mirror of
https://github.com/yggdrasil-network/yggdrasil-go
synced 2024-09-21 01:50:25 +03:00
366 lines
10 KiB
Go
366 lines
10 KiB
Go
package tuntap
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// This manages the tun driver to send/recv packets to/from applications
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import (
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"bytes"
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"errors"
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"fmt"
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"net"
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"sync"
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"time"
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"github.com/gologme/log"
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"golang.org/x/net/icmp"
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"golang.org/x/net/ipv6"
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"github.com/songgao/packets/ethernet"
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"github.com/yggdrasil-network/water"
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"github.com/yggdrasil-network/yggdrasil-go/src/address"
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"github.com/yggdrasil-network/yggdrasil-go/src/config"
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"github.com/yggdrasil-network/yggdrasil-go/src/defaults"
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"github.com/yggdrasil-network/yggdrasil-go/src/util"
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"github.com/yggdrasil-network/yggdrasil-go/src/yggdrasil"
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)
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const tun_IPv6_HEADER_LENGTH = 40
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const tun_ETHER_HEADER_LENGTH = 14
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// TunAdapter represents a running TUN/TAP interface and extends the
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// yggdrasil.Adapter type. In order to use the TUN/TAP adapter with Yggdrasil,
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// you should pass this object to the yggdrasil.SetRouterAdapter() function
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// before calling yggdrasil.Start().
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type TunAdapter struct {
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yggdrasil.Adapter
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addr address.Address
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subnet address.Subnet
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log *log.Logger
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config *config.NodeState
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icmpv6 ICMPv6
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mtu int
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iface *water.Interface
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mutex sync.RWMutex // Protects the below
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isOpen bool
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}
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// Gets the maximum supported MTU for the platform based on the defaults in
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// defaults.GetDefaults().
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func getSupportedMTU(mtu int) int {
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if mtu > defaults.GetDefaults().MaximumIfMTU {
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return defaults.GetDefaults().MaximumIfMTU
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}
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return mtu
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}
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// Name returns the name of the adapter, e.g. "tun0". On Windows, this may
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// return a canonical adapter name instead.
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func (tun *TunAdapter) Name() string {
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return tun.iface.Name()
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}
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// MTU gets the adapter's MTU. This can range between 1280 and 65535, although
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// the maximum value is determined by your platform. The returned value will
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// never exceed that of MaximumMTU().
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func (tun *TunAdapter) MTU() int {
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return getSupportedMTU(tun.mtu)
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}
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// IsTAP returns true if the adapter is a TAP adapter (Layer 2) or false if it
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// is a TUN adapter (Layer 3).
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func (tun *TunAdapter) IsTAP() bool {
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return tun.iface.IsTAP()
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}
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// DefaultName gets the default TUN/TAP interface name for your platform.
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func DefaultName() string {
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return defaults.GetDefaults().DefaultIfName
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}
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// DefaultMTU gets the default TUN/TAP interface MTU for your platform. This can
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// be as high as MaximumMTU(), depending on platform, but is never lower than 1280.
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func DefaultMTU() int {
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return defaults.GetDefaults().DefaultIfMTU
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}
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// DefaultIsTAP returns true if the default adapter mode for the current
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// platform is TAP (Layer 2) and returns false for TUN (Layer 3).
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func DefaultIsTAP() bool {
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return defaults.GetDefaults().DefaultIfTAPMode
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}
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// MaximumMTU returns the maximum supported TUN/TAP interface MTU for your
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// platform. This can be as high as 65535, depending on platform, but is never
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// lower than 1280.
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func MaximumMTU() int {
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return defaults.GetDefaults().MaximumIfMTU
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}
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// Init initialises the TUN/TAP adapter.
