Merge branch 'source-caching'

20 files changed, 1178 insertions, 488 deletions

diff --git a/src/conn.go b/src/conn.go
index 2cf588d..5b40a23 100644
--- a/src/conn.go
+++ b/src/conn.go
@@ -2,10 +2,35 @@ package main
 
 import (
 	"errors"
+	"golang.org/x/net/ipv4"
+	"golang.org/x/net/ipv6"
 	"net"
-	"time"
 )
 
+/* A Bind handles listening on a port for both IPv6 and IPv4 UDP traffic
+ */
+type Bind interface {
+	SetMark(value uint32) error
+	ReceiveIPv6(buff []byte) (int, Endpoint, error)
+	ReceiveIPv4(buff []byte) (int, Endpoint, error)
+	Send(buff []byte, end Endpoint) error
+	Close() error
+}
+
+/* An Endpoint maintains the source/destination caching for a peer
+ *
+ * dst : the remote address of a peer ("endpoint" in uapi terminology)
+ * src : the local address from which datagrams originate going to the peer
+ */
+type Endpoint interface {
+	ClearSrc()           // clears the source address
+	SrcToString() string // returns the local source address (ip:port)
+	DstToString() string // returns the destination address (ip:port)
+	DstToBytes() []byte  // used for mac2 cookie calculations
+	DstIP() net.IP
+	SrcIP() net.IP
+}
+
 func parseEndpoint(s string) (*net.UDPAddr, error) {
 
 	// ensure that the host is an IP address
@@ -27,63 +52,83 @@ func parseEndpoint(s string) (*net.UDPAddr, error) {
 	return addr, err
 }
 
-func updateUDPConn(device *Device) error {
+/* Must hold device and net lock
+ */
+func unsafeCloseUDPListener(device *Device) error {
+	var err error
+	netc := &device.net
+	if netc.bind != nil {
+		err = netc.bind.Close()
+		netc.bind = nil
+	}
+	return err
+}
+
+// must inform all listeners
+func UpdateUDPListener(device *Device) error {
+	device.mutex.Lock()
+	defer device.mutex.Unlock()
+
 	netc := &device.net
 	netc.mutex.Lock()
 	defer netc.mutex.Unlock()
 
-	// close existing connection
+	// close existing sockets
 
-	if netc.conn != nil {
-		netc.conn.Close()
-		netc.conn = nil
-
-		// We need for that fd to be closed in all other go routines, which
-		// means we have to wait. TODO: find less horrible way of doing this.
-		time.Sleep(time.Second / 2)
+	if err := unsafeCloseUDPListener(device); err != nil {
+		return err
 	}
 
-	// open new connection
+	// assumption: netc.update WaitGroup should be exactly 1
+
+	// open new sockets
 
 	if device.tun.isUp.Get() {
 
-		// listen on new address
+		device.log.Debug.Println("UDP bind updating")
 
-		conn, err := net.ListenUDP("udp", netc.addr)
+		// bind to new port
+
+		var err error
+		netc.bind, netc.port, err = CreateBind(netc.port)
 		if err != nil {
+			netc.bind = nil
 			return err
 		}
 
-		// set fwmark
+		// set mark
 
-		err = setMark(netc.conn, netc.fwmark)
+		err = netc.bind.SetMark(netc.fwmark)
 		if err != nil {
 			return err
 		}
 
-		// retrieve port (may have been chosen by kernel)
+		// clear cached source addresses
+
+		for _, peer := range device.peers {
+			peer.mutex.Lock()
+			if peer.endpoint != nil {
+				peer.endpoint.ClearSrc()
+			}
+			peer.mutex.Unlock()
+		}
 
-		addr := conn.LocalAddr()
-		netc.conn = conn
-		netc.addr, _ = net.ResolveUDPAddr(
-			addr.Network(),
-			addr.String(),
-		)
+		// decrease waitgroup to 0
 
-		// notify goroutines
+		go device.RoutineReceiveIncomming(ipv4.Version, netc.bind)
+		go device.RoutineReceiveIncomming(ipv6.Version, netc.bind)
 
-		signalSend(device.signal.newUDPConn)
+		device.log.Debug.Println("UDP bind has been updated")
 	}
 
 	return nil
 }
 
-func closeUDPConn(device *Device) {
-	netc := &device.net
-	netc.mutex.Lock()
-	if netc.conn != nil {
-		netc.conn.Close()
-	}
-	netc.mutex.Unlock()
-	signalSend(device.signal.newUDPConn)
+func CloseUDPListener(device *Device) error {
+	device.mutex.Lock()
+	device.net.mutex.Lock()
+	err := unsafeCloseUDPListener(device)
+	device.net.mutex.Unlock()
+	device.mutex.Unlock()
+	return err
 }
diff --git a/src/conn_default.go b/src/conn_default.go
index e7c60a8..5b73c90 100644
--- a/src/conn_default.go
+++ b/src/conn_default.go
@@ -6,6 +6,126 @@ import (
 	"net"
 )
 
-func setMark(conn *net.UDPConn, value uint32) error {
+/* This code is meant to be a temporary solution
+ * on platforms for which the sticky socket / source caching behavior
+ * has not yet been implemented.
+ *
+ * See conn_linux.go for an implementation on the linux platform.
+ */
+
+type NativeBind struct {
+	ipv4 *net.UDPConn
+	ipv6 *net.UDPConn
+}
+
+type NativeEndpoint net.UDPAddr
+
+var _ Bind = (*NativeBind)(nil)
+var _ Endpoint = (*NativeEndpoint)(nil)
+
+func CreateEndpoint(s string) (Endpoint, error) {
+	addr, err := parseEndpoint(s)
+	return (*NativeEndpoint)(addr), err
+}
+
+func (_ *NativeEndpoint) ClearSrc() {}
+
+func (e *NativeEndpoint) DstIP() net.IP {
+	return (*net.UDPAddr)(e).IP
+}
+
+func (e *NativeEndpoint) SrcIP() net.IP {
+	return nil // not supported
+}
+
+func (e *NativeEndpoint) DstToBytes() []byte {
+	addr := (*net.UDPAddr)(e)
+	out := addr.IP
+	out = append(out, byte(addr.Port&0xff))
+	out = append(out, byte((addr.Port>>8)&0xff))
+	return out
+}
+
+func (e *NativeEndpoint) DstToString() string {
+	return (*net.UDPAddr)(e).String()
+}
+
+func (e *NativeEndpoint) SrcToString() string {
+	return ""
+}
+
+func listenNet(network string, port int) (*net.UDPConn, int, error) {
+
+	// listen
+
+	conn, err := net.ListenUDP(network, &net.UDPAddr{Port: port})
+	if err != nil {
+		return nil, 0, err
+	}
+
+	// retrieve port
+
+	laddr := conn.LocalAddr()
+	uaddr, err := net.ResolveUDPAddr(
+		laddr.Network(),
+		laddr.String(),
+	)
+	if err != nil {
+		return nil, 0, err
+	}
+	return conn, uaddr.Port, nil
+}
+
+func CreateBind(uport uint16) (Bind, uint16, error) {
+	var err error
+	var bind NativeBind
+
+	port := int(uport)
+
+	bind.ipv4, port, err = listenNet("udp4", port)
+	if err != nil {
+		return nil, 0, err
+	}
+
+	bind.ipv6, port, err = listenNet("udp6", port)
+	if err != nil {
+		bind.ipv4.Close()
+		return nil, 0, err
+	}
+
+	return &bind, uint16(port), nil
+}
+
+func (bind *NativeBind) Close() error {
+	err1 := bind.ipv4.Close()
+	err2 := bind.ipv6.Close()
+	if err1 != nil {
+		return err1
+	}
+	return err2
+}
+
+func (bind *NativeBind) ReceiveIPv4(buff []byte) (int, Endpoint, error) {
+	n, endpoint, err := bind.ipv4.ReadFromUDP(buff)
+	return n, (*NativeEndpoint)(endpoint), err
+}
+
+func (bind *NativeBind) ReceiveIPv6(buff []byte) (int, Endpoint, error) {
+	n, endpoint, err := bind.ipv6.ReadFromUDP(buff)
+	return n, (*NativeEndpoint)(endpoint), err
+}
+
+func (bind *NativeBind) Send(buff []byte, endpoint Endpoint) error {
+	var err error
+	nend := endpoint.(*NativeEndpoint)
+	if nend.IP.To16() != nil {
+		_, err = bind.ipv6.WriteToUDP(buff, (*net.UDPAddr)(nend))
+	} else {
+		_, err = bind.ipv4.WriteToUDP(buff, (*net.UDPAddr)(nend))
+	}
+	return err
+}
+
+func (bind *NativeBind) SetMark(_ uint32) error {
 	return nil
 }
diff --git a/src/conn_linux.go b/src/conn_linux.go
index a349a9e..cdba74f 100644
--- a/src/conn_linux.go
+++ b/src/conn_linux.go
@@ -7,6 +7,7 @@
 package main
 
 import (
+	"encoding/binary"
 	"errors"
 	"golang.org/x/sys/unix"
 	"net"
@@ -16,19 +17,229 @@ import (
 
