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tailscale/wgengine/magicsock/endpoint.go

1397 lines
42 KiB
Go

// Copyright (c) Tailscale Inc & AUTHORS
// SPDX-License-Identifier: BSD-3-Clause
package magicsock
import (
"bufio"
"context"
"encoding/binary"
"errors"
"fmt"
"math"
"math/rand"
"net"
"net/netip"
"reflect"
"runtime"
"sync"
"sync/atomic"
"time"
"golang.org/x/crypto/poly1305"
xmaps "golang.org/x/exp/maps"
"golang.org/x/net/ipv4"
"golang.org/x/net/ipv6"
"tailscale.com/disco"
"tailscale.com/ipn/ipnstate"
"tailscale.com/net/stun"
"tailscale.com/net/tstun"
"tailscale.com/tailcfg"
"tailscale.com/tstime/mono"
"tailscale.com/types/key"
"tailscale.com/types/logger"
"tailscale.com/util/mak"
"tailscale.com/util/ringbuffer"
)
var mtuProbePingSizesV4 []int
var mtuProbePingSizesV6 []int
func init() {
for _, m := range tstun.WireMTUsToProbe {
mtuProbePingSizesV4 = append(mtuProbePingSizesV4, pktLenToPingSize(m, false))
mtuProbePingSizesV6 = append(mtuProbePingSizesV6, pktLenToPingSize(m, true))
}
}
// endpoint is a wireguard/conn.Endpoint. In wireguard-go and kernel WireGuard
// there is only one endpoint for a peer, but in Tailscale we distribute a
// number of possible endpoints for a peer which would include the all the
// likely addresses at which a peer may be reachable. This endpoint type holds
// the information required that when wireguard-go wants to send to a
// particular peer (essentially represented by this endpoint type), the send
// function can use the currently best known Tailscale endpoint to send packets
// to the peer.
type endpoint struct {
// atomically accessed; declared first for alignment reasons
lastRecv mono.Time
numStopAndResetAtomic int64
debugUpdates *ringbuffer.RingBuffer[EndpointChange]
// These fields are initialized once and never modified.
c *Conn
nodeID tailcfg.NodeID
publicKey key.NodePublic // peer public key (for WireGuard + DERP)
publicKeyHex string // cached output of publicKey.UntypedHexString
fakeWGAddr netip.AddrPort // the UDP address we tell wireguard-go we're using
nodeAddr netip.Addr // the node's first tailscale address; used for logging & wireguard rate-limiting (Issue 6686)
disco atomic.Pointer[endpointDisco] // if the peer supports disco, the key and short string
// mu protects all following fields.
mu sync.Mutex // Lock ordering: Conn.mu, then endpoint.mu
heartBeatTimer *time.Timer // nil when idle
lastSend mono.Time // last time there was outgoing packets sent to this peer (from wireguard-go)
lastFullPing mono.Time // last time we pinged all disco or wireguard only endpoints
derpAddr netip.AddrPort // fallback/bootstrap path, if non-zero (non-zero for well-behaved clients)
bestAddr addrQuality // best non-DERP path; zero if none
bestAddrAt mono.Time // time best address re-confirmed
trustBestAddrUntil mono.Time // time when bestAddr expires
sentPing map[stun.TxID]sentPing
endpointState map[netip.AddrPort]*endpointState
isCallMeMaybeEP map[netip.AddrPort]bool
// The following fields are related to the new "silent disco"
// implementation that's a WIP as of 2022-10-20.
// See #540 for background.
heartbeatDisabled bool
expired bool // whether the node has expired
isWireguardOnly bool // whether the endpoint is WireGuard only
}
// endpointDisco is the current disco key and short string for an endpoint. This
// structure is immutable.
type endpointDisco struct {
key key.DiscoPublic // for discovery messages.
short string // ShortString of discoKey.
