From: Denis Kenzior <denkenz@gmail.com>
To: Johannes Berg <johannes@sipsolutions.net>,
James Prestwood <prestwoj@gmail.com>,
linux-wireless@vger.kernel.org
Subject: Re: [PATCH 2/2] mac80211: Support LIVE_ADDRESS_CHANGE feature
Date: Tue, 8 Oct 2019 10:37:58 -0500 [thread overview]
Message-ID: <6fa34e4c-5c81-4875-da29-cada1a078e2c@gmail.com> (raw)
In-Reply-To: <f468a8d573ddf401d2084b76eb625fef5950f265.camel@sipsolutions.net>
Hi Johannes,
On 10/7/19 4:16 PM, Johannes Berg wrote:
> Hi,
>
>>>> If you do care about this being more granular then you should check
>>>> *which* interface is scanning, and then you can still switch the
>>>> MAC
>>>> address for *other* interfaces - but I'd still argue it should be
>>>> independent of interface type.
>>
>> So yes these can scan, but this should be covered by the
>> netif_carrier_ok check which is done first.
>
> Not sure what you mean by that.
>
> You could have two interfaces, one which is scanning right now, right?
> And then theoretically you don't care about the other one - it *should*
> be OK to remove/re-add (with new MAC address) the one that *isn't*
> scanning, right?
Actually, I don't think you can? Unless I'm missing something? All the
scan state is stored on struct ieee80211_local, so if that struct is
allocated per phy as you point out below, then what you suggest is
currently not possible?
>
> But we don't have that granularity here for anything - you're just
> checking "sdata->local->something", and by going from sdata to local
> you've now checked the whole NIC, not just a single interface on that
> NIC.
Right. But that seems to be a limitation of mac80211 actually. We
can't run two scans concurrently on different interfaces. This is
rather unintuitive given that scan requests require an ifindex/wdev.
Can this be changed / fixed in mac80211 actually? I would expect that
if a card supports p2p and station simultaneously, then it can scan / go
offchannel on two interfaces simultaneously? Or not? What can iwlwifi
do for example?
>
> Which is fine, no complaint from me, just in that case you end up
> failing when really there isn't much need to fail. In fact, in a case
> like this, actually clearing IFF_UP, changing address and setting IFF_UP
> would work, concurrently with another interface scanning.
>
>> We can just remove the
>> switch entirely, but the roc_list/scanning check only matters for
>> station/p2p_client so checking for the other interface types is kinda
>> pointless and redundant.
>
> But it's also completely confusing to do it this way because you go from
> "sdata" to "local", and at that point the data that you're working on is
> no longer specific to that one interface, it's actually for the whole
> NIC.
I agree its confusing, but that seems to be how mac80211 works?
>
> Basically what I'm saying is this: it's confusing and makes no sense to
> do something like
>
> if (this_is_a_certain_netdev_type)
> check_some_global_data();
>
>> Also I am not sure what you mean by *which* interface. This function is
>> called on a single interface, so checking what other interfaces are
>> doing seems strange...
>
> My point exactly - but that's what you're doing here in the code. Now I
> think perhaps without even realizing?
>
Given the above, I'm not sure I see anything wrong? The switch/case can
probably be gotten rid of, but it actually makes things clear that only
station/p2p_device and adhoc are handled specially.
Regards,
-Denis
next prev parent reply other threads:[~2019-10-08 15:47 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-13 19:59 [PATCH 1/2] nl80211: Add LIVE_ADDR_CHANGE feature James Prestwood
2019-09-13 19:59 ` [PATCH 2/2] mac80211: Support LIVE_ADDRESS_CHANGE feature James Prestwood
2019-10-04 11:56 ` Johannes Berg
2019-10-04 16:25 ` James Prestwood
2019-10-04 16:42 ` James Prestwood
2019-10-07 21:16 ` Johannes Berg
2019-10-08 15:37 ` Denis Kenzior [this message]
2019-10-08 15:52 ` Johannes Berg
2019-10-08 15:53 ` Denis Kenzior
2019-10-08 16:24 ` Johannes Berg
2019-10-08 16:23 ` Denis Kenzior
2019-10-08 17:08 ` Johannes Berg
2019-10-08 18:50 ` Denis Kenzior
2019-10-08 20:16 ` Johannes Berg
2019-10-08 20:55 ` Denis Kenzior
2019-10-10 15:18 ` Johannes Berg
2019-10-07 21:11 ` Johannes Berg
2019-10-08 15:28 ` Denis Kenzior
2019-10-08 15:49 ` Johannes Berg
2019-09-13 20:48 ` [PATCH 1/2] nl80211: Add LIVE_ADDR_CHANGE feature Johannes Berg
2019-09-13 20:56 ` James Prestwood
2019-09-13 21:01 ` Johannes Berg
2019-09-13 21:14 ` James Prestwood
2019-09-17 20:09 ` James Prestwood
2019-10-01 9:14 ` Johannes Berg
2019-10-08 22:13 ` James Prestwood
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