 /* Supports source address caching
  *
- * It is important that the endpoint is only updated after the packet content has been authenticated.
- *
  * Currently there is no way to achieve this within the net package:
  * See e.g. https://github.com/golang/go/issues/17930
+ * So this code is remains platform dependent.
  */
-type Endpoint struct {
-	// source (selected based on dst type)
-	// (could use RawSockaddrAny and unsafe)
-	srcIPv6 unix.RawSockaddrInet6
-	srcIPv4 unix.RawSockaddrInet4
-	srcIf4  int32
-
-	dst unix.RawSockaddrAny
+type NativeEndpoint struct {
+	src unix.RawSockaddrInet6
+	dst unix.RawSockaddrInet6
+}
+
+type NativeBind struct {
+	sock4 int
+	sock6 int
+}
+
+var _ Endpoint = (*NativeEndpoint)(nil)
+var _ Bind = NativeBind{}
+
+type IPv4Source struct {
+	src     unix.RawSockaddrInet4
+	Ifindex int32
+}
+
+func htons(val uint16) uint16 {
+	var out [unsafe.Sizeof(val)]byte
+	binary.BigEndian.PutUint16(out[:], val)
+	return *((*uint16)(unsafe.Pointer(&out[0])))
+}
+
+func ntohs(val uint16) uint16 {
+	tmp := ((*[unsafe.Sizeof(val)]byte)(unsafe.Pointer(&val)))
+	return binary.BigEndian.Uint16((*tmp)[:])
+}
+
+func CreateEndpoint(s string) (Endpoint, error) {
+	var end NativeEndpoint
+	addr, err := parseEndpoint(s)
+	if err != nil {
+		return nil, err
+	}
+
+	ipv4 := addr.IP.To4()
+	if ipv4 != nil {
+		dst := (*unix.RawSockaddrInet4)(unsafe.Pointer(&end.dst))
+		dst.Family = unix.AF_INET
+		dst.Port = htons(uint16(addr.Port))
+		dst.Zero = [8]byte{}
+		copy(dst.Addr[:], ipv4)
+		end.ClearSrc()
+		return &end, nil
+	}
+
+	ipv6 := addr.IP.To16()
+	if ipv6 != nil {
+		zone, err := zoneToUint32(addr.Zone)
+		if err != nil {
+			return nil, err
+		}
+		dst := &end.dst
+		dst.Family = unix.AF_INET6
+		dst.Port = htons(uint16(addr.Port))
+		dst.Flowinfo = 0
+		dst.Scope_id = zone
+		copy(dst.Addr[:], ipv6[:])
+		end.ClearSrc()
+		return &end, nil
+	}
+
+	return nil, errors.New("Failed to recognize IP address format")
+}
+
+func CreateBind(port uint16) (Bind, uint16, error) {
+	var err error
+	var bind NativeBind
+
+	bind.sock6, port, err = create6(port)
+	if err != nil {
+		return nil, port, err
+	}
+
+	bind.sock4, port, err = create4(port)
+	if err != nil {
+		unix.Close(bind.sock6)
+	}
+	return bind, port, err
+}
+
+func (bind NativeBind) SetMark(value uint32) error {
+	err := unix.SetsockoptInt(
+		bind.sock6,
+		unix.SOL_SOCKET,
+		unix.SO_MARK,
+		int(value),
+	)
+
+	if err != nil {
+		return err
+	}
+
+	return unix.SetsockoptInt(
+		bind.sock4,
+		unix.SOL_SOCKET,
+		unix.SO_MARK,
+		int(value),
+	)
+}
+
+func closeUnblock(fd int) error {
+	// shutdown to unblock readers
+	unix.Shutdown(fd, unix.SHUT_RD)
+	return unix.Close(fd)
+}
+
+func (bind NativeBind) Close() error {
+	err1 := closeUnblock(bind.sock6)
+	err2 := closeUnblock(bind.sock4)
+	if err1 != nil {
+		return err1
+	}
+	return err2
+}
+
+func (bind NativeBind) ReceiveIPv6(buff []byte) (int, Endpoint, error) {
+	var end NativeEndpoint
+	n, err := receive6(
+		bind.sock6,
+		buff,
+		&end,
+	)
+	return n, &end, err
+}
+
+func (bind NativeBind) ReceiveIPv4(buff []byte) (int, Endpoint, error) {
+	var end NativeEndpoint
+	n, err := receive4(
+		bind.sock4,
+		buff,
+		&end,
+	)
+	return n, &end, err
+}
+
+func (bind NativeBind) Send(buff []byte, end Endpoint) error {
+	nend := end.(*NativeEndpoint)
+	switch nend.dst.Family {
+	case unix.AF_INET6:
+		return send6(bind.sock6, nend, buff)
+	case unix.AF_INET:
+		return send4(bind.sock4, nend, buff)
+	default:
+		return errors.New("Unknown address family of destination")
+	}
+}
+
+func sockaddrToString(addr unix.RawSockaddrInet6) string {
+	var udpAddr net.UDPAddr
+
+	switch addr.Family {
+	case unix.AF_INET6:
+		udpAddr.Port = int(ntohs(addr.Port))
+		udpAddr.IP = addr.Addr[:]
+		return udpAddr.String()
+
+	case unix.AF_INET:
+		ptr := (*unix.RawSockaddrInet4)(unsafe.Pointer(&addr))
+		udpAddr.Port = int(ntohs(ptr.Port))
+		udpAddr.IP = net.IPv4(
+			ptr.Addr[0],
+			ptr.Addr[1],
+			ptr.Addr[2],
+			ptr.Addr[3],
+		)
+		return udpAddr.String()
+
+	default:
+		return "<unknown address family>"
+	}
+}
+
+func rawAddrToIP(addr unix.RawSockaddrInet6) net.IP {
+	switch addr.Family {
+	case unix.AF_INET6:
+		return addr.Addr[:]
+	case unix.AF_INET:
+		ptr := (*unix.RawSockaddrInet4)(unsafe.Pointer(&addr))
+		return net.IPv4(
+			ptr.Addr[0],
+			ptr.Addr[1],
+			ptr.Addr[2],
+			ptr.Addr[3],
+		)
+	default:
+		return nil
+	}
+}
+
+func (end *NativeEndpoint) SrcIP() net.IP {
+	return rawAddrToIP(end.src)
+}
+
+func (end *NativeEndpoint) DstIP() net.IP {
+	return rawAddrToIP(end.dst)
+}
+
+func (end *NativeEndpoint) DstToBytes() []byte {
+	ptr := unsafe.Pointer(&end.src)
+	arr := (*[unix.SizeofSockaddrInet6]byte)(ptr)
+	return arr[:]
+}
+
+func (end *NativeEndpoint) SrcToString() string {
+	return sockaddrToString(end.src)
+}
+
+func (end *NativeEndpoint) DstToString() string {
+	return sockaddrToString(end.dst)
+}
+
+func (end *NativeEndpoint) ClearDst() {
+	end.dst = unix.RawSockaddrInet6{}
+}
+
+func (end *NativeEndpoint) ClearSrc() {
+	end.src = unix.RawSockaddrInet6{}
 }
 
 func zoneToUint32(zone string) (uint32, error) {
@@ -42,51 +253,116 @@ func zoneToUint32(zone string) (uint32, error) {
 	return uint32(n), err
 }
 
-func (end *Endpoint) ClearSrc() {
-	end.srcIf4 = 0
-	end.srcIPv4 = unix.RawSockaddrInet4{}
-	end.srcIPv6 = unix.RawSockaddrInet6{}
-}
+func create4(port uint16) (int, uint16, error) {
+
+	// create socket
+
+	fd, err := unix.Socket(
+		unix.AF_INET,
+		unix.SOCK_DGRAM,
+		0,
+	)
 
-func (end *Endpoint) Set(s string) error {
-	addr, err := parseEndpoint(s)
 	if err != nil {
-		return err
+		return -1, 0, err
 	}
 
-	ipv6 := addr.IP.To16()
-	if ipv6 != nil {
-		zone, err := zoneToUint32(addr.Zone)
-		if err != nil {
+	addr := unix.SockaddrInet4{
+		Port: int(port),
+	}
+
+	// set sockopts and bind
+
+	if err := func() error {
+		if err := unix.SetsockoptInt(
+			fd,
+			unix.SOL_SOCKET,
+			unix.SO_REUSEADDR,
+			1,
+		); err != nil {
 			return err
 		}
-		ptr := (*unix.RawSockaddrInet6)(unsafe.Pointer(&end.dst))
-		ptr.Family = unix.AF_INET6
-		ptr.Port = uint16(addr.Port)
-		ptr.Flowinfo = 0
-		ptr.Scope_id = zone
-		copy(ptr.Addr[:], ipv6[:])
-		end.ClearSrc()
-		return nil
+
+		if err := unix.SetsockoptInt(
+			fd,
+			unix.IPPROTO_IP,
+			unix.IP_PKTINFO,
+			1,
+		); err != nil {
+			return err
+		}
+
+		return unix.Bind(fd, &addr)
+	}(); err != nil {
+		unix.Close(fd)
 	}
 
-	ipv4 := addr.IP.To4()
-	if ipv4 != nil {
-		ptr := (*unix.RawSockaddrInet4)(unsafe.Pointer(&end.dst))
-		ptr.Family = unix.AF_INET
-		ptr.Port = uint16(addr.Port)
-		ptr.Zero = [8]byte{}
-		copy(ptr.Addr[:], ipv4)
-		end.ClearSrc()
-		return nil
+	return fd, uint16(addr.Port), err
+}
+
+func create6(port uint16) (int, uint16, error) {
+
+	// create socket
+
+	fd, err := unix.Socket(
+		unix.AF_INET6,
+		unix.SOCK_DGRAM,
+		0,
+	)
+
+	if err != nil {
+		return -1, 0, err
+	}
+
+	// set sockopts and bind
+
+	addr := unix.SockaddrInet6{
+		Port: int(port),
+	}
+
+	if err := func() error {
+
+		if err := unix.SetsockoptInt(
+			fd,
+			unix.SOL_SOCKET,
+			unix.SO_REUSEADDR,
+			1,
+		); err != nil {
+			return err
+		}
+
+		if err := unix.SetsockoptInt(
+			fd,
+			unix.IPPROTO_IPV6,
+			unix.IPV6_RECVPKTINFO,
+			1,
+		); err != nil {
+			return err
+		}
+
+		if err := unix.SetsockoptInt(
+			fd,
+			unix.IPPROTO_IPV6,
+			unix.IPV6_V6ONLY,
+			1,
+		); err != nil {
+			return err
+		}
+
+		return unix.Bind(fd, &addr)
+
+	}(); err != nil {
+		unix.Close(fd)
 	}
 
-	return errors.New("Failed to recognize IP address format")
+	return fd, uint16(addr.Port), err
 }
 
-func send6(sock uintptr, end *Endpoint, buff []byte) error {
-	var iovec unix.Iovec
+func send6(sock int, end *NativeEndpoint, buff []byte) error {
+
+	// construct message header
 
+	var iovec unix.Iovec
 	iovec.Base = (*byte)(unsafe.Pointer(&buff[0]))
 	iovec.SetLen(len(buff))
 
@@ -97,11 +373,11 @@ func send6(sock uintptr, end *Endpoint, buff []byte) error {
 		unix.Cmsghdr{
 			Level: unix.IPPROTO_IPV6,
 			Type:  unix.IPV6_PKTINFO,
-			Len:   unix.SizeofInet6Pktinfo,
+			Len:   unix.SizeofInet6Pktinfo + unix.SizeofCmsghdr,
 		},
 		unix.Inet6Pktinfo{
-			Addr:    end.srcIPv6.Addr,
-			Ifindex: end.srcIPv6.Scope_id,
+			Addr:    end.src.Addr,
+			Ifindex: end.src.Scope_id,
 		},
 	}
 
@@ -119,22 +395,41 @@ func send6(sock uintptr, end *Endpoint, buff []byte) error {
 