}
type sentPing struct {
to netip.AddrPort
at mono.Time
timer *time.Timer // timeout timer
purpose discoPingPurpose
size int // size of the disco message
resCB *pingResultAndCallback // or nil for internal use
}
// endpointState is some state and history for a specific endpoint of
// a endpoint. (The subject is the endpoint.endpointState
// map key)
type endpointState struct {
// all fields guarded by endpoint.mu
// lastPing is the last (outgoing) ping time.
lastPing mono.Time
// lastGotPing, if non-zero, means that this was an endpoint
// that we learned about at runtime (from an incoming ping)
// and that is not in the network map. If so, we keep the time
// updated and use it to discard old candidates.
lastGotPing time.Time
// lastGotPingTxID contains the TxID for the last incoming ping. This is
// used to de-dup incoming pings that we may see on both the raw disco
// socket on Linux, and UDP socket. We cannot rely solely on the raw socket
// disco handling due to https://github.com/tailscale/tailscale/issues/7078.
lastGotPingTxID stun.TxID
// callMeMaybeTime, if non-zero, is the time this endpoint
// was advertised last via a call-me-maybe disco message.
callMeMaybeTime time.Time
recentPongs []pongReply // ring buffer up to pongHistoryCount entries
recentPong uint16 // index into recentPongs of most recent; older before, wrapped
index int16 // index in nodecfg.Node.Endpoints; meaningless if lastGotPing non-zero
}
// clear removes all derived / probed state from an endpointState.
func (s *endpointState) clear() {
*s = endpointState{
index: s.index,
lastGotPing: s.lastGotPing,
}
}
// pongHistoryCount is how many pongReply values we keep per endpointState
const pongHistoryCount = 64
type pongReply struct {
latency time.Duration
pongAt mono.Time // when we received the pong
from netip.AddrPort // the pong's src (usually same as endpoint map key)
pongSrc netip.AddrPort // what they reported they heard
}
// EndpointChange is a structure containing information about changes made to a
// particular endpoint. This is not a stable interface and could change at any
// time.
type EndpointChange struct {
When time.Time // when the change occurred
What string // what this change is
From any `json:",omitempty"` // information about the previous state
To any `json:",omitempty"` // information about the new state
}
// shouldDeleteLocked reports whether we should delete this endpoint.
func (st *endpointState) shouldDeleteLocked() bool {
switch {
case !st.callMeMaybeTime.IsZero():
return false
case st.lastGotPing.IsZero():
// This was an endpoint from the network map. Is it still in the network map?
return st.index == indexSentinelDeleted
default:
// This was an endpoint discovered at runtime.
return time.Since(st.lastGotPing) > sessionActiveTimeout
}
}
// latencyLocked returns the most recent latency measurement, if any.
// endpoint.mu must be held.
func (st *endpointState) latencyLocked() (lat time.Duration, ok bool) {
if len(st.recentPongs) == 0 {
return 0, false
}
return st.recentPongs[st.recentPong].latency, true
}
// endpoint.mu must be held.
func (st *endpointState) addPongReplyLocked(r pongReply) {
if n := len(st.recentPongs); n < pongHistoryCount {
st.recentPong = uint16(n)
st.recentPongs = append(st.recentPongs, r)
return
}
i := st.recentPong + 1
if i == pongHistoryCount {
i = 0
}
st.recentPongs[i] = r
st.recentPong = i
}
func (de *endpoint) deleteEndpointLocked(why string, ep netip.AddrPort) {
de.debugUpdates.Add(EndpointChange{
When: time.Now(),
What: "deleteEndpointLocked-" + why,
From: ep,
})
delete(de.endpointState, ep)
if de.bestAddr.AddrPort == ep {
de.debugUpdates.Add(EndpointChange{
When: time.Now(),
What: "deleteEndpointLocked-bestAddr-" + why,
From: de.bestAddr,
})
de.bestAddr = addrQuality{}
}
}
// initFakeUDPAddr populates fakeWGAddr with a globally unique fake UDPAddr.
