Subject: Re: [PATCH] brcmfmac: drop Inter-Access Point Protocol packets by
 default
To: Kalle Valo <kvalo@codeaurora.org>,
        =?UTF-8?B?UmFmYcWCIE1pxYJlY2tp?= <zajec5@gmail.com>
References: <20180314110119.13631-1-zajec5@gmail.com>
 <878tau7n23.fsf@codeaurora.org>
Cc: Franky Lin <franky.lin@broadcom.com>,
        Hante Meuleman <hante.meuleman@broadcom.com>,
        Chi-Hsien Lin <chi-hsien.lin@cypress.com>,
        Wright Feng <wright.feng@cypress.com>,
        Pieter-Paul Giesberts <pieter-paul.giesberts@broadcom.com>,
        James Hughes <james.hughes@raspberrypi.org>,
        linux-wireless@vger.kernel.org,
        brcm80211-dev-list.pdl@broadcom.com,
        brcm80211-dev-list@cypress.com, netdev@vger.kernel.org,
        =?UTF-8?Q?Linus_L=c3=bcssing?= <linus.luessing@c0d3.blue>,
        Felix Fietkau <nbd@nbd.name>,
        bridge@lists.linux-foundation.org,
        =?UTF-8?B?UmFmYcWCIE1pxYJlY2tp?= <rafal@milecki.pl>
From: Arend van Spriel <arend.vanspriel@broadcom.com>
Message-ID: <5AA93530.5040001@broadcom.com> (sfid-20180314_154417_255811_7A0ABC59)
Date: Wed, 14 Mar 2018 15:44:00 +0100
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In-Reply-To: <878tau7n23.fsf@codeaurora.org>
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Sender: linux-wireless-owner@vger.kernel.org

On 3/14/2018 3:24 PM, Kalle Valo wrote:
>> +config BRCMFMAC_IAPP
>> >+	bool "Partial support for obsoleted Inter-Access Point Protocol"
>> >+	depends on BRCMFMAC
>> >+	---help---
>> >+	  Most of Broadcom's firmwares can send 802.11f ADD frame every
>> >+	  time new STA connects to the AP interface. Some recent ones
>> >+	  can also disassociate STA when they receive such a frame.
>> >+
>> >+	  It's important to understand this behavior can lead to a local
>> >+	  DoS security issue. Attacker may trigger disassociation of any
>> >+	  STA by sending a proper Ethernet frame to the wireless
>> >+	  interface.
>> >+
>> >+	  Moreover this feature may break AP interfaces in some specific
>> >+	  setups. This applies e.g. to the bridge with hairpin mode
>> >+	  enabled and IFLA_BRPORT_MCAST_TO_UCAST set. IAPP packet
>> >+	  generated by a firmware will get passed back to the wireless
>> >+	  interface and cause immediate disassociation of just-connected
>> >+	  STA.
> Sorry for jumping late, but does it really make sense to have a Kconfig
> option for this? I don't think we should add a Kconfig option for every
> strange feature, there should be stronger reasons (size savings etc)
> before adding a Kconfig option.
>
> And in this case the size savings can't be much. Wouldn't a module
> parameter be simpler for a functionality change like this?

Hi Kalle,

Good to be wary about Kconfig option. So my reason for asking a Kconfig 
option is that this is directly in the datapaths (tx and rx) so I prefer 
to disable/enable it compile time rather then runtime.

Regards,
Arend