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# dllimport help from c, c++ unmanaged dll to managed wrapper

Posted on 2007-11-21
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Bear in mind I am a vb.net guru and I know very little about c or c++.  I have successfully wrapped one function from an unmanaged dll but  this one is tougher.  I need some help with the interface wrapper.  the dllimport im using so far is:

OH and in the snippit is contained  big stinkin C header file (another thing I know little about!

I need some pointing in the right dirrection here.

<DllImport("airpcap.dll", EntryPoint:="AirpcapGetDeviceList", CharSet:=CharSet.Ansi)> _
Private Shared Function AirpcapGetDeviceList(ByRef desc As System.Char, ByRef int2 As System.Char) As IntPtr
End Function

The dll source code snippit  for the C++ api i am trying to convert is as follows:

BOOL AirpcapGetDeviceList(PAirpcapDeviceDescription *PPAllDevs, PCHAR Ebuf)
{
AirpcapDeviceDescription *alldevs = NULL;

CHAR            DeviceName[256];   // to be generous
UINT            NDevices = 0, NProDevices = 0;
CHAR            Desc[256];
UINT            i;

//
// Find the regular devices
//
for(i = 0; i < MAX_AIRPCAP_CARDS; i++)
{
// Note: we are sure that the list of device names is without gaps, so
// scanning until the open fails is safe and grants to find all the devices
_snprintf(DeviceName, sizeof(DeviceName), DEVICESTRING, i);
DeviceName,
0,
NULL,
OPEN_EXISTING,
0,
0);

{
continue;
}

// Done with the handle, close it

// Create the name
_snprintf(DeviceName, sizeof(DeviceName), DEVICESTRING_NO_PREFIX, i);

// Create the description
_snprintf(Desc,
sizeof(Desc),
"AirPcap USB wireless capture adapter nr. %.2u",
i);

AirpcapInsertDeviceInList(&alldevs, DeviceName, Desc);
NDevices++;
}

//
// Is more than one regular device plugged in this machine?
//
if(NDevices > 1)
{
//
// We have more than one device. See if the ANY device is available.
//

// Try to open the adapter
_snprintf(DeviceName, sizeof(DeviceName), DEVICESTRING_ANY);
DeviceName,
0,
NULL,
OPEN_EXISTING,
0,
0);

{

// Done with the handle, close it

// Create the name
_snprintf(DeviceName, sizeof(DeviceName), DEVICESTRING_ANY_NO_PREFIX);

// Create the description
_snprintf(Desc,
sizeof(Desc),
"AirPcap Multi-Channel Aggregator");

AirpcapInsertDeviceInList(&alldevs, DeviceName, Desc);
NDevices++;
}
}

#ifdef HAVE_AR5416_SUPPORT
#endif

*PPAllDevs = alldevs;

return TRUE;
}

///////////////////////////////////////////////////////////////////

/*
* Copyright (c) 2006-2007 CACE Technologies, Davis (California)
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
*/

#ifdef _MSC_VER
// This disables a VS warning for zero-sized arrays.
#pragma warning( disable : 4200)
// This stops VS2005 ranting against stdio.
#pragma warning( disable : 4996)
#endif

#ifdef __cplusplus
extern "C" {
#endif

/*!
\mainpage AirPcap interface documentation

\section Introduction

This document describes the data structures and the functions exported by the CACE Technologies AirPcap library.
The AirPcap library provides low-level access to the AirPcap devices including advanced capabilities such as channel setting,
link type control and WEP configuration.<br>
This manual includes the following sections:

- \ref airpcapfuncs
- \ref airpcapdefs

\note Throughout this documentation, \e device refers to a physical AirPcap device, while \e adapter is an open API
instance. Most of the AirPcap API operations are adapter-specific but some of them, like setting the channel, are
per-device and will be reflected on all the open adapters. These functions will have "Device" in their name, e.g.
AirpcapSetDeviceChannel().

*/

/** @defgroup airpcapdefs AirPcap definitions and data structures
*  @{
*/

/*!
\brief This string is the fixed prefix in the airpcap adapter name.
It can be used to parse the name field in an AirpcapDeviceDescription structure.
*/
#define AIRPCAP_DEVICE_NAME_PREFIX		"\\\\.\\airpcap"

/*!
\brief This string is the scanf modifier to extract the adapter number from an adapter name.
It can be used to parse the name field in an AirpcapDeviceDescription structure with scanf.
*/
#define AIRPCAP_DEVICE_NUMBER_EXTRACT_STRING		 "\\\\.\\airpcap%u"

/*!
\brief Entry in the list returned by \ref AirpcapGetDeviceList().
*/
typedef struct _AirpcapDeviceDescription
{
struct	_AirpcapDeviceDescription *next;			///< Next element in the list
PCHAR	Name;										///< Device name
PCHAR	Description;								///< Device description
} AirpcapDeviceDescription, *PAirpcapDeviceDescription;

#define MAX_ENCRYPTION_KEYS 64

#define WEP_KEY_MAX_SIZE 32		///< Maximum size of a WEP key, in bytes. This is the size of an entry in the
///< AirpcapWepKeysCollection structure

#ifndef __MINGW32__
#pragma pack(push)
#pragma pack(1)
#endif // __MINGW32__

#define AIRPCAP_KEYTYPE_WEP		0	///< Key type: WEP. The key can have an arbitrary length smaller than 32 bytes.
#define AIRPCAP_KEYTYPE_TKIP	1	///< Key type: TKIP (WPA). NOT SUPPORTED YET.
#define AIRPCAP_KEYTYPE_CCMP	2	///< Key type: CCMP (WPA2). NOT SUPPORTED YET.

