Received-SPF: pass (google.com: best guess record for domain of linux-wireless-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Message-ID: <f7c98da178677cbb0cad3568f4ea4ab85171edd8.camel@sipsolutions.net>
Subject: Re: [RFCv2 1/4] nl80211: Fix broken non-split wiphy dumps
From:   Johannes Berg <johannes@sipsolutions.net>
To:     Denis Kenzior <denkenz@gmail.com>, linux-wireless@vger.kernel.org
Date:   Fri, 30 Aug 2019 11:03:51 +0200
In-Reply-To: <20190816192703.12445-1-denkenz@gmail.com> (sfid-20190816_212729_636741_39C4CEB6)
References: <20190816192703.12445-1-denkenz@gmail.com>
         (sfid-20190816_212729_636741_39C4CEB6)
Content-Type: text/plain; charset="UTF-8"
User-Agent: Evolution 3.30.5 (3.30.5-1.fc29) 
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Sender: linux-wireless-owner@vger.kernel.org
Precedence: bulk

On Fri, 2019-08-16 at 14:27 -0500, Denis Kenzior wrote:
> If a (legacy) client requested a wiphy dump but did not provide the
> NL80211_ATTR_SPLIT_WIPHY_DUMP attribute, the dump was supposed to be
> composed of purely non-split NEW_WIPHY messages, with 1 wiphy per
> message.  At least this was the intent after commit:
> 3713b4e364ef ("nl80211: allow splitting wiphy information in dumps")
> 
> However, in reality the non-split dumps were broken very shortly after.
> Perhaps around commit:
> fe1abafd942f ("nl80211: re-add channel width and extended capa advertising")

Fun. I guess we updated all userspace quickly enough to not actually
have any issues there. As far as I remember, nobody ever complained, so
I guess people just updated their userspace.

Given that it's been 6+ years, maybe we're better off just removing the
whole non-split thing then, instead of fixing it. Seems even less likely
now that somebody would run a 6+yo supplicant (from before its commit
c30a4ab045ce ("nl80211: Fix mode settings with split wiphy dump")).

OTOH, this is a simple fix, would removing the non-split mode result in
any appreciable cleanups? Perhaps not, and we'd have to insert something
instead to reject non-split and log a warning, or whatnot.

johannes