Single (hostap) node on an ad-hoc network never receives ARP requests

[Flavio Grossi]

hi all,

i need help debugging a problem i have with a small device
(http://www.k-team.com/mobile-robotics-products/khepera-iii) using an Ambicom
WL1100C-CF compact flash wireless card, using the hostap driver from
2.6.23 or 2.6.25 kernel (cannot upgrade kernel, since it needs some
vendor-specific patches).

I'm trying to set up a wireless ad-hoc network with my laptop (L from now on,
ip 192.168.0.100) and this device (K from now on, ip 192.168.0.1), and
everything is well configured (details below).

The problem is I cannot reach L from K using ping, unless i first ping from L to
K (ping L -> K always works fine).

Using tcpdump i found that the problem is in the ARP protocol: when i ping L
from K, i can see ARP requests

192.168.0.1$ tcpdump -i wlan0
listening on wifi0, link-type IEEE802_11 (802.11), capture size 68 bytes
00:13:40.596617 arp who-has 192.168.0.2 tell 192.168.0.1
00:13:41.596303 arp who-has 192.168.0.2 tell 192.168.0.1
00:13:42.596174 arp who-has 192.168.0.2 tell 192.168.0.1
00:13:43.626226 arp who-has 192.168.0.2 tell 192.168.0.1
00:13:44.626234 arp who-has 192.168.0.2 tell 192.168.0.1

but the destination never receives the request, and never answer it, so the
communication cannot begin:

192.168.0.2$ tcpdump -i wlan0
listening on wifi0, link-type IEEE802_11 (802.11), capture size 68 bytes
[no output]



Ping from L to K works fine (i can see ARP requests and answers). After a
successfull ping in this direction, K already has the MAC address in his ARP
table, and ping from K to L works good.


Below you can see my network configuration.
Can you help help me with this? What can i do to understand where the problem
is?

Please tell me if you need more info.

Many thanks


192.168.0.1$ ifconfig
wlan0     Link encap:Ethernet  HWaddr 00:10:7A:71:9B:C1
          inet addr:192.168.0.1  Bcast:192.168.0.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:31 errors:0 dropped:0 overruns:0 frame:0
          TX packets:34 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:4470 (4.3 KiB)  TX bytes:6267 (6.1 KiB)
          Interrupt:77
192.168.0.1$ iwconfig
wlan0     IEEE 802.11b  ESSID:"roboMANET"  Nickname:""
          Mode:Ad-Hoc  Frequency:2.412 GHz  Cell: 4E:B2:E2:90:3A:98
          Bit Rate:2 Mb/s   Sensitivity=1/3
          Retry short limit:8   RTS thr:off   Fragment thr:off
          Encryption key:off
          Power Management:off
          Link Quality=55/70  Signal level=-24 dBm  Noise level=-80 dBm
          Rx invalid nwid:0  Rx invalid crypt:2  Rx invalid frag:0
          Tx excessive retries:9  Invalid misc:12   Missed beacon:0
192.168.0.1$ route
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
192.168.0.0      *               255.255.255.0   U     0      0        0 wlan0


laptop$ ifconfig
wlan0     Link encap:Ethernet  HWaddr 00:16:ea:37:c9:ba
          inet addr:192.168.0.100  Bcast:192.168.0.255  Mask:255.255.255.0
          inet6 addr: fe80::216:eaff:fe37:c9ba/64 Scope:Link
          UP BROADCAST MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:10 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:0 (0.0 B)  TX bytes:976 (976.0 B)
laptop$ iwconfig
wlan0     IEEE 802.11abgn  ESSID:"roboMANET"
          Mode:Ad-Hoc  Frequency:2.412 GHz  Cell: 4E:B2:E2:90:3A:98
          Tx-Power=15 dBm
          Retry  long limit:7   RTS thr:off   Fragment thr:off
          Encryption key:off
          Power Management:off
laptop$  route
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
192.168.0.0      *               255.255.255.0   U     0      0        0 wlan0