// The current implementation just uses the pointer value of de jammed into an IPv6
// address, but it could also be, say, a counter.
func (de *endpoint) initFakeUDPAddr() {
var addr [16]byte
addr[0] = 0xfd
addr[1] = 0x00
binary.BigEndian.PutUint64(addr[2:], uint64(reflect.ValueOf(de).Pointer()))
de.fakeWGAddr = netip.AddrPortFrom(netip.AddrFrom16(addr).Unmap(), 12345)
}
// noteRecvActivity records receive activity on de, and invokes
// Conn.noteRecvActivity no more than once every 10s.
func (de *endpoint) noteRecvActivity(ipp netip.AddrPort) {
now := mono.Now()
if de.isWireguardOnly {
de.mu.Lock()
de.bestAddr.AddrPort = ipp
de.bestAddrAt = now
de.trustBestAddrUntil = now.Add(5 * time.Second)
de.mu.Unlock()
} else {
// TODO(jwhited): subject to change as part of silent disco effort.
// Necessary when heartbeat is disabled for the endpoint, otherwise we
// kick off discovery disco pings every trustUDPAddrDuration and mirror
// to DERP.
de.mu.Lock()
if de.heartbeatDisabled && de.bestAddr.AddrPort == ipp {
de.trustBestAddrUntil = now.Add(trustUDPAddrDuration)
}
de.mu.Unlock()
}
elapsed := now.Sub(de.lastRecv.LoadAtomic())
if elapsed > 10*time.Second {
de.lastRecv.StoreAtomic(now)
if de.c.noteRecvActivity == nil {
return
}
de.c.noteRecvActivity(de.publicKey)
}
}
func (de *endpoint) discoShort() string {
var short string
if d := de.disco.Load(); d != nil {
short = d.short
}
return short
}
// String exists purely so wireguard-go internals can log.Printf("%v")
// its internal conn.Endpoints and we don't end up with data races
// from fmt (via log) reading mutex fields and such.
func (de *endpoint) String() string {
return fmt.Sprintf("magicsock.endpoint{%v, %v}", de.publicKey.ShortString(), de.discoShort())
}
func (de *endpoint) ClearSrc() {}
func (de *endpoint) SrcToString() string { panic("unused") } // unused by wireguard-go
func (de *endpoint) SrcIP() netip.Addr { panic("unused") } // unused by wireguard-go
func (de *endpoint) DstToString() string { return de.publicKeyHex }
func (de *endpoint) DstIP() netip.Addr { return de.nodeAddr } // see tailscale/tailscale#6686
func (de *endpoint) DstToBytes() []byte { return packIPPort(de.fakeWGAddr) }
// addrForSendLocked returns the address(es) that should be used for
// sending the next packet. Zero, one, or both of UDP address and DERP
// addr may be non-zero. If the endpoint is WireGuard only and does not have
// latency information, a bool is returned to indicate that the
// WireGuard latency discovery pings should be sent.
//
// de.mu must be held.
//
// TODO(val): Rewrite the addrFor*Locked() variations to share code.
func (de *endpoint) addrForSendLocked(now mono.Time) (udpAddr, derpAddr netip.AddrPort, sendWGPing bool) {
udpAddr = de.bestAddr.AddrPort
if udpAddr.IsValid() && !now.After(de.trustBestAddrUntil) {
return udpAddr, netip.AddrPort{}, false
}
if de.isWireguardOnly {
// If the endpoint is wireguard-only, we don't have a DERP
// address to send to, so we have to send to the UDP address.
udpAddr, shouldPing := de.addrForWireGuardSendLocked(now)
return udpAddr, netip.AddrPort{}, shouldPing
}
// We had a bestAddr but it expired so send both to it
// and DERP.
return udpAddr, de.derpAddr, false
}
// addrForWireGuardSendLocked returns the address that should be used for
// sending the next packet. If a packet has never or not recently been sent to
// the endpoint, then a randomly selected address for the endpoint is returned,
// as well as a bool indiciating that WireGuard discovery pings should be started.