/*!
\brief WEP key container
*/
typedef struct _AirpcapKey
{
UINT KeyType;						///< Type of key, can be on of: \ref AIRPCAP_KEYTYPE_WEP, \ref AIRPCAP_KEYTYPE_TKIP, \ref AIRPCAP_KEYTYPE_CCMP. Only AIRPCAP_KEYTYPE_WEP is supported by the driver at the moment.
UINT KeyLen;						///< Length of the key, in bytes
BYTE KeyData[WEP_KEY_MAX_SIZE];		///< Key Data
}
#ifdef __MINGW32__
__attribute__((__packed__))
#endif // __MINGW32__
AirpcapKey, *PAirpcapKey;

/*!
\brief frequency Band.
802.11 adapters can support different frequency bands, the most important of which are: 2.4GHz (802.11b/g/n)
and 5GHz (802.11a/n).
*/
typedef enum _AirpcapChannelBand
{
AIRPCAP_CB_AUTO = 1,				///< Automatically pick the best frequency band
AIRPCAP_CB_2_4_GHZ = 2,				///< 2.4 GHz frequency band
AIRPCAP_CB_4_GHZ = 4,				///< 4 GHz frequency band
AIRPCAP_CB_5_GHZ = 5				///< 5 GHz frequency band
}AirpcapChannelBand, *PAirpcapChannelBand;

/*!
\brief Type of frame validation the adapter performs.
An adapter can be instructed to accept different kind of frames: correct frames only, frames with wrong Frame Check Sequence (FCS) only, all frames.
*/
typedef enum _AirpcapValidationType
{
AIRPCAP_VT_ACCEPT_EVERYTHING = 1,		///< Accept all the frames the device captures
AIRPCAP_VT_ACCEPT_CORRECT_FRAMES = 2,	///< Accept correct frames only, i.e. frames with correct Frame Check Sequence (FCS).
AIRPCAP_VT_ACCEPT_CORRUPT_FRAMES = 3,	///< Accept corrupt frames only, i.e. frames with worng Frame Check Sequence (FCS).
AIRPCAP_VT_UNKNOWN = 4					///< Unknown validation type. You should see it only in case of error.
}AirpcapValidationType, *PAirpcapValidationType;

/*!
\brief Type of decryption the adapter performs.
An adapter can be instructed to turn decryption (based on the device-configured keys configured
with \ref AirpcapSetDeviceKeys()) on or off.
*/
typedef enum _AirpcapDecryptionState
{
AIRPCAP_DECRYPTION_ON = 1,				///< This adapter performs decryption
AIRPCAP_DECRYPTION_OFF = 2				///< This adapter does not perform decryption
}AirpcapDecryptionState, *PAirpcapDecryptionState;

/*!
\brief Storage for a MAC address
*/
{
}
#ifdef __MINGW32__
__attribute__((__packed__))
#endif // __MINGW32__

/*!
\brief This structure is used to store a collection of WEP keys.
Note that the definition of the structure doesn't contain any key, so be careful to allocate a buffer
with the size of the key, like in the following example:

\code
PAirpcapKeysCollection KeysCollection;
UINT KeysCollectionSize;

KeysCollectionSize = sizeof(AirpcapKeysCollection) + NumKeys * sizeof(AirpcapKey);

KeysCollection = (PAirpcapKeysCollection)malloc(KeysCollectionSize);
if(!KeysCollection)
{
// Error
}
\endcode
*/
typedef struct _AirpcapKeysCollection
{
UINT nKeys;												///< Number of keys in the collection
AirpcapKey Keys[0];										///< Array of nKeys keys.
} AirpcapKeysCollection, *PAirpcapKeysCollection;

/*!

This structure defines the BPF that preceeds every packet delivered to the application.
*/
{
UINT TsSec;			///< Timestamp associated with the captured packet. SECONDS.
UINT TsUsec;		///< Timestamp associated with the captured packet. MICROSECONDS.
UINT Caplen;		///< Length of captured portion. The captured portion <b>can be different</b> from the original packet, because it is possible (with a proper filter) to instruct the driver to capture only a portion of the packets.
UINT Originallen;	///< Original length of packet
USHORT	Hdrlen;		///< Length of bpf header (this struct plus alignment padding). In some cases, a padding could be added between the end of this structure and the packet data for performance reasons. This field can be used to retrieve the actual data of the packet.
}
#ifdef __MINGW32__
__attribute__((__packed__))
#endif // __MINGW32__

/// Helper macros to extract packets coming from the driver. Rounds up to the next even multiple of AIRPCAP_ALIGNMENT.
#define AIRPCAP_ALIGNMENT sizeof(int)
#define AIRPCAP_WORDALIGN(x) (((x)+(AIRPCAP_ALIGNMENT-1))&~(AIRPCAP_ALIGNMENT-1))

#ifndef __MINGW32__
#pragma pack(pop)
#endif // __MINGW32__

#define AIRPCAP_ERRBUF_SIZE 512		///< Size of the error buffer, in bytes

/*!
\brief Channel info flag: the channel is enabled for transmission, too.

To comply with the electomagnetic emission regulations of the different countries, the AirPcap hardware can be programmed
to block transmission on specific channels. This flag is set by AirpcapGetDeviceSupportedChannels() to indicate that a
channel in the list supports transmission.
*/
#define AIRPCAP_CIF_TX_ENABLED	0x1

/*!
\brief Channel information.
Used by \ref AirpcapSetDeviceChannelEx(), \ref AirpcapGetDeviceChannelEx(), \ref AirpcapGetDeviceSupportedChannels()
*/
typedef struct _AirpcapChannelInfo
{
UINT Frequency;		///< Channel frequency, in MHz.
/*!
\brief 802.11n specific. Offset of the extension channel in case of 40MHz channels.

Possible values are -1, 0 +1:
- -1 means that the extension channel should be below the control channel (e.g. Control = 5 and Extension = 1)
- 0 means that no extension channel should be used (20MHz channels or legacy mode)
- +1 means that the extension channel should be above the control channel (e.g. Control = 1 and Extension = 5)

In case of 802.11a/b/g channels (802.11n legacy mode), this field should be set to 0.
*/
CHAR ExtChannel;
UCHAR Flags;		///< Channel Flags. The only flag supported at this time is \ref AIRPCAP_CIF_TX_ENABLED.
UCHAR Reserved[2];	///< Reserved. It should be set to {0,0}.
}
AirpcapChannelInfo, *PAirpcapChannelInfo;

/*!

