macOSのClonable Interface一覧を取るやつ in Golang

ioctl_num.c

#include <stdio.h>
#include <sys/sockio.h>
#include <net/if.h>

int main() {
    printf("%lx", SIOCIFGCLONERS);
    return 0;
}

main.go

package main

import (
	"syscall"
	"unsafe"
	"fmt"
	"os"
	"encoding/json"
	"regexp"
	"strings"
)

const(
	SIOCIFGCLONERS = 0xc0106981
)

type if_clonereq struct {
	ifcr_total  uint32
	ifcr_count  uint32
	ifcr_buffer []byte
}

func formatIfClonereq(req *if_clonereq) string {
	re := regexp.MustCompile("\\s?([^\\x00]+)\\x00*")
	human := re.ReplaceAllString(string(req.ifcr_buffer), "$1 ")

	s := map[string]string{
		"ifcr_total": fmt.Sprint(req.ifcr_total),
		"ifcr_count": fmt.Sprint(req.ifcr_count),
		"ifcr_buffer": strings.Trim(human, " "),
	}
	j, _ := json.MarshalIndent(s, "", "  ")
	return string(j)
}

func main() {
	fd, err := syscall.Socket(syscall.AF_INET, syscall.SOCK_DGRAM, 0)
	if err != nil {
		fmt.Fprint(os.Stderr, err.Error())
		return
	}

	req := if_clonereq{
		ifcr_buffer: []byte{},
	}

	// Retrieve number of clonable ifs
	_, _, errno := syscall.Syscall(syscall.SYS_IOCTL, uintptr(fd), SIOCIFGCLONERS, uintptr(unsafe.Pointer(&req)))
	if errno != 0 {
		fmt.Printf("Errno: %s", errno.Error())
	}

	fmt.Printf("First:\n%s\n\n", formatIfClonereq(&req))

	if req.ifcr_total > 0 {
		req.ifcr_count = req.ifcr_total
		req.ifcr_buffer = make([]byte, syscall.IFNAMSIZ * req.ifcr_total)
	} else {
		return
	}

	// Retrieve names
	_, _, errno = syscall.Syscall(syscall.SYS_IOCTL, uintptr(fd), SIOCIFGCLONERS, uintptr(unsafe.Pointer(&req)))
	if errno != 0 {
		fmt.Printf("Errno: %s", errno.Error())
	}

	fmt.Printf("Second:\n%s\n", formatIfClonereq(&req))
	fmt.Println(string(req.ifcr_buffer))
}