internal/poll, net: use (*FD).SetsockoptInet4Addr in setIPv4MulticastInterface on windows

Change-Id: Ic29d15bf62d8e693ca969354b415d958823bf41d
Reviewed-on: https://go-review.googlesource.com/c/go/+/523915
TryBot-Result: Gopher Robot <[email protected]>
Run-TryBot: Tobias Klauser <[email protected]>
Auto-Submit: Tobias Klauser <[email protected]>
Reviewed-by: Ian Lance Taylor <[email protected]>
Reviewed-by: Damien Neil <[email protected]>

Author: tklauser

src/internal/poll/sockopt_windows.go

@@ -6,15 +6,6 @@ package poll
 
 import "syscall"
 
-// Setsockopt wraps the setsockopt network call.
-func (fd *FD) Setsockopt(level, optname int32, optval *byte, optlen int32) error {
-	if err := fd.incref(); err != nil {
-		return err
-	}
-	defer fd.decref()
-	return syscall.Setsockopt(fd.Sysfd, level, optname, optval, optlen)
-}
-
 // WSAIoctl wraps the WSAIoctl network call.
 func (fd *FD) WSAIoctl(iocc uint32, inbuf *byte, cbif uint32, outbuf *byte, cbob uint32, cbbr *uint32, overlapped *syscall.Overlapped, completionRoutine uintptr) error {
 	if err := fd.incref(); err != nil {

src/net/sockoptip_windows.go

@@ -8,7 +8,6 @@ import (
 	"os"
 	"runtime"
 	"syscall"
-	"unsafe"
 )
 
 func setIPv4MulticastInterface(fd *netFD, ifi *Interface) error {
@@ -18,7 +17,7 @@ func setIPv4MulticastInterface(fd *netFD, ifi *Interface) error {
 	}
 	var a [4]byte
 	copy(a[:], ip.To4())
-	err = fd.pfd.Setsockopt(syscall.IPPROTO_IP, syscall.IP_MULTICAST_IF, (*byte)(unsafe.Pointer(&a[0])), 4)
+	err = fd.pfd.SetsockoptInet4Addr(syscall.IPPROTO_IP, syscall.IP_MULTICAST_IF, a)
 	runtime.KeepAlive(fd)
 	return wrapSyscallError("setsockopt", err)
 }