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wgengine/magicsock: support multiple derp servers, and not just for handshakes

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Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
pull/82/head
Brad Fitzpatrick 5 years ago committed by Brad Fitzpatrick
parent a9bff99a9b
commit d298d5b1f8
3 changed files with 365 additions and 95 deletions
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49
wgengine/magicsock/derpmap.go
Unescape Escape View File

@ -0,0 +1,49 @@
// Copyright 2019 Tailscale & 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 magicsock
import (
"fmt"
"net"
)
// derpFakeIPStr is a fake WireGuard endpoint IP address that means
// to use DERP. When used, the port number of the WireGuard endpoint
// is the DERP server number to use.
const derpMagicIPStr = "127.3.3.40" // 3340 are above the keys DERP on the keyboard
var derpMagicIP = net.IPv4(127, 3, 3, 40) // net.IP version of above
var (
derpHostOfIndex = map[int]string{} // index (fake port number) -> hostname
derpIndexOfHost = map[string]int{} // derpHostOfIndex reversed
)
func init() {
// Just one zone for now:
addDerper(1, "derp.tailscale.com")
}
func addDerper(i int, host string) {
if other, dup := derpHostOfIndex[i]; dup {
panic(fmt.Sprintf("duplicate DERP index %v (host %q and %q)", i, other, host))
}
if other, dup := derpIndexOfHost[host]; dup {
panic(fmt.Sprintf("duplicate DERP host %q (index %v and %v)", host, other, i))
}
derpHostOfIndex[i] = host
derpIndexOfHost[host] = i
}
// derpHost returns the hostname of a DERP server index (a fake port
// number used with derpMagicIP). It always returns a non-empty string.
func derpHost(i int) string {
if h, ok := derpHostOfIndex[i]; ok {
return h
}
if 1 <= i && i <= 64<<10 {
return fmt.Sprintf("derp%v.tailscale.com", i)
}
return "derp.tailscale.com"
}