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func (tun *TunAdapter) Init(config *config.NodeState, log *log.Logger, send chan<- []byte, recv <-chan []byte, reject <-chan yggdrasil.RejectedPacket) {
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tun.config = config
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tun.log = log
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tun.Adapter.Init(config, log, send, recv, reject)
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tun.icmpv6.Init(tun)
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go func() {
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for {
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e := <-tun.Reconfigure
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tun.config.Mutex.RLock()
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updated := tun.config.Current.IfName != tun.config.Previous.IfName ||
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tun.config.Current.IfTAPMode != tun.config.Previous.IfTAPMode ||
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tun.config.Current.IfMTU != tun.config.Previous.IfMTU
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tun.config.Mutex.RUnlock()
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if updated {
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tun.log.Warnln("Reconfiguring TUN/TAP is not supported yet")
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e <- nil
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} else {
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e <- nil
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}
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}
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}()
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}
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// Start the setup process for the TUN/TAP adapter. If successful, starts the
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// read/write goroutines to handle packets on that interface.
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func (tun *TunAdapter) Start(a address.Address, s address.Subnet) error {
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tun.addr = a
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tun.subnet = s
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if tun.config == nil {
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return errors.New("No configuration available to TUN/TAP")
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}
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tun.config.Mutex.RLock()
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ifname := tun.config.Current.IfName
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iftapmode := tun.config.Current.IfTAPMode
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addr := fmt.Sprintf("%s/%d", net.IP(tun.addr[:]).String(), 8*len(address.GetPrefix())-1)
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mtu := tun.config.Current.IfMTU
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tun.config.Mutex.RUnlock()
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if ifname != "none" {
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if err := tun.setup(ifname, iftapmode, addr, mtu); err != nil {
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return err
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}
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}
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if ifname == "none" || ifname == "dummy" {
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tun.log.Debugln("Not starting TUN/TAP as ifname is none or dummy")
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return nil
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}
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tun.mutex.Lock()
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tun.isOpen = true
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tun.mutex.Unlock()
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go func() {
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tun.log.Debugln("Starting TUN/TAP reader goroutine")
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tun.log.Errorln("WARNING: tun.read() exited with error:", tun.read())
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}()
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go func() {
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tun.log.Debugln("Starting TUN/TAP writer goroutine")
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tun.log.Errorln("WARNING: tun.write() exited with error:", tun.write())
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}()
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if iftapmode {
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go func() {
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for {
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if _, ok := tun.icmpv6.peermacs[tun.addr]; ok {
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break
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}
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request, err := tun.icmpv6.CreateNDPL2(tun.addr)
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if err != nil {
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panic(err)
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}
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if _, err := tun.iface.Write(request); err != nil {
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panic(err)
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}
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time.Sleep(time.Second)
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}
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}()
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}
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return nil
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}
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// Writes a packet to the TUN/TAP adapter. If the adapter is running in TAP
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// mode then additional ethernet encapsulation is added for the benefit of the
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// host operating system.
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func (tun *TunAdapter) write() error {
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for {
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select {
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case reject := <-tun.Reject:
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switch reject.Reason {
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case yggdrasil.PacketTooBig:
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if mtu, ok := reject.Detail.(int); ok {
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// Create the Packet Too Big response
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ptb := &icmp.PacketTooBig{
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MTU: int(mtu),
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Data: reject.Packet,
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}
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// Create the ICMPv6 response from it
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icmpv6Buf, err := CreateICMPv6(
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reject.Packet[8:24], reject.Packet[24:40],
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ipv6.ICMPTypePacketTooBig, 0, ptb)
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// Send the ICMPv6 response back to the TUN/TAP adapter
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if err == nil {
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tun.iface.Write(icmpv6Buf)
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}
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}
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fallthrough
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default:
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continue
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}
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case data := <-tun.Recv:
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if tun.iface == nil {
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continue
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}
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if tun.iface.IsTAP() {
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var destAddr address.Address
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if data[0]&0xf0 == 0x60 {
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if len(data) < 40 {
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//panic("Tried to send a packet shorter than an IPv6 header...")
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util.PutBytes(data)
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continue
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}
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copy(destAddr[:16], data[24:])
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} else if data[0]&0xf0 == 0x40 {
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if len(data) < 20 {
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//panic("Tried to send a packet shorter than an IPv4 header...")
