SIOCSIWFREQ while in NL80211_IFTYPE_STATION

On 01/05/2017 03:06 PM, Johannes Berg wrote:
>> I am not sure it matters - if I understood your reply, there is no
>> valid use case to change the frequency in that mode (and all that
>> code should be removed);
> All of wext *is* being removed - slowly :)
> It's not longer default in the kernel configuration now.

ah thanks for the info. I should have checked!

>
> IIRC, there actually was a valid use case here - to set the frequency
> before you set the SSID - to be able to force a connection on that
> channel with wext.

ok, yes I thought this would make sense.

>
>> it seems to me that it is also your view that userspace (iwconfig)
>> should be fixed accordingly to not call the extensions?
> iwconfig should just be deleted and iw be used :-)

understood.

>
>> I am just trying to understand how the current code is supposed to
>> work  by exercising widely available user-space tools while debugging
>> the kernel.
> Heh, ok.
>
>> Actually the frequency gets programmed without errors when reverting
>> your commit http://tinyurl.com/ho4urp8 (which comes as a surprise as
>> well).
> Well, it's not my commit, but that makes sense. I suppose we should
> treat this as a regression, but reverting that doesn't seem like the
> right fix. Actually, I'm not convinced we should do monitor channel
> change anyway when you set the frequency with wext, so we can probably
> just remove that call there - want to send a patch to that effect?

do you mean this?

[jramirez@igloo ~ (debian-qcom-dragonboard410c-16.09-local $)]$ git diff



I tested the change above: we can now modify the channel/frequency when 
the SSID is not set in managed mode.
When the SSID is set however iwconfig does not report any error but 
channel/frequency doesn't change.

if you think this is acceptable I can submit a patch


> johannes

On Thu, 2017-01-05 at 15:38 +0100, Jorge Ramirez wrote:

> do you mean this?
> 
> [jramirez@igloo ~ (debian-qcom-dragonboard410c-16.09-local $)]$ git
> diff
> diff --git a/net/wireless/wext-sme.c b/net/wireless/wext-sme.c
> index a4e8af3..c56bac5 100644
> --- a/net/wireless/wext-sme.c
> +++ b/net/wireless/wext-sme.c
> @@ -106,30 +106,7 @@ int cfg80211_mgd_wext_siwfreq(struct net_device
> *dev,
>                          goto out;
>          }
> 
> -
>          wdev->wext.connect.channel = chan;
> -
> -   /*
> -    * SSID is not set, we just want to switch monitor channel,
> -    * this is really just backward compatibility, if the SSID
> -    * is set then we use the channel to select the BSS to use
> -    * to connect to instead. If we were connected on another
> -    * channel we disconnected above and reconnect below.
> -    */
> -   if (chan && !wdev->wext.connect.ssid_len) {
> -           struct cfg80211_chan_def chandef = {
> -                   .width = NL80211_CHAN_WIDTH_20_NOHT,
> -                   .center_freq1 = freq,
> -           };
> -
> -           chandef.chan = ieee80211_get_channel(&rdev->wiphy, freq);
> -           if (chandef.chan)
> -                   err = cfg80211_set_monitor_channel(rdev,
> &chandef);
> -           else
> -                   err = -EINVAL;
> -           goto out;
> -   }
> -
>          err = cfg80211_mgd_wext_connect(rdev, wdev);
>    out:
>          wdev_unlock(wdev);

Yeah. Frankly, I don't even understand that comment anymore - if the
interface is in managed mode, why set the monitor channel, it's not
monitoring? And if it's not in managed mode we don't get here.

> 
> 
> I tested the change above: we can now modify the channel/frequency
> when 
> the SSID is not set in managed mode.
> When the SSID is set however iwconfig does not report any error but 
> channel/frequency doesn't change.
> 
> if you think this is acceptable I can submit a patch

I think it looks fine, though writing the commit message may be tricky
:)

johannes