AirPcap supports three 802.11 link types:
- plain 802.11 (\ref AIRPCAP_LT_802_11)
- a PPI header is prepended to each packet (\ref AIRPCAP_LT_802_11_PLUS_PPI).
*/
{
AIRPCAP_LT_802_11 = 1,				///< plain 802.11 link type. Every packet in the buffer contains the raw 802.11 frame, including MAC FCS.
AIRPCAP_LT_UNKNOWN = 3,				///< Unknown link type. You should see it only in case of error.
AIRPCAP_LT_802_11_PLUS_PPI = 4		///< 802.11 plus PPI header link type. Every packet in the buffer contains a PPI header followed by the 802.11 frame. MAC FCS is included.

#ifndef __AIRPCAP_DRIVER__

/*!
*/
typedef struct _AirpcapHandle AirpcapHandle, *PAirpcapHandle;
#endif

/*!
\brief Capture statistics.
Returned by \ref AirpcapGetStats().
*/
typedef struct _AirpcapStats
{
UINT Recvs;			///< Number of packets that the driver received by the adapter
///< from the beginning of the current capture. This value includes the packets
///< dropped because of buffer full.
UINT Drops;			///< number of packets that the driver dropped from the beginning of a capture.
///< A packet is lost when the the buffer of the driver is full.
UINT IfDrops;		///< Packets dropped by the card before going to the USB bus.
///< Not supported at the moment.
UINT Capt;			///< number of packets that pass the BPF filter, find place in the kernel buffer and
///< therefore reach the application.
}AirpcapStats, *PAirpcapStats;

// MAC flags
#define AIRPCAP_MF_MONITOR_MODE_ON		1	///< If set, the device is configured to work in monitor mode.
///< When monitor mode is on, the device captures all the frames transmitted on the channel. This includes:
///<    - unicast packets
///<    - multicast packets
///<    - control and management packets
///<
///< When monitor mode is off, the device has a filter on unicast packets to capture only the packets whose MAC
///<   - unicast packets whose destination is the address of the device
///<   - multicast packets
///<   - beacons and probe requests

#define AIRPCAP_MF_ACK_FRAMES_ON		2	///< If set, the device will acknowledge the data frames sent to its address. This is useful when the device needs to interact with other devices on the
///< 802.11 network, bacause handling the ACKs in software is normally too slow.

/*@}*/

/** @defgroup airpcapfuncs AirPcap functions
*  @{
*/

/*!
\brief Returns a string with the API version
\param VersionMajor Pointer to a variable that will be filled with the major version number.
\param VersionMinor Pointer to a variable that will be filled with the minor version number.
\param VersionRev Pointer to a variable that will be filled with the revision number.
\param VersionBuild Pointer to a variable that will be filled with the build number.
*/
void AirpcapGetVersion(PUINT VersionMajor, PUINT VersionMinor, PUINT VersionRev, PUINT VersionBuild);

/*!
\brief Returns the last error related to the specified handle
\return The string with the last error.
*/

/*!
\brief Returns the list of available devices
\param PPAllDevs Address to a caller allocated pointer. On success this pointer will receive the head of a list of available devices.
\param Ebuf String that will contain error information if FALSE is returned. The size of the string must be AIRPCAP_ERRBUF_SIZE bytes.
\return TRUE on success. FALSE is returned on failure, in which case Ebuf is filled in with an appropriate error message.

Here's a snippet of code that shows how to use AirpcapGetDeviceList():

\code
CHAR Ebuf[AIRPCAP_ERRBUF_SIZE];
AirpcapDeviceDescription *Desc, *tDesc;

if(AirpcapGetDeviceList(&Desc, Ebuf) == -1)
{
printf("Unable to get the list of devices: %s\n", Ebuf);
return -1;
}

for(tDesc = Desc; tDesc; tDesc = tDesc->next)
{
printf("%u) %s (%s)\n",
++i,
tDesc->Name,
tDesc->Description);
}

AirpcapFreeDeviceList(Desc);
\endcode
*/
BOOL AirpcapGetDeviceList(PAirpcapDeviceDescription *PPAllDevs, PCHAR Ebuf);

/*!
\brief Frees a list of devices returned by AirpcapGetDeviceList()
\param PAllDevs Head of the list of devices returned by \ref AirpcapGetDeviceList().
*/
VOID AirpcapFreeDeviceList(PAirpcapDeviceDescription PAllDevs);

/*!
\param DeviceName Name of the device to open. Use \ref AirpcapGetDeviceList() to get the list of devices.
\param Ebuf String that will contain error information in case of failure. The size of the string must be AIRPCAP_ERRBUF_SIZE bytes.
\return A PAirpcapHandle handle on success. NULL is returned on failure, in which case Ebuf is filled in with an appropriate error message.
*/
PAirpcapHandle AirpcapOpen(PCHAR DeviceName, PCHAR Ebuf);

/*!
*/

/*!
\brief Sets the device's monitor mode and acknowledgment settings.
\param AirpcapMacFlags Flags word, that contains a bitwise-OR combination of the following flags: \ref AIRPCAP_MF_MONITOR_MODE_ON and \ref AIRPCAP_MF_ACK_FRAMES_ON .
\return TRUE on success.

When an adapter is plugged into the system, it's always configured with monitor mode ON and acknowledgment settings OFF.
These values are not stored persistently, so if you want to turn monitor mode off, you will need to do it
every time you attach the adapter.

\note currently, the AirPcap adapter supports frames acknowleging when the adapter is NOT in monitor mode. This means that
the combinations in which the two flags have the same value will cause AirpcapSetDeviceMacFlags() to fail.
*/

/*!
\brief Gets the device's monitor mode and acknowledgement settings.
\param PAirpcapMacFlags User-provided flags word, that will be filled by the function with an OR combination of the
following flags: \ref AIRPCAP_MF_MONITOR_MODE_ON and \ref AIRPCAP_MF_ACK_FRAMES_ON.
\return TRUE on success.

