package main

import (
	"encoding/hex"
	"fmt"
	"net"
	"strings"
	"syscall"
	"unsafe"
)

func main() {
	getPermanentMacAddr()
}

// If we use bond or team technology
// to use two or more adapters as a virtual one
// use net.Interface.HardwareAddr will get the same mac address
// The following code thinking was borrowed from ethtool's source code ethtool.c
// this code will get the permanent mac address
func getPermanentMacAddr() error {
	var err error
	fd, err := syscall.Socket(syscall.AF_INET, syscall.SOCK_DGRAM, 0)
	if err != nil {
		fd, err = syscall.Socket(syscall.AF_NETLINK, syscall.SOCK_RAW, syscall.NETLINK_GENERIC)
		if err != nil {
			return err
		}
	}

	defer func() {
		_ = syscall.Close(fd)
	}()
	var adapters []net.Interface
	adapters, _ = net.Interfaces()

	for _, adapter := range adapters {
		var data struct {
			cmd  uint32
			size uint32
			data [128]byte
		}

		data.cmd = 0x20
		data.size = 128
		// data.data = make([]byte, 128)

		var ifr struct {
			IfrName [16]byte
			IfrData unsafe.Pointer
		}
		copy(ifr.IfrName[:], adapter.Name)
		ifr.IfrData = unsafe.Pointer(&data)

		_, _, sysErr := syscall.RawSyscall(syscall.SYS_IOCTL,
			uintptr(fd), uintptr(0x8946), uintptr(unsafe.Pointer(&ifr)))

		if sysErr != 0 {
			fmt.Println("调用ioctl获取网口", adapter.Name, "物理MAC地址错误")
			// return errors.New("call ioctl get permanent mac address error")
			continue
		}
		// If mac address is all zero, this is a virtual adapter
		// we ignore it
		bAllZERO := true
		var i uint32 = 0
		for i = 0; i < data.size; i++ {
			if data.data[i] != 0x00 {
				bAllZERO = false
				break
			}
		}

		if bAllZERO {
			continue
		}

		if len(hex.EncodeToString(data.data[0:data.size])) > 12 {
			continue
		}

		mac := strings.ToUpper(hex.EncodeToString(data.data[0:data.size]))
		for i := 10; i > 0; i = i - 2 {
			mac = fmt.Sprintf("%s:%s", mac[:i], mac[i:])
		}

		fmt.Println(mac)
	}

	return nil
}