 	_, _, errno := unix.Syscall(
 		unix.SYS_SENDMSG,
-		sock,
+		uintptr(sock),
 		uintptr(unsafe.Pointer(&msghdr)),
 		0,
 	)
+
+	if errno == 0 {
+		return nil
+	}
+
+	// clear src and retry
+
 	if errno == unix.EINVAL {
 		end.ClearSrc()
+		cmsg.pktinfo = unix.Inet6Pktinfo{}
+		_, _, errno = unix.Syscall(
+			unix.SYS_SENDMSG,
+			uintptr(sock),
+			uintptr(unsafe.Pointer(&msghdr)),
+			0,
+		)
 	}
+
 	return errno
 }
 
-func send4(sock uintptr, end *Endpoint, buff []byte) error {
-	var iovec unix.Iovec
+func send4(sock int, end *NativeEndpoint, buff []byte) error {
 
+	// construct message header
+
+	var iovec unix.Iovec
 	iovec.Base = (*byte)(unsafe.Pointer(&buff[0]))
 	iovec.SetLen(len(buff))
 
+	src4 := (*IPv4Source)(unsafe.Pointer(&end.src))
+
 	cmsg := struct {
 		cmsghdr unix.Cmsghdr
 		pktinfo unix.Inet4Pktinfo
@@ -142,11 +437,11 @@ func send4(sock uintptr, end *Endpoint, buff []byte) error {
 		unix.Cmsghdr{
 			Level: unix.IPPROTO_IP,
 			Type:  unix.IP_PKTINFO,
-			Len:   unix.SizeofInet6Pktinfo,
+			Len:   unix.SizeofInet4Pktinfo + unix.SizeofCmsghdr,
 		},
 		unix.Inet4Pktinfo{
-			Spec_dst: end.srcIPv4.Addr,
-			Ifindex:  end.srcIf4,
+			Spec_dst: src4.src.Addr,
+			Ifindex:  src4.Ifindex,
 		},
 	}
 
@@ -156,51 +451,92 @@ func send4(sock uintptr, end *Endpoint, buff []byte) error {
 		Name:    (*byte)(unsafe.Pointer(&end.dst)),
 		Namelen: unix.SizeofSockaddrInet4,
 		Control: (*byte)(unsafe.Pointer(&cmsg)),
+		Flags:   0,
 	}
-
 	msghdr.SetControllen(int(unsafe.Sizeof(cmsg)))
 
 	// sendmsg(sock, &msghdr, 0)
 
 	_, _, errno := unix.Syscall(
 		unix.SYS_SENDMSG,
-		sock,
+		uintptr(sock),
 		uintptr(unsafe.Pointer(&msghdr)),
 		0,
 	)
+
+	// clear source and try again
+
 	if errno == unix.EINVAL {
 		end.ClearSrc()
+		cmsg.pktinfo = unix.Inet4Pktinfo{}
+		_, _, errno = unix.Syscall(
+			unix.SYS_SENDMSG,
+			uintptr(sock),
+			uintptr(unsafe.Pointer(&msghdr)),
+			0,
+		)
+	}
+
+	// errno = 0 is still an error instance
+
+	if errno == 0 {
+		return nil
 	}
+
 	return errno
 }
 
-func send(c *net.UDPConn, end *Endpoint, buff []byte) error {
+func receive4(sock int, buff []byte, end *NativeEndpoint) (int, error) {
 
-	// extract underlying file descriptor
+	// contruct message header
 
-	file, err := c.File()
-	if err != nil {
-		return err
+	var iovec unix.Iovec
+	iovec.Base = (*byte)(unsafe.Pointer(&buff[0]))
+	iovec.SetLen(len(buff))
+
+	var cmsg struct {
+		cmsghdr unix.Cmsghdr
+		pktinfo unix.Inet4Pktinfo
+	}
+
+	var msghdr unix.Msghdr
+	msghdr.Iov = &iovec
+	msghdr.Iovlen = 1
+	msghdr.Name = (*byte)(unsafe.Pointer(&end.dst))
+	msghdr.Namelen = unix.SizeofSockaddrInet4
+	msghdr.Control = (*byte)(unsafe.Pointer(&cmsg))
+	msghdr.SetControllen(int(unsafe.Sizeof(cmsg)))
+
+	// recvmsg(sock, &mskhdr, 0)
+
+	size, _, errno := unix.Syscall(
+		unix.SYS_RECVMSG,
+		uintptr(sock),
+		uintptr(unsafe.Pointer(&msghdr)),
+		0,
+	)
+
+	if errno != 0 {
+		return 0, errno
 	}
-	sock := file.Fd()
 
-	// send depending on address family of dst
+	// update source cache
 
-	family := *((*uint16)(unsafe.Pointer(&end.dst)))
-	if family == unix.AF_INET {
-		return send4(sock, end, buff)
-	} else if family == unix.AF_INET6 {
-		return send6(sock, end, buff)
+	if cmsg.cmsghdr.Level == unix.IPPROTO_IP &&
+		cmsg.cmsghdr.Type == unix.IP_PKTINFO &&
+		cmsg.cmsghdr.Len >= unix.SizeofInet4Pktinfo {
+		src4 := (*IPv4Source)(unsafe.Pointer(&end.src))
+		src4.src.Family = unix.AF_INET
+		src4.src.Addr = cmsg.pktinfo.Spec_dst
+		src4.Ifindex = cmsg.pktinfo.Ifindex
 	}
-	return errors.New("Unknown address family of source")
+
+	return int(size), nil
 }
 
-func receiveIPv4(end *Endpoint, c *net.UDPConn, buff []byte) (error, *net.UDPAddr, *net.UDPAddr) {
+func receive6(sock int, buff []byte, end *NativeEndpoint) (int, error) {
 
-	file, err := c.File()
-	if err != nil {
-		return err, nil, nil
-	}
+	// contruct message header
 
 	var iovec unix.Iovec
 	iovec.Base = (*byte)(unsafe.Pointer(&buff[0]))
@@ -208,60 +544,39 @@ func receiveIPv4(end *Endpoint, c *net.UDPConn, buff []byte) (error, *net.UDPAdd
 
 	var cmsg struct {
 		cmsghdr unix.Cmsghdr
-		pktinfo unix.Inet6Pktinfo // big enough
+		pktinfo unix.Inet6Pktinfo
 	}
 
 	var msg unix.Msghdr
 	msg.Iov = &iovec
 	msg.Iovlen = 1
 	msg.Name = (*byte)(unsafe.Pointer(&end.dst))
-	msg.Namelen = uint32(unix.SizeofSockaddrAny)
+	msg.Namelen = uint32(unix.SizeofSockaddrInet6)
 	msg.Control = (*byte)(unsafe.Pointer(&cmsg))
 	msg.SetControllen(int(unsafe.Sizeof(cmsg)))
 
-	_, _, errno := unix.Syscall(
+	// recvmsg(sock, &mskhdr, 0)
+
+	size, _, errno := unix.Syscall(
 		unix.SYS_RECVMSG,
-		file.Fd(),
+		uintptr(sock),
 		uintptr(unsafe.Pointer(&msg)),
 		0,
 	)
 
 	if errno != 0 {
-		return errno, nil, nil
+		return 0, errno
 	}
 
+	// update source cache
+
 	if cmsg.cmsghdr.Level == unix.IPPROTO_IPV6 &&
 		cmsg.cmsghdr.Type == unix.IPV6_PKTINFO &&
 		cmsg.cmsghdr.Len >= unix.SizeofInet6Pktinfo {
-
-	}
-
-	if cmsg.cmsghdr.Level == unix.IPPROTO_IP &&
-		cmsg.cmsghdr.Type == unix.IP_PKTINFO &&
-		cmsg.cmsghdr.Len >= unix.SizeofInet4Pktinfo {
-
-		info := (*unix.Inet4Pktinfo)(unsafe.Pointer(&cmsg.pktinfo))
-		println(info)
-
-	}
-
-	return nil, nil, nil
-}
-
-func setMark(conn *net.UDPConn, value uint32) error {
-	if conn == nil {
-		return nil
+		end.src.Family = unix.AF_INET6
+		end.src.Addr = cmsg.pktinfo.Addr
+		end.src.Scope_id = cmsg.pktinfo.Ifindex
 	}
 
-	file, err := conn.File()
-	if err != nil {
-		return err
-	}
-
-	return unix.SetsockoptInt(
-		int(file.Fd()),
-		unix.SOL_SOCKET,
-		unix.SO_MARK,
-		int(value),
-	)
+	return int(size), nil
 }
diff --git a/src/cookie.go b/src/cookie.go
index a81819b..a13ad49 100644
--- a/src/cookie.go
+++ b/src/cookie.go
@@ -5,10 +5,8 @@ import (
 	"crypto/rand"
 	"golang.org/x/crypto/blake2s"
 	"golang.org/x/crypto/chacha20poly1305"
-	"net"
 	"sync"
 	"time"
-	"unsafe"
 )
 
 type CookieChecker struct {
@@ -76,7 +74,7 @@ func (st *CookieChecker) CheckMAC1(msg []byte) bool {
 	return hmac.Equal(mac1[:], msg[smac1:smac2])
 }
 
-func (st *CookieChecker) CheckMAC2(msg []byte, src *net.UDPAddr) bool {
+func (st *CookieChecker) CheckMAC2(msg []byte, src []byte) bool {
 	st.mutex.RLock()
 	defer st.mutex.RUnlock()
 
@@ -89,8 +87,7 @@ func (st *CookieChecker) CheckMAC2(msg []byte, src *net.UDPAddr) bool {
 	var cookie [blake2s.Size128]byte
 	func() {
 		mac, _ := blake2s.New128(st.mac2.secret[:])
-		mac.Write(src.IP)
-		mac.Write((*[unsafe.Sizeof(src.Port)]byte)(unsafe.Pointer(&src.Port))[:])
+		mac.Write(src)
 		mac.Sum(cookie[:0])
 	}()
 
@@ -111,7 +108,7 @@ func (st *CookieChecker) CheckMAC2(msg []byte, src *net.UDPAddr) bool {
 func (st *CookieChecker) CreateReply(
 	msg []byte,
 	recv uint32,
-	src *net.UDPAddr,
+	src []byte,
 ) (*MessageCookieReply, error) {
 
 	st.mutex.RLock()
@@ -136,8 +133,7 @@ func (st *CookieChecker) CreateReply(
 	var cookie [blake2s.Size128]byte
 	func() {
 		mac, _ := blake2s.New128(st.mac2.secret[:])
-		mac.Write(src.IP)
-		mac.Write((*[unsafe.Sizeof(src.Port)]byte)(unsafe.Pointer(&src.Port))[:])
+		mac.Write(src)
 		mac.Sum(cookie[:0])
 	}()
 
diff --git a/src/cookie_test.go b/src/cookie_test.go
index 193a76e..d745fe7 100644
--- a/src/cookie_test.go
+++ b/src/cookie_test.go
@@ -1,7 +1,6 @@
 package main
 
 import (
-	"net"
 	"testing"
 )
 
