Type of expression is ambiguous without more context

Question

I'm trying to convert the code of objective C mentioned here - https://gist.github.com/Coeur/1409855/f6df10c79f8cdd0fcb2a0735b99f4b3a74b9f954 to swift

The code I've wrote till now in swift -

class func getMacAddress(_ ifName: String?) -> String? {

        var mgmtInfoBase = [Int32](repeating: 0, count: 6)
        var msgBuffer: Int8? = nil
        var length: size_t
        var macAddress = [UInt8](repeating: 0, count: 6)
        var interfaceMsgStruct: if_msghdr?
        var socketStruct: sockaddr_dl?
        var errorFlag: String? = nil
        
        // Setup the management Information Base (mib)
        mgmtInfoBase[0] = Int32(Int(CTL_NET)) // Request network subsystem
        mgmtInfoBase[1] = Int32(Int(AF_ROUTE)) // Routing table info
        mgmtInfoBase[2] = 0
        mgmtInfoBase[3] = Int32(Int(AF_LINK)) // Request link layer information
        mgmtInfoBase[4] = Int32(Int(NET_RT_IFLIST)) // Request all configured interfaces
        
        mgmtInfoBase[5] = Int32(if_nametoindex(ifName?.utf8CString)) //ERROR: Type of expression is ambiguous without more context
        
        // With all configured interfaces requested, get handle index
        if ( mgmtInfoBase[5] == 0) {
                errorFlag = "if_nametoindex failure"
            } else {
                // Get the size of the data available (store in len)
                if sysctl(&mgmtInfoBase, 6, nil, &length, nil, 0) < 0 {
                    errorFlag = "sysctl mgmtInfoBase failure"
                } else {
                    // Alloc memory based on above call
                    if (msgBuffer = Int8((length))) == nil {
                        errorFlag = "buffer allocation failure"
                    } else {
                        // Get system information, store in buffer
                        if sysctl(&mgmtInfoBase, 6, &msgBuffer, &length, nil, 0) < 0 {
                            errorFlag = "sysctl msgBuffer failure"
                        }
                    }
                }
            }
        
        
        // Before going any further...
        if errorFlag != nil {
            // Release the buffer memory
            if (msgBuffer != nil) {
                free(&msgBuffer)
            }
            return nil
        }

        // Map msgbuffer to interface message structure
        interfaceMsgStruct = msgBuffer as? if_msghdr

        // Map to link-level socket structure
        socketStruct = (interfaceMsgStruct + 1) as? sockaddr_dl // ERROR: Cannot convert value of type 'if_msghdr?' to expected argument type 'Int'

        // Copy link layer address data in socket structure to an array
        if socketStruct == nil {
            return nil
        }
        memcpy(&macAddress, socketStruct.sdl_data + socketStruct.sdl_nlen, 6) // ERROR: Type of expression is ambiguous without more context
        
        // Read from char array into a string object, into traditional Mac address format
            let macAddressString = String(format: "%02X:%02X:%02X:%02X:%02X:%02X", macAddress[0], macAddress[1], macAddress[2], macAddress[3], macAddress[4], macAddress[5])

            // Release the buffer memory
            free(&msgBuffer)

            return macAddressString
    }

I'm getting the errors that I've mentioned. I searched and tried every possible thing and read articles from the documentation but still I couldn't get away with these errors. Please help.

The definitions of the functions for which I'm getting error as mentioned in Darwin.posix.net.if -

public func if_nametoindex(_: UnsafePointer<Int8>!) -> UInt32

public struct if_msghdr {

    public var ifm_msglen: UInt16 /* to skip non-understood messages */

    public var ifm_version: UInt8 /* future binary compatability */

    public var ifm_type: UInt8 /* message type */

    public var ifm_addrs: Int32 /* like rtm_addrs */

    public var ifm_flags: Int32 /* value of if_flags */

    public var ifm_index: UInt16 /* index for associated ifp */

    public var ifm_data: if_data /* statistics and other data about if */

    public init()

    public init(ifm_msglen: UInt16, ifm_version: UInt8, ifm_type: UInt8, ifm_addrs: Int32, ifm_flags: Int32, ifm_index: UInt16, ifm_data: if_data)
}

public func memcpy(_ __dst: UnsafeMutableRawPointer!, _ __src: UnsafeRawPointer!, _ __n: Int) -> UnsafeMutableRawPointer!````