net-predictable/mac.go

package main

import (
	"fmt"
	"io"
	"net"
	"os"
	"strings"
)

func (i *iface) ProcMAC() (err error) {
	var (
		sb     strings.Builder
		file   *os.File
		cbytes []byte
	)
	macpath := strings.Join([]string{i.netpath, "address"}, "/")
	if file, err = os.Open(macpath); err != nil {
		err = fmt.Errorf("Failed to open file: %w", err)
		return
	}
	defer file.Close()

	if cbytes, err = io.ReadAll(file); err != nil {
		err = fmt.Errorf("Failed to read file: %w", err)
		return
	}
	var (
		strmac string
		ok     bool
	)
	if strmac, ok = strings.CutSuffix(string(cbytes), "\n"); !ok {
		err = ErrParseMac
		return
	}

	var addr net.HardwareAddr
	if addr, err = net.ParseMAC(strmac); err != nil {
		err = fmt.Errorf("%w: %w", ErrParseMac, err)
		return
	}

	_, err = sb.WriteString(i.pfx)
	_, err = sb.WriteString("x")
	for _, v := range addr {
		_, err = sb.WriteString(fmt.Sprintf("%02x", v))
	}

	i.names[IfNameMAC] = sb.String()
	return
}