// If the addresses have latency information available, then the address with the
// best latency is used.
//
// de.mu must be held.
func (de *endpoint) addrForWireGuardSendLocked(now mono.Time) (udpAddr netip.AddrPort, shouldPing bool) {
if len(de.endpointState) == 0 {
de.c.logf("magicsock: addrForSendWireguardLocked: [unexpected] no candidates available for endpoint")
return udpAddr, false
}
// lowestLatency is a high duration initially, so we
// can be sure we're going to have a duration lower than this
// for the first latency retrieved.
lowestLatency := time.Hour
var oldestPing mono.Time
for ipp, state := range de.endpointState {
if oldestPing.IsZero() {
oldestPing = state.lastPing
} else if state.lastPing.Before(oldestPing) {
oldestPing = state.lastPing
}
if latency, ok := state.latencyLocked(); ok {
if latency < lowestLatency || latency == lowestLatency && ipp.Addr().Is6() {
// If we have the same latency,IPv6 is prioritized.
// TODO(catzkorn): Consider a small increase in latency to use
// IPv6 in comparison to IPv4, when possible.
lowestLatency = latency
udpAddr = ipp
}
}
}
needPing := len(de.endpointState) > 1 && now.Sub(oldestPing) > wireguardPingInterval
if !udpAddr.IsValid() {
candidates := xmaps.Keys(de.endpointState)
// Randomly select an address to use until we retrieve latency information
// and give it a short trustBestAddrUntil time so we avoid flapping between
// addresses while waiting on latency information to be populated.
udpAddr = candidates[rand.Intn(len(candidates))]
}
de.bestAddr.AddrPort = udpAddr
// Only extend trustBestAddrUntil by one second to avoid packet
// reordering and/or CPU usage from random selection during the first
// second. We should receive a response due to a WireGuard handshake in
// less than one second in good cases, in which case this will be then
// extended to 15 seconds.
de.trustBestAddrUntil = now.Add(time.Second)
return udpAddr, needPing
}
// addrForPingSizeLocked returns the address(es) that should be used for sending
// the next ping. It will only return addrs with a large enough path MTU to
// permit a ping payload of size bytes to be delivered (DERP is always one such
// addr as it is a TCP connection). If it returns a zero-value udpAddr, then we
// should continue probing the MTU of all paths to this endpoint. Zero, one, or
// both of the returned UDP address and DERP address may be non-zero.
//
// de.mu must be held.
func (de *endpoint) addrForPingSizeLocked(now mono.Time, size int) (udpAddr, derpAddr netip.AddrPort) {
if size == 0 {
udpAddr, derpAddr, _ = de.addrForSendLocked(now)
return
}
udpAddr = de.bestAddr.AddrPort
pathMTU := de.bestAddr.wireMTU
requestedMTU := pingSizeToPktLen(size, udpAddr.Addr().Is6())
mtuOk := requestedMTU <= pathMTU
if udpAddr.IsValid() && mtuOk {
if !now.After(de.trustBestAddrUntil) {
return udpAddr, netip.AddrPort{}
}
// We had a bestAddr with large enough MTU but it expired, so
// send both to it and DERP.
return udpAddr, de.derpAddr
}
// The UDP address isn't valid or it doesn't have a path MTU big enough
// for the packet. Return a zero-value udpAddr to signal that we should
// keep probing the path MTU to all addresses for this endpoint, and a
// valid DERP addr to signal that we should also send via DERP.
return netip.AddrPort{}, de.derpAddr
}
// heartbeat is called every heartbeatInterval to keep the best UDP path alive,
// or kick off discovery of other paths.
func (de *endpoint) heartbeat() {
de.mu.Lock()
defer de.mu.Unlock()
de.heartBeatTimer = nil
if de.heartbeatDisabled {
// If control override to disable heartBeatTimer set, return early.
