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Ticket #1121 (new defect)

Opened 15 years ago

Last modified 15 years ago

spurious frame reception in monitor mode

Reported by: zdarsky@informatik.uni-kl.de Assigned to:
Priority: major Milestone:
Component: madwifi: other Version: trunk
Keywords: Cc:
Patch is attached: 0 Pending:

Description

While capturing frames with Wireshark on a single VAP interface in monitor mode I occasionally see spurious frames that always occur in pairs (with different time stamps) and mostly have bogus content (sometimes an existing MAC address or parts of a prism header).

I've tried to at least pin-point the bug in the code, but without success. I commented out all calls to ieee80211_input_monitor and also all calls to netif_rx, with the effect that no more frames were received, of course ... except for those spurious frames. No idea where else these frames might emanate from. Btw, the bug is independent on whether any monitoring headers (Prism/Radiotap) are activated.

After toggling between monitor mode and managed mode with

wlanconfig ath0 create wlandev wifi0 wlanmode monitor
wlanconfig ath0 destroy
wlanconfig ath0 create wlandev wifi0 wlanmode managed
wlanconfig ath0 destroy
wlanconfig ath0 create wlandev wifi0 wlanmode monitor

all received frames are of the type described in the first paragraph. My speculation therefore is that the bug has to do with some data structures not being properly reinitialized on monitor VAP creation.

I've first noticed this behavior in MadWiFi r1747, but it is still present in r2059.

Attachments

monitor_mode_bug.pcap (1.3 kB) - added by zdarsky@informatik.uni-kl.de on 02/01/07 12:03:17.
Attached a capture file with an example of these spurious frames.

Change History

02/01/07 12:03:17 changed by zdarsky@informatik.uni-kl.de

  • attachment monitor_mode_bug.pcap added.

Attached a capture file with an example of these spurious frames.

02/02/07 06:27:04 changed by mrenzmann

  • version set to trunk.