When an adapter is plugged into the system, it's always configured with monitor mode ON and acknowledgment settings OFF.
These values are not stored persistently, so if you want to turn monitor mode off, you will need to do it
every time you attach the adapter.
*/

/*!
\return TRUE on success.

the "link type" determines how the driver will encode the packets captured from the network.
- \ref AIRPCAP_LT_802_11, to capture 802.11 frames (including control frames) without any
power information. Look at the "Capture_no_radio" example application in the developer's pack
for a reference on how to decode 802.11 frames with this link type.
the developer's pack can be used as a reference on how to decode 802.11 frames with radiotap headers.
- \ref AIRPCAP_LT_802_11_PLUS_PPI, to capture 802.11 frames (including control frames) with a Per Packet Information (PPI)
header that contains per-packet meta information like channel and power information. More details on the PPI header can
be found in the PPI online documentation (TODO).
*/

/*!
\return TRUE on success.

the "link type" determines how the driver will encode the packets captured from the network.
- \ref AIRPCAP_LT_802_11, to capture 802.11 frames (including control frames) without any
power information. Look at the "Capture_no_radio" example application in the developer's pack
for a reference on how to decode 802.11 frames with this link type.
the developer's pack can be used as a reference on how to decode 802.11 frames with radiotap headers.
- \ref AIRPCAP_LT_802_11_PLUS_PPI, to capture 802.11 frames (including control frames) with a Per Packet Information (PPI)
header that contains per-packet meta information like channel and power information. More details on the PPI header can
be found in the PPI online documentation (TODO).
*/

/*!
\brief Configures the adapter on whether to include the MAC Frame Check Sequence in the captured packets.
\param IsFcsPresent TRUE if the packets should include the FCS. FALSE otherwise
\return TRUE on success.

In the default configuration, the adapter includes the FCS in the captured packets. The MAC Frame Check Sequence
is 4 bytes and is located at the end of the 802.11 packet, with \ref AIRPCAP_LT_802_11, \ref AIRPCAP_LT_802_11_PLUS_RADIO and
that precedes each frame has two additional fields at the end: Padding and FCS. These two fields are not present
when FCS inclusion is off.
*/

/*!
\brief Returns TRUE if the specified adapter includes the MAC Frame Check Sequence in the captured packets
\param PIsFcsPresent User-provided variable that will be set to true if the adapter is including the FCS.
\return TRUE if the operation is successful. FALSE otherwise.

In the default configuration, the adapter includes the FCS in the captured packets. The MAC Frame Check Sequence
is 4 bytes and is located at the end of the 802.11 packet, with \ref AIRPCAP_LT_802_11, \ref AIRPCAP_LT_802_11_PLUS_RADIO and
that precedes each frame has two additional fields at the end: Padding and FCS. These two fields are not present
when FCS inclusion is off.
*/

/*!
\brief Configures the adapter to accept or drop frames with an incorrect Frame Check sequence (FCS).
\param ValidationType The type of validation the driver will perform. See the documentation of \ref AirpcapValidationType for details.
\return TRUE on success.

\note By default, the driver is configured in \ref AIRPCAP_VT_ACCEPT_EVERYTHING mode.
*/

/*!
\brief Checks if the specified adapter is configured to capture frames with incorrect an incorrect Frame Check Sequence (FCS).
\param ValidationType Pointer to a user supplied variable that will contain the type of validation the driver will perform. See the documentation of \ref AirpcapValidationType for details.
\return TRUE if the operation is succesful. FALSE otherwise.

\note By default, the driver is configured in \ref AIRPCAP_VT_ACCEPT_EVERYTHING mode.
*/

/*!
\brief Sets the list of decryption keys that AirPcap is going to use with the specified device.
\param KeysCollection Pointer to a \ref PAirpcapKeysCollection structure that contains the keys to be set in the device.
\return TRUE if the operation is successful. FALSE otherwise.

AirPcap is able to use a set of decryption keys to decrypt the traffic transmitted on a specific SSID. If one of the
keys corresponds to the one the frame has been encrypted with, the driver will perform decryption and return the cleartext frames
to the application.

This function allows to set the <b>device-specific</b> set of keys. These keys will be used by the specified device only,
and will not be used by other airpcap devices besides the specified one.

At this time, the only supported decryption method is WEP.

The keys are applied to the packets in the same order they appear in the KeysCollection structure until the packet is
correctly decrypted, therefore putting frequently used keys at the beginning of the structure improves performance.

\note When you change the set of keys from an open capture instance, the change will be
immediately reflected on all the other capture instances on the same device.
*/

/*!
\brief Returns the list of decryption keys that are currently associated with the specified device
\param KeysCollection User-allocated PAirpcapKeysCollection structure that will be filled with the keys.
\param PKeysCollectionSize
- \b IN: pointer to a user-allocated variable that contains the length of the KeysCollection structure, in bytes.
- \b OUT: amount of data moved by AirPcap in the buffer pointed by KeysBuffer, in bytes.
\return TRUE if the operation is successful. If an error occurs, the return value is FALSE and KeysCollectionSize is zero.
If the provided buffer is too small to contain the keys, the return value is FALSE and KeysCollectionSize contains the
needed KeysCollection length, in bytes. If the device doesn't have any decryption key configured, the return value is TRUE, and
KeysCollectionSize will be zero.

This function returns the <b>device-specific</b> set of keys. These keys are used by the specified device only,
and not by other airpcap devices besides the specified one.

AirPcap is able to use a set of decryption keys to decrypt the traffic transmitted on a specific SSID. If one of the
keys corresponds to the one the frame has been encrypted with, the driver will perform decryption and return the cleartext frames
to the application.
AirPcap supports, for every device, multiple keys at the same time.

The configured decryption keys are device-specific, therefore AirpcapGetDeviceKeys() will return a different set of keys
when called on different devices.

At this time, the only supported decryption method is WEP.
*/
BOOL AirpcapGetDeviceKeys(PAirpcapHandle AdapterHandle, PAirpcapKeysCollection KeysCollection, PUINT PKeysCollectionSize);

/*!
\brief Set the global list of decryption keys that AirPcap is going to use with all the devices.
\param KeysCollection Pointer to a \ref PAirpcapKeysCollection structure that contains the keys to be set globally.
\return TRUE if the operation is successful. FALSE otherwise.

