Connexion wifi sur ubuntu

$ iwconfig
eth0      no wireless extensions.

wlan0     IEEE 802.11abgn  ESSID:off/any  
          Mode:Managed  Access Point: Not-Associated   Tx-Power=0 dBm   
          Retry short limit:7   RTS thr:off   Fragment thr:off
          Power Management:on
          
lo        no wireless extensions.

$ IFCONFIG
ETH0      LINK ENCAP:ETHERNET  HWADDR xx:xx:xx:xx:xx:xx  
          UP BROADCAST MULTICAST  MTU:1500  METRIC:1
          PACKETS REÇUS:0 ERREURS:0 :0 OVERRUNS:0 FRAME:0
          TX PACKETS:0 ERRORS:0 DROPPED:0 OVERRUNS:0 CARRIER:0
          COLLISIONS:0 LG FILE TRANSMISSION:1000 
          OCTETS REÇUS:0 (0.0 B) OCTETS TRANSMIS:0 (0.0 B)

LO        LINK ENCAP:BOUCLE LOCALE  
          INET ADR:127.0.0.1  MASQUE:255.0.0.0
          ADR INET6: ::1/128 SCOPE:HÔTE
          UP LOOPBACK RUNNING  MTU:65536  METRIC:1
          PACKETS REÇUS:96 ERREURS:0 :0 OVERRUNS:0 FRAME:0
          TX PACKETS:96 ERRORS:0 DROPPED:0 OVERRUNS:0 CARRIER:0
          COLLISIONS:0 LG FILE TRANSMISSION:0 
          OCTETS REÇUS:7312 (7.3 KB) OCTETS TRANSMIS:7312 (7.3 KB)

WLAN0     LINK ENCAP:ETHERNET  HWADDR xx:xx:xx:xx:xx:xx 
          UP BROADCAST MULTICAST  MTU:1500  METRIC:1
          PACKETS REÇUS:0 ERREURS:0 :0 OVERRUNS:0 FRAME:0
          TX PACKETS:0 ERRORS:0 DROPPED:0 OVERRUNS:0 CARRIER:0
          COLLISIONS:0 LG FILE TRANSMISSION:1000 
          OCTETS REÇUS:0 (0.0 B) OCTETS TRANSMIS:0 (0.0 B)

WLAN0:AVAHI LINK ENCAP:ETHERNET  HWADDR xx:xx:xx:xx:xx:xx
          INET ADR:169.254.7.87  BCAST:169.254.255.255  MASQUE:255.255.0.0
          UP BROADCAST MULTICAST  MTU:1500  METRIC:1

$ /sbin/route -n
Table de routage IP du noyau
Destination     Passerelle      Genmask         Indic Metric Ref    Use Iface
0.0.0.0         0.0.0.0         0.0.0.0         U     1003   0        0 wlan0
169.254.0.0     0.0.0.0         255.255.0.0     U     0      0        0 wlan0

$ cat /etc/resolv.conf
# Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)
#     DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN


$ nslookup www.google.fr
;; connection timed out; no servers could be reached

$  more /etc/network/interfaces
# interfaces(5) file used by ifup(8) and ifdown(8)
auto lo
iface lo inet loopback
auto wlan0
iface wlan0 inet dhcp
        wpa-conf /etc/wpa_supplicant/wpa_supplicant.conf


$ cat /etc/wpa_supplicant/wpa_supplicant.conf 
ctrl_interface=/var/run/wpa_supplicant
eapol_version=1
ap_scan=1
fast_reauth=1

network={
        ssid="xxxx"
        scan_ssid=1
        proto=WPA
        key_mgmt=WPA-PSK
        psk=xxxxxxxxxxxxxxxxx
        priority=5
}