DGNum/hostapd
6
0
Fork 0
Code Issues Pull requests 1 Projects Releases Packages Wiki Activity Actions

nl80211: Fix AP scan with STA fallback error path

Browse source 
I've run into a case where I can bring a 2.4 GHz AP up without it being
in a bridge while I used the 'bridge=' config option. This happens when
the HT scan needed for 40 MHz operation failed to start from the get go
because another dev on the same phy was already in a scan. At the end
the AP is up and running but not added into any bridge.

Upon looking at the code, it seems that some hardware fails to issue a
scan while in AP and thus we have a fallback that switches the interface
from AP to STA before retrying another scan (it will change it back to
AP later on when finished). As we cannot have a (non-WDS) STA in a
bridge, during that procedure, we also remove/add the AP/STA from/to the
bridge as needed.

However, in wpa_driver_nl80211_scan() we do not set
drv->ap_scan_as_station until the end of the switch-to-sta &
retry-scan-start block. This means that when the recursive call to
wpa_driver_nl80211_scan() fails (the hardware is busy in my case) we
restore the interface to AP with wpa_driver_nl80211_set_mode() but that
will not add it back to the bridge. Problem.

To fix this lets always set drv->ap_scan_as_station before calling
wpa_driver_nl80211_set_mode(). In case wpa_driver_nl80211_set_mode() or
wpa_driver_nl80211_scan() fails lets call nl80211_restore_ap_mode() that
will set the mode back to AP but also handle the bridge thing as needed.

Signed-off-by: Nicolas Escande <nico.escande@gmail.com>
This commit is contained in:
Nicolas Escande 2024-04-26 14:35:53 +02:00 • committed by Jouni Malinen
parent 6ad59779c2
commit 7b8517d197
1 changed files with 4 additions and 9 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

13
src/drivers/driver_nl80211_scan.c
View file

@ -402,23 +402,18 @@ int wpa_driver_nl80211_scan(struct i802_bss *bss,
wpa_printf(MSG_DEBUG, "nl80211: Scan trigger failed: ret=%d " wpa_printf(MSG_DEBUG, "nl80211: Scan trigger failed: ret=%d "
"(%s)", ret, strerror(-ret)); "(%s)", ret, strerror(-ret));
if (drv->hostapd && is_ap_interface(drv->nlmode)) { if (drv->hostapd && is_ap_interface(drv->nlmode)) {
enum nl80211_iftype old_mode = drv->nlmode;
/* /*
* mac80211 does not allow scan requests in AP mode, so * mac80211 does not allow scan requests in AP mode, so
* try to do this in station mode. * try to do this in station mode.
*/ */
drv->ap_scan_as_station = drv->nlmode;
if (wpa_driver_nl80211_set_mode( if (wpa_driver_nl80211_set_mode(
bss, NL80211_IFTYPE_STATION)) bss, NL80211_IFTYPE_STATION) ||
goto fail; wpa_driver_nl80211_scan(bss, params)) {
nl80211_restore_ap_mode(bss);
if (wpa_driver_nl80211_scan(bss, params)) {
wpa_driver_nl80211_set_mode(bss, old_mode);
goto fail; goto fail;
} }
/* Restore AP mode when processing scan results */
drv->ap_scan_as_station = old_mode;
ret = 0; ret = 0;
} else } else
goto fail; goto fail;