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<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Hi! All,<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>I have written a simple application using WinPcap to send
and receive L2-level (MAC) packets to a hardware device connected to my PC
through Ethernet. The details of the setup are as follows:<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<ol style='margin-top:0in' start=1 type=1>
<li class=MsoNormal style='mso-list:l0 level1 lfo1'><font size=2 face=Arial><span
style='font-size:10.0pt;font-family:Arial'>The device runs software which
sends back the packets received through the RJ-45 cable. The device has an
integrated VMAC and its MAC address is known to the application running on
PC beforehand.<o:p></o:p></span></font></li>
<li class=MsoNormal style='mso-list:l0 level1 lfo1'><font size=2 face=Arial><span
style='font-size:10.0pt;font-family:Arial'>The host (Windows PC running XP)
has a Network adaptor card and its MAC address is known to the application.<o:p></o:p></span></font></li>
<li class=MsoNormal style='mso-list:l0 level1 lfo1'><font size=2 face=Arial><span
style='font-size:10.0pt;font-family:Arial'>The Application on PC-host
prepares L2 packets in the following format: <b><span
style='font-weight:bold'>| Dest MAC Addr | Src MAC addr | Protocol
Type=0x88e1| PAYLOAD |<o:p></o:p></span></b></span></font></li>
<li class=MsoNormal style='mso-list:l0 level1 lfo1'><font size=2 face=Arial><span
style='font-size:10.0pt;font-family:Arial'>The application then uses WinPcap
APIs to send and receive packets to the hardware device; on a Request - Response
basis.<o:p></o:p></span></font></li>
<li class=MsoNormal style='mso-list:l0 level1 lfo1'><font size=2 face=Arial><span
style='font-size:10.0pt;font-family:Arial'>The host is not connected to
any LAN. It has been assigned a static IP, but it has other services running
which keep sending out queries as if the PC were on a LAN.<o:p></o:p></span></font></li>
</ol>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Problem Description:<o:p></o:p></span></font></p>
<ol style='margin-top:0in' start=1 type=1>
<li class=MsoNormal style='mso-list:l1 level1 lfo2'><font size=2 face=Arial><span
style='font-size:10.0pt;font-family:Arial'>The packets which are sent out for
the device are also received by the handler registered with WinPcap. This was
mitigated by putting a filter in the handler using the protocol type (0x88e1)
and the source Mac address as criteria—so that application gets only
those packets which are SENT by the device to the PC.<o:p></o:p></span></font></li>
<li class=MsoNormal style='mso-list:l1 level1 lfo2'><font size=2 face=Arial><span
style='font-size:10.0pt;font-family:Arial'>A bigger problem is that sometimes,
after some “other” packets are received (and duly rejected by
the handler), the communication seems to stop/hang. There is no crash as
such, but the packet handler seems stop working.<o:p></o:p></span></font></li>
</ol>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>I am new to WinPcap; if you guys had a similar experience
then please give me some clues. Thanks! <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Regards,</span></font><o:p></o:p></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Har Yash</span></font><o:p></o:p></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'> <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
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