From: Arend van Spriel <arend.vanspriel-dY08KVG/lbpWk0Htik3J/w@public•gmane.org>
To: "Rafał Miłecki" <rafal-g1n6cQUeyibVItvQsEIGlw@public•gmane.org>
Cc: "Rafał Miłecki" <zajec5-Re5JQEeQqe8AvxtiuMwx3w@public•gmane.org>,
"Kalle Valo" <kvalo-sgV2jX0FEOL9JmXXK+q4OQ@public•gmane.org>,
"Franky Lin" <franky.lin-dY08KVG/lbpWk0Htik3J/w@public•gmane.org>,
"Hante Meuleman"
<hante.meuleman-dY08KVG/lbpWk0Htik3J/w@public•gmane.org>,
"Chi-Hsien Lin"
<chi-hsien.lin-+wT8y+m8/X5BDgjK7y7TUQ@public•gmane.org>,
"Wright Feng"
<wright.feng-+wT8y+m8/X5BDgjK7y7TUQ@public•gmane.org>,
"Pieter-Paul Giesberts"
<pieter-paul.giesberts-dY08KVG/lbpWk0Htik3J/w@public•gmane.org>,
"James Hughes"
<james.hughes-FnsA7b+Nu9XbIbC87yuRow@public•gmane.org>,
linux-wireless-u79uwXL29TY76Z2rM5mHXA@public•gmane.org,
brcm80211-dev-list.pdl-dY08KVG/lbpWk0Htik3J/w@public•gmane.org,
brcm80211-dev-list-+wT8y+m8/X5BDgjK7y7TUQ@public•gmane.org,
netdev-u79uwXL29TY76Z2rM5mHXA@public•gmane.org,
"Linus Lüssing"
<linus.luessing-djzkFPsfvsizQB+pC5nmwQ@public•gmane.org>,
"Felix Fietkau" <nbd-Vt+b4OUoWG0@public•gmane.org>,
bridge-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public•gmane.org
Subject: Re: [PATCH] brcmfmac: drop Inter-Access Point Protocol packets by default
Date: Wed, 14 Mar 2018 21:44:21 +0100 [thread overview]
Message-ID: <5AA989A5.5060400@broadcom.com> (raw)
In-Reply-To: <ec7ef5fd9fb4193f92c0e0189cbe5e3e-g1n6cQUeyibVItvQsEIGlw@public.gmane.org>
On 3/14/2018 4:57 PM, Rafał Miłecki wrote:
> On 2018-03-14 16:39, Rafał Miłecki wrote:
>> On 2018-03-14 13:58, Arend van Spriel wrote:
>>> On 3/14/2018 12:01 PM, Rafał Miłecki wrote:
>>>> From: Rafał Miłecki <rafal-g1n6cQUeyibVItvQsEIGlw@public•gmane.org>
>>>>
>>>> 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. This is an 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 by a newly added
>>>> Kconfig option.
>>>
>>> Thanks for taking this approach. Looks fine except for .... (see below)
>>>
>>> Reviewed-by: Arend van Spriel <arend.vanspriel-dY08KVG/lbpWk0Htik3J/w@public•gmane.org>
>>>> Signed-off-by: Rafał Miłecki <rafal-g1n6cQUeyibVItvQsEIGlw@public•gmane.org>
>>>> ---
>>>> drivers/net/wireless/broadcom/brcm80211/Kconfig | 20 +++++++++++
>>>> .../wireless/broadcom/brcm80211/brcmfmac/core.c | 39
>>>> ++++++++++++++++++++++
>>>> 2 files changed, 59 insertions(+)
>>>>
>>>> diff --git a/drivers/net/wireless/broadcom/brcm80211/Kconfig
>>>> b/drivers/net/wireless/broadcom/brcm80211/Kconfig
>>>> index 9d99eb42d917..876787ef991a 100644
>>>> --- a/drivers/net/wireless/broadcom/brcm80211/Kconfig
>>>> +++ b/drivers/net/wireless/broadcom/brcm80211/Kconfig
>>>> @@ -68,6 +68,26 @@ config BRCMFMAC_PCIE
>>>> IEEE802.11ac embedded FullMAC WLAN driver. Say Y if you want to
>>>> use the driver for an PCIE wireless card.
>>>>
>>>> +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.
>>>
>>> I do not see any evidence that this would occur only for recent
>>> firmware. That stuff is old and not touched recently.
>>
>> My evidence is comparing firmwares for 4366b1: 10.10.69.3309 (r610991)
>> vs. 10.10 (TOB) (r663589).
