[Winpcap-users] Technical 802.11 question - winpcap related

Gianluca Varenni gianluca.varenni at cacetech.com
Fri May 11 17:27:21 GMT 2007

  ----- Original Message ----- 
  From: eddie harari 
  To: winpcap-users at winpcap.org 
  Sent: Wednesday, May 09, 2007 5:43 AM
  Subject: [Winpcap-users] Technical 802.11 question - winpcap related

  Hi , 

     I have the folowing question trubling me and i cant seem to find an answer for it:

   I was able to inject packets to my wireless network using winpcap llibrary and some C source code i wrote under cygwin.

   my problem is that i could not change my MAC address in the packets i send, technically speaking all i do is make a "frame format" buffer , i put 
   the correct values in it and then i send it over the wireless interface. 
   when i put another MAC ADDRESS insted of my real MAC address , the packet will be ignored by the AP ( i guess ).

   what i am trying to understand:

   1. the buffer i provide is basically like an ethernet frame format.  I do not try to control the 802.11 frame format. ( i dont know how to take control over it  with the current API ). Is there something in the 802.11 frame header that will cause my 
  "crafted" packets to be ignored when i fake my mac address ?

As Steighton already pointed out, those are fake ethernet packets that are converted into 802.11 frames by the wireless driver. It's entirely possible that 
1. the wireless driver silently discards them
2. it changes the MAC source to the MAC of your card.

The only way to understand this is to sniff the air with a real wireless sniffer, being it AirPcap or a machine running linux/bsd/macosx and a card put in monitor mode.

   2. anyone knows of an API that will give me control on the 802.11 frame header ?

There's no such API, as WinPcap does not have any control over how the wireless miniport drivers convert fake ethernet frames into 802.11 frames.

Have a nice day

   thanks , 


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