The AirPcap driver is able to use a set of decryption keys to decrypt the traffic transmitted on a specific SSID. If one of the
keys corresponds to the one the frame has been encrypted with, the driver will perform decryption and return the cleartext frames
to the application.

This function allows to set the <b>global</b> set of keys. These keys will be used by all the devices plugged in
the machine.

At this time, the only supported decryption method is WEP.

The keys are applied to the packets in the same order they appear in the KeysCollection structure until the packet is
correctly decrypted, therefore putting frequently used keys at the beginning of the structure improves performance.

\note When you change the set of keys from an open capture instance, the change will be
immediately reflected on all the other capture instances.
*/

/*!
\brief Returns the global list of decryption keys that AirPcap is using with all the devices.
\param KeysCollection User-allocated PAirpcapKeysCollection structure that will be filled with the keys.
\param PKeysCollectionSize
- \b IN: pointer to a user-allocated variable that contains the length of the KeysCollection structure, in bytes.
- \b OUT: amount of data moved by AirPcap in the buffer pointed by KeysBuffer, in bytes.
\return TRUE if the operation is successful. If an error occurs, the return value is FALSE and KeysCollectionSize is zero.
If the provided buffer is too small to contain the keys, the return value is FALSE and KeysCollectionSize contains the
needed KeysCollection length, in bytes. If no global decryption keys are configured, the return value is TRUE, and
KeysCollectionSize will be zero.

This function returns the <b>global</b> set of keys. These keys will be used by all the devices plugged in
the machine.

The AirPcap driver is able to use a set of decryption keys to decrypt the traffic transmitted on a specific SSID. If one of the
keys corresponds to the one the frame has been encrypted with, the driver will perform decryption and return the cleartext frames
to the application.

At this time, the only supported decryption method is WEP.
*/
BOOL AirpcapGetDriverKeys(PAirpcapHandle AdapterHandle, PAirpcapKeysCollection KeysCollection, PUINT PKeysCollectionSize);

/*!
\brief Turns on or off the decryption of the incoming frames with the <b>device-specific</b> keys.
\param Enable Either \ref AIRPCAP_DECRYPTION_ON or \ref AIRPCAP_DECRYPTION_OFF
\return TRUE on success.

The device-specific decryption keys can be configured with the \ref AirpcapSetDeviceKeys() function.
\note By default, the driver is configured with \ref AIRPCAP_DECRYPTION_ON.
*/

/*!
\brief Tells if this open instance is configured to perform the decryption of the incoming frames with the <b>device-specific</b> keys.
\param PEnable Pointer to a user supplied variable that will contain the decryption configuration. See \ref PAirpcapDecryptionState for details.
\return TRUE if the operation is succesful. FALSE otherwise.

The device-specific decryption keys can be configured with the \ref AirpcapSetDeviceKeys() function.
\note By default, the driver is configured with \ref AIRPCAP_DECRYPTION_ON.
*/

/*!
\brief Turns on or off the decryption of the incoming frames with the <b>global</b> set of keys.
\param Enable Either \ref AIRPCAP_DECRYPTION_ON or \ref AIRPCAP_DECRYPTION_OFF
\return TRUE on success.

The global decryption keys can be configured with the \ref AirpcapSetDriverKeys() function.
\note By default, the driver is configured with \ref AIRPCAP_DECRYPTION_ON.
*/

/*!
\brief Tells if this open instance is configured to perform the decryption of the incoming frames with the <b>global</b> set of keys.
\param PEnable Pointer to a user supplied variable that will contain the decryption configuration. See \ref PAirpcapDecryptionState for details.
\return TRUE if the operation is successful. FALSE otherwise.

The global decryption keys can be configured with the \ref AirpcapSetDriverKeys() function.
\note By default, the driver is configured with \ref AIRPCAP_DECRYPTION_ON.
*/

/*!
\brief Sets the radio channel of a device
\param Channel the new channel to set.
\return TRUE on success.

The list of available channels can be retrieved with \ref AirpcapGetDeviceSupportedChannels(). The default channel setting is 6.

\note This is a device-related function: when you change the channel from an open capture instance, the change will be
immediately reflected on all the other capture instances.
*/

/*!
\brief Gets the radio channel of a device
\param PChannel Pointer to a user-supplied variable into which the function will copy the currently configured radio channel.
\return TRUE on success.

The list of available channels can be retrieved with \ref AirpcapGetDeviceSupportedChannels(). The default channel setting is 6.

\note This is a device-related function: when you change the channel from an open capture instance, the change will be
immediately reflected on all the other capture instances.
*/

/*!
\brief Sets the channel of a device through its radio frequency. In case of 802.11n enabled devices, it sets the extension channel, if used.
\param ChannelInfo The new channel information to set.
\return TRUE on success.

\note This is a device-related function: when you change the channel from an open capture instance, the change will be
immediately reflected on all the other capture instances.
*/

/*!
\brief Gets the channel of a device through its radio frequency. In case of 802.11n enabled devices, it gets the extension channel, if in use.
\param PChannelInfo Pointer to a user-supplied variable into which the function will copy the currently configured channel information.
\return TRUE on success.

\note This is a device-related function: when you change the channel from an open capture instance, the change will be
immediately reflected on all the other capture instances.
*/

/*!
\brief Gets the list of supported channels for a given device. In case of a 802.11n capable device, information related to supported extension channels is also reported.

Every control channel is listed multiple times, one for each different supported extension channel. For example channel 6 (2437MHz)  is usually listed three times:
- <b>Frequency 2437 Extension +1</b>. Control channel is 6, extension channel is 10.
- <b>Frequency 2437 Extension 0</b>. Control channel is 6, no extension channel is used (20MHz channel and legacy mode).
- <b>Frequency 2437 Extension -1</b>. Control channel is 6, extension channel is 2.
\param ppChannelInfo Pointer to a user-supplied variable that will point to an array of supported channel. Such list must not be freed by the caller
\param pNumChannelInfo Number of channels returned in the array.
\return TRUE on success.

\note The supported channels are not listed in any specific order.
*/
BOOL AirpcapGetDeviceSupportedChannels(PAirpcapHandle AdapterHandle, PAirpcapChannelInfo *ppChannelInfo, PUINT pNumChannelInfo);

/*!
\brief Converts a given frequency to the corresponding channel.

