/// <summary>
/// Assign a filter to this device given a filterExpression
/// </summary>
/// <param name="filterExpression">The filter expression to compile</param>
protected void SetFilter(string filterExpression)
{
// save the filter string
_filterString = filterExpression;
int res;
// pcap_setfilter() requires a valid pcap_t which isn't present if
// the device hasn't been opened
ThrowIfNotOpen("device is not open");
// attempt to compile the program
if (!CompileFilter(PcapHandle, filterExpression, 0, out IntPtr bpfProgram, out string errorString))
{
string err = string.Format("Can't compile filter ({0}) : {1} ", filterExpression, errorString);
throw new PcapException(err);
}
//associate the filter with this device
res = LibPcapSafeNativeMethods.pcap_setfilter(PcapHandle, bpfProgram);
// Free the program whether or not we were successful in setting the filter
// we don't want to leak unmanaged memory if we throw an exception.
FreeBpfProgram(bpfProgram);
//watch for errors
if (res < 0)
{
errorString = string.Format("Can't set filter ({0}) : {1}", filterExpression, LastError);
throw new PcapException(errorString);
}
}