linux-kernel - Re: [PATCH 2/2] cfg80211: Use 5MHz bandwidth by default when checking usable channels

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <53A83DE1.4050106@openwrt.org>
Date:	Mon, 23 Jun 2014 16:46:57 +0200
From:	Felix Fietkau <nbd@...nwrt.org>
To:	Rostislav Lisovy <lisovy@...il.com>,
	Johannes Berg <johannes@...solutions.net>
CC:	"John W. Linville" <linville@...driver.com>,
	linux-wireless@...r.kernel.org, linux-kernel@...r.kernel.org,
	Michal Sojka <sojkam1@....cvut.cz>, s.sander@...dsys.de,
	jan-niklas.meier@...kswagen.de,
	Rostislav Lisovy <rostislav.lisovy@....cvut.cz>
Subject: Re: [PATCH 2/2] cfg80211: Use 5MHz bandwidth by default when checking
 usable channels

On 2014-06-23 16:38, Rostislav Lisovy wrote:
> On Mon, 2014-06-23 at 12:05 +0200, Johannes Berg wrote:
>> On Mon, 2014-06-23 at 12:04 +0200, Felix Fietkau wrote:
>> > On 2014-06-23 11:08, Johannes Berg wrote:
>> > > On Sun, 2014-06-22 at 13:41 +0200, Felix Fietkau wrote:
>> > >> On 2014-04-15 14:37, Rostislav Lisovy wrote:
>> > >> > Current code checks if the 20MHz bandwidth is allowed for
>> > >> > particular channel -- if it is not, the channel is disabled.
>> > >> > Since we need to use 5/10 MHz channels, this code is modified in
>> > >> > the way that the default bandwidth to check is 5MHz. If the
>> > >> > maximum bandwidth allowed by the channel is smaller than 5MHz,
>> > >> > the channel is disabled. Otherwise the channel is used and the
>> > >> > flags are set according to the bandwidth allowed by the channel.
>> > >> > 
>> > >> > Signed-off-by: Rostislav Lisovy <rostislav.lisovy@....cvut.cz>
>> > > 
>> > >> This change causes a regression and needs to be reverted or fixed.
>> > > 
>> > > Noted, I've reverted it in mac80211.git.
>> > > 
>> > >> It leaves Channel 12 enabled for US regdomain and does not prevent
>> > >> bringing up AP mode on it (IEEE80211_CHAN_NO_20MHZ does not get set).
>> > > 
>> > > I'm not sure this makes sense - CHAN_NO_20MHZ shouldn't get set on that
>> > > channel? It should be disabled for other reasons for AP mode - e.g.
>> > > NO_IR.
>> > I was thinking it could be valid in AP mode for 5 MHz operation.
>> 
>> Huh, ok, maybe. I guess Rostislav can look into the details :)
>> 
> 
> I am a bit confused right now. The regression is that the channel used
> to be completely disabled and now it is not? The regulatory restrictions
> prohibit the 20MHz BW for this channel but 5MHz BW is alright?
Correct. The matching rule is this:
        (2402 - 2472 @ 40), (N/A, 30), (N/A)

Channel 11 (2462 MHz) is allowed, because 2472 MHz is below the limit.
Channel 12 (2467 MHz) is not allowed, because 2477 MHz is too high.

With your change, Channel 12 was enabled and usable for AP mode.

- Felix
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/