>>
>> The first one is from linux-firmware.git and it doesn't implement IAPP
>> in the TX path. The later one is what I got from you privately and it
>> implements it.
>>
>> Also a firmware for 4366c0: 10.10.122.20 (r683106) which is relatively
>> new implements IAPP in the TX path.
>>
>>
>>>> diff --git a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/core.c
>>>> b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/core.c
>>>> index 19048526b4af..db6987015fb1 100644
>>>> --- a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/core.c
>>>> +++ b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/core.c
>>>
>>> [...]
>>>
>>>> static netdev_tx_t brcmf_netdev_start_xmit(struct sk_buff *skb,
>>>> struct net_device *ndev)
>>>> {
>>>> @@ -250,6 +278,12 @@ static netdev_tx_t
>>>> brcmf_netdev_start_xmit(struct sk_buff *skb,
>>>> goto done;
>>>> }
>>>>
>>>> + if (!IS_ENABLED(CONFIG_BRCMFMAC_IAPP) && brcmf_skb_is_iapp(skb)) {
>>>> + dev_kfree_skb(skb);
>>>> + ret = -EINVAL;
>>>> + goto done;
>>>> + }
>>>
>>> This is not right. The function must return netdev_tx_t type. Here is
>>> kerneldoc of .start_xmit():
>>>
>>> * netdev_tx_t (*ndo_start_xmit)(struct sk_buff *skb,
>>> * struct net_device *dev);
>>> * Called when a packet needs to be transmitted.
>>> * Returns NETDEV_TX_OK. Can return NETDEV_TX_BUSY, but you
>>> should stop
>>> * the queue before that can happen; it's for obsolete devices and
>>> weird
>>> * corner cases, but the stack really does a non-trivial amount
>>> * of useless work if you return NETDEV_TX_BUSY.
>>> * Required; cannot be NULL.
>>
>> Please take a closer look at how brcmf_netdev_start_xmit() works. Above
>> code *will* return netdev_tx_t.
>>
>>
>>> You may want to increase dropped netstat or add driver internal
>>> statistic counter so there is visibility of IAPP packets being
>>> dropped.
>>
>> OK, I'll try to find a stat to increase.
>
> So after checking brcmf_netdev_start_xmit() again, I realized I actually
> *do* that. Doing:
> ret = -EINVAL;
> goto done;
> results in increasing tx_dropped.
Okay, okay. Admittedly I only looked at the patch. Feel free to remove
the Reviewed-by.
Regards,
Arend
next prev parent reply other threads:[~2018-03-14 20:44 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-03-14 11:01 [PATCH] brcmfmac: drop Inter-Access Point Protocol packets by default Rafał Miłecki
[not found] ` <20180314110119.13631-1-zajec5-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2018-03-14 12:58 ` Arend van Spriel
[not found] ` <5AA91C67.90001-dY08KVG/lbpWk0Htik3J/w@public.gmane.org>
2018-03-14 15:39 ` Rafał Miłecki
[not found] ` <f145e568e9033db57a436ed3e2dad2c8-g1n6cQUeyibVItvQsEIGlw@public.gmane.org>
2018-03-14 15:40 ` Rafał Miłecki
2018-03-14 15:57 ` Rafał Miłecki
[not found] ` <ec7ef5fd9fb4193f92c0e0189cbe5e3e-g1n6cQUeyibVItvQsEIGlw@public.gmane.org>
2018-03-14 20:44 ` Arend van Spriel [this message]
2018-03-14 14:24 ` Kalle Valo
[not found] ` <878tau7n23.fsf-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>
2018-03-14 14:44 ` Arend van Spriel
[not found] ` <5AA93530.5040001-dY08KVG/lbpWk0Htik3J/w@public.gmane.org>
2018-03-14 15:08 ` Kalle Valo
[not found] ` <87o9jq66f3.fsf-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>
2018-03-14 15:27 ` Stephen Hemminger
2018-03-14 15:28 ` Rafał Miłecki
2018-03-14 15:44 ` Rafał Miłecki
[not found] ` <52b1812dd3e843adb63ff67fbe95975f-g1n6cQUeyibVItvQsEIGlw@public.gmane.org>
2018-03-14 16:10 ` Kalle Valo
[not found] ` <877eqe63kr.fsf-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>
2018-03-14 20:55 ` Arend van Spriel
[not found] ` <5AA98C3B.2070406-dY08KVG/lbpWk0Htik3J/w@public.gmane.org>
2018-03-15 9:23 ` Kalle Valo
2018-03-14 15:08 ` Stephen Hemminger
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