From 659106bd6d7a6f40310e5704812c6c9fbb96f06c Mon Sep 17 00:00:00 2001
From: "Jason A. Donenfeld" <Jason@zx2c4.com>
Date: Mon, 14 May 2018 02:14:33 +0200
Subject: Ensure go routines can exit

---
 device.go    |  2 +-
 tun_linux.go | 99 +++++++++++++++++++++++++++++++-----------------------------
 2 files changed, 52 insertions(+), 49 deletions(-)

diff --git a/device.go b/device.go
index cc12ac9..08a6471 100644
--- a/device.go
+++ b/device.go
@@ -293,7 +293,7 @@ func NewDevice(tun TUNDevice, logger *Logger) *Device {
 
 	// prepare signals
 
-	device.signals.stop = make(chan struct{}, 1)
+	device.signals.stop = make(chan struct{}, 0)
 
 	// prepare net
 
diff --git a/tun_linux.go b/tun_linux.go
index 3510f94..c642fe7 100644
--- a/tun_linux.go
+++ b/tun_linux.go
@@ -31,13 +31,15 @@ const (
 )
 
 type NativeTun struct {
-	fd       *os.File
-	index    int32         // if index
-	name     string        // name of interface
-	errors   chan error    // async error handling
-	events   chan TUNEvent // device related events
-	nopi     bool          // the device was pased IFF_NO_PI
-	rwcancel *rwcancel.RWCancel
+	fd                   *os.File
+	index                int32         // if index
+	name                 string        // name of interface
+	errors               chan error    // async error handling
+	events               chan TUNEvent // device related events
+	nopi                 bool          // the device was pased IFF_NO_PI
+	rwcancel             *rwcancel.RWCancel
+	netlinkSock          int
+	shutdownHackListener chan struct{}
 }
 
 func (tun *NativeTun) File() *os.File {
@@ -45,10 +47,6 @@ func (tun *NativeTun) File() *os.File {
 }
 
 func (tun *NativeTun) RoutineHackListener() {
-	// TODO: This function never actually exits in response to anything,
-	// a go routine that goes forever. We'll want to fix that if this is
-	// to ever be used as any sort of library.
-
 	/* This is needed for the detection to work across network namespaces
 	 * If you are reading this and know a better method, please get in touch.
 	 */
@@ -61,47 +59,38 @@ func (tun *NativeTun) RoutineHackListener() {
 		case unix.EIO:
 			tun.events <- TUNEventDown
 		default:
+			return
+		}
+		select {
+		case <-time.After(time.Second / 10):
+		case <-tun.shutdownHackListener:
+			return
 		}
-		time.Sleep(time.Second / 10)
 	}
 }
 
-func toRTMGRP(sc uint) uint {
-	return 1 << (sc - 1)
-}
-
-func (tun *NativeTun) RoutineNetlinkListener() {
-
-	groups := toRTMGRP(unix.RTNLGRP_LINK)
-	groups |= toRTMGRP(unix.RTNLGRP_IPV4_IFADDR)
-	groups |= toRTMGRP(unix.RTNLGRP_IPV6_IFADDR)
+func createNetlinkSocket() (int, error) {
 	sock, err := unix.Socket(unix.AF_NETLINK, unix.SOCK_RAW, unix.NETLINK_ROUTE)
 	if err != nil {
-		tun.errors <- errors.New("Failed to create netlink event listener socket")
-		return
+		return -1, err
 	}
-	defer unix.Close(sock)
 	saddr := &unix.SockaddrNetlink{
 		Family: unix.AF_NETLINK,
-		Groups: uint32(groups),
+		Groups: uint32((1 << (unix.RTNLGRP_LINK - 1)) | (1 << (unix.RTNLGRP_IPV4_IFADDR - 1)) | (1 << (unix.RTNLGRP_IPV6_IFADDR - 1))),
 	}
 	err = unix.Bind(sock, saddr)
 	if err != nil {
-		tun.errors <- errors.New("Failed to bind netlink event listener socket")
-		return
+		return -1, err
 	}
+	return sock, nil
+}
 
-	// TODO: This function never actually exits in response to anything,
-	// a go routine that goes forever. We'll want to fix that if this is
-	// to ever be used as any sort of library. See what we've done with
-	// calling shutdown() on the netlink socket in conn_linux.go, and
-	// change this to be more like that.
-
+func (tun *NativeTun) RoutineNetlinkListener() {
 	for msg := make([]byte, 1<<16); ; {
 
-		msgn, _, _, _, err := unix.Recvmsg(sock, msg[:], nil, 0)
+		msgn, _, _, _, err := unix.Recvmsg(tun.netlinkSock, msg[:], nil, 0)
 		if err != nil {
-			tun.errors <- fmt.Errorf("Failed to receive netlink message: %s", err.Error())
+			tun.errors <- fmt.Errorf("failed to receive netlink message: %s", err.Error())
 			return
 		}
 
@@ -339,13 +328,16 @@ func (tun *NativeTun) Events() chan TUNEvent {
 }
 
 func (tun *NativeTun) Close() error {
-	err := tun.fd.Close()
-	if err != nil {
-		return err
-	}
+	err1 := tun.fd.Close()
+	err2 := closeUnblock(tun.netlinkSock)
 	tun.rwcancel.Cancel()
 	close(tun.events)
-	return nil
+	close(tun.shutdownHackListener)
+
+	if err1 != nil {
+		return err1
+	}
+	return err2
 }
 
 func CreateTUN(name string) (TUNDevice, error) {
@@ -375,7 +367,7 @@ func CreateTUN(name string) (TUNDevice, error) {
 	var flags uint16 = unix.IFF_TUN // | unix.IFF_NO_PI (disabled for TUN status hack)
 	nameBytes := []byte(name)
 	if len(nameBytes) >= unix.IFNAMSIZ {
-		return nil, errors.New("Interface name too long")
+		return nil, errors.New("interface name too long")
 	}
 	copy(ifr[:], nameBytes)
 	binary.LittleEndian.PutUint16(ifr[16:], flags)
@@ -395,10 +387,11 @@ func CreateTUN(name string) (TUNDevice, error) {
 
 func CreateTUNFromFile(fd *os.File) (TUNDevice, error) {
 	device := &NativeTun{
-		fd:     fd,
-		events: make(chan TUNEvent, 5),
-		errors: make(chan error, 5),
-		nopi:   false,
+		fd:                   fd,
+		events:               make(chan TUNEvent, 5),
+		errors:               make(chan error, 5),
+		shutdownHackListener: make(chan struct{}, 0),
+		nopi:                 false,
 	}
 	var err error
 
@@ -419,10 +412,20 @@ func CreateTUNFromFile(fd *os.File) (TUNDevice, error) {
 		return nil, err
 	}
 
+	// set default MTU
+
+	err = device.setMTU(DefaultMTU)
+	if err != nil {
+		return nil, err
+	}
+
+	device.netlinkSock, err = createNetlinkSocket()
+	if err != nil {
+		return nil, err
+	}
+
 	go device.RoutineNetlinkListener()
 	go device.RoutineHackListener() // cross namespace
 
-	// set default MTU
-
-	return device, device.setMTU(DefaultMTU)
+	return device, nil
 }
-- 
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