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tailscale/wgengine/userspace.go

733 lines
19 KiB
Go

// Copyright (c) 2020 Tailscale Inc & AUTHORS All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package wgengine
import (
"bufio"
"bytes"
"context"
"errors"
"fmt"
"io"
"log"
"net"
"os"
"os/exec"
"runtime"
"strings"
"sync"
"time"
"github.com/tailscale/wireguard-go/device"
"github.com/tailscale/wireguard-go/tun"
"github.com/tailscale/wireguard-go/wgcfg"
"go4.org/mem"
"tailscale.com/ipn/ipnstate"
"tailscale.com/net/interfaces"
"tailscale.com/tailcfg"
"tailscale.com/types/key"
"tailscale.com/types/logger"
"tailscale.com/wgengine/filter"
"tailscale.com/wgengine/magicsock"
"tailscale.com/wgengine/monitor"
"tailscale.com/wgengine/packet"
"tailscale.com/wgengine/router"
"tailscale.com/wgengine/tstun"
)
// minimalMTU is the MTU we set on tailscale's tuntap
// interface. wireguard-go defaults to 1420 bytes, which only works if
// the "outer" MTU is 1500 bytes. This breaks on DSL connections
// (typically 1492 MTU) and on GCE (1460 MTU?!).
//
// 1280 is the smallest MTU allowed for IPv6, which is a sensible
// "probably works everywhere" setting until we develop proper PMTU
// discovery.
const minimalMTU = 1280
type userspaceEngine struct {
logf logger.Logf
reqCh chan struct{}
waitCh chan struct{} // chan is closed when first Close call completes; contrast with closing bool
tundev *tstun.TUN
wgdev *device.Device
router router.Router
magicConn *magicsock.Conn
linkMon *monitor.Mon
wgLock sync.Mutex // serializes all wgdev operations; see lock order comment below
lastReconfig string
lastCfg wgcfg.Config
mu sync.Mutex // guards following; see lock order comment below
closing bool // Close was called (even if we're still closing)
statusCallback StatusCallback
peerSequence []wgcfg.Key
endpoints []string
pingers map[wgcfg.Key]context.CancelFunc // mu must be held to call CancelFunc
linkState *interfaces.State
// Lock ordering: wgLock, then mu.
}
type Loggify struct {
f logger.Logf
}
func (l *Loggify) Write(b []byte) (int, error) {
l.f(string(b))
return len(b), nil
}
func NewFakeUserspaceEngine(logf logger.Logf, listenPort uint16) (Engine, error) {
logf("Starting userspace wireguard engine (FAKE tuntap device).")
tundev := tstun.WrapTUN(logf, tstun.NewFakeTUN())
return NewUserspaceEngineAdvanced(logf, tundev, router.NewFake, listenPort)
}
// NewUserspaceEngine creates the named tun device and returns a
// Tailscale Engine running on it.
func NewUserspaceEngine(logf logger.Logf, tunname string, listenPort uint16) (Engine, error) {
if tunname == "" {
return nil, fmt.Errorf("--tun name must not be blank")
}
logf("Starting userspace wireguard engine with tun device %q", tunname)
tun, err := tun.CreateTUN(tunname, minimalMTU)
if err != nil {
diagnoseTUNFailure(logf)
logf("CreateTUN: %v", err)
return nil, err
}
logf("CreateTUN ok.")
tundev := tstun.WrapTUN(logf, tun)
e, err := NewUserspaceEngineAdvanced(logf, tundev, router.New, listenPort)
if err != nil {
return nil, err
}
return e, err
}
// RouterGen is the signature for a function that creates a
// router.Router.
type RouterGen func(logf logger.Logf, wgdev *device.Device, tundev tun.Device) (router.Router, error)
// NewUserspaceEngineAdvanced is like NewUserspaceEngine but takes a pre-created TUN device and allows specifing
// a custom router constructor and listening port.
func NewUserspaceEngineAdvanced(logf logger.Logf, tundev *tstun.TUN, routerGen RouterGen, listenPort uint16) (Engine, error) {
return newUserspaceEngineAdvanced(logf, tundev, routerGen, listenPort)
}
func newUserspaceEngineAdvanced(logf logger.Logf, tundev *tstun.TUN, routerGen RouterGen, listenPort uint16) (_ Engine, reterr error) {
e := &userspaceEngine{
logf: logf,
reqCh: make(chan struct{}, 1),
waitCh: make(chan struct{}),
tundev: tundev,
pingers: make(map[wgcfg.Key]context.CancelFunc),
}
e.linkState, _ = getLinkState()
mon, err := monitor.New(logf, func() { e.LinkChange(false) })
if err != nil {
tundev.Close()
return nil, err
}
e.linkMon = mon
endpointsFn := func(endpoints []string) {
e.mu.Lock()
e.endpoints = append(e.endpoints[:0], endpoints...)
