netdev - Re: [PATCH] brcmfmac: drop Inter-Access Point Protocol packets by default

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Message-ID: <5AA93530.5040001@broadcom.com>
Date:   Wed, 14 Mar 2018 15:44:00 +0100
From:   Arend van Spriel <arend.vanspriel@...adcom.com>
To:     Kalle Valo <kvalo@...eaurora.org>,
        Rafał Miłecki <zajec5@...il.com>
Cc:     Franky Lin <franky.lin@...adcom.com>,
        Hante Meuleman <hante.meuleman@...adcom.com>,
        Chi-Hsien Lin <chi-hsien.lin@...ress.com>,
        Wright Feng <wright.feng@...ress.com>,
        Pieter-Paul Giesberts <pieter-paul.giesberts@...adcom.com>,
        James Hughes <james.hughes@...pberrypi.org>,
        linux-wireless@...r.kernel.org,
        brcm80211-dev-list.pdl@...adcom.com,
        brcm80211-dev-list@...ress.com, netdev@...r.kernel.org,
        Linus Lüssing <linus.luessing@...3.blue>,
        Felix Fietkau <nbd@....name>,
        bridge@...ts.linux-foundation.org,
        Rafał Miłecki <rafal@...ecki.pl>
Subject: Re: [PATCH] brcmfmac: drop Inter-Access Point Protocol packets by
 default

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