/*

     File: GetPrimaryMACAddress.c

 Abstract: Command-line tool demonstrating how to do retrieve the Ethernet MAC

 address of the built-in Ethernet interface from the I/O Registry on Mac OS X.

 Techniques shown include finding the primary (built-in) Ethernet interface,

 finding the parent Ethernet controller, and retrieving properties from the

 controller's I/O Registry entry.

  Version: 1.3

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*/

#include <stdio.h>

#include <CoreFoundation/CoreFoundation.h>

#include <IOKit/IOKitLib.h>

#include <IOKit/network/IOEthernetInterface.h>

#include <IOKit/network/IONetworkInterface.h>

#include <IOKit/network/IOEthernetController.h>

static kern_return_t FindEthernetInterfaces(io_iterator_t *matchingServices);

static kern_return_t GetMACAddress(io_iterator_t intfIterator, UInt8 *MACAddress, UInt8 bufferSize);

// Returns an iterator containing the primary (built-in) Ethernet interface. The caller is responsible for

// releasing the iterator after the caller is done with it.

static kern_return_t FindEthernetInterfaces(io_iterator_t *matchingServices)

{

    kern_return_t           kernResult; 

    CFMutableDictionaryRef  matchingDict;

    CFMutableDictionaryRef  propertyMatchDict;

    // Ethernet interfaces are instances of class kIOEthernetInterfaceClass. 

    // IOServiceMatching is a convenience function to create a dictionary with the key kIOProviderClassKey and 

    // the specified value.

    matchingDict = IOServiceMatching(kIOEthernetInterfaceClass);

    // Note that another option here would be:

    // matchingDict = IOBSDMatching("en0");

    // but en0: isn't necessarily the primary interface, especially on systems with multiple Ethernet ports.

    if (NULL == matchingDict) {

        printf("IOServiceMatching returned a NULL dictionary.\n");

    }

    else {

        // Each IONetworkInterface object has a Boolean property with the key kIOPrimaryInterface. Only the

        // primary (built-in) interface has this property set to TRUE.

        // IOServiceGetMatchingServices uses the default matching criteria defined by IOService. This considers

        // only the following properties plus any family-specific matching in this order of precedence 

        // (see IOService::passiveMatch):

        //

        // kIOProviderClassKey (IOServiceMatching)

        // kIONameMatchKey (IOServiceNameMatching)

        // kIOPropertyMatchKey

        // kIOPathMatchKey

        // kIOMatchedServiceCountKey

        // family-specific matching

        // kIOBSDNameKey (IOBSDNameMatching)

        // kIOLocationMatchKey

        // The IONetworkingFamily does not define any family-specific matching. This means that in            

        // order to have IOServiceGetMatchingServices consider the kIOPrimaryInterface property, we must

        // add that property to a separate dictionary and then add that to our matching dictionary

        // specifying kIOPropertyMatchKey.

        propertyMatchDict = CFDictionaryCreateMutable(kCFAllocatorDefault, 0,

                                                      &kCFTypeDictionaryKeyCallBacks,

                                                      &kCFTypeDictionaryValueCallBacks);

        if (NULL == propertyMatchDict) {

            printf("CFDictionaryCreateMutable returned a NULL dictionary.\n");

        }

        else {

            // Set the value in the dictionary of the property with the given key, or add the key 

            // to the dictionary if it doesn't exist. This call retains the value object passed in.

            CFDictionarySetValue(propertyMatchDict, CFSTR(kIOPrimaryInterface), kCFBooleanTrue); 

            // Now add the dictionary containing the matching value for kIOPrimaryInterface to our main

            // matching dictionary. This call will retain propertyMatchDict, so we can release our reference 

            // on propertyMatchDict after adding it to matchingDict.

            CFDictionarySetValue(matchingDict, CFSTR(kIOPropertyMatchKey), propertyMatchDict);

            CFRelease(propertyMatchDict);

        }

    }

    // IOServiceGetMatchingServices retains the returned iterator, so release the iterator when we're done with it.

