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wgengine/magicsock: hook up discovery messages, upgrade to LAN works
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Ping messages now go out somewhat regularly, pong replies are sent,
and pong replies are now partially handled enough to upgrade off DERP
to LAN.

CallMeMaybe packets are sent & received over DERP, but aren't yet
handled. That's next (and regular maintenance timers), and then WAN
should work.

Updates #483
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@bradfitz
bradfitz committed Jul 1, 2020
1 parent 9b8ca21 commit 77d3ef3
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Showing 4 changed files with 135 additions and 29 deletions.
6 changes: 6 additions & 0 deletions disco/disco.go
View file
Expand Up @@ -28,6 +28,12 @@ import (
"inet.af/netaddr"
)

// Magic is the 6 byte header of all discovery messages.
const Magic = "TS💬" // 6 bytes: 0x54 53 f0 9f 92 ac

// NonceLen is the length of the nonces used by nacl secretboxes.
const NonceLen = 24

type MessageType byte

const (
Expand Down
2 changes: 1 addition & 1 deletion go.mod
View file
Expand Up @@ -29,6 +29,6 @@ require (
golang.org/x/sys v0.0.0-20200501052902-10377860bb8e
golang.org/x/time v0.0.0-20191024005414-555d28b269f0
honnef.co/go/tools v0.0.1-2020.1.4 // indirect
inet.af/netaddr v0.0.0-20200701171350-6509743f79d9
inet.af/netaddr v0.0.0-20200701194149-10bc159763c4
rsc.io/goversion v1.2.0
)
2 changes: 2 additions & 0 deletions go.sum
View file
Expand Up @@ -164,5 +164,7 @@ inet.af/netaddr v0.0.0-20200629220211-f44a6d25c536 h1:XFVw2MVOtmHBidx70M+I6vIw2F
inet.af/netaddr v0.0.0-20200629220211-f44a6d25c536/go.mod h1:qqYzz/2whtrbWJvt+DNWQyvekNN4ePQZcg2xc2/Yjww=
inet.af/netaddr v0.0.0-20200701171350-6509743f79d9 h1:F41nQsn8UGDPDXsOPwZQiaK8BmItPzyb0PYgjJSYIzw=
inet.af/netaddr v0.0.0-20200701171350-6509743f79d9/go.mod h1:qqYzz/2whtrbWJvt+DNWQyvekNN4ePQZcg2xc2/Yjww=
inet.af/netaddr v0.0.0-20200701194149-10bc159763c4 h1:dSXrLpRy86h4wfZWvzjyA2tuhMzX/lx0st4hzAh1VMA=
inet.af/netaddr v0.0.0-20200701194149-10bc159763c4/go.mod h1:qqYzz/2whtrbWJvt+DNWQyvekNN4ePQZcg2xc2/Yjww=
rsc.io/goversion v1.2.0 h1:SPn+NLTiAG7w30IRK/DKp1BjvpWabYgxlLp/+kx5J8w=
rsc.io/goversion v1.2.0/go.mod h1:Eih9y/uIBS3ulggl7KNJ09xGSLcuNaLgmvvqa07sgfo=
154 changes: 126 additions & 28 deletions wgengine/magicsock/magicsock.go
View file
Expand Up @@ -9,6 +9,7 @@ package magicsock
import (
"bufio"
"context"
crand "crypto/rand"
"encoding/binary"
"errors"
"fmt"
Expand Down Expand Up @@ -93,6 +94,7 @@ type Conn struct {
peerSet map[key.Public]struct{}

discoPrivate key.Private
discoPublic tailcfg.DiscoKey // public of discoPrivate
nodeOfDisco map[tailcfg.DiscoKey]*tailcfg.Node
discoOfNode map[tailcfg.NodeKey]tailcfg.DiscoKey