@@ -25,7 +24,7 @@ func TestCookieMAC1(t *testing.T) {
 
 	// check mac1
 
-	src, _ := net.ResolveUDPAddr("udp", "192.168.13.37:4000")
+	src := []byte{192, 168, 13, 37, 10, 10, 10}
 
 	checkMAC1 := func(msg []byte) {
 		generator.AddMacs(msg)
@@ -128,12 +127,12 @@ func TestCookieMAC1(t *testing.T) {
 
 		msg[5] ^= 0x20
 
-		srcBad1, _ := net.ResolveUDPAddr("udp", "192.168.13.37:4001")
+		srcBad1 := []byte{192, 168, 13, 37, 40, 01}
 		if checker.CheckMAC2(msg, srcBad1) {
 			t.Fatal("MAC2 generation/verification failed")
 		}
 
-		srcBad2, _ := net.ResolveUDPAddr("udp", "192.168.13.38:4000")
+		srcBad2 := []byte{192, 168, 13, 38, 40, 01}
 		if checker.CheckMAC2(msg, srcBad2) {
 			t.Fatal("MAC2 generation/verification failed")
 		}
diff --git a/src/daemon_linux.go b/src/daemon_linux.go
index 730f89e..e1aaede 100644
--- a/src/daemon_linux.go
+++ b/src/daemon_linux.go
@@ -2,29 +2,25 @@ package main
 
 import (
 	"os"
+	"os/exec"
 )
 
 /* Daemonizes the process on linux
  *
  * This is done by spawning and releasing a copy with the --foreground flag
- *
- * TODO: Use env variable to spawn in background
  */
+func Daemonize(attr *os.ProcAttr) error {
+	// I would like to use os.Executable,
+	// however this means dropping support for Go <1.8
+	path, err := exec.LookPath(os.Args[0])
+	if err != nil {
+		return err
+	}
 
-func Daemonize() error {
 	argv := []string{os.Args[0], "--foreground"}
 	argv = append(argv, os.Args[1:]...)
-	attr := &os.ProcAttr{
-		Dir: ".",
-		Env: os.Environ(),
-		Files: []*os.File{
-			os.Stdin,
-			nil,
-			nil,
-		},
-	}
 	process, err := os.StartProcess(
-		argv[0],
+		path,
 		argv,
 		attr,
 	)
diff --git a/src/device.go b/src/device.go
index 8567a36..76235bd 100644
--- a/src/device.go
+++ b/src/device.go
@@ -1,7 +1,6 @@
 package main
 
 import (
-	"net"
 	"runtime"
 	"sync"
 	"sync/atomic"
@@ -9,8 +8,9 @@ import (
 )
 
 type Device struct {
-	log       *Logger // collection of loggers for levels
-	idCounter uint    // for assigning debug ids to peers
+	closed    AtomicBool // device is closed? (acting as guard)
+	log       *Logger    // collection of loggers for levels
+	idCounter uint       // for assigning debug ids to peers
 	fwMark    uint32
 	tun       struct {
 		device TUNDevice
@@ -22,9 +22,9 @@ type Device struct {
 	}
 	net struct {
 		mutex  sync.RWMutex
-		addr   *net.UDPAddr // UDP source address
-		conn   *net.UDPConn // UDP "connection"
-		fwmark uint32
+		bind   Bind   // bind interface
+		port   uint16 // listening port
+		fwmark uint32 // mark value (0 = disabled)
 	}
 	mutex        sync.RWMutex
 	privateKey   NoisePrivateKey
@@ -37,8 +37,7 @@ type Device struct {
 		handshake  chan QueueHandshakeElement
 	}
 	signal struct {
-		stop       chan struct{} // halts all go routines
-		newUDPConn chan struct{} // a net.conn was set (consumed by the receiver routine)
+		stop chan struct{}
 	}
 	underLoadUntil atomic.Value
 	ratelimiter    Ratelimiter
@@ -128,21 +127,23 @@ func (device *Device) PutMessageBuffer(msg *[MaxMessageSize]byte) {
 	device.pool.messageBuffers.Put(msg)
 }
 
-func NewDevice(tun TUNDevice, logLevel int) *Device {
+func NewDevice(tun TUNDevice, logger *Logger) *Device {
 	device := new(Device)
 
 	device.mutex.Lock()
 	defer device.mutex.Unlock()
 
-	device.log = NewLogger(logLevel, "("+tun.Name()+") ")
+	device.log = logger
 	device.peers = make(map[NoisePublicKey]*Peer)
 	device.tun.device = tun
+
 	device.indices.Init()
 	device.ratelimiter.Init()
+
 	device.routingTable.Reset()
 	device.underLoadUntil.Store(time.Time{})
 
-	// setup pools
+	// setup buffer pool
 
 	device.pool.messageBuffers = sync.Pool{
 		New: func() interface{} {
@@ -159,7 +160,11 @@ func NewDevice(tun TUNDevice, logLevel int) *Device {
 	// prepare signals
 
 	device.signal.stop = make(chan struct{})
-	device.signal.newUDPConn = make(chan struct{}, 1)
+
+	// prepare net
+
+	device.net.port = 0
+	device.net.bind = nil
 
 	// start workers
 
@@ -168,12 +173,9 @@ func NewDevice(tun TUNDevice, logLevel int) *Device {
 		go device.RoutineDecryption()
 		go device.RoutineHandshake()
 	}
-
+	go device.RoutineReadFromTUN()
 	go device.RoutineTUNEventReader()
 	go device.ratelimiter.RoutineGarbageCollector(device.signal.stop)
-	go device.RoutineReadFromTUN()
-	go device.RoutineReceiveIncomming()
-
 	return device
 }
 
@@ -202,9 +204,13 @@ func (device *Device) RemoveAllPeers() {
 }
 
 func (device *Device) Close() {
+	if device.closed.Swap(true) {
+		return
+	}
+	device.log.Info.Println("Closing device")
 	device.RemoveAllPeers()
 	close(device.signal.stop)
-	closeUDPConn(device)
+	CloseUDPListener(device)
 	device.tun.device.Close()
 }
 
diff --git a/src/helper_test.go b/src/helper_test.go
index fc171e8..8548121 100644
--- a/src/helper_test.go
+++ b/src/helper_test.go
@@ -2,6 +2,7 @@ package main
 
 import (
 	"bytes"
+	"os"
 	"testing"
 )
 
@@ -15,6 +16,10 @@ type DummyTUN struct {
 	events  chan TUNEvent
 }
 
+func (tun *DummyTUN) File() *os.File {
+	return nil
+}
+
 func (tun *DummyTUN) Name() string {
 	return tun.name
 }
@@ -67,7 +72,8 @@ func randDevice(t *testing.T) *Device {
 		t.Fatal(err)
 	}
 	tun, _ := CreateDummyTUN("dummy")
-	device := NewDevice(tun, LogLevelError)
+	logger := NewLogger(LogLevelError, "")
+	device := NewDevice(tun, logger)
 	device.SetPrivateKey(sk)
 	return device
 }
diff --git a/src/main.go b/src/main.go
index 196a4c6..7d86716 100644
--- a/src/main.go
+++ b/src/main.go
@@ -2,10 +2,15 @@ package main
 
 import (
 	"fmt"
-	"log"
 	"os"
 	"os/signal"
 	"runtime"
+	"strconv"
+)
+
+const (
+	ENV_WG_TUN_FD  = "WG_TUN_FD"
+	ENV_WG_UAPI_FD = "WG_UAPI_FD"
 )
 
 func printUsage() {
@@ -43,28 +48,6 @@ func main() {
 		interfaceName = os.Args[1]
 	}
 
-	// daemonize the process
-
-	if !foreground {
-		err := Daemonize()
-		if err != nil {
-			log.Println("Failed to daemonize:", err)
-		}
-		return
-	}
-
-	// increase number of go workers (for Go <1.5)
-
-	runtime.GOMAXPROCS(runtime.NumCPU())
-
-	// open TUN device
-
-	tun, err := CreateTUN(interfaceName)
-	if err != nil {
-		log.Println("Failed to create tun device:", err)
-		return
-	}
-
 	// get log level (default: info)
 
 	logLevel := func() int {
@@ -79,25 +62,103 @@ func main() {
 		return LogLevelInfo
 	}()
 
-	// create wireguard device
+	logger := NewLogger(
+		logLevel,
+		fmt.Sprintf("(%s) ", interfaceName),
+	)
+
+	logger.Debug.Println("Debug log enabled")
+
+	// open TUN device (or use supplied fd)
+
+	tun, err := func() (TUNDevice, error) {
+		tunFdStr := os.Getenv(ENV_WG_TUN_FD)
+		if tunFdStr == "" {
+			return CreateTUN(interfaceName)
+		}
+
+		// construct tun device from supplied fd
+
+		fd, err := strconv.ParseUint(tunFdStr, 10, 32)
+		if err != nil {
+			return nil, err
+		}
+
+		file := os.NewFile(uintptr(fd), "")
+		return CreateTUNFromFile(interfaceName, file)
+	}()
+
+	if err != nil {
+		logger.Error.Println("Failed to create TUN device:", err)
+		os.Exit(ExitSetupFailed)
+	}
 
-	device := NewDevice(tun, logLevel)
+	// open UAPI file (or use supplied fd)
 
-	logInfo := device.log.Info
-	logError := device.log.Error
-	logInfo.Println("Starting device")
+	fileUAPI, err := func() (*os.File, error) {
+		uapiFdStr := os.Getenv(ENV_WG_UAPI_FD)
+		if uapiFdStr == "" {
+			return UAPIOpen(interfaceName)
+		}
+
+		// use supplied fd
 
-	// start configuration lister
+		fd, err := strconv.ParseUint(uapiFdStr, 10, 32)
+		if err != nil {
+			return nil, err
+		}
+
+		return os.NewFile(uintptr(fd), ""), nil
+	}()
 
-	uapi, err := NewUAPIListener(interfaceName)
 	if err != nil {
-		logError.Fatal("UAPI listen error:", err)
+		logger.Error.Println("UAPI listen error:", err)
+		os.Exit(ExitSetupFailed)
+		return
 	}
+	// daemonize the process
+
+	if !foreground {
+		env := os.Environ()
+		env = append(env, fmt.Sprintf("%s=3", ENV_WG_TUN_FD))
+		env = append(env, fmt.Sprintf("%s=4", ENV_WG_UAPI_FD))
+		attr := &os.ProcAttr{
+			Files: []*os.File{
+				nil, // stdin
+				nil, // stdout
+				nil, // stderr
+				tun.File(),
+				fileUAPI,
+			},
+			Dir: ".",
+			Env: env,
+		}
+		err = Daemonize(attr)
+		if err != nil {
+			logger.Error.Println("Failed to daemonize:", err)
+			os.Exit(ExitSetupFailed)
+		}
+		return
+	}
+
+	// increase number of go workers (for Go <1.5)
+
+	runtime.GOMAXPROCS(runtime.NumCPU())
+
+	// create wireguard device
+
+	device := NewDevice(tun, logger)
+
+	logger.Info.Println("Device started")
+
+	// start uapi listener
 
 	errs := make(chan error)
 	term := make(chan os.Signal)
 	wait := device.WaitChannel()
 
