yggdrasil-go/src/yggdrasil/tun.go

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package yggdrasil
// This manages the tun driver to send/recv packets to/from applications
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import (
"bytes"
"errors"
"time"
"yggdrasil/defaults"
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"github.com/songgao/packets/ethernet"
"github.com/yggdrasil-network/water"
)
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const tun_IPv6_HEADER_LENGTH = 40
const tun_ETHER_HEADER_LENGTH = 14
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// Represents a running TUN/TAP interface.
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type tunDevice struct {
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core *Core
icmpv6 icmpv6
send chan<- []byte
recv <-chan []byte
mtu int
iface *water.Interface
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}
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// Gets the maximum supported MTU for the platform based on the defaults in
// defaults.GetDefaults().
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func getSupportedMTU(mtu int) int {
if mtu > defaults.GetDefaults().MaximumIfMTU {
return defaults.GetDefaults().MaximumIfMTU
}
return mtu
}
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// Initialises the TUN/TAP adapter.
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func (tun *tunDevice) init(core *Core) {
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tun.core = core
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tun.icmpv6.init(tun)
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}
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// Starts the setup process for the TUN/TAP adapter, and if successful, starts
// the read/write goroutines to handle packets on that interface.
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func (tun *tunDevice) start(ifname string, iftapmode bool, addr string, mtu int) error {
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if ifname == "none" {
return nil
}
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if err := tun.setup(ifname, iftapmode, addr, mtu); err != nil {
return err
}
go func() { panic(tun.read()) }()
go func() { panic(tun.write()) }()
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if iftapmode {
go func() {
for {
if _, ok := tun.icmpv6.peermacs[tun.core.router.addr]; ok {
break
}
request, err := tun.icmpv6.create_ndp_tap(tun.core.router.addr)
if err != nil {
panic(err)
}
if _, err := tun.iface.Write(request); err != nil {
panic(err)
}
time.Sleep(time.Second)
}
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}()
}
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return nil
}
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// Writes a packet to the TUN/TAP adapter. If the adapter is running in TAP
// mode then additional ethernet encapsulation is added for the benefit of the
// host operating system.
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func (tun *tunDevice) write() error {
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for {
data := <-tun.recv
if tun.iface == nil {
continue
}
if tun.iface.IsTAP() {
var destAddr address
if data[0]&0xf0 == 0x60 {
if len(data) < 40 {
panic("Tried to send a packet shorter than an IPv6 header...")
}
copy(destAddr[:16], data[24:])
} else if data[0]&0xf0 == 0x40 {
if len(data) < 20 {
panic("Tried to send a packet shorter than an IPv4 header...")
}
copy(destAddr[:4], data[16:])
} else {
return errors.New("Invalid address family")
}
sendndp := func(destAddr address) {
neigh, known := tun.icmpv6.peermacs[destAddr]
known = known && (time.Since(neigh.lastsolicitation).Seconds() < 30)
if !known {
request, err := tun.icmpv6.create_ndp_tap(destAddr)
if err != nil {
panic(err)
}
if _, err := tun.iface.Write(request); err != nil {
panic(err)
}
tun.icmpv6.peermacs[destAddr] = neighbor{
lastsolicitation: time.Now(),
}
}
}
var peermac macAddress
var peerknown bool
if data[0]&0xf0 == 0x40 {
destAddr = tun.core.router.addr
} else if data[0]&0xf0 == 0x60 {
if !bytes.Equal(tun.core.router.addr[:16], destAddr[:16]) && !bytes.Equal(tun.core.router.subnet[:8], destAddr[:8]) {
destAddr = tun.core.router.addr
}
}
if neighbor, ok := tun.icmpv6.peermacs[destAddr]; ok && neighbor.learned {
peermac = neighbor.mac
peerknown = true
} else if neighbor, ok := tun.icmpv6.peermacs[tun.core.router.addr]; ok && neighbor.learned {
peermac = neighbor.mac
peerknown = true
sendndp(destAddr)
} else {
sendndp(tun.core.router.addr)
}
if peerknown {
var proto ethernet.Ethertype
switch {
case data[0]&0xf0 == 0x60:
proto = ethernet.IPv6
case data[0]&0xf0 == 0x40:
proto = ethernet.IPv4
}
var frame ethernet.Frame
frame.Prepare(
peermac[:6], // Destination MAC address
tun.icmpv6.mymac[:6], // Source MAC address
ethernet.NotTagged, // VLAN tagging
proto, // Ethertype
len(data)) // Payload length
copy(frame[tun_ETHER_HEADER_LENGTH:], data[:])
if _, err := tun.iface.Write(frame); err != nil {
panic(err)
}
}
} else {
if _, err := tun.iface.Write(data); err != nil {
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panic(err)
}
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}
util_putBytes(data)
}
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}
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// Reads any packets that are waiting on the TUN/TAP adapter. If the adapter
// is running in TAP mode then the ethernet headers will automatically be
// processed and stripped if necessary. If an ICMPv6 packet is found, then
// the relevant helper functions in icmpv6.go are called.
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func (tun *tunDevice) read() error {
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mtu := tun.mtu
if tun.iface.IsTAP() {
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mtu += tun_ETHER_HEADER_LENGTH
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}
buf := make([]byte, mtu)
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for {
n, err := tun.iface.Read(buf)
if err != nil {
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// panic(err)
return err
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}
o := 0
if tun.iface.IsTAP() {
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o = tun_ETHER_HEADER_LENGTH
}
switch {
case buf[o]&0xf0 == 0x60 && n == 256*int(buf[o+4])+int(buf[o+5])+tun_IPv6_HEADER_LENGTH+o:
case buf[o]&0xf0 == 0x40 && n == 256*int(buf[o+2])+int(buf[o+3])+o:
default:
continue
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}
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if buf[o+6] == 58 {
// Found an ICMPv6 packet
b := make([]byte, n)
copy(b, buf)
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// tun.icmpv6.recv <- b
go tun.icmpv6.parse_packet(b)
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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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// Closes the TUN/TAP adapter. This is only usually called when the Yggdrasil
// 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 *tunDevice) close() error {
if tun.iface == nil {
return nil
}
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return tun.iface.Close()
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}