Expand Down Expand Up @@ -511,7 +513,8 @@ func (c *Conn) SetDiscoPrivateKey(k key.Private) {
panic("unsupported")
}
c.discoPrivate = k
c.logf("magicsock: disco key set; public: %x", k.Public())
c.discoPublic = tailcfg.DiscoKey(k.Public())
c.logf("magicsock: disco key set; public: %x", c.discoPublic)
}

// c.mu must NOT be held.
Expand Down Expand Up @@ -658,7 +661,9 @@ func shouldSprayPacket(b []byte) bool {
return false
}

var logPacketDests, _ = strconv.ParseBool(os.Getenv("DEBUG_LOG_PACKET_DESTS"))
var logPacketDests, _ = strconv.ParseBool(os.Getenv("TS_DEBUG_LOG_PACKET_DESTS"))

var logDisco, _ = strconv.ParseBool(os.Getenv("TS_DEBUG_DISCO"))

const sprayPeriod = 3 * time.Second

Expand Down Expand Up @@ -1367,6 +1372,25 @@ func (c *Conn) ReceiveIPv6(b []byte) (int, conn.Endpoint, *net.UDPAddr, error) {
}
}

func (c *Conn) sendDiscoMessage(dst netaddr.IPPort, dstKey key.Public, dstDisco tailcfg.DiscoKey, m disco.Message) error {
c.mu.Lock()
var nonce [disco.NonceLen]byte
if _, err := crand.Read(nonce[:]); err != nil {
panic(err) // worth dying for
}
pkt := make([]byte, 0, 512) // TODO: size it correctly? pool? if it matters.
pkt = append(pkt, disco.Magic...)
pkt = append(pkt, c.discoPublic[:]...)
pkt = append(pkt, nonce[:]...)
sharedKey := c.sharedDiscoKeyLocked(dstDisco)
c.mu.Unlock()

pkt = box.SealAfterPrecomputation(pkt, m.AppendMarshal(nil), &nonce, sharedKey)
err := c.sendAddr(dst, dstKey, pkt)
c.logf("magicsock: disco: sent %T to %v; err=%v", m, dst, err)
return err
}

// handleDiscoMessage reports whether msg was a Tailscale inter-node discovery message
// that was handled.
//
Expand All @@ -1380,34 +1404,41 @@ func (c *Conn) ReceiveIPv6(b []byte) (int, conn.Endpoint, *net.UDPAddr, error) {
// For messages received over DERP, the addr will be derpMagicIP (with
// port being the region)
func (c *Conn) handleDiscoMessage(msg []byte, src netaddr.IPPort) bool {
const magic = "TS💬"
const nonceLen = 24
const headerLen = len(magic) + len(tailcfg.DiscoKey{}) + nonceLen
if len(msg) < headerLen || string(msg[:len(magic)]) != magic {
const headerLen = len(disco.Magic) + len(tailcfg.DiscoKey{}) + disco.NonceLen
if len(msg) < headerLen || string(msg[:len(disco.Magic)]) != disco.Magic {
return false
}
var sender tailcfg.DiscoKey
copy(sender[:], msg[len(magic):])
copy(sender[:], msg[len(disco.Magic):])

c.mu.Lock()
defer c.mu.Unlock()

if logDisco {
c.logf("magicsock: disco: got disco-looking frame %v", sender)
}
if c.discoPrivate.IsZero() {
if logDisco {
c.logf("magicsock: disco: ignoring disco-looking frame, no local key")
}
return false
}

senderNode, ok := c.nodeOfDisco[sender]
if !ok {
// Returning false keeps passing it down, to WireGuard.
// WireGuard will almost surely reject it, but give it a chance.
if logDisco {
c.logf("magicsock: disco: ignoring disco-looking frame, don't know about %v", sender)
}
return false
}

// First, do we even know (and thus care) about this sender? If not,
// don't bother decrypting it.

