Berg
2019-08-20 19:53 ` James Prestwood
2019-08-20 20:06 ` Johannes Berg
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