Added padding

Added plaintext padding and fixed default interface MTU

diff --git a/src/device.go b/src/device.go
index a15961a6e6d8da6ec31216c498d094acc28db641..4981f51fe7385ed125a0c2574df4362724eb4b4d 100644 (file)
--- a/src/device.go
+++ b/src/device.go
@@ -4,10 +4,12 @@ import (
        "net"
        "runtime"
        "sync"
+       "sync/atomic"
+       "time"
 )
 
 type Device struct {
-       mtu       int
+       mtu       int32
        log       *Logger // collection of loggers for levels
        idCounter uint    // for assigning debug ids to peers
        fwMark    uint32
@@ -118,6 +120,7 @@ func NewDevice(tun TUNDevice, logLevel int) *Device {
        }
 
        go device.RoutineBusyMonitor()
+       go device.RoutineMTUUpdater(tun)
        go device.RoutineWriteToTUN(tun)
        go device.RoutineReadFromTUN(tun)
        go device.RoutineReceiveIncomming()
@@ -126,6 +129,18 @@ func NewDevice(tun TUNDevice, logLevel int) *Device {
        return device
 }
 
+func (device *Device) RoutineMTUUpdater(tun TUNDevice) {
+       logError := device.log.Error
+       for ; ; time.Sleep(time.Second) {
+               mtu, err := tun.MTU()
+               if err != nil {
+                       logError.Println("Failed to load updated MTU of device:", err)
+                       continue
+               }
+               atomic.StoreInt32(&device.mtu, int32(mtu))
+       }
+}
+
 func (device *Device) LookupPeer(pk NoisePublicKey) *Peer {
        device.mutex.RLock()
        defer device.mutex.RUnlock()

diff --git a/src/send.go b/src/send.go
index 7a2fe44f95a0ca8340a37c4e466026052911c36e..2db74ba477ef4afcadc02a2ec0a331640281fdc8 100644 (file)
--- a/src/send.go
+++ b/src/send.go
@@ -281,17 +281,22 @@ func (device *Device) RoutineEncryption() {
 
                // populate header fields
 
-               func() {
-                       header := work.buffer[:MessageTransportHeaderSize]
+               header := work.buffer[:MessageTransportHeaderSize]
 
-                       fieldType := header[0:4]
-                       fieldReceiver := header[4:8]
-                       fieldNonce := header[8:16]
+               fieldType := header[0:4]
+               fieldReceiver := header[4:8]
+               fieldNonce := header[8:16]
 
-                       binary.LittleEndian.PutUint32(fieldType, MessageTransportType)
-                       binary.LittleEndian.PutUint32(fieldReceiver, work.keyPair.remoteIndex)
-                       binary.LittleEndian.PutUint64(fieldNonce, work.nonce)
-               }()
+               binary.LittleEndian.PutUint32(fieldType, MessageTransportType)
+               binary.LittleEndian.PutUint32(fieldReceiver, work.keyPair.remoteIndex)
+               binary.LittleEndian.PutUint64(fieldNonce, work.nonce)
+
+               // pad content to MTU size
+
+               mtu := int(atomic.LoadInt32(&device.mtu))
+               for i := len(work.packet); i < mtu; i++ {
+                       work.packet = append(work.packet, 0)
+               }
 
                // encrypt content
 

diff --git a/src/tun.go b/src/tun.go
index 85735a657ebd1076fe85b1892febf9caf47dc511..f529c54f5ea25a64a9e1368ba39757e3d74da385 100644 (file)
--- a/src/tun.go
+++ b/src/tun.go
@@ -1,5 +1,11 @@
 package main
 
+/*
+ * The default MTU of the new device must be 1420
+ */
+
+const DefaultMTU = 1420
+
 type TUNDevice interface {
        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)

diff --git a/src/tun_linux.go b/src/tun_linux.go
index 63c38869cd11da3aa96553814271a4dbcb1d56f9..d0e9761f358f31e67156f14274bc04b1c07f0485 100644 (file)
--- a/src/tun_linux.go
+++ b/src/tun_linux.go
@@ -23,6 +23,39 @@ func (tun *NativeTun) Name() string {
        return tun.name
 }
 
+func (tun *NativeTun) setMTU(n int) error {
+
+       // open datagram socket
+
+       fd, err := syscall.Socket(
+               syscall.AF_INET,
+               syscall.SOCK_DGRAM,
+               0,
+       )
+
+       if err != nil {
+               return err
+       }
+
+       // do ioctl call
+
+       var ifr [64]byte
+       copy(ifr[:], tun.name)
+       binary.LittleEndian.PutUint32(ifr[16:20], uint32(n))
+       _, _, errno := syscall.Syscall(
+               syscall.SYS_IOCTL,
+               uintptr(fd),
+               uintptr(syscall.SIOCSIFMTU),
+               uintptr(unsafe.Pointer(&ifr[0])),
+       )
+
+       if errno != 0 {
+               return errors.New("Failed to set MTU of TUN device")
+       }
+
+       return nil
+}
+
 func (tun *NativeTun) MTU() (int, error) {
 
        // open datagram socket
@@ -40,9 +73,7 @@ func (tun *NativeTun) MTU() (int, error) {
        // do ioctl call
 
        var ifr [64]byte
-       var flags uint16
        copy(ifr[:], tun.name)
-       binary.LittleEndian.PutUint16(ifr[16:], flags)
        _, _, errno := syscall.Syscall(
                syscall.SYS_IOCTL,
                uintptr(fd),
@@ -79,7 +110,7 @@ func CreateTUN(name string) (TUNDevice, error) {
                return nil, err
        }
 
-       // prepare ifreq struct
+       // create new device
 
        var ifr [64]byte
        var flags uint16 = syscall.IFF_TUN | syscall.IFF_NO_PI
@@ -90,8 +121,6 @@ func CreateTUN(name string) (TUNDevice, error) {
        copy(ifr[:], nameBytes)
        binary.LittleEndian.PutUint16(ifr[16:], flags)
 
-       // create new device
-
        _, _, errno := syscall.Syscall(
                syscall.SYS_IOCTL,
                uintptr(fd.Fd()),
@@ -106,8 +135,13 @@ func CreateTUN(name string) (TUNDevice, error) {
 
        newName := string(ifr[:])
        newName = newName[:strings.Index(newName, "\000")]
-       return &NativeTun{
+       device := &NativeTun{
                fd:   fd,
                name: newName,
-       }, nil
+       }
+
+       // set default MTU
+
+       err = device.setMTU(DefaultMTU)
+       return device, err
 }