+	uapi, err := UAPIListen(interfaceName, fileUAPI)
+
 	go func() {
 		for {
 			conn, err := uapi.Accept()
@@ -109,7 +170,7 @@ func main() {
 		}
 	}()
 
-	logInfo.Println("UAPI listener started")
+	logger.Info.Println("UAPI listener started")
 
 	// wait for program to terminate
 
@@ -122,9 +183,10 @@ func main() {
 	case <-errs:
 	}
 
-	// clean up UAPI bind
+	// clean up
 
 	uapi.Close()
+	device.Close()
 
-	logInfo.Println("Closing")
+	logger.Info.Println("Shutting down")
 }
diff --git a/src/misc.go b/src/misc.go
index bbe0d68..b43e97e 100644
--- a/src/misc.go
+++ b/src/misc.go
@@ -21,6 +21,14 @@ func (a *AtomicBool) Get() bool {
 	return atomic.LoadInt32(&a.flag) == AtomicTrue
 }
 
+func (a *AtomicBool) Swap(val bool) bool {
+	flag := AtomicFalse
+	if val {
+		flag = AtomicTrue
+	}
+	return atomic.SwapInt32(&a.flag, flag) == AtomicTrue
+}
+
 func (a *AtomicBool) Set(val bool) {
 	flag := AtomicFalse
 	if val {
diff --git a/src/noise_test.go b/src/noise_test.go
index 48408f9..0d7f0e9 100644
--- a/src/noise_test.go
+++ b/src/noise_test.go
@@ -117,8 +117,8 @@ func TestNoiseHandshake(t *testing.T) {
 		var err error
 		var out []byte
 		var nonce [12]byte
-		out = key1.send.aead.Seal(out, nonce[:], testMsg, nil)
-		out, err = key2.receive.aead.Open(out[:0], nonce[:], out, nil)
+		out = key1.send.Seal(out, nonce[:], testMsg, nil)
+		out, err = key2.receive.Open(out[:0], nonce[:], out, nil)
 		assertNil(t, err)
 		assertEqual(t, out, testMsg)
 	}()
@@ -128,8 +128,8 @@ func TestNoiseHandshake(t *testing.T) {
 		var err error
 		var out []byte
 		var nonce [12]byte
-		out = key2.send.aead.Seal(out, nonce[:], testMsg, nil)
-		out, err = key1.receive.aead.Open(out[:0], nonce[:], out, nil)
+		out = key2.send.Seal(out, nonce[:], testMsg, nil)
+		out, err = key1.receive.Open(out[:0], nonce[:], out, nil)
 		assertNil(t, err)
 		assertEqual(t, out, testMsg)
 	}()
diff --git a/src/peer.go b/src/peer.go
index 6fea829..f3eb6c2 100644
--- a/src/peer.go
+++ b/src/peer.go
@@ -4,7 +4,6 @@ import (
 	"encoding/base64"
 	"errors"
 	"fmt"
-	"net"
 	"sync"
 	"time"
 )
@@ -16,7 +15,7 @@ type Peer struct {
 	keyPairs                    KeyPairs
 	handshake                   Handshake
 	device                      *Device
-	endpoint                    *net.UDPAddr
+	endpoint                    Endpoint
 	stats                       struct {
 		txBytes           uint64 // bytes send to peer (endpoint)
 		rxBytes           uint64 // bytes received from peer
@@ -106,6 +105,10 @@ func (device *Device) NewPeer(pk NoisePublicKey) (*Peer, error) {
 	handshake.precomputedStaticStatic = device.privateKey.sharedSecret(handshake.remoteStatic)
 	handshake.mutex.Unlock()
 
+	// reset endpoint
+
+	peer.endpoint = nil
+
 	// prepare queuing
 
 	peer.queue.nonce = make(chan *QueueOutboundElement, QueueOutboundSize)
@@ -130,11 +133,31 @@ func (device *Device) NewPeer(pk NoisePublicKey) (*Peer, error) {
 	return peer, nil
 }
 
+func (peer *Peer) SendBuffer(buffer []byte) error {
+	peer.device.net.mutex.RLock()
+	defer peer.device.net.mutex.RUnlock()
+	peer.mutex.RLock()
+	defer peer.mutex.RUnlock()
+	if peer.endpoint == nil {
+		return errors.New("No known endpoint for peer")
+	}
+	return peer.device.net.bind.Send(buffer, peer.endpoint)
+}
+
+/* Returns a short string identification for logging
+ */
 func (peer *Peer) String() string {
+	if peer.endpoint == nil {
+		return fmt.Sprintf(
+			"peer(%d unknown %s)",
+			peer.id,
+			base64.StdEncoding.EncodeToString(peer.handshake.remoteStatic[:]),
+		)
+	}
 	return fmt.Sprintf(
 		"peer(%d %s %s)",
 		peer.id,
-		peer.endpoint.String(),
+		peer.endpoint.DstToString(),
 		base64.StdEncoding.EncodeToString(peer.handshake.remoteStatic[:]),
 	)
 }
diff --git a/src/receive.go b/src/receive.go
index 52c2718..27fdb8a 100644
--- a/src/receive.go
+++ b/src/receive.go
@@ -13,19 +13,20 @@ import (
 )
 
 type QueueHandshakeElement struct {
-	msgType uint32
-	packet  []byte
-	buffer  *[MaxMessageSize]byte
-	source  *net.UDPAddr
+	msgType  uint32
+	packet   []byte
+	endpoint Endpoint
+	buffer   *[MaxMessageSize]byte
 }
 
 type QueueInboundElement struct {
-	dropped int32
-	mutex   sync.Mutex
-	buffer  *[MaxMessageSize]byte
-	packet  []byte
-	counter uint64
-	keyPair *KeyPair
+	dropped  int32
+	mutex    sync.Mutex
+	buffer   *[MaxMessageSize]byte
+	packet   []byte
+	counter  uint64
+	keyPair  *KeyPair
+	endpoint Endpoint
 }
 
 func (elem *QueueInboundElement) Drop() {
@@ -92,130 +93,122 @@ func (device *Device) addToHandshakeQueue(
 	}
 }
 
-func (device *Device) RoutineReceiveIncomming() {
+func (device *Device) RoutineReceiveIncomming(IP int, bind Bind) {
 
 	logDebug := device.log.Debug
-	logDebug.Println("Routine, receive incomming, started")
+	logDebug.Println("Routine, receive incomming, IP version:", IP)
 
 	for {
 
-		// wait for new conn
+		// receive datagrams until conn is closed
 
-		logDebug.Println("Waiting for udp socket")
+		buffer := device.GetMessageBuffer()
 
-		select {
-		case <-device.signal.stop:
-			return
+		var (
+			err      error
+			size     int
+			endpoint Endpoint
+		)
 
-		case <-device.signal.newUDPConn:
+		for {
 
-			// fetch connection
+			// read next datagram
 
-			device.net.mutex.RLock()
-			conn := device.net.conn
-			device.net.mutex.RUnlock()
-			if conn == nil {
+			switch IP {
+			case ipv4.Version:
+				size, endpoint, err = bind.ReceiveIPv4(buffer[:])
+			case ipv6.Version:
+				size, endpoint, err = bind.ReceiveIPv6(buffer[:])
+			default:
+				return
+			}
+
+			if err != nil {
+				break
+			}
+
+			if size < MinMessageSize {
 				continue
 			}
 
-			logDebug.Println("Listening for inbound packets")
+			// check size of packet
 
-			// receive datagrams until conn is closed
+			packet := buffer[:size]
+			msgType := binary.LittleEndian.Uint32(packet[:4])
 
-			buffer := device.GetMessageBuffer()
+			var okay bool
 
-			for {
+			switch msgType {
 
-				// read next datagram
+			// check if transport
 
-				size, raddr, err := conn.ReadFromUDP(buffer[:])
+			case MessageTransportType:
 
-				if err != nil {
-					break
-				}
+				// check size
 
-				if size < MinMessageSize {
+				if len(packet) < MessageTransportType {
 					continue
 				}
 
-				// check size of packet
-
-				packet := buffer[:size]
-				msgType := binary.LittleEndian.Uint32(packet[:4])
-
-				var okay bool
+				// lookup key pair
 
-				switch msgType {
-
-				// check if transport
-
-				case MessageTransportType:
-
-					// check size
-
-					if len(packet) < MessageTransportType {
-						continue
-					}
-
-					// lookup key pair
-
-					receiver := binary.LittleEndian.Uint32(
-						packet[MessageTransportOffsetReceiver:MessageTransportOffsetCounter],
-					)
-					value := device.indices.Lookup(receiver)
-					keyPair := value.keyPair
-					if keyPair == nil {
-						continue
-					}
+				receiver := binary.LittleEndian.Uint32(
+					packet[MessageTransportOffsetReceiver:MessageTransportOffsetCounter],
+				)
+				value := device.indices.Lookup(receiver)
+				keyPair := value.keyPair
+				if keyPair == nil {
+					continue
+				}
 
-					// check key-pair expiry
+				// check key-pair expiry
 
-					if keyPair.created.Add(RejectAfterTime).Before(time.Now()) {
-						continue
-					}
+				if keyPair.created.Add(RejectAfterTime).Before(time.Now()) {
+					continue
+				}
 
-					// create work element
+				// create work element
 
-					peer := value.peer
-					elem := &QueueInboundElement{
-						packet:  packet,
-						buffer:  buffer,
-						keyPair: keyPair,
-						dropped: AtomicFalse,
-					}
-					elem.mutex.Lock()
+				peer := value.peer
+				elem := &QueueInboundElement{
+					packet:   packet,
+					buffer:   buffer,
+					keyPair:  keyPair,
+					dropped:  AtomicFalse,
+					endpoint: endpoint,
+				}
+				elem.mutex.Lock()
 
-					// add to decryption queues
+				// add to decryption queues
 
-					device.addToDecryptionQueue(device.queue.decryption, elem)
-					device.addToInboundQueue(peer.queue.inbound, elem)
-					buffer = device.GetMessageBuffer()
-					continue
+				device.addToDecryptionQueue(device.queue.decryption, elem)
+				device.addToInboundQueue(peer.queue.inbound, elem)
+				buffer = device.GetMessageBuffer()
+				continue
 
