[Winpcap-users] Delay receiving packets - wrong functionality of pcap_setmintocopy()

Anton Tremsin ast at ssl.berkeley.edu
Fri Jan 28 11:49:35 PST 2011

I hope someone can help my problem receiving packets in Windows7

I am sending data by UDP packets from an FPGA through 10GB card 
(Chelsio). Using VC++ 2010 to compile code to receive them.

All packets arrive, no losses seen, but the problem is with the proper 
*operation of pcap_setmintocopy() function.*

*I send 64 packets with 8234 bytes each. Receiving them through 
pcp_next_ex() and I only get 31 packets (sometimes 62, sometimes 47, 50 
packets) before the timeout occurs. After timeout the rest of the 
packets arrives.
I set the minimum amount of data in the kernel buffer that causes a read 
from the application to return (unless the timeout expires) to be 1 byte 
or it to be all 8234x64 bytes, no difference. Looks like the setmintocpy 
function has no effect on my kernel buffer to be copied to my 
application. If I send another set of 64 packets - data arrives into 
pcp_next_ex(), still only in lamp of 31 (62, 47,50) packets

That is a big problem for my application.

*Is there anything I am doing wrong or need to change something in the 
system/driver to make setmintocopy function to operate properly?
Thanks a lot for your help,

Anton Tremsin


Anton S. Tremsin, Ph.D.
Space Sciences Laboratory
University of California at Berkeley
Berkeley, CA 94720
Tel: (510) 642 4554

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