[Winpcap-users] winpcap and ip change

[Thorsten Stoffregen]

Hi David,

thanks for your replay. 
Yes, Profinet depends on TCP/IP but it alsp uses
special ethernet frames for real-time
communication. That makes it really fast 
(about 1 millisecond cycle Time). 

Let say you have a robot-arm.
TCP/IP itself is needed for configuration of the robot.

But the real action - the movement - happens on low level with
ethernet frames only, without an overlying protocol.
For this reason I use WinPcap to capture these packages.
So far it works like a charm.

But now there are ethernet-profinet packages who say:
Ok, Adapter with mac Foo has now IP Bar
(The concept is similar to DHCP).
So I need to reconfigure the Windows IP Stack and keep listening
to the Low-Level Packages. And after the IP change I don't
get the Low Level Packages with WinPcap. TCP/IP and other services 
are working well.

I found the following solution: 
Close and reopen the capture device with pcap:

pcap_close(pcap_t ...);
changeIp(.....);
Sleep(5000);
pcap_open(pcap_t ...);

But now I have to wait several seconds between close and open!
Without the Waiting it will not work, wait for 5 seconds 
and it works. So it's a solution, but waiting for 5 seconds.... 
Seems not a very good solution for me.

Is there a way to explicit re-initialise the kernel driver?
Or even better, to let him do it by himself ;-)



----- Ursprüngliche Mail -----
> Thorsten Stoffregen wrote:
> 
> > Hi,
> >
> > I am building an application which listen to Level 2
> > Realtime Traffic. My problem is, that the overlying
> > application has to change the ip address of the interface
> > on which I am listening with pcap.
> >
> > After changing the ip I there are packets missing in the
> > capture. Especially pakets with Ethernet.Type = 0x8892
> > (Profinet), standard traffic like arp request is still
> > visible.
> 
> PROFINET appears to be a TCP/IP protocol:
> 
> http://en.wikipedia.org/wiki/PROFINET
> 
> As such, it likely depends on a valid IP address in order to work
> correctly,
> yes?
> 
> Since you're changing the IP address of the adapter it's hardly
> surprising
> that Profinet packets are being lost.
> 
> ARP does not rely on IP. That's why it continues to work, regardless
> of what
> the adapter's IP address is.
> 
> Do you have any documentation on Profinet? What its various packet
> layouts
> looks like?
> 
> --
> "Fish" (David B. Trout)
> fish at softdevlabs.com
> 
> 
> 
> 
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