[Winpcap-users] RE: problem with WinPcap... stops working!

Har Yash Bahadur har.bahadur at conexant.com
Fri Apr 4 05:59:21 GMT 2008

For the 2nd point on Problem Description:

Another point to note is that I can see the traffic on Ethereal, both
the request and response are taking place, but the handler registered by
the application with WinPcap is not getting invoked after it was invoked
due to a "spurious" pkt.



From: Har Yash Bahadur 
Sent: Friday, April 04, 2008 11:18 AM
To: winpcap-users at winpcap.org
Subject: problem with WinPcap... stops working!


Hi! All,


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:


1.	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.
2.	The host (Windows PC running XP) has a Network adaptor card and
its MAC address is known to the application.
3.	The Application on PC-host prepares L2 packets in the following
format:    | Dest MAC Addr | Src MAC addr | Protocol Type=0x88e1|
4.	The application then uses WinPcap APIs to send and receive
packets to the hardware device; on a Request - Response basis.
5.	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.


Problem Description:

1.	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.
2.	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.


I am new to WinPcap; if you guys had a similar experience then please
give me some clues.  Thanks! 



Har Yash



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