Re: Setting the Buffer Size Without Restarting the NIC?

[Guy Harris <guy () alum mit edu>]

On Feb 6, 2014, at 8:13 AM, Michal Sekletar <msekleta () redhat com> wrote:

> Activated refers to pcap_t handle. Before you can do capture on the device
> you have to have handle and after that capture parameters are set and finally
> handle is marked as activated. So it doesn't refer to status of the device in
> OS.

Yes.

With pcap_open_live(), there is a fixed set of parameters that can be specified - promiscuous mode, snapshot length, 
and buffering timeout.

Paolo Abeni added support for the memory-mapped capture mode, and wanted the ability to configure the ring buffer size 
from the program.  I wanted one to configure the capture buffer size for other platforms as well; there was already one 
in WinPcap for Windows, but that was a call you make after pcap_open_live(), and that wouldn't work for BPF on *BSD/OS 
X.

I also wanted the ability to add new parameters in the future, rather than just having a 
pcap_open_live_with_buffer_size() call that just added the buffer size, with a new open call having to be added for 
each new parameter.

After some discussion on tcpdump-workers, we came up with a scheme where:

        you create a handle for a device with pcap_create();

        you make calls to routines to set various parameters, handing them that handle;

        when you've set all the parameters, you call pcap_activate() to "activate" the handle, opening the device with 
the specified parameters.
_______________________________________________
tcpdump-workers mailing list
tcpdump-workers () lists tcpdump org
https://lists.sandelman.ca/mailman/listinfo/tcpdump-workers