[Feature]: Add Get/Set MAC addresses

README.md

@@ -51,6 +51,15 @@ func main() {
 	if err != nil {
 		log.Fatal(err)
 	}
+
+        ifce.SetMAC("d6:db:b0:42:2c:7e")
+
+        mac, err := ifce.GetMAC()
+        if err != nil {
+                log.Fatal(err)
+        }
+        fmt.Println("MAC address:", mac)
+
 	var frame ethernet.Frame
 
 	for {

if.go

@@ -3,6 +3,10 @@ package water
 import (
 	"errors"
 	"io"
+	"net"
+	"os"
+	"syscall"
+	"unsafe"
 )
 
 // Interface is a TUN/TAP interface.
@@ -78,3 +82,57 @@ func (ifce *Interface) IsTAP() bool {
 func (ifce *Interface) Name() string {
 	return ifce.name
 }
+
+// GetMAC returns the created interface's MAC address
+func (ifce *Interface) GetMAC() (string, error) {
+	var req ifReq
+	req.Flags = syscall.AF_UNIX
+	copy(req.Name[:], ifce.name)
+
+	fd, err := syscall.Socket(syscall.AF_INET, syscall.SOCK_DGRAM, 0)
+	if err != nil {
+		return "", os.NewSyscallError("socket", err)
+	}
+	defer syscall.Close(fd)
+
+	err = syscall.SetsockoptInt(fd, syscall.SOL_SOCKET, syscall.SO_REUSEADDR, 1)
+	if err != nil {
+		return "", os.NewSyscallError("setsockopt", err)
+	}
+
+	err = ioctl(uintptr(fd), syscall.SIOCGIFHWADDR, uintptr(unsafe.Pointer(&req)))
+	if err != nil {
+		return "", err
+	}
+	return net.HardwareAddr(req.Mac[:]).String(), nil
+}
+
+// SetMAC sets the MAC address for the interface
+func (ifce *Interface) SetMAC(mac string) error {
+	var req ifReq
+	req.Flags = syscall.AF_UNIX
+	copy(req.Name[:], ifce.name)
+
+	macBytes, err := net.ParseMAC(mac)
+	if err != nil {
+		return err
+	}
+	copy(req.Mac[:], macBytes)
+
+	fd, err := syscall.Socket(syscall.AF_INET, syscall.SOCK_DGRAM, 0)
+	if err != nil {
+		return os.NewSyscallError("socket", err)
+	}
+	defer syscall.Close(fd)
+
+	err = syscall.SetsockoptInt(fd, syscall.SOL_SOCKET, syscall.SO_REUSEADDR, 1)
+	if err != nil {
+		return os.NewSyscallError("setsockopt", err)
+	}
+
+	err = ioctl(uintptr(fd), syscall.SIOCSIFHWADDR, uintptr(unsafe.Pointer(&req)))
+	if err != nil {
+		return err
+	}
+	return nil
+}

syscalls_linux.go

@@ -17,7 +17,8 @@ const (
 type ifReq struct {
 	Name  [0x10]byte
 	Flags uint16
-	pad   [0x28 - 0x10 - 2]byte
+	Mac   [6]byte
+	pad   [0x28 - 0x10 - 8]byte
 }
 
 func ioctl(fd uintptr, request uintptr, argp uintptr) error {