Disabling SMPS (Spatial multiplexing power save) when 802.11n is not used

On Fri, Mar 18, 2016 at 02:11:13PM +0100, Jose Blanquicet wrote:
> You are probably right, the problem could be that smps attribute is added
> without verify if it is going to do HT. In function wpa_driver_nl80211_set_ap:
> 
> if (nla_put_u32(msg, NL80211_ATTR_SMPS_MODE, smps_mode))
>            goto fail;
> 
> When I set it to HT_CAP_INFO_SMPS_DISABLED, nl80211 shoul ignore it
> and that's the reason why it works.

Which driver are you using when testing this and what kind of
wpa_supplicant configuration? I was unable to reproduce the error
message with mac80211_hwsim, i.e., the AP did come up with HT disabled
when configuring the network with disable_ht=1.

That said, the attribute should not be there and the proper fix would
likely look like this:

I am using the Marvell driver sd8887 without any particular wpa_supplicant
configuration.

I also agree that your fix is more appropriated. I tried it and it
works also with
Marvell driver. I think that mac80211_hwsim does not take into account
smps_mode parameter when ht is disabled, which is right. But instead,
Marvell driver and maybe others report error -22 (Invalid argument) if they
receive smps_mode and it is set to a value different than OFF; of course
when disable_ht=1.

On the other hand, I would like to make a question (I do not know if it should
be done in another discussion, if so let me know and I will create a new one).
The fact is that I have been able to use a, g, n and ac 802.11 modes but not
b. I get 802.11n or ac using disable_ht and disable_vht parameters.
Additionally, if I disable both parameters I get 802.11g mode and if I also set
frequency to a channel in 5GHz I get 802.11a mode. But I do not know how
to properly set the network parameters to enable 802.11b mode. How can I
do this?

Thanks for your help!

On Fri, Mar 18, 2016 at 3:16 PM, Jouni Malinen <j@w1.fi> wrote:
> On Fri, Mar 18, 2016 at 02:11:13PM +0100, Jose Blanquicet wrote:
>> You are probably right, the problem could be that smps attribute is added
>> without verify if it is going to do HT. In function wpa_driver_nl80211_set_ap:
>>
>> if (nla_put_u32(msg, NL80211_ATTR_SMPS_MODE, smps_mode))
>>            goto fail;
>>
>> When I set it to HT_CAP_INFO_SMPS_DISABLED, nl80211 shoul ignore it
>> and that's the reason why it works.
>
> Which driver are you using when testing this and what kind of
> wpa_supplicant configuration? I was unable to reproduce the error
> message with mac80211_hwsim, i.e., the AP did come up with HT disabled
> when configuring the network with disable_ht=1.
>
> That said, the attribute should not be there and the proper fix would
> likely look like this:
>
>
> diff --git a/src/drivers/driver_nl80211.c b/src/drivers/driver_nl80211.c
> index 5fb6652..b4c3462 100644
> --- a/src/drivers/driver_nl80211.c
> +++ b/src/drivers/driver_nl80211.c
> @@ -3526,24 +3526,26 @@ static int wpa_driver_nl80211_set_ap(void *priv,
>             nla_put_u32(msg, NL80211_ATTR_CIPHER_SUITE_GROUP, suite))
>                 goto fail;
>
> -       switch (params->smps_mode) {
> -       case HT_CAP_INFO_SMPS_DYNAMIC:
> -               wpa_printf(MSG_DEBUG, "nl80211: SMPS mode - dynamic");
> -               smps_mode = NL80211_SMPS_DYNAMIC;
> -               break;
> -       case HT_CAP_INFO_SMPS_STATIC:
> -               wpa_printf(MSG_DEBUG, "nl80211: SMPS mode - static");
> -               smps_mode = NL80211_SMPS_STATIC;
> -               break;
> -       default:
> -               /* invalid - fallback to smps off */
> -       case HT_CAP_INFO_SMPS_DISABLED:
> -               wpa_printf(MSG_DEBUG, "nl80211: SMPS mode - off");
> -               smps_mode = NL80211_SMPS_OFF;
> -               break;
> +       if (params->ht_opmode != -1) {
> +               switch (params->smps_mode) {
> +               case HT_CAP_INFO_SMPS_DYNAMIC:
> +                       wpa_printf(MSG_DEBUG, "nl80211: SMPS mode - dynamic");
> +                       smps_mode = NL80211_SMPS_DYNAMIC;
> +                       break;
> +               case HT_CAP_INFO_SMPS_STATIC:
> +                       wpa_printf(MSG_DEBUG, "nl80211: SMPS mode - static");
> +                       smps_mode = NL80211_SMPS_STATIC;
> +                       break;
> +               default:
> +                       /* invalid - fallback to smps off */
> +               case HT_CAP_INFO_SMPS_DISABLED:
> +                       wpa_printf(MSG_DEBUG, "nl80211: SMPS mode - off");
> +                       smps_mode = NL80211_SMPS_OFF;
> +                       break;
> +               }
> +               if (nla_put_u32(msg, NL80211_ATTR_SMPS_MODE, smps_mode))
> +                       goto fail;
>         }
> -       if (nla_put_u32(msg, NL80211_ATTR_SMPS_MODE, smps_mode))
> -               goto fail;
>
>         if (params->beacon_ies) {
>                 wpa_hexdump_buf(MSG_DEBUG, "nl80211: beacon_ies",
>
>
> --
> Jouni Malinen                                            PGP id EFC895FA

