tun: use netpoll instead of rwcancel

The new sysconn function of Go 1.12 makes this possible:

package main

import "log"
import "os"
import "unsafe"
import "time"
import "syscall"
import "sync"
import "golang.org/x/sys/unix"

func main() {
	fd, err := os.OpenFile("/dev/net/tun", os.O_RDWR, 0)
	if err != nil {
		log.Fatal(err)
	}

	var ifr [unix.IFNAMSIZ + 64]byte
	copy(ifr[:], []byte("cheese"))
	*(*uint16)(unsafe.Pointer(&ifr[unix.IFNAMSIZ])) = unix.IFF_TUN

	var errno syscall.Errno
	s, _ := fd.SyscallConn()
	s.Control(func(fd uintptr) {
		_, _, errno = unix.Syscall(
			unix.SYS_IOCTL,
			fd,
			uintptr(unix.TUNSETIFF),
			uintptr(unsafe.Pointer(&ifr[0])),
		)
	})
	if errno != 0 {
		log.Fatal(errno)
	}

	b := [4]byte{}
	wait := sync.WaitGroup{}
	wait.Add(1)
	go func() {
		_, err := fd.Read(b[:])
		log.Print("Read errored: ", err)
		wait.Done()
	}()
	time.Sleep(time.Second)
	log.Print("Closing")
	err = fd.Close()
	if err != nil {
		log.Print("Close errored: " , err)
	}
	wait.Wait()
	log.Print("Exiting")
}

1 files changed, 6 insertions, 32 deletions

diff --git a/tun/tun_freebsd.go b/tun/tun_freebsd.go
index 1aec123..9e5c5ad 100644
--- a/tun/tun_freebsd.go
+++ b/tun/tun_freebsd.go
@@ -11,7 +11,6 @@ import (
 	"fmt"
 	"golang.org/x/net/ipv6"
 	"golang.org/x/sys/unix"
-	"golang.zx2c4.com/wireguard/rwcancel"
 	"net"
 	"os"
 	"syscall"
@@ -52,7 +51,6 @@ type ifstat struct {
 type nativeTun struct {
 	name        string
 	tunFile     *os.File
-	rwcancel    *rwcancel.RWCancel
 	events      chan TUNEvent
 	errors      chan error
 	routeSocket int
@@ -333,14 +331,6 @@ func CreateTUNFromFile(file *os.File, mtu int) (TUNDevice, error) {
 		return nil, err
 	}
 
-	tun.operateOnFd(func(fd uintptr) {
-		tun.rwcancel, err = rwcancel.NewRWCancel(int(fd))
-	})
-	if err != nil {
-		tun.tunFile.Close()
-		return nil, err
-	}
-
 	tun.routeSocket, err = unix.Socket(unix.AF_ROUTE, unix.SOCK_RAW, unix.AF_UNSPEC)
 	if err != nil {
 		tun.tunFile.Close()
@@ -379,7 +369,7 @@ func (tun *nativeTun) Events() chan TUNEvent {
 	return tun.events
 }
 
-func (tun *nativeTun) doRead(buff []byte, offset int) (int, error) {
+func (tun *nativeTun) Read(buff []byte, offset int) (int, error) {
 	select {
 	case err := <-tun.errors:
 		return 0, err
@@ -393,18 +383,6 @@ func (tun *nativeTun) doRead(buff []byte, offset int) (int, error) {
 	}
 }
 
-func (tun *nativeTun) Read(buff []byte, offset int) (int, error) {
-	for {
-		n, err := tun.doRead(buff, offset)
-		if err == nil || !rwcancel.RetryAfterError(err) {
-			return n, err
-		}
-		if !tun.rwcancel.ReadyRead() {
-			return 0, errors.New("tun device closed")
-		}
-	}
-}
-
 func (tun *nativeTun) Write(buff []byte, offset int) (int, error) {
 
 	// reserve space for header
@@ -429,13 +407,12 @@ func (tun *nativeTun) Write(buff []byte, offset int) (int, error) {
 }
 
 func (tun *nativeTun) Close() error {
-	var err4 error
-	err1 := tun.rwcancel.Cancel()
-	err2 := tun.tunFile.Close()
-	err3 := tunDestroy(tun.name)
+	var err3 error
+	err1 := tun.tunFile.Close()
+	err2 := tunDestroy(tun.name)
 	if tun.routeSocket != -1 {
 		unix.Shutdown(tun.routeSocket, unix.SHUT_RDWR)
-		err4 = unix.Close(tun.routeSocket)
+		err3 = unix.Close(tun.routeSocket)
 		tun.routeSocket = -1
 	} else if tun.events != nil {
 		close(tun.events)
@@ -446,10 +423,7 @@ func (tun *nativeTun) Close() error {
 	if err2 != nil {
 		return err2
 	}
-	if err3 != nil {
-		return err3
-	}
-	return err4
+	return err3
 }
 
 func (tun *nativeTun) setMTU(n int) error {