e.mu.Unlock()
e.RequestStatus()
}
magicsockOpts := magicsock.Options{
Logf: logf,
Port: listenPort,
EndpointsFunc: endpointsFn,
}
e.magicConn, err = magicsock.NewConn(magicsockOpts)
if err != nil {
tundev.Close()
return nil, fmt.Errorf("wgengine: %v", err)
}
// flags==0 because logf is already nested in another logger.
// The outer one can display the preferred log prefixes, etc.
dlog := log.New(&Loggify{logf}, "", 0)
logger := device.Logger{
Debug: dlog,
Info: dlog,
Error: dlog,
}
opts := &device.DeviceOptions{
Logger: &logger,
HandshakeDone: func(peerKey wgcfg.Key, allowedIPs []net.IPNet) {
// Send an unsolicited status event every time a
// handshake completes. This makes sure our UI can
// update quickly as soon as it connects to a peer.
//
// We use a goroutine here to avoid deadlocking
// wireguard, since RequestStatus() will call back
// into it, and wireguard is what called us to get
// here.
go e.RequestStatus()
// Ping every single-IP that peer routes.
// These synthetic packets are used to traverse NATs.
var ips []wgcfg.IP
for _, ipNet := range allowedIPs {
if ones, bits := ipNet.Mask.Size(); ones == bits && ones != 0 {
var ip wgcfg.IP
copy(ip.Addr[:], ipNet.IP.To16())
ips = append(ips, ip)
}
}
if len(ips) > 0 {
go e.pinger(peerKey, ips)
} else {
logf("[unexpected] peer %s has no single-IP routes: %v", peerKey.ShortString(), allowedIPs)
}
},
CreateBind: e.magicConn.CreateBind,
CreateEndpoint: e.magicConn.CreateEndpoint,
SkipBindUpdate: true,
}
// wgdev takes ownership of tundev, will close it when closed.
e.wgdev = device.NewDevice(e.tundev, opts)
defer func() {
if reterr != nil {
e.wgdev.Close()
}
}()
// Pass the underlying tun.(*NativeDevice) to the router:
// routers do not Read or Write, but do access native interfaces.
e.router, err = routerGen(logf, e.wgdev, e.tundev.Unwrap())
if err != nil {
e.magicConn.Close()
return nil, err
}
go func() {
up := false
for event := range e.tundev.Events() {
if event&tun.EventMTUUpdate != 0 {
mtu, err := e.tundev.MTU()
e.logf("external route MTU: %d (%v)", mtu, err)
}
if event&tun.EventUp != 0 && !up {
e.logf("external route: up")
e.RequestStatus()
up = true
}
if event&tun.EventDown != 0 && up {
e.logf("external route: down")
e.RequestStatus()
up = false
}
}
}()
e.wgdev.Up()
if err := e.router.Up(); err != nil {
e.magicConn.Close()
e.wgdev.Close()
return nil, err
}
// TODO(danderson): we should delete this. It's pointless to apply
// a no-op settings here.
if err := e.router.Set(nil); err != nil {
e.magicConn.Close()
e.wgdev.Close()
return nil, err
}
e.linkMon.Start()
e.magicConn.Start()
return e, nil
}
// pinger sends ping packets for a few seconds.
//
// These generated packets are used to ensure we trigger the spray logic in
// the magicsock package for NAT traversal.
func (e *userspaceEngine) pinger(peerKey wgcfg.Key, ips []wgcfg.IP) {
e.logf("generating initial ping traffic to %s (%v)", peerKey.ShortString(), ips)
var srcIP packet.IP
e.wgLock.Lock()
if len(e.lastCfg.Addresses) > 0 {
srcIP = packet.NewIP(e.lastCfg.Addresses[0].IP.IP())
}
e.wgLock.Unlock()
if srcIP == 0 {
e.logf("generating initial ping traffic: no source IP")
return
}
e.mu.Lock()
if cancel := e.pingers[peerKey]; cancel != nil {
cancel()
}
ctx, cancel := context.WithCancel(context.Background())
e.pingers[peerKey] = cancel
e.mu.Unlock()
// sendFreq is slightly longer than sprayFreq in magicsock to ensure
// that if these ping packets are the only source of early packets
// sent to the peer, that each one will be sprayed.
