I will try to answer your question, please correct me if I'm wrong.
On 01/29/2015 11:55 PM, Rafał Miłecki wrote:
Hi,
I'm looking at deauthentication& disassociation with cfg80211 API.
AFAIK both frames can be send by STA as well as AP (according to the
standard). I was looking info few cfg80211 callbacks and have few
questions.
1) @disassoc
I think it's just for disassociating from AP. Is that correct?
I also think so, since all code is located in the mlme section
Did not look into that in detail though, so I could be wrong.
2) @del_station
Now, this gets tricky for me. I think this callback is for AP mode to
deauthenticae/disassociate a STA.
correct, this is only allowed for iftypes of NL80211_IFTYPE_AP,
NL80211_IFTYPE_AP_VLAN, NL80211_IFTYPE_MESH_POINT or
NL80211_IFTYPE_P2P_GO. (see net/wireless/nl80211.c: nl80211_del_station)
It seems hostapd follows the same
idea as in driver_nl80211.c it uses NL80211_CMD_DEL_STATION for both:
deauth and disassoc (without building own frame).
So I started analyzing this with the base case: mac80211
(ieee80211_del_station). I expected to find a place where mac80211
constructs deauth/disassoc management frame and transmits it. But I
really couldn't. It seems that all ieee80211_del_station does is
calling __sta_info_destroy / __sta_info_destroy_part1 /
__sta_info_destroy_part2.
Did I miss something? Or does mac80211 really ignore sending proper
management frames in this case?
If you look further into __sta_info_destroy, you will notice a callback
to cfg80211_del_sta (net/wireless/nl80211.c), notifying the removal of
the station information.
cfg80211_del_sta composes a netlink message, notifying everyone
interested about the removal of the station:
hdr = nl80211hdr_put(msg, 0, 0, 0, NL80211_CMD_DEL_STATION);
In hostapd, there is a routine that monitors such netlink messages,
process_global_event, which eventually parses the CMD_DEL_STATION event
in nl80211_del_station_event, where a call is made to drv_event_disassoc
if the current device is indeed in AP mode.
So eventually, it is the hostapd that triggers the transmission of the
disassociation packet.
I hope my explanation is correct and it helps you to make things more clear.
Wim.
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