405
wgengine/magicsock/magicsock.go
Unescape Escape View File

@ -9,6 +9,7 @@ package magicsock
import (
"context"
"encoding/binary"
"errors"
"fmt"
"log"
"net"
@ -31,11 +32,12 @@ import (
type Conn struct {
pconn *RebindingUDPConn
pconnPort uint16
privateKey key.Private
stunServers []string
derpServer string
startEpUpdate chan struct{} // send to trigger endpoint update
epFunc func(endpoints []string)
logf func(format string, args ...interface{})
donec chan struct{} // closed on Conn.Close
epUpdateCtx context.Context // endpoint updater context
epUpdateCancel func() // the func to cancel epUpdateCtx
@ -58,8 +60,12 @@ type Conn struct {
// Its Loaded value is always non-nil.
stunReceiveFunc atomic.Value // of func(p []byte, fromAddr *net.UDPAddr)
derpMu sync.Mutex
derp *derphttp.Client
udpRecvCh chan udpReadResult
derpRecvCh chan derpReadResult
derpMu sync.Mutex
derpConn map[int]*derphttp.Client // magic derp port (see derpmap.go) to its client
derpWriteCh map[int]chan<- derpWriteRequest
}
// udpAddr is the key in the indexedAddrs map.
@ -81,8 +87,6 @@ type indexedAddrSet struct {
// The current default (zero) means to auto-select a random free port.
const DefaultPort = 0
const DefaultDERP = "https://derp.tailscale.com/derp"
var DefaultSTUN = []string{
"stun.l.google.com:19302",
"stun3.l.google.com:19302",
@ -95,7 +99,6 @@ type Options struct {
Port uint16
STUN []string
DERP string
// EndpointsFunc optionally provides a func to be called when
// endpoints change. The called func does not own the slice.
@ -136,14 +139,16 @@ func Listen(opts Options) (*Conn, error) {
epUpdateCtx, epUpdateCancel := context.WithCancel(context.Background())
c := &Conn{
pconn: new(RebindingUDPConn),
donec: make(chan struct{}),
stunServers: append([]string{}, opts.STUN...),
derpServer: opts.DERP,
startEpUpdate: make(chan struct{}, 1),
epUpdateCtx: epUpdateCtx,
epUpdateCancel: epUpdateCancel,
epFunc: opts.endpointsFunc(),
logf: log.Printf,
indexedAddrs: make(map[udpAddr]indexedAddrSet),
derpRecvCh: make(chan derpReadResult),
udpRecvCh: make(chan udpReadResult),
}
c.ignoreSTUNPackets()
c.pconn.Reset(packetConn.(*net.UDPConn))
@ -355,55 +360,225 @@ func (c *Conn) LocalPort() uint16 {
return uint16(laddr.Port)
}
func (c *Conn) Send(b []byte, ep device.Endpoint) error {
a := ep.(*AddrSet)
func shouldSprayPacket(b []byte) bool {
if len(b) < 4 {
return false
}
msgType := binary.LittleEndian.Uint32(b[:4])
switch msgType {
case device.MessageInitiationType, device.MessageResponseType, device.MessageCookieReplyType:
// Part of the wireguard handshake.
// Send to every potential endpoint we have for a peer.
a.mu.Lock()
roamAddr := a.roamAddr
a.mu.Unlock()
var err error
var success bool
if roamAddr != nil {
_, err = c.pconn.WriteTo(b, roamAddr)
if err == nil {
success = true
}
case device.MessageInitiationType,
device.MessageResponseType,
device.MessageCookieReplyType: // TODO: necessary?
return true
}
return false
}
// appendDests appends to dsts the destinations that b should be
// written to in order to reach as. Some of the returned UDPAddrs may
// be fake addrs representing DERP servers.
//
// It also returns as's current roamAddr, if any.
func appendDests(dsts []*net.UDPAddr, as *AddrSet, b []byte) (_ []*net.UDPAddr, roamAddr *net.UDPAddr) {
spray := shouldSprayPacket(b)
as.mu.Lock()
defer as.mu.Unlock()
roamAddr = as.roamAddr
if roamAddr != nil {
dsts = append(dsts, roamAddr)
if !spray {
return dsts, roamAddr
}
for i := len(a.addrs) - 1; i >= 0; i-- {
addr := &a.addrs[i]
_, err = c.pconn.WriteTo(b, addr)
if err == nil {
success = true
}
}
for i := len(as.addrs) - 1; i >= 0; i-- {
addr := &as.addrs[i]
if spray || as.curAddr == -1 || as.curAddr == i {
dsts = append(dsts, addr)
}
if !spray && len(dsts) != 0 {
break
}
}
return dsts, roamAddr
}
var errNoDestinations = errors.New("magicsock: no destinations")
func (c *Conn) Send(b []byte, ep device.Endpoint) error {
as := ep.(*AddrSet)
var addrBuf [8]*net.UDPAddr
dsts, roamAddr := appendDests(addrBuf[:0], as, b)
if len(dsts) == 0 {
return errNoDestinations
}
var success bool
var ret error
for _, addr := range dsts {
err := c.sendAddr(addr, as.publicKey, b)
if err == nil {
success = true
} else if ret == nil {
ret = err
}
if err != nil && addr != roamAddr {
log.Printf("magicsock: Conn.Send(%v): %v", addr, err)
}
}
if success {
return nil
}
return ret
}
if msgType == device.MessageInitiationType {
// Send initial handshake messages via DERP.
c.derpMu.Lock()
derp := c.derp
c.derpMu.Unlock()
var errConnClosed = errors.New("Conn closed")
if derp != nil {
if err := derp.Send(a.publicKey, b); err != nil {
log.Printf("derp send failed: %v", err)
