public static bool CompileFilter(IntPtr pcapHandle,
string filterExpression,
uint mask,
out IntPtr bpfProgram,
out string errorString)
{
errorString = null;
//Alocate an unmanaged buffer
bpfProgram = Marshal.AllocHGlobal(Marshal.SizeOf(typeof(PcapUnmanagedStructures.bpf_program)));
//compile the expressions
var result = LibPcapSafeNativeMethods.pcap_compile(pcapHandle,
bpfProgram,
filterExpression,
1,
mask);
if (result < 0)
{
var err = GetLastError(pcapHandle);
// free up the program memory
Marshal.FreeHGlobal(bpfProgram);
bpfProgram = IntPtr.Zero; // make sure not to pass out a valid pointer
// set the error string
errorString = err;
return(false);
}
return(true);
}
public static BpfProgram TryCreate(PcapHandle pcapHandle, string filter, int optimize = 1, uint netmask = 0)
{
var bpfProgram = new BpfProgram();
int result;
// Compile the expressions
if (ThreadSafeCompile)
{
result = LibPcapSafeNativeMethods.pcap_compile(pcapHandle,
bpfProgram,
filter,
optimize,
netmask);
}
else
{
lock (SyncCompile)
{
result = LibPcapSafeNativeMethods.pcap_compile(pcapHandle,
bpfProgram,
filter,
optimize,
netmask);
}
}
if (result < 0)
{
// Don't use Dispose since we don't want pcap_freecode to be called here
Marshal.FreeHGlobal(bpfProgram.handle);
bpfProgram.SetHandle(IntPtr.Zero);
bpfProgram = null;
}
return(bpfProgram);
}