const sendFreq = 300 * time.Millisecond
const stopAfter = 3 * time.Second
start := time.Now()
var dstIPs []packet.IP
for _, ip := range ips {
dstIPs = append(dstIPs, packet.NewIP(ip.IP()))
}
payload := []byte("magicsock_spray") // no meaning
defer func() {
e.mu.Lock()
defer e.mu.Unlock()
select {
case <-ctx.Done():
return
default:
}
// If the pinger context is not done, then the
// CancelFunc is still in the pingers map.
delete(e.pingers, peerKey)
}()
ipid := uint16(1)
t := time.NewTicker(sendFreq)
defer t.Stop()
for {
select {
case <-ctx.Done():
return
case <-t.C:
}
if time.Since(start) > stopAfter {
return
}
for _, dstIP := range dstIPs {
b := packet.GenICMP(srcIP, dstIP, ipid, packet.ICMPEchoRequest, 0, payload)
e.tundev.InjectOutbound(b)
}
ipid++
}
}
func configSignature(cfg *wgcfg.Config, routerCfg *router.Config) (string, error) {
// TODO(apenwarr): get rid of uapi stuff for in-process comms
uapi, err := cfg.ToUAPI()
if err != nil {
return "", err
}
return fmt.Sprintf("%s %v", uapi, routerCfg), nil
}
func (e *userspaceEngine) Reconfig(cfg *wgcfg.Config, routerCfg *router.Config) error {
e.wgLock.Lock()
defer e.wgLock.Unlock()
peerSet := make(map[key.Public]struct{}, len(cfg.Peers))
e.mu.Lock()
e.peerSequence = e.peerSequence[:0]
for _, p := range cfg.Peers {
e.peerSequence = append(e.peerSequence, p.PublicKey)
peerSet[key.Public(p.PublicKey)] = struct{}{}
}
e.mu.Unlock()
rc, err := configSignature(cfg, routerCfg)
if err != nil {
return err
}
if rc == e.lastReconfig {
return ErrNoChanges
}
e.logf("wgengine: Reconfig: configuring userspace wireguard engine")
e.lastReconfig = rc
e.lastCfg = cfg.Copy()
// Tell magicsock about the new (or initial) private key
// (which is needed by DERP) before wgdev gets it, as wgdev
// will start trying to handshake, which we want to be able to
// go over DERP.
if err := e.magicConn.SetPrivateKey(cfg.PrivateKey); err != nil {
e.logf("wgengine: Reconfig: SetPrivateKey: %v", err)
}
if err := e.wgdev.Reconfig(cfg); err != nil {
e.logf("wgdev.Reconfig: %v", err)
return err
}
e.magicConn.UpdatePeers(peerSet)
if err := e.router.Set(routerCfg); err != nil {
return err
}
e.logf("wgengine: Reconfig done")
return nil
}
func (e *userspaceEngine) GetFilter() *filter.Filter {
return e.tundev.GetFilter()
}
func (e *userspaceEngine) SetFilter(filt *filter.Filter) {
e.tundev.SetFilter(filt)
}
func (e *userspaceEngine) SetStatusCallback(cb StatusCallback) {
e.mu.Lock()
defer e.mu.Unlock()
e.statusCallback = cb
}
func (e *userspaceEngine) getStatusCallback() StatusCallback {
e.mu.Lock()
defer e.mu.Unlock()
return e.statusCallback
}
// TODO: this function returns an error but it's always nil, and when
// there's actually a problem it just calls log.Fatal. Why?
func (e *userspaceEngine) getStatus() (*Status, error) {
e.wgLock.Lock()
defer e.wgLock.Unlock()
e.mu.Lock()
closing := e.closing
e.mu.Unlock()
if closing {
return nil, errors.New("engine closing; no status")
}
if e.wgdev == nil {
// RequestStatus was invoked before the wgengine has
// finished initializing. This can happen when wgegine
// provides a callback to magicsock for endpoint
// updates that calls RequestStatus.
return nil, nil
}
// lineLen is the max UAPI line we expect. The longest I see is
// len("preshared_key=")+64 hex+"\n" == 79. Add some slop.
const lineLen = 100
pr, pw := io.Pipe()
errc := make(chan error, 1)
go func() {
defer pw.Close()
bw := bufio.NewWriterSize(pw, lineLen)
// TODO(apenwarr): get rid of silly uapi stuff for in-process comms
// FIXME: get notified of status changes instead of polling.
