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[70.114.247.242]) by smtp.googlemail.com with ESMTPSA id t18sm2067030otk.73.2019.08.30.09.32.57 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 30 Aug 2019 09:32:58 -0700 (PDT) Subject: Re: [RFCv2 1/4] nl80211: Fix broken non-split wiphy dumps To: Johannes Berg , linux-wireless@vger.kernel.org References: <20190816192703.12445-1-denkenz@gmail.com> From: Denis Kenzior Message-ID: <5fc07547-80fe-99ee-a83d-5fabe3c92a1b@gmail.com> Date: Fri, 30 Aug 2019 11:32:57 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-wireless-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-wireless@vger.kernel.org Hi Johannes, On 8/30/19 4:03 AM, Johannes Berg wrote: > 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")). > That would be my vote, given that we're probably one of a handful of people in this world that understand that code path. But... How would we handle non-dump versions of GET_WIPHY? To this day I have dhcpcd issuing fun stuff like: < Request: Get Wiphy (0x01) len 8 [ack] 0.374832 Interface Index: 59 (0x0000003b) > 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. > Getting rid of the legacy non-split case would simplify things. We could also be a-lot smarter about how we split up the messages in order to utilize buffer space more efficiently. I think you cover this in your other replies, but I haven't processed those yet. Regards, -Denis