wpa_supplicant.: Simulating handoff between wifi's access points.

Carlos Patricio Amigo Haering camigo at udec.cl
Tue Dec 18 15:03:52 EST 2012


Hi everybody,

I'm working on a seamless handover but i don't want to walk long 
distances with the client to trigger the handover so i need to simulate 
it. Basically i have two AP with the same SSID and different MAC and i 
want to disconnect a client from one of them to connect it to the other 
one.  First i tried with iwconfig(iwconfig wlan0 ap <mac>)  but this did 
not do nothing, apparently this tool it's deprecated.

Reading and asking, somebody told me about wpa_supplicant and i've been 
looking for some good tutorial but all of them are a little bit simple 
and normally uses dhcp and my AP doesn't have dhcp server. Anyway i've 
made something using a mix of info of internet but without good results, 
indeed i can't connect the client to a AP yet. I hope that you help me 
to figure out what i'm doing wrong.

I'm using Ubuntu 10.10 with kernel 2.6.35-22-generic and a network 
controller: Intel Corporation PRO/Wireless 4945ABG.

# ifconfig wlan0 down
# ifconfig wlan0 up
# iw wlan0 scan
BSS 20:aa:4b:48:7e:ca (on wlan0)
	TSF: 3914550832 usec (0d, 01:05:14)
	freq: 2462
	beacon interval: 100
	capability: ESS Privacy ShortSlotTime (0x0411)
	signal: -15.00 dBm
	last seen: 1500 ms ago
	SSID: OF
	Supported rates: 1.0* 2.0* 5.5* 11.0* 6.0 9.0 12.0 18.0
	DS Parameter set: channel 11
	ERP: Barker_Preamble_Mode
	Extended supported rates: 24.0 36.0 48.0 54.0
	RSN:	 * Version: 1
		 * Group cipher: CCMP
		 * Pairwise ciphers: CCMP
		 * Authentication suites: PSK
		 * Capabilities: 16-PTKSA-RC (0x000c)
	WMM:	 * Parameter version 1
		 * BE: CW 15-1023, AIFSN 3
		 * BK: CW 15-1023, AIFSN 7
		 * VI: CW 7-15, AIFSN 2, TXOP 3008 usec
		 * VO: CW 3-7, AIFSN 2, TXOP 1504 usec

# wpa_supplicant -v
wpa_supplicant v0.6.10
Copyright (c) 2003-2009, Jouni Malinen <j at w1.fi> and contributors.

# cat /etc/wpa_supplicant/wpa_supplicant.conf
ctrl_interface=/var/run/wpa_supplicant

network={
	ssid="OF"
	bssid=20:aa:4b:48:7e:ca
	key_mgmt=WPA-PSK
	group=CCMP TKIP
	pairwise=CCMP TKIP
	proto=RSN
	psk=4825dfb64863f17ff2db453445a123191468752148d88ffe4491bc79cae5f95f
	id_str="my_static_lan"
}

Note: The psk= was the output of wpa_passphrase <ssid> <password>.

# cat /etc/network/interfaces
auto lo
iface lo inet loopback

wpa-driver wext
wpa-conf /etc/wpa_supplicant/wpa_supplicant.conf

iface my_static_lan inet static
	address 192.168.1.11
	netmask 255.255.255.0
	network 192.168.1.0
	broadcast 192.168.1.255

# wpa_supplicant -B -Dwext -i wlan0 -c 
/etc/wpa_supplicant/wpa_supplicant.conf
#
# ip addr show wlan0
3: wlan0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc mq state 
DOWN qlen 1000
     link/ether 00:1b:77:15:7d:d1 brd ff:ff:ff:ff:ff:ff
     inet6 fe80::21b:77ff:fe15:7dd1/64 scope link
        valid_lft forever preferred_lft forever

(Doesn't seem connected.)

# ping 192.168.1.13 (pinging a iphone connected to the same AP)
connect: Network is unreachable


As you see i don't have any error but the client is not associated to 
the AP. I really appreciate a little help.

thanks in advance.


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