\param Frequency Frequency of the channel, in MHz.
\param PChannel Pointer to a user-supplied variable that will contain the channel number on success.
\param PBand Pointer to a user-supplied variable that will contain the band (a or b/g) of the given channel.
\return TRUE on success, i.e. the frequency corresponds to a valid a or b/g channel.
*/
BOOL AirpcapConvertFrequencyToChannel(UINT Frequency, PUINT PChannel, PAirpcapChannelBand PBand);

/*!
\brief Converts a given channel to the corresponding frequency.

\param Channel Channel number to be converted.
\param PFrequency Pointer to a user-supplied variable that will contain the channel frequency in MHz on success.
\return TRUE on success, i.e. the given channel number exists.
*/
BOOL AirpcapConvertChannelToFrequency(UINT Channel, PUINT PFrequency);

/*!
\brief Sets the size of the kernel packet buffer for this adapter
\param BufferSize New size, in bytes.
\return TRUE on success.

Every AirPcap open instance has an associated kernel buffer, whose default size is 1 Mbyte.
This function can be used to change the size of this buffer, and can be called at any time.
A bigger kernel buffer size decreases the risk of dropping packets during network bursts or when the
application is busy, at the cost of higher kernel memory usage.

\note Don't use this function unless you know what you are doing. Due to caching issues and bigger non-paged
memory consumption, bigger buffer sizes can decrease the capture performace instead of improving it.
*/

/*!
\brief Gets the size of the kernel packet buffer for this adapter
\param PSizeBytes User-allocated variable that will be filled with the size of the kernel buffer.
\return TRUE on success.

Every AirPcap open instance has an associated kernel buffer, whose default size is 1 Mbyte.
This function can be used to get the size of this buffer.
*/

/*!
\brief Saves the configuration of the specified adapter in the registry, so that it becomes the default for this adapter.
\return TRUE on success. FALSE on failure.

Almost all the AirPcap calls that modify the configuration (\ref AirpcapSetLinkType(), \ref AirpcapSetFcsPresence(),
\ref AirpcapSetFcsValidation(), \ref AirpcapSetKernelBuffer(), \ref AirpcapSetMinToCopy())
affect only the referenced AirPcap open instance. This means that if you do another \ref AirpcapOpen() on the same
adapter, the configuration changes will not be remembered, and the new adapter handle will have default configuration
settings.

Exceptions to this rule are the \ref AirpcapSetDeviceChannel() and \ref AirpcapSetDeviceKeys() functions: a channel change is
reflected on all the open instances, and remembered until the next call to \ref AirpcapSetDeviceChannel(), until the adapter
is unplugged, or until the machine is powered off. Same thing for the configuration of the WEP keys.

AirpcapStoreCurConfigAsAdapterDefault() stores the configuration of the give open instance as the default for the adapter:
all the instances opened in the future will have the same configuration that this adapter currently has.
The configuration is stored in the registry, therefore it is remembered even when the adapter is unplugged or the
machine is turned off. However, an adapter doesn't bring its configuration with it from machine to machine.

the configuration information saved in the registry includes the following parameters:
- channel
- kernel buffer size
- mintocopy
- CRC presence
- Encryption keys
- Encryption Enabled/Disabled state

The configuration is device-specific. This means that changing the configuration of a device
doesn't modify the one of the other devices that are currently used or that will be used in the future.

will fail if more than one AirPcap handle is opened at the same time for this device.
is not a local machine administrator.
*/

/*!
\brief Sets the BPF kernel filter for an adapter
\param Instructions pointer to the first BPF instruction in the array. Corresponds to the  bf_insns
in a bpf_program structure (see the WinPcap documentation at http://www.winpcap.org/devel.htm).
\param Len Number of instructions in the array pointed by the previous field. Corresponds to the bf_len in
a a bpf_program structure (see the WinPcap documentation at http://www.winpcap.org/devel.htm).
\return TRUE on success.

The AirPcap driver is able to perform kernel-level filtering using the standard BPF pseudo-machine format. You can read
the WinPcap documentation at http://www.winpcap.org/devel.htm for more details on the BPF filtering mechaism.

A filter can be automatically created by using the pcap_compile() function of the WinPcap API. This function
converts a human readable text expression with the tcpdump/libpcap syntax into a BPF program.
If your program doesn't link wpcap, but you need to generate the code for a particular filter, you can run WinDump
with the -d or -dd or -ddd flags to obtain the pseudocode.

*/
BOOL AirpcapSetFilter(PAirpcapHandle AdapterHandle, PVOID Instructions, UINT Len);

/*!
\brief Returns the MAC address of a device.
\return TRUE on success.
*/

/*!
\brief Sets the MAC address of a device.
\return TRUE on success. FALSE on failure, or if the adapter doesn't support changing the address.

Using this function, the programmer can change the MAC address of the device. This is useful when disabling monitor
mode with \ref AirpcapSetDeviceMacFlags(), because the device will acknowledge the data frames sent to its MAC address.

\note The address change is temporary: when the device is unplugged or when the host PC is turned off, the address is reset to the original
value.
*/

/*!
\brief Sets the mintocopy parameter for an open adapter.
\param MinToCopy is the mintocopy size in bytes.
\return TRUE on success.

When the number of bytes in the kernel buffer changes from less than mintocopy bytes to greater than or equal to mintocopy bytes,
the read event is signalled (see \ref AirpcapGetReadEvent()). A high value for mintocopy results in poor responsiveness since the
driver may signal the application "long" after the arrival of the packet. And a high value results in low CPU loading
by minimizing the number of user/kernel context switches.
A low MinToCopy results in good responsiveness since the driver will signal the application close to the arrival time of
*/

/*!
\brief Gets an event that is signalled when packets are available in the kernel buffer (see \ref AirpcapSetMinToCopy()).
\param PReadEvent Pointer to a user-supplied handle in which the read event will be copied.
\return TRUE on success.

