netdev - Re: [PATCH V2] brcmfmac: drop Inter-Access Point Protocol packets by default

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Message-ID: <CACna6ryQjhzXTbB0SBC_e_sJibhYyDjctOowhiVv_FMF6jEh3A@mail.gmail.com>
Date:   Thu, 15 Mar 2018 08:34:36 +0100
From:   Rafał Miłecki <zajec5@...il.com>
To:     Kalle Valo <kvalo@...eaurora.org>
Cc:     Arend van Spriel <arend.vanspriel@...adcom.com>,
        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" <linux-wireless@...r.kernel.org>,
        "open list:BROADCOM BRCM80211 IEEE802.11n WIRELESS DRIVER" 
        <brcm80211-dev-list.pdl@...adcom.com>,
        "open list:BROADCOM BRCM80211 IEEE802.11n WIRELESS DRIVER
        <brcm80211-dev-list.pdl@...adcom.com>," 
        <brcm80211-dev-list@...ress.com>,
        Network Development <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 V2] brcmfmac: drop Inter-Access Point Protocol packets by default

On 15 March 2018 at 08:29, Rafał Miłecki <zajec5@...il.com> wrote:
> From: Rafał Miłecki <rafal@...ecki.pl>
>
> Testing brcmfmac with more recent firmwares resulted in AP interfaces
> not working in some specific setups. Debugging resulted in discovering
> support for IAPP in Broadcom's firmwares.
>
> Older firmwares were only generating 802.11f frames. Newer ones like:
> 1) 10.10 (TOB) (r663589)
> 2) 10.10.122.20 (r683106)
> for 4366b1 and 4366c0 respectively seem to also /respect/ 802.11f frames
> in the Tx path by performing a STA disassociation.
>
> This obsoleted standard and its implementation is something that:
> 1) Most people don't need / want to use
> 2) Can allow local DoS attacks
> 3) Breaks AP interfaces in some specific bridge setups
>
> To solve issues it can cause this commit modifies brcmfmac to drop IAPP
> packets. If affects:
> 1) Rx path: driver won't be sending these unwanted packets up.
> 2) Tx path: driver will reject packets that would trigger STA
>    disassociation perfromed by a firmware (possible local DoS attack).
>
> It appears there are some Broadcom's clients/users who care about this
> feature despite the drawbacks. They can switch it on using a new module
> param.
>
> This change results in only two more comparisons (check for module param
> and check for Ethernet packet length) for 99.9% of packets. Its overhead
> should be very minimal.
>
> Signed-off-by: Rafał Miłecki <rafal@...ecki.pl>
> ---

I forgot to include the changelog, sorry.

V2: Use module param to don't /abuse/ Kconfig
    Slightly optimize brcmf_skb_is_iapp
    Move some description from Kconfig to the code
    Update commit description: specify affected fws & mention impact