}
var errDropDerpPacket = errors.New("too many DERP packets queued; dropping")
// sendAddr sends packet b to addr, which is either a real UDP address
// or a fake UDP address representing a DERP server (see derpmap.go).
// The provided public key identifies the recipient.
func (c *Conn) sendAddr(addr *net.UDPAddr, pubKey key.Public, b []byte) error {
if ch := c.derpWriteChanOfAddr(addr); ch != nil {
errc := make(chan error, 1)
select {
case <-c.donec:
return errConnClosed
case ch <- derpWriteRequest{addr, pubKey, b, errc}:
select {
case <-c.donec:
return errConnClosed
case err := <-errc:
return err // usually nil
}
default:
// Too many writes queued. Drop packet.
return errDropDerpPacket
}
}
_, err := c.pconn.WriteTo(b, addr)
return err
}
if success {
// bufferedDerpWritesBeforeDrop is how many packets writes can be
// queued up the DERP client to write on the wire before we start
// dropping.
//
// TODO: this is currently arbitrary. Figure out something better?
const bufferedDerpWritesBeforeDrop = 4
// derpWriteChanOfAddr returns a DERP client for fake UDP addresses that
// represent DERP servers, creating them as necessary. For real UDP
// addresses, it returns nil.
func (c *Conn) derpWriteChanOfAddr(addr *net.UDPAddr) chan<- derpWriteRequest {
if !addr.IP.Equal(derpMagicIP) {
return nil
}
c.derpMu.Lock()
defer c.derpMu.Unlock()
ch, ok := c.derpWriteCh[addr.Port]
if !ok {
if c.derpWriteCh == nil {
c.derpWriteCh = make(map[int]chan<- derpWriteRequest)
c.derpConn = make(map[int]*derphttp.Client)
}
host := derpHost(addr.Port)
dc, err := derphttp.NewClient(c.privateKey, "https://"+host+"/derp", log.Printf)
if err != nil {
log.Printf("derphttp.NewClient: port %d, host %q invalid? err: %v", addr.Port, host, err)
return nil
}
bidiCh := make(chan derpWriteRequest, bufferedDerpWritesBeforeDrop)
ch = bidiCh
c.derpConn[addr.Port] = dc
c.derpWriteCh[addr.Port] = ch
go c.runDerpReader(addr, dc)
go c.runDerpWriter(addr, dc, bidiCh)
}
return ch
}
// Write to the highest-priority address we have seen so far.
_, err := c.pconn.WriteTo(b, a.dst())
return err
// derpReadResult is the type sent by runDerpClient to ReceiveIPv4
// when a DERP packet is available.
type derpReadResult struct {
derpAddr *net.UDPAddr
n int // length of data received
// copyBuf is called to copy the data to dst. It returns how
// much data was copied, which will be n if dst is large
// enough.
copyBuf func(dst []byte) int
}
// runDerpReader runs in a goroutine for the life of a DERP
// connection, handling received packets.
func (c *Conn) runDerpReader(derpFakeAddr *net.UDPAddr, dc *derphttp.Client) {
didCopy := make(chan struct{}, 1)
var buf [64 << 10]byte
var bufValid int // bytes in buf that are valid
copyFn := func(dst []byte) int {
n := copy(dst, buf[:bufValid])
didCopy <- struct{}{}
return n
}
for {
var err error // no := on next line to not shadow bufValid
bufValid, err = dc.Recv(buf[:])
if err != nil {
if err == derphttp.ErrClientClosed {
return
}
select {
case <-c.donec:
return
default:
}
log.Printf("derp.Recv: %v", err)
time.Sleep(250 * time.Millisecond)
continue
}
log.Printf("got derp %v packet: %q", derpFakeAddr, buf[:bufValid])
select {
case <-c.donec:
return
case c.derpRecvCh <- derpReadResult{derpFakeAddr, bufValid, copyFn}:
<-didCopy
}
}
}
type derpWriteRequest struct {
addr *net.UDPAddr
pubKey key.Public
b []byte
errc chan<- error
}
// runDerpWriter runs in a goroutine for the life of a DERP
// connection, handling received packets.
func (c *Conn) runDerpWriter(derpFakeAddr *net.UDPAddr, dc *derphttp.Client, ch <-chan derpWriteRequest) {
for {
select {
case <-c.donec:
return
case wr := <-ch:
err := dc.Send(wr.pubKey, wr.b)
if err != nil {
log.Printf("magicsock: derp.Send(%v): %v", wr.addr, err)
}
select {
case wr.errc <- err:
case <-c.donec:
return
}
}
}
}
func (c *Conn) findIndexedAddrSet(addr *net.UDPAddr) (addrSet *AddrSet, index int) {
@ -421,21 +596,75 @@ func (c *Conn) findIndexedAddrSet(addr *net.UDPAddr) (addrSet *AddrSet, index in
return indAddr.addr, indAddr.index
}
type udpReadResult struct {
n int
err error
addr *net.UDPAddr
}
// aLongTimeAgo is a non-zero time, far in the past, used for
// immediate cancellation of network operations.
var aLongTimeAgo = time.Unix(233431200, 0)
func (c *Conn) ReceiveIPv4(b []byte) (n int, ep device.Endpoint, addr *net.UDPAddr, err error) {
// Read a packet, and process any STUN packets before returning.
for {
var pAddr net.Addr
n, pAddr, err = c.pconn.ReadFrom(b)
if err != nil {
return n, nil, nil, err
go func() {
// Read a packet, and process any STUN packets before returning.
for {
var pAddr net.Addr
n, pAddr, err = c.pconn.ReadFrom(b)
