[Winpcap-users] Where does the Winpcap timestamp come from? andothers

John Wang locationdev at gmail.com
Sat May 2 20:45:48 PDT 2009

Hi ,

>>2. Which function in the NPF or Packet.dll can be used as a trigger to
> request CPU timer, like queryperformancecounter (), to >>timestamp the
> arrival packet to obatin higher precision?
> >>--GV--
> >>There is no way to obtain higher precision than we are currently using in
> WinPcap, apart from using custom hardware that >>timestamps the packets in
> the hardware itself.
> >>--GV--

Is there any possible to know that which function inside WinPcap is used to
timestamp the packets?

> >>4. Can I reduce the size of the user buffer inside the NPF to set it
> small enough to triger the CPU timer to timestamp when >>every packet is
> arrival?
> >>-GV--
> >>Timestamps are generated before the packet is stored in the buffers. So
> changing the buffer size doesn't help.
> >>--GV--
Because I try to timestamp the arrival packets again by using my timing
functions, I'm looking for a trigger. As I know, the frequency of NPF
copying the arrival packets from kernel space to user space depends on the
size of user buffer. If I can set the size of user buffer as same as the
size of one arrival packet, then, the NPF would copy every single packet
from kernel space to user space
once the packet arrives. And I can use this operation as a trigger to
timestamp the arrival packet again with my timing functions, am I right?


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