iPhone在哪些情况下无法获取mac地址成功？

Question

使用下面的方法，99.5%的情况下都能正常工作，但是AppStore中很少有用户反射(reflect)无法获取mac地址(我们使用identifier进行认证每次服务器调用)。

失败案例基于 iPhone 4S，IOS 版本为 5.0.1。

你知道在什么情况下(除了低内存)它会失败吗？

/* 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, NULL, 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, 6, msgBuffer, &length, NULL, 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;
}

非常感谢任何帮助。

Answer 1

我在将 iPhone 升级到 iOS 5 后遇到了这样的情况，问题是臭名昭著的 wifi 错误。你不会喜欢这个答案，但唯一的解决办法是将设备带回 Apple 并获得一台可以正常工作的新设备。可以将代码更改为在 mac 地址查找失败时不会崩溃，但是当 REST 调用需要唯一标识符时，这无济于事。作为开发人员，您进退两难。