    // IOServiceGetMatchingServices also consumes a reference on the matching dictionary so we don't need to release

    // the dictionary explicitly.

    kernResult = IOServiceGetMatchingServices(kIOMasterPortDefault, matchingDict, matchingServices);    

    if (KERN_SUCCESS != kernResult) {

        printf("IOServiceGetMatchingServices returned 0x%08x\n", kernResult);

    }

    return kernResult;

}

// Given an iterator across a set of Ethernet interfaces, return the MAC address of the last one.

// If no interfaces are found the MAC address is set to an empty string.

// In this sample the iterator should contain just the primary interface.

static kern_return_t GetMACAddress(io_iterator_t intfIterator, UInt8 *MACAddress, UInt8 bufferSize)

{

    io_object_t     intfService;

    io_object_t     controllerService;

    kern_return_t   kernResult = KERN_FAILURE;

    // Make sure the caller provided enough buffer space. Protect against buffer overflow problems.

    if (bufferSize < kIOEthernetAddressSize) {

        return kernResult;

    }

    // Initialize the returned address

    bzero(MACAddress, bufferSize);

    // IOIteratorNext retains the returned object, so release it when we're done with it.

    while ((intfService = IOIteratorNext(intfIterator)))

    {

        CFTypeRef   MACAddressAsCFData;        

        // IONetworkControllers can't be found directly by the IOServiceGetMatchingServices call, 

        // since they are hardware nubs and do not participate in driver matching. In other words,

        // registerService() is never called on them. So we've found the IONetworkInterface and will 

        // get its parent controller by asking for it specifically.

        // IORegistryEntryGetParentEntry retains the returned object, so release it when we're done with it.

        kernResult = IORegistryEntryGetParentEntry(intfService,

                                                   kIOServicePlane,

                                                   &controllerService);

        if (KERN_SUCCESS != kernResult) {

            printf("IORegistryEntryGetParentEntry returned 0x%08x\n", kernResult);

        }

        else {

            // Retrieve the MAC address property from the I/O Registry in the form of a CFData

            MACAddressAsCFData = IORegistryEntryCreateCFProperty(controllerService,

                                                                 CFSTR(kIOMACAddress),

                                                                 kCFAllocatorDefault,

                                                                 0);

            if (MACAddressAsCFData) {

                CFShow(MACAddressAsCFData); // for display purposes only; output goes to stderr

                // Get the raw bytes of the MAC address from the CFData

                CFDataGetBytes(MACAddressAsCFData, CFRangeMake(0, kIOEthernetAddressSize), MACAddress);

                CFRelease(MACAddressAsCFData);

            }

            // Done with the parent Ethernet controller object so we release it.

            (void) IOObjectRelease(controllerService);

        }

        // Done with the Ethernet interface object so we release it.

        (void) IOObjectRelease(intfService);

    }

    return kernResult;

}

int main(int argc, char *argv[])

{

    kern_return_t   kernResult = KERN_SUCCESS;

    io_iterator_t   intfIterator;

    UInt8           MACAddress[kIOEthernetAddressSize];

    kernResult = FindEthernetInterfaces(&intfIterator);

    if (KERN_SUCCESS != kernResult) {

        printf("FindEthernetInterfaces returned 0x%08x\n", kernResult);

    }

    else {

        kernResult = GetMACAddress(intfIterator, MACAddress, sizeof(MACAddress));

        if (KERN_SUCCESS != kernResult) {

            printf("GetMACAddress returned 0x%08x\n", kernResult);

        }

        else {

            printf("This system's built-in MAC address is %02x:%02x:%02x:%02x:%02x:%02x.\n",

                    MACAddress[0], MACAddress[1], MACAddress[2], MACAddress[3], MACAddress[4], MACAddress[5]);

        }

    }

    (void) IOObjectRelease(intfIterator);   // Release the iterator.

    return kernResult;

}