On Fri, Mar 18, 2016 at 05:13:28PM +0100, Jose Blanquicet wrote:
> I am using the Marvell driver sd8887 without any particular wpa_supplicant
> configuration.
> 
> I also agree that your fix is more appropriated. I tried it and it
> works also with
> Marvell driver.

Thanks.

> I think that mac80211_hwsim does not take into account
> smps_mode parameter when ht is disabled, which is right. But instead,
> Marvell driver and maybe others report error -22 (Invalid argument) if they
> receive smps_mode and it is set to a value different than OFF; of course
> when disable_ht=1.

Well, wpa_supplicant should not really be adding this attribute in such
a case and I'll push in the fix for that.

> On the other hand, I would like to make a question (I do not know if it should
> be done in another discussion, if so let me know and I will create a new one).
> The fact is that I have been able to use a, g, n and ac 802.11 modes but not
> b. I get 802.11n or ac using disable_ht and disable_vht parameters.
> Additionally, if I disable both parameters I get 802.11g mode and if I also set
> frequency to a channel in 5GHz I get 802.11a mode. But I do not know how
> to properly set the network parameters to enable 802.11b mode. How can I
> do this?

I don't think wpa_supplicant supports this. You can use hostapd to be
configure AP with hw_mode=b if you need to configure this special (i.e.,
obsolete..) case.

Hello,


On Fri, Mar 18, 2016 at 6:54 PM, Jouni Malinen <j@w1.fi> wrote:
> On Fri, Mar 18, 2016 at 05:13:28PM +0100, Jose Blanquicet wrote:
>> I am using the Marvell driver sd8887 without any particular wpa_supplicant
>> configuration.
>>
>> I also agree that your fix is more appropriated. I tried it and it
>> works also with
>> Marvell driver.
>
> Thanks.
>
>> I think that mac80211_hwsim does not take into account
>> smps_mode parameter when ht is disabled, which is right. But instead,
>> Marvell driver and maybe others report error -22 (Invalid argument) if they
>> receive smps_mode and it is set to a value different than OFF; of course
>> when disable_ht=1.
>
> Well, wpa_supplicant should not really be adding this attribute in such
> a case and I'll push in the fix for that.
>

I agree. Thanks!

>> On the other hand, I would like to make a question (I do not know if it should
>> be done in another discussion, if so let me know and I will create a new one).
>> The fact is that I have been able to use a, g, n and ac 802.11 modes but not
>> b. I get 802.11n or ac using disable_ht and disable_vht parameters.
>> Additionally, if I disable both parameters I get 802.11g mode and if I also set
>> frequency to a channel in 5GHz I get 802.11a mode. But I do not know how
>> to properly set the network parameters to enable 802.11b mode. How can I
>> do this?
>
> I don't think wpa_supplicant supports this. You can use hostapd to be
> configure AP with hw_mode=b if you need to configure this special (i.e.,
> obsolete..) case.
>

I know nobody will use 802.11b mode but in order to get the Wi-Fi
Alliance Certification in 802.11n, the system must be able to be
configured in a/b/g/n modes. Therefore, as I explained before, I was
trying to understand how to set properly the network parameters to get
all those modes. The wpa_supplicant already provides the way to enable
a/g/n/ac modes, thus I would expect that it also provides a way to use
b mode.

As you told, the hostapd provides very easy way to configure the mode
but I will always try to keep the system as simple as possible,
therefore I would add an additional module, hostapd in this case, only
if it is absolutely required.

Best regards,

Jose Blanquicet


> --
> Jouni Malinen                                            PGP id EFC895FA