var nonce [nonceLen]byte
copy(nonce[:], msg[len(magic)+len(key.Public{}):])
var nonce [disco.NonceLen]byte
copy(nonce[:], msg[len(disco.Magic)+len(key.Public{}):])
sealedBox := msg[headerLen:]
payload, ok := box.OpenAfterPrecomputation(nil, sealedBox, &nonce, c.sharedDiscoKeyLocked(sender))
if !ok {
Expand All @@ -1416,14 +1447,20 @@ func (c *Conn) handleDiscoMessage(msg []byte, src netaddr.IPPort) bool {
// and old packets might've still been in flight (or
// scheduled). This is particularly the case for LANs
// or non-NATed endpoints.
// Not worth logging. Pass on to wireguard, in case
// Don't log in normal case. Pass on to wireguard, in case
// it's actually a a wireguard packet (super unlikely,
// but).
if logDisco {
c.logf("magicsock: disco: failed to open naclbox from %v (wrong rcpt?)", sender)
}
// TODO(bradfitz): add some counter for this that logs rarely
return false
}

dm, err := disco.Parse(payload)
if logDisco {
c.logf("magicsock: disco: disco.Parse = %T, %v", dm, err)
}
if err != nil {
// Couldn't parse it, but it was inside a correctly
// signed box, so just ignore it, assuming it's from a
Expand Down Expand Up @@ -1452,17 +1489,20 @@ func (c *Conn) handleDiscoMessage(msg []byte, src netaddr.IPPort) bool {
}

func (c *Conn) handlePongLocked(m *disco.Pong, n *tailcfg.Node, dk tailcfg.DiscoKey, from netaddr.IPPort) {
de, ok := c.endpointOfDisco[dk]
if !ok {
return
}
c.logf("magicsock: disco: got pong from %s, tx=%x, disco=%x, src=%v (they saw %v)", n.Key.ShortString(), m.TxID, dk[:8], from, m.Src)
// TODO: implement
go de.handlePong(m)
}

func (c *Conn) handlePingLocked(m *disco.Ping, n *tailcfg.Node, dk tailcfg.DiscoKey, from netaddr.IPPort) {
c.logf("magicsock: disco: got ping tx %x from %s/%x at %v", m.TxID, n.Key.ShortString(), dk[:8], from)
reply := &disco.Pong{
go c.sendDiscoMessage(from, key.Public(n.Key), dk, &disco.Pong{
TxID: m.TxID,
Src: from,
}
go c.sendAddr(from, key.Public(n.Key), reply.AppendMarshal(nil))
})
}

// handleCallMeMaybeLocked is called when a discovery message arrives
Expand All @@ -1471,7 +1511,7 @@ func (c *Conn) handlePingLocked(m *disco.Ping, n *tailcfg.Node, dk tailcfg.Disco
// stateful firewall should be open. Now we can Ping back and make it
// through.
func (c *Conn) handleCallMeMaybeLocked(n *tailcfg.Node, dk tailcfg.DiscoKey) {
c.logf("magicsock: disco: got call-me-maybe packet from %s (disco=%x)", n.Key.ShortString, dk[:8])
c.logf("magicsock: disco: got call-me-maybe packet from %s (disco=%x)", n.Key.ShortString(), dk[:8])
// TODO: implement
}

Expand Down Expand Up @@ -2491,22 +2531,24 @@ type discoEndpoint struct {
lastSend time.Time
derpAddr netaddr.IPPort // fallback/bootstrap path, if non-zero (non-zero for well-behaved clients)

bestAddr netaddr.IPPort // best non-DERP path; zero if none
sentPing map[stun.TxID]sentPing
endpointState map[netaddr.IPPort]*endpointState
bestAddr netaddr.IPPort // best non-DERP path; zero if none
bestAddrLatency time.Duration
bestAddrAt time.Time // time best address re-confirmed
sentPing map[stun.TxID]sentPing
endpointState map[netaddr.IPPort]*endpointState

timers map[*time.Timer]bool
}

type endpointState struct {
// TODO: lastPing time.Time
lastPing time.Time
// TODO: lastPong time.Time
index int // index in nodecfg.Node.Endpoints
}

type sentPing struct {
// TODO: to netaddr.IPPort
// TODO: at time.Time
to netaddr.IPPort
at time.Time
}

