iwlwifi 6235 AGN: hardware limitation on number of stations that can connect in ap mode ?

iwlwifi 6235 AGN: hardware limitation on number of stations that can connect in ap mode ?

[Sander Eikelenboom]

Hi Johannes,

I'm trying to use an Intel Corporation Centrino Advanced-N 6235 (rev 24) with 
openwrt and hostapd to provide router functionality.
That all works fine, except that it at max accepts 12 wireless clients.
I have tried a few kernels (including 3.18-rc7) and versions of openwrt 
(including trunk) already, but all to no avail.

So i'm wondering is there a hardware limitation of stations that can connect to 
this mini-pci card in ap-mode ?

[   10.621530] iwlwifi 0000:00:05.0: loaded firmware version 18.168.6.1 op_mode iwldvm
[   10.621546] iwlwifi 0000:00:05.0: CONFIG_IWLWIFI_DEBUG enabled
[   10.621548] iwlwifi 0000:00:05.0: CONFIG_IWLWIFI_DEBUGFS enabled
[   10.621549] iwlwifi 0000:00:05.0: CONFIG_IWLWIFI_DEVICE_TRACING disabled
[   10.621550] iwlwifi 0000:00:05.0: Detected Intel(R) Centrino(R) Advanced-N 6235 AGN, REV=0xB0
[   10.621976] iwlwifi 0000:00:05.0: L1 Disabled - LTR Disabled
[   10.640696] cfg80211: Ignoring regulatory request set by core since the driver uses its own custom regulatory domain
[   10.640832] ieee80211 phy0: Selected rate control algorithm 'iwl-agn-rs'
...
[   10.654858] lib80211: common routines for IEEE802.11 drivers
[   10.654859] lib80211_crypt: registered algorithm 'NULL'
[   10.654864] lib80211_crypt: registered algorithm 'WEP'
[   10.654866] lib80211_crypt: registered algorithm 'CCMP'
[   10.654869] lib80211_crypt: registered algorithm 'TKIP'
..
[   31.016196] cfg80211: Calling CRDA to update world regulatory domain
[   32.253288] iwlwifi 0000:00:05.0: L1 Disabled - LTR Disabled
[   32.364036] iwlwifi 0000:00:05.0: Radio type=0x2-0x1-0x0
[   33.008507] iwlwifi 0000:00:05.0: L1 Disabled - LTR Disabled
[   33.116331] iwlwifi 0000:00:05.0: Radio type=0x2-0x1-0x0


the first clients connect perfectly well but after 12 client have connected, for 
the 13th i get:

[  784.301106] wlan0: Allocated STA 00:0d:f0:2e:ee:02
[  784.301117] wlan0: moving STA 00:0d:f0:2e:ee:02 to state 2
[  784.301122] wlan0: moving STA 00:0d:f0:2e:ee:02 to state 3
[  784.301141] iwlwifi 0000:00:05.0: Unable to prepare station 00:0d:f0:2e:ee:02 for addition
[  784.481399] iwlwifi 0000:00:05.0: Unable to add station 00:0d:f0:2e:ee:02 (-22)
[  784.647835] wlan0: Destroyed STA 00:0d:f0:2e:ee:02
[  785.828588] wlan0: Allocated STA 00:0d:f0:2e:ee:02
[  785.828600] wlan0: moving STA 00:0d:f0:2e:ee:02 to state 2
[  785.828605] wlan0: moving STA 00:0d:f0:2e:ee:02 to state 3
[  785.828624] iwlwifi 0000:00:05.0: Unable to prepare station 00:0d:f0:2e:ee:02 for addition
[  786.044379] iwlwifi 0000:00:05.0: Unable to add station 00:0d:f0:2e:ee:02 (-22)
[  786.219632] wlan0: Destroyed STA 00:0d:f0:2e:ee:02

The firmware seems to be the latest available for download.

If this isn't a hardware limitation, could you give a pointer to the debug 
values to use so i can get the debug output you would be interested in ?

If it is a hardware limitation, are there any other intel mini-pci adapters that 
don't have this hardware limitation (or at least a highter one).

--
Sander


lspci:

00:05.0 Network controller: Intel Corporation Centrino Advanced-N 6235 (rev 24)
        Subsystem: Intel Corporation Centrino Advanced-N 6235 AGN
        Physical Slot: 5
        Flags: bus master, fast devsel, latency 0, IRQ 70
        Memory at f3090000 (64-bit, non-prefetchable) [size=8K]
        Capabilities: [c8] Power Management version 3
        Capabilities: [d0] MSI: Enable+ Count=1/1 Maskable- 64bit+
        Capabilities: [e0] Express Endpoint, MSI 00
        Kernel driver in use: iwlwifi

Re: iwlwifi 6235 AGN: hardware limitation on number of stations that can connect in ap mode ?