-				// otherwise it is a handshake related packet
+			// otherwise it is a fixed size & handshake related packet
 
-				case MessageInitiationType:
-					okay = len(packet) == MessageInitiationSize
+			case MessageInitiationType:
+				okay = len(packet) == MessageInitiationSize
 
-				case MessageResponseType:
-					okay = len(packet) == MessageResponseSize
+			case MessageResponseType:
+				okay = len(packet) == MessageResponseSize
 
-				case MessageCookieReplyType:
-					okay = len(packet) == MessageCookieReplySize
-				}
+			case MessageCookieReplyType:
+				okay = len(packet) == MessageCookieReplySize
+			}
 
-				if okay {
-					device.addToHandshakeQueue(
-						device.queue.handshake,
-						QueueHandshakeElement{
-							msgType: msgType,
-							buffer:  buffer,
-							packet:  packet,
-							source:  raddr,
-						},
-					)
-					buffer = device.GetMessageBuffer()
-				}
+			if okay {
+				device.addToHandshakeQueue(
+					device.queue.handshake,
+					QueueHandshakeElement{
+						msgType:  msgType,
+						buffer:   buffer,
+						packet:   packet,
+						endpoint: endpoint,
+					},
+				)
+				buffer = device.GetMessageBuffer()
 			}
 		}
 	}
@@ -293,8 +286,6 @@ func (device *Device) RoutineHandshake() {
 
 			// unmarshal packet
 
-			logDebug.Println("Process cookie reply from:", elem.source.String())
-
 			var reply MessageCookieReply
 			reader := bytes.NewReader(elem.packet)
 			err := binary.Read(reader, binary.LittleEndian, &reply)
@@ -321,15 +312,25 @@ func (device *Device) RoutineHandshake() {
 				return
 			}
 
+			// endpoints destination address is the source of the datagram
+
+			srcBytes := elem.endpoint.DstToBytes()
+
 			if device.IsUnderLoad() {
-				if !device.mac.CheckMAC2(elem.packet, elem.source) {
+
+				// verify MAC2 field
+
+				if !device.mac.CheckMAC2(elem.packet, srcBytes) {
 
 					// construct cookie reply
 
-					logDebug.Println("Sending cookie reply to:", elem.source.String())
+					logDebug.Println(
+						"Sending cookie reply to:",
+						elem.endpoint.DstToString(),
+					)
 
-					sender := binary.LittleEndian.Uint32(elem.packet[4:8]) // "sender" always follows "type"
-					reply, err := device.mac.CreateReply(elem.packet, sender, elem.source)
+					sender := binary.LittleEndian.Uint32(elem.packet[4:8])
+					reply, err := device.mac.CreateReply(elem.packet, sender, srcBytes)
 					if err != nil {
 						logError.Println("Failed to create cookie reply:", err)
 						return
@@ -339,17 +340,16 @@ func (device *Device) RoutineHandshake() {
 
 					writer := bytes.NewBuffer(temp[:0])
 					binary.Write(writer, binary.LittleEndian, reply)
-					_, err = device.net.conn.WriteToUDP(
-						writer.Bytes(),
-						elem.source,
-					)
+					device.net.bind.Send(writer.Bytes(), elem.endpoint)
 					if err != nil {
 						logDebug.Println("Failed to send cookie reply:", err)
 					}
 					continue
 				}
 
-				if !device.ratelimiter.Allow(elem.source.IP) {
+				// check ratelimiter
+
+				if !device.ratelimiter.Allow(elem.endpoint.DstIP()) {
 					continue
 				}
 			}
@@ -380,8 +380,7 @@ func (device *Device) RoutineHandshake() {
 			if peer == nil {
 				logInfo.Println(
 					"Recieved invalid initiation message from",
-					elem.source.IP.String(),
-					elem.source.Port,
+					elem.endpoint.DstToString(),
 				)
 				continue
 			}
@@ -392,10 +391,9 @@ func (device *Device) RoutineHandshake() {
 			peer.TimerAnyAuthenticatedPacketReceived()
 
 			// update endpoint
-			// TODO: Discover destination address also, only update on change
 
 			peer.mutex.Lock()
-			peer.endpoint = elem.source
+			peer.endpoint = elem.endpoint
 			peer.mutex.Unlock()
 
 			// create response
@@ -418,9 +416,11 @@ func (device *Device) RoutineHandshake() {
 
 			// send response
 
-			_, err = peer.SendBuffer(packet)
+			err = peer.SendBuffer(packet)
 			if err == nil {
 				peer.TimerAnyAuthenticatedPacketTraversal()
+			} else {
+				logError.Println("Failed to send response to:", peer.String(), err)
 			}
 
 		case MessageResponseType:
@@ -441,12 +441,17 @@ func (device *Device) RoutineHandshake() {
 			if peer == nil {
 				logInfo.Println(
 					"Recieved invalid response message from",
-					elem.source.IP.String(),
-					elem.source.Port,
+					elem.endpoint.DstToString(),
 				)
 				continue
 			}
 
+			// update endpoint
+
+			peer.mutex.Lock()
+			peer.endpoint = elem.endpoint
+			peer.mutex.Unlock()
+
 			logDebug.Println("Received handshake initation from", peer)
 
 			peer.TimerEphemeralKeyCreated()
@@ -515,6 +520,12 @@ func (peer *Peer) RoutineSequentialReceiver() {
 			}
 			kp.mutex.Unlock()
 
+			// update endpoint
+
+			peer.mutex.Lock()
+			peer.endpoint = elem.endpoint
+			peer.mutex.Unlock()
+
 			// check for keep-alive
 
 			if len(elem.packet) == 0 {
@@ -546,7 +557,10 @@ func (peer *Peer) RoutineSequentialReceiver() {
 
 				src := elem.packet[IPv4offsetSrc : IPv4offsetSrc+net.IPv4len]
 				if device.routingTable.LookupIPv4(src) != peer {
-					logInfo.Println("Packet with unallowed source IP from", peer.String())
+					logInfo.Println(
+						"IPv4 packet with unallowed source address from",
+						peer.String(),
+					)
 					continue
 				}
 
@@ -571,7 +585,10 @@ func (peer *Peer) RoutineSequentialReceiver() {
 
 				src := elem.packet[IPv6offsetSrc : IPv6offsetSrc+net.IPv6len]
 				if device.routingTable.LookupIPv6(src) != peer {
-					logInfo.Println("Packet with unallowed source IP from", peer.String())
+					logInfo.Println(
+						"IPv6 packet with unallowed source address from",
+						peer.String(),
+					)
 					continue
 				}
 
@@ -580,7 +597,7 @@ func (peer *Peer) RoutineSequentialReceiver() {
 				continue
 			}
 
-			// write to tun
+			// write to tun device
 
 			atomic.AddUint64(&peer.stats.rxBytes, uint64(len(elem.packet)))
 			_, err := device.tun.device.Write(elem.packet)
diff --git a/src/send.go b/src/send.go
index 5c88ead..52872f6 100644
--- a/src/send.go
+++ b/src/send.go
@@ -2,7 +2,6 @@ package main
 
 import (
 	"encoding/binary"
-	"errors"
 	"golang.org/x/crypto/chacha20poly1305"
 	"golang.org/x/net/ipv4"
 	"golang.org/x/net/ipv6"
@@ -105,26 +104,6 @@ func addToEncryptionQueue(
 	}
 }
 
-func (peer *Peer) SendBuffer(buffer []byte) (int, error) {
-	peer.device.net.mutex.RLock()
-	defer peer.device.net.mutex.RUnlock()
-
-	peer.mutex.RLock()
-	defer peer.mutex.RUnlock()
-
-	endpoint := peer.endpoint
-	if endpoint == nil {
-		return 0, errors.New("No known endpoint for peer")
-	}
-
-	conn := peer.device.net.conn
-	if conn == nil {
-		return 0, errors.New("No UDP socket for device")
-	}
-
-	return conn.WriteToUDP(buffer, endpoint)
-}
-
 /* Reads packets from the TUN and inserts
  * into nonce queue for peer
  *
@@ -343,7 +322,7 @@ func (peer *Peer) RoutineSequentialSender() {
 			// send message and return buffer to pool
 
 			length := uint64(len(elem.packet))
-			_, err := peer.SendBuffer(elem.packet)
+			err := peer.SendBuffer(elem.packet)
 			device.PutMessageBuffer(elem.buffer)
 			if err != nil {
 				logDebug.Println("Failed to send authenticated packet to peer", peer.String())
diff --git a/src/tests/netns.sh b/src/tests/netns.sh
index 043da3e..22abea8 100755
--- a/src/tests/netns.sh
+++ b/src/tests/netns.sh
@@ -20,6 +20,14 @@
 # wireguard peers in $ns1 and $ns2. Note that $ns0 is the endpoint for the wg1
 # interfaces in $ns1 and $ns2. See https://www.wireguard.com/netns/ for further
 # details on how this is accomplished.
+
+# This code is ported to the WireGuard-Go directly from the kernel project.
+#
+# Please ensure that you have installed the newest version of the WireGuard
+# tools from the WireGuard project and before running these tests as:
+#
+# ./netns.sh <path to wireguard-go>
+
 set -e
 
 exec 3>&1
@@ -27,8 +35,8 @@ export WG_HIDE_KEYS=never
 netns0="wg-test-$$-0"
 netns1="wg-test-$$-1"
 netns2="wg-test-$$-2"
-program="../wireguard-go"
-export LOG_LEVEL="error"
+program=$1
+export LOG_LEVEL="info"
 
 pretty() { echo -e "\x1b[32m\x1b[1m[+] ${1:+NS$1: }${2}\x1b[0m" >&3; }
 pp() { pretty "" "$*"; "$@"; }
@@ -72,13 +80,11 @@ pp ip netns add $netns2
 ip0 link set up dev lo
 
 # ip0 link add dev wg1 type wireguard
-n0 $program -f wg1 &
-sleep 1
+n0 $program wg1
 ip0 link set wg1 netns $netns1
 
 # ip0 link add dev wg1 type wireguard
-n0 $program -f wg2 &
-sleep 1
+n0 $program wg2
 ip0 link set wg2 netns $netns2
 
 key1="$(pp wg genkey)"
@@ -185,14 +191,14 @@ ip0 -4 addr del 127.0.0.1/8 dev lo
 ip0 -4 addr add 127.212.121.99/8 dev lo
 n0 wg set wg1 listen-port 9999
 n0 wg set wg1 peer "$pub2" endpoint 127.0.0.1:20000
-n1 ping6 -W 1 -c 1 fd00::20000
-[[ $(n2 wg show wg2 endpoints) == "$pub1    127.212.121.99:9999" ]]
+n1 ping6 -W 1 -c 1 fd00::2
+[[ $(n2 wg show wg2 endpoints) == "$pub1	127.212.121.99:9999" ]]
 
