broadcast packets are being lost

Khaled 982 at fuzzbuzz.org
Wed Mar 5 15:37:00 EST 2014


Hello

I'm new to hostap and this mailing list, so please redirect me if I'm not asking in the right place.

I'm trying to use a RaspberryPi with a WIFI dongle (containing an RTL-8188 chip, I believe) as a WIFI router.



I'm using this for hostapd.conf:

#############################################
ctrl_interface=/var/run/hostapd
ctrl_interface_group=wheel

# Some usable default settings...
macaddr_acl=0
auth_algs=1
ignore_broadcast_ssid=0

# Most modern wireless drivers in the kernel need driver=nl80211
driver=nl80211

# Customize these for your local configuration...
interface=wlan0
hw_mode=g
channel=6
ssid=FuzzWifi4
wpa=2
wpa_passphrase=mypassword
################################################



This configuration is mostly working well. All my devices can connect, IPs are assigned via DHCP, and regular (unicast) traffic is flowing nicely. I've also found it to be reliable, downloading for days continuously without issues.

*However*: I'm noticing strange behaviour with regards to broadcasts. When sending broadcast packets from any connected WIFI device, those packets are reliably received by the RaspberryPi (the access point) itself. However, all other clients on the same WIFI only see about 5% of those packets.

For example, if host (a) and (b) are connected via WIFI and host (a) starts broadcasting (for example, with ping -b), the RPi will see 100% of those pings, but host (b) will only see the occasional ping (about 5% only). Same is true for the reverse: when b is broadcasting, (a) doesn't see most broadcasts, but the RPi sees all of them. I'm confirming this using tcpdump on all three devices.

No other issues are observed: clients can send unicast traffic without any issues.

Any ideas what could be the problem here? Any help is appreciated.

Thanks
-Khaled


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