Re: SIOCSIWFREQ while in NL80211_IFTYPE_STATION

On 01/05/2017 03:06 PM, Johannes Berg wrote:

quoted

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.

quoted

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.

quoted

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.

quoted

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

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);

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