 # Test using IPv6 that roaming works
 n1 wg set wg1 listen-port 9998
 n1 wg set wg1 peer "$pub2" endpoint [::1]:20000
 n1 ping -W 1 -c 1 192.168.241.2
-[[ $(n2 wg show wg2 endpoints) == "$pub1    [::1]:9998" ]]
+[[ $(n2 wg show wg2 endpoints) == "$pub1	[::1]:9998" ]]
 
 # Test that crypto-RP filter works
 n1 wg set wg1 peer "$pub2" allowed-ips 192.168.241.0/24
@@ -212,7 +218,7 @@ n2 ncat -u 192.168.241.1 1111 <<<"X"
 ! read -r -N 1 -t 1 out <&4
 kill $nmap_pid
 n0 wg set wg1 peer "$more_specific_key" remove
-[[ $(n1 wg show wg1 endpoints) == "$pub2    [::1]:9997" ]]
+[[ $(n1 wg show wg1 endpoints) == "$pub2	[::1]:9997" ]]
 
 ip1 link del wg1
 ip2 link del wg2
@@ -263,7 +269,7 @@ n0 iptables -t nat -A POSTROUTING -s 192.168.1.0/24 -d 10.0.0.0/24 -j SNAT --to
 n0 wg set wg1 peer "$pub2" endpoint 10.0.0.100:20000 persistent-keepalive 1
 n1 ping -W 1 -c 1 192.168.241.2
 n2 ping -W 1 -c 1 192.168.241.1
-[[ $(n2 wg show wg2 endpoints) == "$pub1    10.0.0.1:10000" ]]
+[[ $(n2 wg show wg2 endpoints) == "$pub1	10.0.0.1:10000" ]]
 # Demonstrate n2 can still send packets to n1, since persistent-keepalive will prevent connection tracking entry from expiring (to see entries: `n0 conntrack -L`).
 pp sleep 3
 n2 ping -W 1 -c 1 192.168.241.1
@@ -289,7 +295,7 @@ ip2 link del wg2
 # ip1 link add dev wg1 type wireguard
 # ip2 link add dev wg1 type wireguard
 n1 $program wg1
-n2 $program wg1
+n2 $program wg2
 
 configure_peers
 
@@ -336,17 +342,83 @@ waitiface $netns1 veth1
 waitiface $netns2 veth2
 n0 wg set wg2 peer "$pub1" endpoint 10.0.0.1:10000
 n2 ping -W 1 -c 1 192.168.241.1
-[[ $(n0 wg show wg2 endpoints) == "$pub1    10.0.0.1:10000" ]]
+[[ $(n0 wg show wg2 endpoints) == "$pub1	10.0.0.1:10000" ]]
 n0 wg set wg2 peer "$pub1" endpoint [fd00:aa::1]:10000
 n2 ping -W 1 -c 1 192.168.241.1
-[[ $(n0 wg show wg2 endpoints) == "$pub1    [fd00:aa::1]:10000" ]]
+[[ $(n0 wg show wg2 endpoints) == "$pub1	[fd00:aa::1]:10000" ]]
 n0 wg set wg2 peer "$pub1" endpoint 10.0.0.2:10000
 n2 ping -W 1 -c 1 192.168.241.1
-[[ $(n0 wg show wg2 endpoints) == "$pub1    10.0.0.2:10000" ]]
+[[ $(n0 wg show wg2 endpoints) == "$pub1	10.0.0.2:10000" ]]
 n0 wg set wg2 peer "$pub1" endpoint [fd00:aa::2]:10000
 n2 ping -W 1 -c 1 192.168.241.1
-[[ $(n0 wg show wg2 endpoints) == "$pub1    [fd00:aa::2]:10000" ]]
+[[ $(n0 wg show wg2 endpoints) == "$pub1	[fd00:aa::2]:10000" ]]
 
 ip1 link del veth1
 ip1 link del wg1
 ip2 link del wg2
+
+# Test that Netlink/IPC is working properly by doing things that usually cause split responses
+
+n0 $program wg0
+sleep 5
+config=( "[Interface]" "PrivateKey=$(wg genkey)" "[Peer]" "PublicKey=$(wg genkey)" )
+for a in {1..255}; do
+    for b in {0..255}; do
+        config+=( "AllowedIPs=$a.$b.0.0/16,$a::$b/128" )
+    done
+done
+n0 wg setconf wg0 <(printf '%s\n' "${config[@]}")
+i=0
+for ip in $(n0 wg show wg0 allowed-ips); do
+    ((++i))
+done
+((i == 255*256*2+1))
+ip0 link del wg0
+
+n0 $program wg0
+config=( "[Interface]" "PrivateKey=$(wg genkey)" )
+for a in {1..40}; do
+    config+=( "[Peer]" "PublicKey=$(wg genkey)" )
+    for b in {1..52}; do
+        config+=( "AllowedIPs=$a.$b.0.0/16" )
+    done
+done
+n0 wg setconf wg0 <(printf '%s\n' "${config[@]}")
+i=0
+while read -r line; do
+    j=0
+    for ip in $line; do
+        ((++j))
+    done
+    ((j == 53))
+    ((++i))
+done < <(n0 wg show wg0 allowed-ips)
+((i == 40))
+ip0 link del wg0
+
+n0 $program wg0
+config=( )
+for i in {1..29}; do
+    config+=( "[Peer]" "PublicKey=$(wg genkey)" )
+done
+config+=( "[Peer]" "PublicKey=$(wg genkey)" "AllowedIPs=255.2.3.4/32,abcd::255/128" )
+n0 wg setconf wg0 <(printf '%s\n' "${config[@]}")
+n0 wg showconf wg0 > /dev/null
+ip0 link del wg0
+
+! n0 wg show doesnotexist || false
+
+declare -A objects
+while read -t 0.1 -r line 2>/dev/null || [[ $? -ne 142 ]]; do
+    [[ $line =~ .*(wg[0-9]+:\ [A-Z][a-z]+\ [0-9]+)\ .*(created|destroyed).* ]] || continue
+    objects["${BASH_REMATCH[1]}"]+="${BASH_REMATCH[2]}"
+done < /dev/kmsg
+alldeleted=1
+for object in "${!objects[@]}"; do
+    if [[ ${objects["$object"]} != *createddestroyed ]]; then
+        echo "Error: $object: merely ${objects["$object"]}" >&3
+        alldeleted=0
+    fi
+done
+[[ $alldeleted -eq 1 ]]
+pretty "" "Objects that were created were also destroyed."
diff --git a/src/timers.go b/src/timers.go
index 99695ba..31165a3 100644
--- a/src/timers.go
+++ b/src/timers.go
@@ -279,34 +279,31 @@ func (peer *Peer) RoutineHandshakeInitiator() {
 				break AttemptHandshakes

 			}

 

-			jitter := time.Millisecond * time.Duration(rand.Uint32()%334)

-

-			// marshal and send

+			// marshal handshake message

 

 			writer := bytes.NewBuffer(temp[:0])

 			binary.Write(writer, binary.LittleEndian, msg)

 			packet := writer.Bytes()

 			peer.mac.AddMacs(packet)

 

-			_, err = peer.SendBuffer(packet)

-			if err != nil {

+			// send to endpoint

+

+			err = peer.SendBuffer(packet)

+			jitter := time.Millisecond * time.Duration(rand.Uint32()%334)

+			timeout := time.NewTimer(RekeyTimeout + jitter)

+			if err == nil {

+				peer.TimerAnyAuthenticatedPacketTraversal()

+				logDebug.Println(

+					"Handshake initiation attempt",

+					attempts, "sent to", peer.String(),

+				)

+			} else {

 				logError.Println(

 					"Failed to send handshake initiation message to",

 					peer.String(), ":", err,

 				)

-				continue

 			}

 

-			peer.TimerAnyAuthenticatedPacketTraversal()

-

-			// set handshake timeout

-

-			timeout := time.NewTimer(RekeyTimeout + jitter)

-			logDebug.Println(

-				"Handshake initiation attempt",

-				attempts, "sent to", peer.String(),

-			)

-

 			// wait for handshake or timeout

 

 			select {

diff --git a/src/tun.go b/src/tun.go
index 8e8c759..5bdac0e 100644
--- a/src/tun.go
+++ b/src/tun.go
@@ -1,6 +1,7 @@
 package main
 
 import (
+	"os"
 	"sync/atomic"
 )
 
@@ -15,6 +16,7 @@ const (
 )
 
 type TUNDevice interface {
+	File() *os.File            // returns the file descriptor of the device
 	Read([]byte) (int, error)  // read a packet from the device (without any additional headers)
 	Write([]byte) (int, error) // writes a packet to the device (without any additional headers)
 	MTU() (int, error)         // returns the MTU of the device
@@ -47,7 +49,7 @@ func (device *Device) RoutineTUNEventReader() {
 			if !device.tun.isUp.Get() {
 				logInfo.Println("Interface set up")
 				device.tun.isUp.Set(true)
-				updateUDPConn(device)
+				UpdateUDPListener(device)
 			}
 		}
 
@@ -55,7 +57,7 @@ func (device *Device) RoutineTUNEventReader() {
 			if device.tun.isUp.Get() {
 				logInfo.Println("Interface set down")
 				device.tun.isUp.Set(false)
-				closeUDPConn(device)
+				CloseUDPListener(device)
 			}
 		}
 	}
diff --git a/src/tun_linux.go b/src/tun_linux.go
index accc6c6..a728a48 100644
--- a/src/tun_linux.go
+++ b/src/tun_linux.go
@@ -56,6 +56,10 @@ type NativeTun struct {
 	events chan TUNEvent // device related events
 }
 
+func (tun *NativeTun) File() *os.File {
+	return tun.fd
+}
+
 func (tun *NativeTun) RoutineNetlinkListener() {
 	sock := int(C.bind_rtmgrp())
 	if sock < 0 {
@@ -222,7 +226,7 @@ func (tun *NativeTun) MTU() (int, error) {
 
 	val := binary.LittleEndian.Uint32(ifr[16:20])
 	if val >= (1 << 31) {
-		return int(val-(1<<31)) - (1 << 31), nil
+		return int(toInt32(val)), nil
 	}
 	return int(val), nil
 }
@@ -248,6 +252,29 @@ func (tun *NativeTun) Close() error {
 	return nil
 }
 