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util.PutBytes(data)
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continue
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}
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copy(destAddr[:4], data[16:])
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} else {
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return errors.New("Invalid address family")
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}
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sendndp := func(destAddr address.Address) {
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neigh, known := tun.icmpv6.peermacs[destAddr]
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known = known && (time.Since(neigh.lastsolicitation).Seconds() < 30)
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if !known {
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request, err := tun.icmpv6.CreateNDPL2(destAddr)
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if err != nil {
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panic(err)
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}
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if _, err := tun.iface.Write(request); err != nil {
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panic(err)
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}
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tun.icmpv6.peermacs[destAddr] = neighbor{
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lastsolicitation: time.Now(),
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}
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}
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}
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var peermac macAddress
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var peerknown bool
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if data[0]&0xf0 == 0x40 {
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destAddr = tun.addr
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} else if data[0]&0xf0 == 0x60 {
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if !bytes.Equal(tun.addr[:16], destAddr[:16]) && !bytes.Equal(tun.subnet[:8], destAddr[:8]) {
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destAddr = tun.addr
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}
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}
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if neighbor, ok := tun.icmpv6.peermacs[destAddr]; ok && neighbor.learned {
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peermac = neighbor.mac
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peerknown = true
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} else if neighbor, ok := tun.icmpv6.peermacs[tun.addr]; ok && neighbor.learned {
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peermac = neighbor.mac
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peerknown = true
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sendndp(destAddr)
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} else {
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sendndp(tun.addr)
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}
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if peerknown {
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var proto ethernet.Ethertype
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switch {
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case data[0]&0xf0 == 0x60:
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proto = ethernet.IPv6
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case data[0]&0xf0 == 0x40:
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proto = ethernet.IPv4
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}
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var frame ethernet.Frame
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frame.Prepare(
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peermac[:6], // Destination MAC address
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tun.icmpv6.mymac[:6], // Source MAC address
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ethernet.NotTagged, // VLAN tagging
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proto, // Ethertype
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len(data)) // Payload length
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copy(frame[tun_ETHER_HEADER_LENGTH:], data[:])
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if _, err := tun.iface.Write(frame); err != nil {
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tun.mutex.RLock()
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open := tun.isOpen
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tun.mutex.RUnlock()
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if !open {
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return nil
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} else {
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panic(err)
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}
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}
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}
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} else {
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if _, err := tun.iface.Write(data); err != nil {
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tun.mutex.RLock()
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open := tun.isOpen
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tun.mutex.RUnlock()
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if !open {
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return nil
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} else {
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panic(err)
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}
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}
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}
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util.PutBytes(data)
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}
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}
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}
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// Reads any packets that are waiting on the TUN/TAP adapter. If the adapter
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// is running in TAP mode then the ethernet headers will automatically be
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// processed and stripped if necessary. If an ICMPv6 packet is found, then
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// the relevant helper functions in icmpv6.go are called.
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func (tun *TunAdapter) read() error {
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mtu := tun.mtu
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if tun.iface.IsTAP() {
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mtu += tun_ETHER_HEADER_LENGTH
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}
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buf := make([]byte, mtu)
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for {
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n, err := tun.iface.Read(buf)
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if err != nil {
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tun.mutex.RLock()
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open := tun.isOpen
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tun.mutex.RUnlock()
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if !open {
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return nil
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} else {
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return err
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}
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}
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o := 0
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if tun.iface.IsTAP() {
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o = tun_ETHER_HEADER_LENGTH
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}
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switch {
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case buf[o]&0xf0 == 0x60 && n == 256*int(buf[o+4])+int(buf[o+5])+tun_IPv6_HEADER_LENGTH+o:
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case buf[o]&0xf0 == 0x40 && n == 256*int(buf[o+2])+int(buf[o+3])+o:
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default:
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continue
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}
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if buf[o+6] == 58 {
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if tun.iface.IsTAP() {
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// Found an ICMPv6 packet
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b := make([]byte, n)
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copy(b, buf)
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go tun.icmpv6.ParsePacket(b)
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}
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}
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packet := append(util.GetBytes(), buf[o:n]...)
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tun.Send <- packet
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}
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}
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// Closes the TUN/TAP adapter. This is only usually called when the Yggdrasil
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// process stops. Typically this operation will happen quickly, but on macOS
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// it can block until a read operation is completed.
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func (tun *TunAdapter) Close() error {
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tun.mutex.Lock()
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tun.isOpen = false
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tun.mutex.Unlock()
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if tun.iface == nil {
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return nil
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}
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return tun.iface.Close()
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}
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