\note The event is signalled when at least mintocopy bytes are present in the kernel buffer (see \ref AirpcapSetMinToCopy()).
This event can be used by WaitForSingleObject() and WaitForMultipleObjects() to create blocking behavior when reading
*/

/*!
\brief Fills a user-provided buffer with zero or more packets that have been captured on the referenced adapter.
\param Buffer pointer to the buffer that will be filled with captured packets.
\param BufSize size of the input buffer that will contain the packets, in bytes.
\param PReceievedBytes Pointer to a user supplied variable that will receive the number of bytes copied by AirpcapRead.
Can be smaller than BufSize.
\return TRUE on success.

802.11 frames are returned by the driver in buffers. Every 802.11 frame in the buffer is preceded by a \ref AirpcapBpfHeader structure.
The suggested way to use an AirPcap adapter is through the pcap API exported by wpcap.dll. If this is not
possible, the Capture_radio and Capture_no_radio examples in the AirPcap developer's pack show how to properly decode the

\note This function is NOT blocking. Blocking behavior can be obtained using the event returned
*/

/*!
\brief Transmits a packet.
\param TxPacket Pointer to a buffer that contains the packet to be transmitted.
\param PacketLen Length of the buffer pointed by the TxPacket argument, in bytes.
\return TRUE on success.

The packet will be transmitted on the channel the device is currently set. To change the device adapter, use the
\ref AirpcapSetDeviceChannel() function.

If the link type of the adapter is AIRPCAP_LT_802_11, the buffer pointed by TxPacket should contain just the 802.11
packet, without additional information. The packet will be transmitted at 1Mbps.

header followed by the 802.11 packet. AirpcapWrite will use the rate information in the radiotap header when
transmitting the packet.

If the link type of the adapter is AIRPCAP_LT_802_11_PLUS_PPI, ????? TODO ????
*/
BOOL AirpcapWrite(PAirpcapHandle AdapterHandle, PCHAR TxPacket, ULONG PacketLen);

/*!
\brief Gets per-adapter WinPcap-compatible capture statistics.
\param PStats pointer to a user-allocated AirpcapStats structure that will be filled with statistical information.
\return TRUE on success.
*/

/*!
\brief Gets the number of LEDs the referenced adapter has available.
\param NumberOfLeds Number of LEDs available on this adapter.
\return TRUE on success.
*/

/*!
\brief Turns on one of the adapter's LEDs.
\param LedNumber zero-based identifier of the LED to turn on.
\return TRUE on success.
*/

/*!
\brief Turns off one of the adapter's LEDs.
\param LedNumber zero-based identifier of the LED to turn off.
\return TRUE on success.
*/

/*@}*/

#endif // __AIRPCAP_DRIVER__

#ifdef __cplusplus
}
#endif


0
Question by:mileyja
• 12
• 3

LVL 3

Expert Comment

ID: 20333354
Fot this BOOL AirpcapGetDeviceList(PAirpcapDeviceDescription *PPAllDevs, PCHAR Ebuf) maybe (see code snippet). You have to test by yourself ofcourse. You can find a lot of samples at pinvoke.net. Maybe you can ask here from real experts?)

I'm not shure you can do that with MarshalAs attribute. This attribute can't be used to apply array sub type string size. Maybe you should write your own C++ dll to wrap around airpcap.dll. Or you can write your own custom marshaler - i'm not shure. Also, maybe unsafe code can be used - you can create by your hands (in C# something like this (not shure, never used unsafe code, but i know C)): char * * buf = new char*[100]; buf[0] = new char[256]...) buffer for device names (array of LPStr) and put it in as IntPtr - try this.

[DllImport("airpcap.dll")]
public extern static int AirpcapGetDeviceList([Out] [MarshalAs(UnmanagedType.LPArray, ArraySubType = UnmanagedType.LPStr, SizeParamIndex = 1)] string[] PPAllDevs, [In, Out] ref int Ebuf)

0

Author Comment

ID: 20336301
well about writing my own c++ wrapper, I don't know c++ at all .  Ill look into the pinvoke.net later tonight or tomorrow (in-laws are here for holiday). Ill let you know.
0

Author Comment

ID: 20341118
The code below returns 5 blank strings.  I think we are moving closer, not quite there.
 public Form1()
{
InitializeComponent();
}
[DllImport("airpcap.dll")]
public extern static AirpcapGetDeviceList([MarshalAs(UnmanagedType.LPArray, ArraySubType = UnmanagedType.LPStr, SizeParamIndex = 1)] string[] PPAllDevs, [In, Out] ref int Ebuf);
private unsafe void Form1_Load(object sender, EventArgs e)
{
int test1 = -1;
string[] Stringg = new String[5];
//string s = "";

AirpcapGetDeviceList(Stringg, ref test1);
textBox1.Text = test1.ToString();
foreach (string s in Stringg)
{
MessageBox.Show(s);
}
}

0

LVL 3

Expert Comment

ID: 20342934
Try this:
[STAThread]
static void Main() {
//
unsafe {
int dSize = 100;
char*[] dBuf = new char*[dSize];
ArrayList xList = new ArrayList();
for ( int i = 0; i < 100; i++ ) {
char * xSubBufi = stackalloc char[256];
dBuf[i] = xSubBufi;
}
AirpcapGetDeviceList(dBuf, &dSize);
//
}
}

[DllImport("airpcap.dll")]
public extern static unsafe int AirpcapGetDeviceList(char*[] ppDevices, int * pBuf);

0

Author Comment

ID: 20344338
I know very little c# also, so if you could put that in a context more like what I have above, like in a form context.

its telling me
Error      7      Expected class, delegate, enum, interface, or struct      C:\Documents and Settings\mileyja\My Documents\Visual Studio 2005\Projects\WindowsApplication1\WindowsApplication1\Form1.cs      18      31      WindowsApplication
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using System.Runtime.InteropServices;

namespace WindowsApplication1
{
static void Main() {
//
unsafe {
int dSize = 100;
char*[] dBuf = new char*[dSize];
ArrayList xList = new ArrayList();
for ( int i = 0; i < 100; i++ ) {
char * xSubBufi = stackalloc char[256];
dBuf[i] = xSubBufi;
}
AirpcapGetDeviceList(dBuf, &dSize);
//
}
}

