Multiple-BSSID issues with hostapd

DISCUSSION Arend van Spriel 3 participants 5 messages Nov 28, 2014 – Mar 1, 2015

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Arend van Spriel

author

2014-11-28 09:27 UTC #0 lore raw

Hi Jouni,

For the brcmfmac we started working on Multiple-BSSID support and came across some issues with hostapd that are listed listed below.

BSS1 setup on netdev wlan0
BSS2 setup on netdev wlan0_0

* get_station() done on wrong netdev

observed:
Upon association of STA1 with BSS2 (wlan0_0) a get_station() is done for STA1 with wlan0 as netdev.
expected:
get_station() for STA1 with wlan0_0 as netdev. We verified that wlan0_0 ifindex was used in NL80211_CMD_NEW_STATION event.

* cleanup of wlan0_0 not done upon terminating hostapd

observed:
Upon terminating hostapd, only change interface from AP->STA is received for wlan0_0 and wlan0. The stop_ap is only done for BSS1. So ending up with additional netdev, ie. wlan0_0.
expected:
following sequence seems more appropriate:
stop_ap() for BSS2
if_remove() for BSS2
stop_ap() for BSS1
if_change() AP->STA for BSS1

Do you think it makes sense to correct these scenarios according the described expected behaviour? Maybe the behaviour is only expected by me and there is a good reason for the current behaviour.

Regards,
Arend

Rafał Miłecki

2014-12-04 12:03 UTC #1 lore raw

Quoted 6 lines · Arend van Spriel

For the brcmfmac we started working on Multiple-BSSID support and came across some issues with hostapd that are listed listed below.
BSS1 setup on netdev wlan0
BSS2 setup on netdev wlan0_0

Quoted 8 lines

* get_station() done on wrong netdev
observed:
Upon association of STA1 with BSS2 (wlan0_0) a get_station() is done for STA1 with wlan0 as netdev.
expected:
get_station() for STA1 with wlan0_0 as netdev. We verified that wlan0_0 ifindex was used in NL80211_CMD_NEW_STATION event.

Did you do any progress on this?

According to the nl80211.h you are correct of course, every NL80211_CMD_foo_STATION command should include NL80211_ATTR_IFINDEX.

There are two functions in driver_nl80211.c where
NL80211_CMD_GET_STATION is used.

1) nl80211_get_link_signal
It fills NL80211_ATTR_IFINDEX in the following way:
NLA_PUT_U32(msg, NL80211_ATTR_IFINDEX, drv->ifindex);

2) i802_read_sta_data
It fills NL80211_ATTR_IFINDEX in the following way:
NLA_PUT_U32(msg, NL80211_ATTR_IFINDEX, if_nametoindex(bss->ifname));

Did you track down which of the above functions in the one sending wrong NL80211_ATTR_IFINDEX?

Arend van Spriel

author

2014-12-04 19:04 UTC #2 lore raw

Quoted 9 lines · Rafał Miłecki

Quoted 8 lines · Arend van Spriel
For the brcmfmac we started working on Multiple-BSSID support and came across some issues with hostapd that are listed listed below.
BSS1 setup on netdev wlan0
BSS2 setup on netdev wlan0_0
* get_station() done on wrong netdev

Quoted 8 lines

Quoted 6 lines
observed:
Upon association of STA1 with BSS2 (wlan0_0) a get_station() is done for STA1 with wlan0 as netdev.
expected:
get_station() for STA1 with wlan0_0 as netdev. We verified that wlan0_0 ifindex was used in NL80211_CMD_NEW_STATION event.
Did you do any progress on this?

Nope.

Quoted 10 lines

According to the nl80211.h you are correct of course, every NL80211_CMD_foo_STATION command should include NL80211_ATTR_IFINDEX.
There are two functions in driver_nl80211.c where
NL80211_CMD_GET_STATION is used.
1) nl80211_get_link_signal
It fills NL80211_ATTR_IFINDEX in the following way:
NLA_PUT_U32(msg, NL80211_ATTR_IFINDEX, drv->ifindex);

Quoted 6 lines

2) i802_read_sta_data
It fills NL80211_ATTR_IFINDEX in the following way:
NLA_PUT_U32(msg, NL80211_ATTR_IFINDEX, if_nametoindex(bss->ifname));
Did you track down which of the above functions in the one sending wrong NL80211_ATTR_IFINDEX?

Nope. We simply return empty sta_info. We used the hostapd that comes with Ubuntu 12.04 (i think) to assure it is usable. I suppose the code you mention here is driver_nl80211.c from the git repo. I intended to retry the scenario with hostapd build from git.

Regards,
Arend

Jouni Malinen

2015-03-01 17:12 UTC #3 lore raw

In reply to Arend van Spriel

Quoted 2 lines · Arend van Spriel

For the brcmfmac we started working on Multiple-BSSID support and came across some issues with hostapd that are listed listed below.

Did you get test these with a more recent hostapd version (ideally, hostap.git master branch snapshot)? I was unable to reproduce either issue..

Quoted 11 lines

BSS1 setup on netdev wlan0
BSS2 setup on netdev wlan0_0
* get_station() done on wrong netdev
observed:
Upon association of STA1 with BSS2 (wlan0_0) a get_station() is done for STA1 with wlan0 as netdev.
expected:
get_station() for STA1 with wlan0_0 as netdev. We verified that wlan0_0 ifindex was used in NL80211_CMD_NEW_STATION event.

I'm not sure which get_station operation would happen upon association.. Anyway, hostapd uses get_station() to fetch STA statistics for accounting and inactivity checking. The former can be triggered through control interface, so I used that to test this. In multi-BSS configuration, NL80211_CMD_GET_STATION was issued to the correct ifindex depending on which BSS the STA was associated with.

Quoted 12 lines

* cleanup of wlan0_0 not done upon terminating hostapd
observed:
Upon terminating hostapd, only change interface from AP->STA is received for wlan0_0 and wlan0. The stop_ap is only done for BSS1. So ending up with additional netdev, ie. wlan0_0.
expected:
following sequence seems more appropriate:
stop_ap() for BSS2
if_remove() for BSS2
stop_ap() for BSS1
if_change() AP->STA for BSS1

All dynamically added interfaces get removed in my tests.

Quoted 3 lines

Do you think it makes sense to correct these scenarios according the described expected behaviour? Maybe the behaviour is only expected by me and there is a good reason for the current behaviour.

Your expectation sounds correct and that matches what I see hostapd doing currently..

Signature · 1 line

Jouni Malinen                                            PGP id EFC895FA

Rafał Miłecki

2015-03-01 17:30 UTC #4 lore raw

Quoted 7 lines · Jouni Malinen

Quoted 2 lines · Arend van Spriel
For the brcmfmac we started working on Multiple-BSSID support and came across some issues with hostapd that are listed listed below.
Did you get test these with a more recent hostapd version (ideally, hostap.git master branch snapshot)? I was unable to reproduce either issue..

Could this be something similar to the problem handled in:
nl80211: report new station / assoc event for the correct BSS
http://patchwork.ozlabs.org/patch/418401/
http://w1.fi/cgit/hostap/commit/?id=7c4027f60411aca6e90a0074499c5427c8268baa

NL80211_CMD_GET_STATION is not handled in driver_nl80211_event.c, but maybe there is similar place somewhere else?