if err := e.wgdev.IpcGetOperation(bw); err != nil {
errc <- fmt.Errorf("IpcGetOperation: %w", err)
return
}
errc <- bw.Flush()
}()
pp := make(map[wgcfg.Key]*PeerStatus)
p := &PeerStatus{}
var hst1, hst2, n int64
var err error
bs := bufio.NewScanner(pr)
bs.Buffer(make([]byte, lineLen), lineLen)
for bs.Scan() {
line := bs.Bytes()
k := line
var v mem.RO
if i := bytes.IndexByte(line, '='); i != -1 {
k = line[:i]
v = mem.B(line[i+1:])
}
switch string(k) {
case "public_key":
pk, err := key.NewPublicFromHexMem(v)
if err != nil {
log.Fatalf("IpcGetOperation: invalid key %#v", v)
}
p = &PeerStatus{}
pp[wgcfg.Key(pk)] = p
key := tailcfg.NodeKey(pk)
p.NodeKey = key
case "rx_bytes":
n, err = v.ParseInt(10, 64)
p.RxBytes = ByteCount(n)
if err != nil {
log.Fatalf("IpcGetOperation: rx_bytes invalid: %#v", line)
}
case "tx_bytes":
n, err = v.ParseInt(10, 64)
p.TxBytes = ByteCount(n)
if err != nil {
log.Fatalf("IpcGetOperation: tx_bytes invalid: %#v", line)
}
case "last_handshake_time_sec":
hst1, err = v.ParseInt(10, 64)
if err != nil {
log.Fatalf("IpcGetOperation: hst1 invalid: %#v", line)
}
case "last_handshake_time_nsec":
hst2, err = v.ParseInt(10, 64)
if err != nil {
log.Fatalf("IpcGetOperation: hst2 invalid: %#v", line)
}
if hst1 != 0 || hst2 != 0 {
p.LastHandshake = time.Unix(hst1, hst2)
} // else leave at time.IsZero()
}
}
if err := bs.Err(); err != nil {
log.Fatalf("reading IpcGetOperation output: %v", err)
}
if err := <-errc; err != nil {
log.Fatalf("IpcGetOperation: %v", err)
}
e.mu.Lock()
defer e.mu.Unlock()
var peers []PeerStatus
for _, pk := range e.peerSequence {
p := pp[pk]
if p == nil {
p = &PeerStatus{}
}
peers = append(peers, *p)
}
if len(pp) != len(e.peerSequence) {
e.logf("wg status returned %v peers, expected %v", len(pp), len(e.peerSequence))
}
return &Status{
LocalAddrs: append([]string(nil), e.endpoints...),
Peers: peers,
DERPs: e.magicConn.DERPs(),
}, nil
}
func (e *userspaceEngine) RequestStatus() {
// This is slightly tricky. e.getStatus() can theoretically get
// blocked inside wireguard for a while, and RequestStatus() is
// sometimes called from a goroutine, so we don't want a lot of
// them hanging around. On the other hand, requesting multiple
// status updates simultaneously is pointless anyway; they will
// all say the same thing.
// Enqueue at most one request. If one is in progress already, this
// adds one more to the queue. If one has been requested but not
// started, it is a no-op.
select {
case e.reqCh <- struct{}{}:
default:
}
// Dequeue at most one request. Another thread may have already
// dequeued the request we enqueued above, which is fine, since the
// information is guaranteed to be at least as recent as the current
// call to RequestStatus().
