From b4cef2524f3b2be11f905c4114e2e747a8101160 Mon Sep 17 00:00:00 2001
From: "Jason A. Donenfeld" <Jason@zx2c4.com>
Date: Tue, 22 May 2018 18:33:50 +0200
Subject: [PATCH] Fix integer conversions

---
 tun_darwin.go  | 8 +-------
 tun_freebsd.go | 8 +-------
 tun_linux.go   | 8 +-------
 tun_openbsd.go | 8 +-------
 uapi_bsd.go    | 5 ++++-
 5 files changed, 8 insertions(+), 29 deletions(-)

diff --git a/tun_darwin.go b/tun_darwin.go
index 8e4b970..e5a01a7 100644
--- a/tun_darwin.go
+++ b/tun_darwin.go
@@ -380,11 +380,5 @@ func (tun *NativeTun) MTU() (int, error) {
 		return 0, fmt.Errorf("failed to get MTU on %s", tun.name)
 	}
 
-	// convert result to signed 32-bit int
-
-	val := binary.LittleEndian.Uint32(ifr[16:20])
-	if val >= (1 << 31) {
-		return int(val-(1<<31)) - (1 << 31), nil
-	}
-	return int(val), nil
+	return int(*(*int32)(unsafe.Pointer(&ifr[16]))), nil
 }
diff --git a/tun_freebsd.go b/tun_freebsd.go
index dfd5d46..5461c45 100644
--- a/tun_freebsd.go
+++ b/tun_freebsd.go
@@ -515,11 +515,5 @@ func (tun *NativeTun) MTU() (int, error) {
 		return 0, fmt.Errorf("failed to get MTU on %s", tun.name)
 	}
 
-	// convert result to signed 32-bit int
-	mtu := ifr.MTU
-	if mtu >= (1 << 31) {
-		return int(mtu-(1<<31)) - (1 << 31), nil
-	}
-	return int(mtu), nil
-
+	return int(*(*int32)(unsafe.Pointer(&ifr.MTU))), nil
 }
diff --git a/tun_linux.go b/tun_linux.go
index b43ded8..db9cb51 100644
--- a/tun_linux.go
+++ b/tun_linux.go
@@ -263,13 +263,7 @@ func (tun *NativeTun) MTU() (int, error) {
 		return 0, errors.New("failed to get MTU of TUN device: " + strconv.FormatInt(int64(errno), 10))
 	}
 
-	// convert result to signed 32-bit int
-
-	val := binary.LittleEndian.Uint32(ifr[16:20])
-	if val >= (1 << 31) {
-		return int(toInt32(val)), nil
-	}
-	return int(val), nil
+	return int(*(*int32)(unsafe.Pointer(&ifr[16]))), nil
 }
 
 func (tun *NativeTun) Name() (string, error) {
diff --git a/tun_openbsd.go b/tun_openbsd.go
index 97d8f38..932404e 100644
--- a/tun_openbsd.go
+++ b/tun_openbsd.go
@@ -356,11 +356,5 @@ func (tun *NativeTun) MTU() (int, error) {
 		return 0, fmt.Errorf("failed to get MTU on %s", tun.name)
 	}
 
-	// convert result to signed 32-bit int
-	mtu := ifr.MTU
-	if mtu >= (1 << 31) {
-		return int(mtu-(1<<31)) - (1 << 31), nil
-	}
-	return int(mtu), nil
-
+	return int(*(*int32)(unsafe.Pointer(&ifr.MTU))), nil
 }
diff --git a/uapi_bsd.go b/uapi_bsd.go
index e949918..b2a7644 100644
--- a/uapi_bsd.go
+++ b/uapi_bsd.go
@@ -15,6 +15,7 @@ import (
 	"net"
 	"os"
 	"path"
+	"unsafe"
 )
 
 const (
@@ -101,11 +102,13 @@ func UAPIListen(name string, file *os.File) (net.Listener, error) {
 
 	go func(l *UAPIListener) {
 		event := unix.Kevent_t{
-			Ident:  uint64(uapi.keventFd),
 			Filter: unix.EVFILT_VNODE,
 			Flags:  unix.EV_ADD | unix.EV_ENABLE | unix.EV_ONESHOT,
 			Fflags: unix.NOTE_WRITE,
 		}
+		// Allow this assignment to work with both the 32-bit and 64-bit version
+		// of the above struct. If you know another way, please submit a patch.
+		*(*uintptr)(unsafe.Pointer(&event.Ident)) = uintptr(uapi.keventFd)
 		events := make([]unix.Kevent_t, 1)
 		n := 1
 		var kerr error