[Dan Williams]

On Fri, 2014-12-05 at 10:55 +0100, Sander Eikelenboom wrote:
> Hi Johannes,
> 
> I'm trying to use an Intel Corporation Centrino Advanced-N 6235 (rev 24) with 
> openwrt and hostapd to provide router functionality.
> That all works fine, except that it at max accepts 12 wireless clients.
> I have tried a few kernels (including 3.18-rc7) and versions of openwrt 
> (including trunk) already, but all to no avail.
> 
> So i'm wondering is there a hardware limitation of stations that can connect to 
> this mini-pci card in ap-mode ?
> 
> [   10.621530] iwlwifi 0000:00:05.0: loaded firmware version 18.168.6.1 op_mode iwldvm
> [   10.621546] iwlwifi 0000:00:05.0: CONFIG_IWLWIFI_DEBUG enabled
> [   10.621548] iwlwifi 0000:00:05.0: CONFIG_IWLWIFI_DEBUGFS enabled
> [   10.621549] iwlwifi 0000:00:05.0: CONFIG_IWLWIFI_DEVICE_TRACING disabled
> [   10.621550] iwlwifi 0000:00:05.0: Detected Intel(R) Centrino(R) Advanced-N 6235 AGN, REV=0xB0
> [   10.621976] iwlwifi 0000:00:05.0: L1 Disabled - LTR Disabled
> [   10.640696] cfg80211: Ignoring regulatory request set by core since the driver uses its own custom regulatory domain
> [   10.640832] ieee80211 phy0: Selected rate control algorithm 'iwl-agn-rs'
> ...
> [   10.654858] lib80211: common routines for IEEE802.11 drivers
> [   10.654859] lib80211_crypt: registered algorithm 'NULL'
> [   10.654864] lib80211_crypt: registered algorithm 'WEP'
> [   10.654866] lib80211_crypt: registered algorithm 'CCMP'
> [   10.654869] lib80211_crypt: registered algorithm 'TKIP'
> ..
> [   31.016196] cfg80211: Calling CRDA to update world regulatory domain
> [   32.253288] iwlwifi 0000:00:05.0: L1 Disabled - LTR Disabled
> [   32.364036] iwlwifi 0000:00:05.0: Radio type=0x2-0x1-0x0
> [   33.008507] iwlwifi 0000:00:05.0: L1 Disabled - LTR Disabled
> [   33.116331] iwlwifi 0000:00:05.0: Radio type=0x2-0x1-0x0
> 
> 
> the first clients connect perfectly well but after 12 client have connected, for 
> the 13th i get:
> 
> [  784.301106] wlan0: Allocated STA 00:0d:f0:2e:ee:02
> [  784.301117] wlan0: moving STA 00:0d:f0:2e:ee:02 to state 2
> [  784.301122] wlan0: moving STA 00:0d:f0:2e:ee:02 to state 3
> [  784.301141] iwlwifi 0000:00:05.0: Unable to prepare station 00:0d:f0:2e:ee:02 for addition
> [  784.481399] iwlwifi 0000:00:05.0: Unable to add station 00:0d:f0:2e:ee:02 (-22)
> [  784.647835] wlan0: Destroyed STA 00:0d:f0:2e:ee:02
> [  785.828588] wlan0: Allocated STA 00:0d:f0:2e:ee:02
> [  785.828600] wlan0: moving STA 00:0d:f0:2e:ee:02 to state 2
> [  785.828605] wlan0: moving STA 00:0d:f0:2e:ee:02 to state 3
> [  785.828624] iwlwifi 0000:00:05.0: Unable to prepare station 00:0d:f0:2e:ee:02 for addition
> [  786.044379] iwlwifi 0000:00:05.0: Unable to add station 00:0d:f0:2e:ee:02 (-22)
> [  786.219632] wlan0: Destroyed STA 00:0d:f0:2e:ee:02
> 
> The firmware seems to be the latest available for download.
> 
> If this isn't a hardware limitation, could you give a pointer to the debug 
> values to use so i can get the debug output you would be interested in ?

You might be running into:

dvm/commands.h:#define  IWLAGN_STATION_COUNT    16

I think a couple of those slots are used for book-keeping stuff, which
might be why you run out of them at 12.  Johannes or Emmanuel would know
more though.

Dan

> If it is a hardware limitation, are there any other intel mini-pci adapters that 
> don't have this hardware limitation (or at least a highter one).
> 
> --
> Sander
> 
> 
> lspci:
> 
> 00:05.0 Network controller: Intel Corporation Centrino Advanced-N 6235 (rev 24)
>         Subsystem: Intel Corporation Centrino Advanced-N 6235 AGN
>         Physical Slot: 5
>         Flags: bus master, fast devsel, latency 0, IRQ 70
>         Memory at f3090000 (64-bit, non-prefetchable) [size=8K]
>         Capabilities: [c8] Power Management version 3
>         Capabilities: [d0] MSI: Enable+ Count=1/1 Maskable- 64bit+
>         Capabilities: [e0] Express Endpoint, MSI 00
>         Kernel driver in use: iwlwifi
> 
> 
> --
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Re: iwlwifi 6235 AGN: hardware limitation on number of stations that can connect in ap mode ?

[Johannes Berg]

Hi Sander,

> So i'm wondering is there a hardware limitation of stations that can connect to 
> this mini-pci card in ap-mode ?

Yes, there's a hardware/firmware limitation of 16 "station entries".