+func CreateTUNFromFile(name string, fd *os.File) (TUNDevice, error) {
+	device := &NativeTun{
+		fd:     fd,
+		name:   name,
+		events: make(chan TUNEvent, 5),
+		errors: make(chan error, 5),
+	}
+
+	// start event listener
+
+	var err error
+	device.index, err = getIFIndex(device.name)
+	if err != nil {
+		return nil, err
+	}
+
+	go device.RoutineNetlinkListener()
+
+	// set default MTU
+
+	return device, device.setMTU(DefaultMTU)
+}
+
 func CreateTUN(name string) (TUNDevice, error) {
 
 	// open clone device
diff --git a/src/uapi.go b/src/uapi.go
index 326216b..dc8be66 100644
--- a/src/uapi.go
+++ b/src/uapi.go
@@ -39,9 +39,10 @@ func ipcGetOperation(device *Device, socket *bufio.ReadWriter) *IPCError {
 		send("private_key=" + device.privateKey.ToHex())
 	}
 
-	if device.net.addr != nil {
-		send(fmt.Sprintf("listen_port=%d", device.net.addr.Port))
+	if device.net.port != 0 {
+		send(fmt.Sprintf("listen_port=%d", device.net.port))
 	}
+
 	if device.net.fwmark != 0 {
 		send(fmt.Sprintf("fwmark=%d", device.net.fwmark))
 	}
@@ -53,7 +54,7 @@ func ipcGetOperation(device *Device, socket *bufio.ReadWriter) *IPCError {
 			send("public_key=" + peer.handshake.remoteStatic.ToHex())
 			send("preshared_key=" + peer.handshake.presharedKey.ToHex())
 			if peer.endpoint != nil {
-				send("endpoint=" + peer.endpoint.String())
+				send("endpoint=" + peer.endpoint.DstToString())
 			}
 
 			nano := atomic.LoadInt64(&peer.stats.lastHandshakeNano)
@@ -134,56 +135,38 @@ func ipcSetOperation(device *Device, socket *bufio.ReadWriter) *IPCError {
 			case "listen_port":
 				port, err := strconv.ParseUint(value, 10, 16)
 				if err != nil {
-					logError.Println("Failed to set listen_port:", err)
+					logError.Println("Failed to parse listen_port:", err)
 					return &IPCError{Code: ipcErrorInvalid}
 				}
-
-				addr, err := net.ResolveUDPAddr("udp", fmt.Sprintf(":%d", port))
-				if err != nil {
+				device.net.port = uint16(port)
+				if err := UpdateUDPListener(device); err != nil {
 					logError.Println("Failed to set listen_port:", err)
-					return &IPCError{Code: ipcErrorInvalid}
+					return &IPCError{Code: ipcErrorPortInUse}
 				}
 
-				device.net.mutex.Lock()
-				device.net.addr = addr
-				device.net.mutex.Unlock()
+			case "fwmark":
 
-				err = updateUDPConn(device)
-				if err != nil {
-					logError.Println("Failed to set listen_port:", err)
-					return &IPCError{Code: ipcErrorPortInUse}
-				}
+				// parse fwmark field
 
-				// TODO: Clear source address of all peers
+				fwmark, err := func() (uint32, error) {
+					if value == "" {
+						return 0, nil
+					}
+					mark, err := strconv.ParseUint(value, 10, 32)
+					return uint32(mark), err
+				}()
 
-			case "fwmark":
-				fwmark, err := strconv.ParseUint(value, 10, 32)
 				if err != nil {
 					logError.Println("Invalid fwmark", err)
 					return &IPCError{Code: ipcErrorInvalid}
 				}
 
 				device.net.mutex.Lock()
-				if fwmark > 0 || device.net.fwmark > 0 {
-					device.net.fwmark = uint32(fwmark)
-					err := setMark(
-						device.net.conn,
-						device.net.fwmark,
-					)
-					if err != nil {
-						logError.Println("Failed to set fwmark:", err)
-						device.net.mutex.Unlock()
-						return &IPCError{Code: ipcErrorIO}
-					}
-
-					// TODO: Clear source address of all peers
-				}
+				device.net.fwmark = uint32(fwmark)
 				device.net.mutex.Unlock()
 
 			case "public_key":
-
 				// switch to peer configuration
-
 				deviceConfig = false
 
 			case "replace_peers":
@@ -218,7 +201,7 @@ func ipcSetOperation(device *Device, socket *bufio.ReadWriter) *IPCError {
 				device.mutex.RLock()
 				if device.publicKey.Equals(pubKey) {
 
-					// create dummy instance
+					// create dummy instance (not added to device)
 
 					peer = &Peer{}
 					dummy = true
@@ -244,6 +227,9 @@ func ipcSetOperation(device *Device, socket *bufio.ReadWriter) *IPCError {
 				}
 
 			case "remove":
+
+				// remove currently selected peer from device
+
 				if value != "true" {
 					logError.Println("Failed to set remove, invalid value:", value)
 					return &IPCError{Code: ipcErrorInvalid}
@@ -256,6 +242,9 @@ func ipcSetOperation(device *Device, socket *bufio.ReadWriter) *IPCError {
 				dummy = true
 
 			case "preshared_key":
+
+				// update PSK
+
 				peer.mutex.Lock()
 				err := peer.handshake.presharedKey.FromHex(value)
 				peer.mutex.Unlock()
@@ -265,15 +254,25 @@ func ipcSetOperation(device *Device, socket *bufio.ReadWriter) *IPCError {
 				}
 
 			case "endpoint":
-				addr, err := parseEndpoint(value)
+
+				// set endpoint destination
+
+				err := func() error {
+					peer.mutex.Lock()
+					defer peer.mutex.Unlock()
+					endpoint, err := CreateEndpoint(value)
+					if err != nil {
+						return err
+					}
+					peer.endpoint = endpoint
+					signalSend(peer.signal.handshakeReset)
+					return nil
+				}()
+
 				if err != nil {
 					logError.Println("Failed to set endpoint:", value)
 					return &IPCError{Code: ipcErrorInvalid}
 				}
-				peer.mutex.Lock()
-				peer.endpoint = addr
-				peer.mutex.Unlock()
-				signalSend(peer.signal.handshakeReset)
 
 			case "persistent_keepalive_interval":
 
diff --git a/src/uapi_linux.go b/src/uapi_linux.go
index cb9d858..f97a18a 100644
--- a/src/uapi_linux.go
+++ b/src/uapi_linux.go
@@ -10,12 +10,12 @@ import (
 )
 
 const (
-	ipcErrorIO         = -int64(unix.EIO)
-	ipcErrorProtocol   = -int64(unix.EPROTO)
-	ipcErrorInvalid    = -int64(unix.EINVAL)
-	ipcErrorPortInUse  = -int64(unix.EADDRINUSE)
-	socketDirectory    = "/var/run/wireguard"
-	socketName         = "%s.sock"
+	ipcErrorIO        = -int64(unix.EIO)
+	ipcErrorProtocol  = -int64(unix.EPROTO)
+	ipcErrorInvalid   = -int64(unix.EINVAL)
+	ipcErrorPortInUse = -int64(unix.EADDRINUSE)
+	socketDirectory   = "/var/run/wireguard"
+	socketName        = "%s.sock"
 )
 
 type UAPIListener struct {
@@ -50,49 +50,11 @@ func (l *UAPIListener) Addr() net.Addr {
 	return nil
 }
 
-func connectUnixSocket(path string) (net.Listener, error) {
+func UAPIListen(name string, file *os.File) (net.Listener, error) {
 
-	// attempt inital connection
+	// wrap file in listener
 
-	listener, err := net.Listen("unix", path)
-	if err == nil {
-		return listener, nil
-	}
-
-	// check if active
-
-	_, err = net.Dial("unix", path)
-	if err == nil {
-		return nil, errors.New("Unix socket in use")
-	}
-
-	// attempt cleanup
-
-	err = os.Remove(path)
-	if err != nil {
-		return nil, err
-	}
-
-	return net.Listen("unix", path)
-}
-
-func NewUAPIListener(name string) (net.Listener, error) {
-
-	// check if path exist
-
-	err := os.MkdirAll(socketDirectory, 077)
-	if err != nil && !os.IsExist(err) {
-		return nil, err
-	}
-
-	// open UNIX socket
-
-	socketPath := path.Join(
-		socketDirectory,
-		fmt.Sprintf(socketName, name),
-	)
-
-	listener, err := connectUnixSocket(socketPath)
+	listener, err := net.FileListener(file)
 	if err != nil {
 		return nil, err
 	}
@@ -105,6 +67,11 @@ func NewUAPIListener(name string) (net.Listener, error) {
 
 	// watch for deletion of socket
 
+	socketPath := path.Join(
+		socketDirectory,
+		fmt.Sprintf(socketName, name),
+	)
+
 	uapi.inotifyFd, err = unix.InotifyInit()
 	if err != nil {
 		return nil, err
@@ -125,11 +92,12 @@ func NewUAPIListener(name string) (net.Listener, error) {
 	go func(l *UAPIListener) {
 		var buff [4096]byte
 		for {
-			unix.Read(uapi.inotifyFd, buff[:])
+			// start with lstat to avoid race condition
 			if _, err := os.Lstat(socketPath); os.IsNotExist(err) {
 				l.connErr <- err
 				return
 			}
+			unix.Read(uapi.inotifyFd, buff[:])
 		}
 	}(uapi)
 
@@ -148,3 +116,56 @@ func NewUAPIListener(name string) (net.Listener, error) {
 
 	return uapi, nil
 }
+
+func UAPIOpen(name string) (*os.File, error) {
+
+	// check if path exist
+
+	err := os.MkdirAll(socketDirectory, 0600)
+	if err != nil && !os.IsExist(err) {
+		return nil, err
+	}
+
+	// open UNIX socket
+
+	socketPath := path.Join(
+		socketDirectory,
+		fmt.Sprintf(socketName, name),
+	)
+
+	addr, err := net.ResolveUnixAddr("unix", socketPath)
+	if err != nil {
+		return nil, err
+	}
+
+	listener, err := func() (*net.UnixListener, error) {
+
+		// initial connection attempt
+
+		listener, err := net.ListenUnix("unix", addr)
+		if err == nil {
+			return listener, nil
+		}
+
+		// check if socket already active
+
+		_, err = net.Dial("unix", socketPath)
+		if err == nil {
+			return nil, errors.New("unix socket in use")
+		}
+
+		// cleanup & attempt again
+
+		err = os.Remove(socketPath)
+		if err != nil {
+			return nil, err
+		}
+		return net.ListenUnix("unix", addr)
+	}()
+
+	if err != nil {
+		return nil, err
+	}
+
+	return listener.File()
+}