diff --git a/unix/syscall_darwin.go b/unix/syscall_darwin.go
index 5b0e831..7fc58d6 100644
--- a/unix/syscall_darwin.go
+++ b/unix/syscall_darwin.go
@@ -264,6 +264,29 @@
 	return err
 }
 
+// IfreqMTU is struct ifreq used to get or set a network device's MTU.
+type IfreqMTU struct {
+	Name [IFNAMSIZ]byte
+	MTU  int32
+}
+
+// IoctlGetIfreqMTU performs the SIOCGIFMTU ioctl operation on fd to get the MTU
+// of the network device specified by ifname.
+func IoctlGetIfreqMTU(fd int, ifname string) (*IfreqMTU, error) {
+	var ifreq IfreqMTU
+	copy(ifreq.Name[:], ifname)
+	err := ioctl(fd, SIOCGIFMTU, uintptr(unsafe.Pointer(&ifreq)))
+	return &ifreq, err
+}
+
+// IoctlSetIfreqMTU performs the SIOCSIFMTU ioctl operation on fd to set the MTU
+// of the network device specified by ifreq.Name.
+func IoctlSetIfreqMTU(fd int, ifreq *IfreqMTU) error {
+	err := ioctl(fd, SIOCSIFMTU, uintptr(unsafe.Pointer(ifreq)))
+	runtime.KeepAlive(ifreq)
+	return err
+}
+
 //sys   sysctl(mib []_C_int, old *byte, oldlen *uintptr, new *byte, newlen uintptr) (err error) = SYS_SYSCTL
 
 func Uname(uname *Utsname) error {