Multicast packets dropped on atheros wireless link

Sam Leffler sam at errno.com
Sat Dec 17 11:00:50 PST 2005


Nate Nielsen wrote:
> Certain multicast packets are not making it through an Atheros based
> 802.11 wireless link. Other drivers/cards (ie: wi) work fine.
> 
> Two boxes sitting next to each other running FreeBSD 6.0. The cards are
> set up simply:
> 
> ifconfig ath0 inet 172.28.2.18/30 ssid tel2 channel 52 \
> 	mediaopt adhoc
> 
> An OSPF daemon is running on both sides of the wireless link, causing
> multicast packets to be sent over the ath0 NICs on both boxes. The
> multicast packets link local multicast (ie: not routeable multicast).
> Although I'm using OSPF it seems any multicast packets would have the
> same behaviour.
> 
> Running 'tcpdump -pnti ath0' on the first box (which indicentally is the
> BSSID for the adhoc link) shows packet pairs like this:
> 
> 
>>IP 172.28.2.18 > 224.0.0.5: OSPFv2, Hello, length: 48
>>IP 172.28.2.17 > 224.0.0.5: OSPFv2, Hello, length: 44
>>IP 172.28.2.18 > 224.0.0.5: OSPFv2, Hello, length: 48
>>IP 172.28.2.17 > 224.0.0.5: OSPFv2, Hello, length: 44
> 
> 
> These are packets from both OSPF daemons showing up on the ath0 NIC.
> This is the expected behaviour.
> 
> However running 'tcpdump -pnti ath0' on the second box we see only:
> 
> 
>>IP 172.28.2.17 > 224.0.0.5: OSPFv2, Hello, length: 44
>>IP 172.28.2.17 > 224.0.0.5: OSPFv2, Hello, length: 44
> 
> 
> The packets from the BSSID box never make it over the wireless link.
> 
> FWIW, setting up the two boxes as hostap/client mode doesn't fix the
> problem. The multicast packets from the hostap box aren't received on
> the client.
> 
> Any ideas on where I should poke around?

wlanstats, wlandebug input.

	Sam


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