[Guy Harris <gharris@xxxxxxxxx>]

rupesh gautam wrote:
>   what is the name of variable for buffer length in libpcap...

There isn't one.

The buffer is in the OS kernel.  If it's settable at all, it's set in a 
platform-dependent fashion.  There's an ioctl to set it in BPF; it 
currently tries to pick a size (you might be able to use sysctl to set 
the default size on some systems to change what it does).  On systems 
where capturing is done on a socket (Linux, Irix), there might be a 
setsockopt() call to set the socket buffer size.  There might be other 
mechanisms for DLPI or the Digital UNIX mechanism.