> the first clients connect perfectly well but after 12 client have connected, for 
> the 13th i get:
> 
> [  784.301106] wlan0: Allocated STA 00:0d:f0:2e:ee:02
> [  784.301117] wlan0: moving STA 00:0d:f0:2e:ee:02 to state 2
> [  784.301122] wlan0: moving STA 00:0d:f0:2e:ee:02 to state 3
> [  784.301141] iwlwifi 0000:00:05.0: Unable to prepare station 00:0d:f0:2e:ee:02 for addition
> [  784.481399] iwlwifi 0000:00:05.0: Unable to add station 00:0d:f0:2e:ee:02 (-22)
> [  784.647835] wlan0: Destroyed STA 00:0d:f0:2e:ee:02
> [  785.828588] wlan0: Allocated STA 00:0d:f0:2e:ee:02
> [  785.828600] wlan0: moving STA 00:0d:f0:2e:ee:02 to state 2
> [  785.828605] wlan0: moving STA 00:0d:f0:2e:ee:02 to state 3
> [  785.828624] iwlwifi 0000:00:05.0: Unable to prepare station 00:0d:f0:2e:ee:02 for addition
> [  786.044379] iwlwifi 0000:00:05.0: Unable to add station 00:0d:f0:2e:ee:02 (-22)
> [  786.219632] wlan0: Destroyed STA 00:0d:f0:2e:ee:02

Right. I'm not exactly sure why we put -EINVAL rather than -ENOSPC or
something like that, but this is a limitation.

> If it is a hardware limitation, are there any other intel mini-pci adapters that 
> don't have this hardware limitation (or at least a highter one).

With the newer 7260/7265 adapters you might be able to go up to 14 or 15
stations (I haven't checked exactly), but that's not a significant
increase - the fundamental limit of 16 station entries is still there
and at least one is needed for internal tracking for multi-/broadcast
transmit transmit (and another one might be reserved for P2P on those
devices, and I might be forgetting another one perhaps which would mean
13 is the max)

I don't believe that the driver (or even firmware) would be able to work
around this.

johannes

Re: iwlwifi 6235 AGN: hardware limitation on number of stations that can connect in ap mode ?

[Sander Eikelenboom]

Saturday, December 6, 2014, 9:18:41 AM, you wrote:

> Hi Sander,

>> So i'm wondering is there a hardware limitation of stations that can connect to 
>> this mini-pci card in ap-mode ?

> Yes, there's a hardware/firmware limitation of 16 "station entries".

>> the first clients connect perfectly well but after 12 client have connected, for 
>> the 13th i get:
>> 
>> [  784.301106] wlan0: Allocated STA 00:0d:f0:2e:ee:02
>> [  784.301117] wlan0: moving STA 00:0d:f0:2e:ee:02 to state 2
>> [  784.301122] wlan0: moving STA 00:0d:f0:2e:ee:02 to state 3
>> [  784.301141] iwlwifi 0000:00:05.0: Unable to prepare station 00:0d:f0:2e:ee:02 for addition
>> [  784.481399] iwlwifi 0000:00:05.0: Unable to add station 00:0d:f0:2e:ee:02 (-22)
>> [  784.647835] wlan0: Destroyed STA 00:0d:f0:2e:ee:02
>> [  785.828588] wlan0: Allocated STA 00:0d:f0:2e:ee:02
>> [  785.828600] wlan0: moving STA 00:0d:f0:2e:ee:02 to state 2
>> [  785.828605] wlan0: moving STA 00:0d:f0:2e:ee:02 to state 3
>> [  785.828624] iwlwifi 0000:00:05.0: Unable to prepare station 00:0d:f0:2e:ee:02 for addition
>> [  786.044379] iwlwifi 0000:00:05.0: Unable to add station 00:0d:f0:2e:ee:02 (-22)
>> [  786.219632] wlan0: Destroyed STA 00:0d:f0:2e:ee:02

> Right. I'm not exactly sure why we put -EINVAL rather than -ENOSPC or
> something like that, but this is a limitation.

>> If it is a hardware limitation, are there any other intel mini-pci adapters that 
>> don't have this hardware limitation (or at least a highter one).

> With the newer 7260/7265 adapters you might be able to go up to 14 or 15
> stations (I haven't checked exactly), but that's not a significant
> increase - the fundamental limit of 16 station entries is still there
> and at least one is needed for internal tracking for multi-/broadcast
> transmit transmit (and another one might be reserved for P2P on those
> devices, and I might be forgetting another one perhaps which would mean
> 13 is the max)

> I don't believe that the driver (or even firmware) would be able to work
> around this.

> johannes

Johannes / Dan,

Thanks for the info and fast reply, very useful and appreciated !

It makes clear what i have to try and verify with other hardware/drivers,
to see if i can get better results with that, unfortunately it's not something
that is clearly communicated since it is a niche and most router chips are 
integrated, so it stays unclear if a same chipset is used on routers will behave 
the same on a mini-pcie card (the driver of course does if openwrt and thus 
linux can be used, but the hardware + firmware could be different.

Any how, thanks again !

--
Sander