// initFakeUDPAddr populates fakeWGAddr with a globally unique fake UDPAddr.
Expand Down Expand Up @@ -2554,15 +2596,12 @@ func (de *discoEndpoint) UpdateDst(addr *net.UDPAddr) error {
func (de *discoEndpoint) send(b []byte) error {
now := time.Now()

// TODO: all the disco messaging & state tracking & spraying,
// bringing over relevant AddrSet code. For now, just do DERP
// as a crutch while I work on other bits.
de.mu.Lock()
de.lastSend = now
derpAddr := de.derpAddr
bestAddr := de.bestAddr
if bestAddr.Port == 0 {
de.sendPingsLocked()
if bestAddr.IsZero() || de.bestAddrAt.Before(now.Add(-5*time.Second)) {
de.sendPingsLocked(now)
}
de.mu.Unlock()

Expand All @@ -2575,8 +2614,36 @@ func (de *discoEndpoint) send(b []byte) error {
return de.c.sendAddr(bestAddr, de.publicKey, b)
}

func (de *discoEndpoint) sendPingsLocked() {
// TODO
func (de *discoEndpoint) sendPingsLocked(now time.Time) {
sent := false
for ep, st := range de.endpointState {
if !st.lastPing.IsZero() && now.Sub(st.lastPing) < 5*time.Second {
continue
}
st.lastPing = now

txid := stun.NewTxID()
de.sentPing[txid] = sentPing{
to: ep,
at: now,
}
sent = true
go de.sendDiscoMessage(ep, &disco.Ping{TxID: [12]byte(txid)})
}
derpAddr := de.derpAddr
if sent && derpAddr.Port != 0 {
// In just a bit of a time (for goroutines above to schedule and run),
// send a message to peer via DERP informing them that we've sent
// so our firewall ports are probably open and now would be a good time
// for them to connect.
time.AfterFunc(5*time.Millisecond, func() {
de.sendDiscoMessage(derpAddr, disco.CallMeMaybe{})
})
}
}

func (de *discoEndpoint) sendDiscoMessage(dst netaddr.IPPort, dm disco.Message) error {
return de.c.sendDiscoMessage(dst, de.publicKey, de.discoKey, dm)
}

func (de *discoEndpoint) updateFromNode(n *tailcfg.Node) {
Expand Down Expand Up @@ -2629,6 +2696,37 @@ func (de *discoEndpoint) noteConnectivityChange() {
// TODO: reset state
}

func (de *discoEndpoint) handlePong(m *disco.Pong) {
de.mu.Lock()
defer de.mu.Unlock()

sp, ok := de.sentPing[m.TxID]
if !ok {
// This is not a pong for a ping we sent. Ignore.
return
}
delete(de.sentPing, m.TxID)

now := time.Now()
delay := now.Sub(sp.at)
de.c.logf("magicsock: disco: got pong reply after %v", delay)

// Expire our best address if we haven't heard from it in awhile.
tooOld := now.Add(-15 * time.Second)
if !de.bestAddr.IsZero() && de.bestAddrAt.Before(tooOld) {
de.bestAddr = netaddr.IPPort{}
}

// Promote this pong response to our current best address if it's lower latency.
// TODO(bradfitz): decide how latency vs. preference order affects decision
if de.bestAddr.IsZero() || delay < de.bestAddrLatency {
de.bestAddr = sp.to
de.bestAddrLatency = delay
de.bestAddrAt = now
de.c.logf("magicsock: disco: promoted %v to best address for %v", sp.to, de.publicKey.ShortString())
}
}

// cleanup is called when a discovery endpoint is no longer present in the NetworkMap.
// This is where we can do cleanup such as closing goroutines or canceling timers.
func (de *discoEndpoint) cleanup() {
Expand Down

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