[DllImport("airpcap.dll")]
public extern static unsafe int AirpcapGetDeviceList(char*[] ppDevices, int * pBuf);

0

Author Comment

ID: 20344383
this returns a 100 sized array but not a lot of info comes back, they all contain the same thing or appear to.  Im slightly confused.

return look slike this   -  0'\0'

Im still doin something wrong.  :(
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using System.Runtime.InteropServices;
using System.Collections;

namespace GetDeviceList2
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}

[DllImport("airpcap.dll")]
public extern static unsafe int AirpcapGetDeviceList(char*[] ppDevices, int* pBuf);

private void Form1_Load(object sender, EventArgs e)
{
//
unsafe {
int dSize = 100;
char*[] dBuf = new char*[dSize];
ArrayList xList = new ArrayList();
for ( int i = 0; i < 100; i++ ) {
char * xSubBufi = stackalloc char[256];
dBuf[i] = xSubBufi;
}
AirpcapGetDeviceList(dBuf, &dSize);
//
}

}
}
}

0

Author Comment

ID: 20344388
I think its supposed to return a bunch of different values in the arrays

like this:
CHAR            DeviceName[256];   // to be generous
UINT            NDevices = 0, NProDevices = 0;
CHAR            Desc[256];
UINT            i;

any thoughts on the above code as to how that works.
0

Author Comment

ID: 20344400
0

Author Comment

ID: 20344534
Here is also some documentation info on the exact function I am trying to wrap

Returns the list of available devices.

Parameters:
PPAllDevs       Address to a caller allocated pointer. On success this pointer will receive the head of a list of available devices.
Ebuf       String that will contain error information if FALSE is returned. The size of the string must be AIRPCAP_ERRBUF_SIZE bytes.

Returns:
TRUE on success. FALSE is returned on failure, in which case Ebuf is filled in with an appropriate error message.

Here's a snippet of code that shows how to use AirpcapGetDeviceList():

CHAR Ebuf[AIRPCAP_ERRBUF_SIZE];
AirpcapDeviceDescription *Desc, *tDesc;

if(AirpcapGetDeviceList(&Desc, Ebuf) == -1)
{
printf("Unable to get the list of devices: %s\n", Ebuf);
return -1;
}

for(tDesc = Desc; tDesc; tDesc = tDesc->next)
{
printf("%u) %s (%s)\n",
++i,
tDesc->Name,
tDesc->Description);
}

AirpcapFreeDeviceList(Desc);

0

LVL 3

Accepted Solution

wizrr earned 500 total points
ID: 20344685
Sorry. Now i see. I supposed that AirpcapDeviceDescription is string array (because of function name and e.g.).

typedef struct _AirpcapDeviceDescription
{
struct      _AirpcapDeviceDescription *next;                  ///< Next element in the list
PCHAR      Name;                                                            ///< Device name
PCHAR      Description;                                                ///< Device description
}

- this is your function parameter.

also i found that in your code

#define AIRPCAP_ERRBUF_SIZE 512

means that your buffer size is 512

Solution is (i don't know how to marshal pointer to pointer, so i provided unsafe code) - see attached code please.

Is there any docs how to free memory used to store AirpcapDeviceDescription you want to get from AirpcapGetDeviceList? This is important. This memory must be deleted to reuse.

Ahh. I see now AirpcapFreeDeviceList(Desc); - is called to free struct array.

[StructLayout(LayoutKind.Sequential)]
private struct APCDeviceDescription {
public IntPtr next;
public IntPtr name;
public IntPtr description;
}

public class APCDevice {
public string name;
public string description;
}

[DllImport("airpcap.dll")]
private extern static unsafe int AirpcapGetDeviceList(APCDeviceDescription** ppDevices, char* pBuf);

[DllImport("airpcap.dll")]
private extern static unsafe int AirpcapFreeDeviceList(APCDeviceDescription* pDevices);

public static unsafe int AirpcapGetDeviceListWrap(out APCDevice[] outDevices, ref string outErrors) {
List<APCDevice> devicesToRet = new List<APCDevice>();
APCDeviceDescription* pDevices = (APCDeviceDescription*)0;
APCDeviceDescription** ppDevices = &pDevices;
char*pErrorBuffer = stackalloc char[513];
int result = 0;
try {
result = AirpcapGetDeviceList(ppDevices, pErrorBuffer);
} finally {
if (result != 0) {
APCDeviceDescription* pDevice = pDevices;
while (pDevice != (APCDeviceDescription*)0) {
APCDevice newDev = new APCDevice();
newDev.name = Marshal.PtrToStringAnsi(pDevice->name);
newDev.description = Marshal.PtrToStringAnsi(pDevice->description);
pDevice = (APCDeviceDescription*)pDevice->next;
}
AirpcapFreeDeviceList(pDevices);
//
outDevices = devicesToRet.ToArray();
outErrors = null;
} else {
List<char> listChars = new List<char>();
char charFromBuf = pErrorBuffer[0];
while (charFromBuf != 0) {
}
char[] errorsCharArray = listChars.ToArray();
//
outErrors = new String(errorsCharArray);
outDevices = null;
}
}
return ( result );
}

0

Author Comment

ID: 20345845
there is a FreeDeviceList function, thats the next one I get to wrap.  Im hoping after I knock a few of thsee functions out I will have learned enough to start putting 2 and 2 together myself.  I will be sure to post a different function in a different question for ya though. :)  Ill give this a try after church.
0

Author Comment

ID: 20346736
This is working, now everything hinges on the adapter open function.  Ill set up another questoin for that and send you a link to it.  Ill accept this answer.
0

Author Closing Comment

ID: 31410517
I don't know c# and c/c++ at all really so that made it difficult to understand
0

Author Comment

ID: 20346905
0

Author Comment

ID: 20347408
you might like this one too.  I need to benchmark referencing a C# dll in a vb.net project, I am very curious on how to convert this to vb.net if possible, the question for that is here.

http://www.experts-exchange.com/Microsoft/Development/.NET/Visual_CSharp/Q_22981349.html
0

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