iPhone哪些案例无法获得mac地址成功？

失败的案例基于iPhone 4S和IOS版本5.0.1.

大家好,

你知道哪种情况(除了低内存)它会失败吗？任何想法或讨论将不胜感激.谢谢.

/* Original source code courtesy John from iOSDeveloperTips.com */

#include <sys/socket.h>
#include <sys/sysctl.h>
#include <net/if.h>
#include <net/if_dl.h>

- (NSString *)getMacAddress
{
    int                 mgmtInfoBase[6];
    char                *msgBuffer = NULL;
    NSString            *errorFlag = NULL;
    size_t              length;

    // Setup the management Information Base (mib)
    mgmtInfoBase[0] = CTL_NET;        // Request network subsystem
    mgmtInfoBase[1] = AF_ROUTE;       // Routing table info
    mgmtInfoBase[2] = 0;              
    mgmtInfoBase[3] = AF_LINK;        // Request link layer information
    mgmtInfoBase[4] = NET_RT_IFLIST;  // Request all configured interfaces

    // With all configured interfaces requested,get handle index
    if ((mgmtInfoBase[5] = if_nametoindex("en0")) == 0) 
        errorFlag = @"if_nametoindex failure";
    // Get the size of the data available (store in len)
    else if (sysctl(mgmtInfoBase,6,NULL,&length,0) < 0) 
        errorFlag = @"sysctl mgmtInfoBase failure";
    // Alloc memory based on above call
    else if ((msgBuffer = malloc(length)) == NULL)
        errorFlag = @"buffer allocation failure";
    // Get system information,store in buffer
    else if (sysctl(mgmtInfoBase,msgBuffer,0) < 0)
    {
        free(msgBuffer);
        errorFlag = @"sysctl msgBuffer failure";
    }
    else
    {
        // Map msgbuffer to interface message structure
        struct if_msghdr *interfaceMsgStruct = (struct if_msghdr *) msgBuffer;

        // Map to link-level socket structure
        struct sockaddr_dl *socketStruct = (struct sockaddr_dl *) (interfaceMsgStruct + 1);

        // Copy link layer address data in socket structure to an array
        unsigned char macAddress[6];
        memcpy(&macAddress,socketStruct->sdl_data + socketStruct->sdl_nlen,6);

        // Read from char array into a string object,into traditional Mac address format
        NSString *macAddressString = [NSString stringWithFormat:@"%02X:%02X:%02X:%02X:%02X:%02X",macAddress[0],macAddress[1],macAddress[2],macAddress[3],macAddress[4],macAddress[5]];
        NSLog(@"Mac Address: %@",macAddressString);

        // Release the buffer memory
        free(msgBuffer);

        return macAddressString;
    }

    // Error...
    NSLog(@"Error: %@",errorFlag);

    return errorFlag;
}

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