select {
case <-e.reqCh:
s, err := e.getStatus()
if s == nil && err == nil {
e.logf("RequestStatus: weird: both s and err are nil")
return
}
if cb := e.getStatusCallback(); cb != nil {
cb(s, err)
}
default:
}
}
func (e *userspaceEngine) Close() {
e.mu.Lock()
if e.closing {
e.mu.Unlock()
return
}
e.closing = true
for key, cancel := range e.pingers {
delete(e.pingers, key)
cancel()
}
e.mu.Unlock()
r := bufio.NewReader(strings.NewReader(""))
e.wgdev.IpcSetOperation(r)
e.wgdev.Close()
e.linkMon.Close()
e.router.Close()
e.magicConn.Close()
close(e.waitCh)
}
func (e *userspaceEngine) Wait() {
<-e.waitCh
}
func (e *userspaceEngine) setLinkState(st *interfaces.State) (changed bool) {
if st == nil {
return false
}
e.mu.Lock()
defer e.mu.Unlock()
changed = e.linkState == nil || !st.Equal(e.linkState)
e.linkState = st
return changed
}
func (e *userspaceEngine) LinkChange(isExpensive bool) {
cur, err := getLinkState()
if err != nil {
e.logf("LinkChange: interfaces.GetState: %v", err)
return
}
cur.IsExpensive = isExpensive
needRebind := e.setLinkState(cur)
e.logf("LinkChange(isExpensive=%v); needsRebind=%v", isExpensive, needRebind)
why := "link-change-minor"
if needRebind {
why = "link-change-major"
e.magicConn.Rebind()
}
e.magicConn.ReSTUN(why)
}
func getLinkState() (*interfaces.State, error) {
s, err := interfaces.GetState()
if s != nil {
s.RemoveTailscaleInterfaces()
}
return s, err
}
func (e *userspaceEngine) SetNetInfoCallback(cb NetInfoCallback) {
e.magicConn.SetNetInfoCallback(cb)
}
func (e *userspaceEngine) SetDERPMap(dm *tailcfg.DERPMap) {
e.magicConn.SetDERPMap(dm)
}
func (e *userspaceEngine) UpdateStatus(sb *ipnstate.StatusBuilder) {
st, err := e.getStatus()
if err != nil {
e.logf("wgengine: getStatus: %v", err)
return
}
for _, ps := range st.Peers {
sb.AddPeer(key.Public(ps.NodeKey), &ipnstate.PeerStatus{
RxBytes: int64(ps.RxBytes),
TxBytes: int64(ps.TxBytes),
LastHandshake: ps.LastHandshake,
InEngine: true,
})
}
e.magicConn.UpdateStatus(sb)
}
// diagnoseTUNFailure is called if tun.CreateTUN fails, to poke around
// the system and log some diagnostic info that might help debug why
// TUN failed. Because TUN's already failed and things the program's
// about to end, we might as well log a lot.
func diagnoseTUNFailure(logf logger.Logf) {
switch runtime.GOOS {
case "linux":
diagnoseLinuxTUNFailure(logf)
default:
logf("no TUN failure diagnostics for OS %q", runtime.GOOS)
}
}
func diagnoseLinuxTUNFailure(logf logger.Logf) {
kernel, err := exec.Command("uname", "-r").Output()
kernel = bytes.TrimSpace(kernel)
if err != nil {
logf("no TUN, and failed to look up kernel version: %v", err)
return
}
logf("Linux kernel version: %s", kernel)
modprobeOut, err := exec.Command("/sbin/modprobe", "tun").CombinedOutput()
if err == nil {
logf("'modprobe tun' successful")
// Either tun is currently loaded, or it's statically
// compiled into the kernel (which modprobe checks
// with /lib/modules/$(uname -r)/modules.builtin)
//
// So if there's a problem at this point, it's
// probably because /dev/net/tun doesn't exist.
const dev = "/dev/net/tun"
if fi, err := os.Stat(dev); err != nil {
logf("tun module loaded in kernel, but %s does not exist", dev)
} else {
logf("%s: %v", dev, fi.Mode())
}
// We failed to find why it failed. Just let our
// caller report the error it got from wireguard-go.
return
}
logf("is CONFIG_TUN enabled in your kernel? `modprobe tun` failed with: %s", modprobeOut)
distro := linuxDistro()
switch distro {
case "debian":
dpkgOut, err := exec.Command("dpkg", "-S", "kernel/drivers/net/tun.ko").CombinedOutput()
if len(bytes.TrimSpace(dpkgOut)) == 0 || err != nil {
logf("tun module not loaded nor found on disk")
return
}
if !bytes.Contains(dpkgOut, kernel) {
logf("kernel/drivers/net/tun.ko found on disk, but not for current kernel; are you in middle of a system update and haven't rebooted? found: %s", dpkgOut)
}
case "arch":
findOut, err := exec.Command("find", "/lib/modules/", "-path", "*/net/tun.ko*").CombinedOutput()
if len(bytes.TrimSpace(findOut)) == 0 || err != nil {
logf("tun module not loaded nor found on disk")
return
}
if !bytes.Contains(findOut, kernel) {
logf("kernel/drivers/net/tun.ko found on disk, but not for current kernel; are you in middle of a system update and haven't rebooted? found: %s", findOut)
}
}
}
func linuxDistro() string {
if _, err := os.Stat("/etc/debian_version"); err == nil {
return "debian"
}
if _, err := os.Stat("/etc/arch-release"); err == nil {
return "arch"
}
return ""
}