if err != nil {
select {
case c.udpRecvCh <- udpReadResult{err: err}:
case <-c.donec:
}
return
}
if stun.Is(b[:n]) {
c.stunReceiveFunc.Load().(func([]byte, *net.UDPAddr))(b, addr)
continue
}
addr := pAddr.(*net.UDPAddr)
addr.IP = addr.IP.To4()
select {
case c.udpRecvCh <- udpReadResult{n: n, addr: addr}:
case <-c.donec:
}
return
}
addr = pAddr.(*net.UDPAddr)
addr.IP = addr.IP.To4()
}()
if !stun.Is(b[:n]) {
break
select {
case dm := <-c.derpRecvCh:
// Cancel the pconn read goroutine
c.pconn.SetReadDeadline(aLongTimeAgo)
select {
case <-c.udpRecvCh:
// It's likely an error, since we just canceled the read.
// But there's a small window where the pconn.ReadFrom could've
// succeeded but not yet sent, and we got into the derp recv path
// first. In that case this udpReadResult is a real non-err packet
// and we need to choose which to use. Currently, arbitrarily, we currently
// select DERP and discard this result entirely.
// The main point of this receive, though, is to make sure that the goroutine
// is done with our b []byte buf.
c.pconn.SetReadDeadline(time.Time{})
case <-c.donec:
return 0, nil, nil, errors.New("Conn closed")
}
c.stunReceiveFunc.Load().(func([]byte, *net.UDPAddr))(b, addr)
n, addr = dm.n, dm.derpAddr
ncopy := dm.copyBuf(b)
if ncopy != n {
err = fmt.Errorf("received DERP packet of length %d that's too big for WireGuard ReceiveIPv4 buf size %d", n, ncopy)
log.Printf("magicsock: %v", err)
return 0, nil, nil, err
}
case um := <-c.udpRecvCh:
if um.err != nil {
return 0, nil, nil, err
}
n, addr = um.n, um.addr
}
addrSet, _ := c.findIndexedAddrSet(addr)
@ -455,51 +684,23 @@ func (c *Conn) ReceiveIPv6(buff []byte) (int, device.Endpoint, *net.UDPAddr, err
}
func (c *Conn) SetPrivateKey(privateKey wgcfg.PrivateKey) error {
if c.derpServer == "" {
return nil
}
derp, err := derphttp.NewClient(key.Private(privateKey), c.derpServer, log.Printf)
if err != nil {
return err
}
go func() {
var b [64 << 10]byte
for {
n, err := derp.Recv(b[:])
if err != nil {
if err == derphttp.ErrClientClosed {
return
}
log.Printf("derp.Recv: %v", err)
time.Sleep(250 * time.Millisecond)
}
c.reSTUN()
addr := c.pconn.LocalAddr()
if _, err := c.pconn.WriteToUDP(b[:n], addr); err != nil {
log.Printf("%v", err)
}
}
}()
c.derpMu.Lock()
if c.derp != nil {
if err := c.derp.Close(); err != nil {
log.Printf("derp.Close: %v", err)
}
}
c.derp = derp
c.derpMu.Unlock()
c.privateKey = key.Private(privateKey)
return nil
}
func (c *Conn) SetMark(value uint32) error { return nil }
func (c *Conn) Close() error {
select {
case <-c.donec:
return nil
default:
}
close(c.donec)
c.epUpdateCancel()
for _, dc := range c.derpConn {
dc.Close()
}
return c.pconn.Close()
}
@ -543,8 +744,16 @@ type AddrSet struct {
publicKey key.Public // peer public key used for DERP communication
addrs []net.UDPAddr // ordered priority list provided by wgengine
mu sync.Mutex // guards roamAddr and curAddr
roamAddr *net.UDPAddr // peer addr determined from incoming packets
mu sync.Mutex // guards roamAddr and curAddr
// roamAddr is non-nil if/when we receive a correctly signed
// WireGuard packet from an unexpected address. If so, we
// remember it and send responses there in the future, but
// this should hopefully never be used (or at least used
// rarely) in the case that all the components of Tailscale
// are correctly learning/sharing the network map details.
roamAddr *net.UDPAddr
// curAddr is an index into addrs of the highest-priority
// address a valid packet has been received from so far.
// If no valid packet from addrs has been received, curAddr is -1.
@ -641,7 +850,7 @@ func (a *AddrSet) UpdateDst(new *net.UDPAddr) error {
a.roamAddr = new
case a.roamAddr != nil:
log.Printf("magicsock: rx %s from known %s (%d), replacs roaming address %s", pk, new, index, a.roamAddr)
log.Printf("magicsock: rx %s from known %s (%d), replaces roaming address %s", pk, new, index, a.roamAddr)
a.roamAddr = nil
a.curAddr = index
@ -814,6 +1023,12 @@ func (c *RebindingUDPConn) Close() error {
return c.pconn.Close()
}
func (c *RebindingUDPConn) SetReadDeadline(t time.Time) {
c.mu.Lock()
defer c.mu.Unlock()
c.pconn.SetReadDeadline(t)
}
func (c *RebindingUDPConn) WriteToUDP(b []byte, addr *net.UDPAddr) (int, error) {
for {
c.mu.Lock()

6
wgengine/magicsock/magicsock_test.go
Unescape Escape View File

@ -71,3 +71,9 @@ func pickPort(t *testing.T) uint16 {
defer conn.Close()
return uint16(conn.LocalAddr().(*net.UDPAddr).Port)
}
func TestDerpIPConstant(t *testing.T) {
if derpMagicIPStr != derpMagicIP.String() {
t.Errorf("str %q != IP %v", derpMagicIPStr, derpMagicIP)
}
}

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