[Winpcap-users] Winpcap-users Digest, Vol 72, Issue 8

[Fish" (David B. Trout]

Does the following help any?


BIOCSRTIMEOUT: IOCTL code: set the read timeout.

  This command sets the maximum timeout after which a read is released, also
if no data packets were received. IMPORTANT NOTE: the value '0' (zero) means
INFINITE, whereas the value '-1' (minus 1) means "immediate" (i.e. no
timeout). This is the complete opposite of WIN32
WaitForSingle/MultipleObjects.


BIOCSMINTOCOPY: IOCTL code: set minimum amount of data in the kernel buffer
that unlocks a read call.

  This command sets the OPEN_INSTANCE::MinToCopy member.


BIOCSETEVENTHANDLE: This IOCTL passes the read event HANDLE allocated by the
user (packet.dll) to kernel level.

  Parameter: HANDLE Parameter size: sizeof(HANDLE). If the caller is 32 bit,
the parameter size is 4 bytes, even if sizeof(HANDLE) at kernel level is 8
bytes. That's why in this IOCTL code handler we detect a 32bit calling
process and do the necessary thunking.



Sample PSEUDO code:

  hShutdownEvent = CreateEvent(NULL,TRUE,FALSE,NULL);

  hPacketsEvent = CreateEvent(NULL,TRUE,FALSE,NULL);
  DeviceIoControl( pcap, BIOCSETEVENTHANDLE, hPacketsEvent... );

  DWORD dwMinBytes = 0; // (max responsiveness)
  DeviceIoControl( pcap, BIOCSMINTOCOPY, dwMinBytes ...);

  DWORD dwTimeout = -1; // (max responsiveness)
  DeviceIoControl( pcap, BIOCSRTIMEOUT, dwTimeout ...);

  do
  {
    DWORD dwBytesRead = 0;
    while((dwBytesRead = ReadWinPCap()) > 0)
      ProcessPackets();
    WaitForMultipleEvents( hShutdownEvent, hPacketsEvent, INFINITE );
    ResetEvent( hPacketsEvent );
  }
  while (WaitForSingleEvent( hShutdownEvent, 0 ) != WAIT_OBJECT_0);



Note: the above is for illustrative purposes only. you should use the
official packet.dll functions and not call the driver directly.


-- 
"Fish" (David B. Trout) 
 fish at softdevlabs.com