return
}
if de.lastSend.IsZero() {
// Shouldn't happen.
return
}
if mono.Since(de.lastSend) > sessionActiveTimeout {
// Session's idle. Stop heartbeating.
de.c.dlogf("[v1] magicsock: disco: ending heartbeats for idle session to %v (%v)", de.publicKey.ShortString(), de.discoShort())
return
}
now := mono.Now()
udpAddr, _, _ := de.addrForSendLocked(now)
if udpAddr.IsValid() {
// We have a preferred path. Ping that every 2 seconds.
de.startDiscoPingLocked(udpAddr, now, pingHeartbeat, 0, nil)
}
if de.wantFullPingLocked(now) {
de.sendDiscoPingsLocked(now, true)
}
de.heartBeatTimer = time.AfterFunc(heartbeatInterval, de.heartbeat)
}
// setHeartbeatDisabled sets heartbeatDisabled to the provided value.
func (de *endpoint) setHeartbeatDisabled(v bool) {
de.mu.Lock()
defer de.mu.Unlock()
de.heartbeatDisabled = v
}
// wantFullPingLocked reports whether we should ping to all our peers looking for
// a better path.
//
// de.mu must be held.
func (de *endpoint) wantFullPingLocked(now mono.Time) bool {
if runtime.GOOS == "js" {
return false
}
if !de.bestAddr.IsValid() || de.lastFullPing.IsZero() {
return true
}
if now.After(de.trustBestAddrUntil) {
return true
}
if de.bestAddr.latency <= goodEnoughLatency {
return false
}
if now.Sub(de.lastFullPing) >= upgradeInterval {
return true
}
return false
}
func (de *endpoint) noteActiveLocked() {
de.lastSend = mono.Now()
if de.heartBeatTimer == nil && !de.heartbeatDisabled {
de.heartBeatTimer = time.AfterFunc(heartbeatInterval, de.heartbeat)
}
}
// MaxDiscoPingSize is the largest useful ping message size that we
// can send - the maximum packet size minus the IPv4 and UDP headers.
var MaxDiscoPingSize = tstun.MaxPacketSize - 20 - 8
type pingResultAndCallback struct {
taken atomic.Bool // first CompareAndSwamp from false to true takes ownership of res
res *ipnstate.PingResult
cb func(*ipnstate.PingResult)
}
func (p *pingResultAndCallback) reply() bool {
return p != nil && p.taken.CompareAndSwap(false, true)
}
// discoPing starts a disco-level ping for the "tailscale ping" command (or other
// callers, such as c2n). res is value to call cb with, already partially
// filled. cb must be called at most once. Once called, ownership of res passes to cb.
func (de *endpoint) discoPing(res *ipnstate.PingResult, size int, cb func(*ipnstate.PingResult)) {
de.mu.Lock()
defer de.mu.Unlock()
if de.expired {
res.Err = errExpired.Error()
cb(res)
return
}
if size > MaxDiscoPingSize {
res.Err = errPingTooBig.Error()
cb(res)
return
}
resCB := &pingResultAndCallback{res: res, cb: cb}
now := mono.Now()
udpAddr, derpAddr := de.addrForPingSizeLocked(now, size)
if derpAddr.IsValid() {
de.startDiscoPingLocked(derpAddr, now, pingCLI, size, resCB)
}
if udpAddr.IsValid() && now.Before(de.trustBestAddrUntil) {
// Already have an active session, so just ping the address we're using.
// Otherwise "tailscale ping" results to a node on the local network
// can look like they're bouncing between, say 10.0.0.0/9 and the peer's
// IPv6 address, both 1ms away, and it's random who replies first.
de.startDiscoPingLocked(udpAddr, now, pingCLI, size, resCB)
} else {
for ep := range de.endpointState {
de.startDiscoPingLocked(ep, now, pingCLI, size, resCB)
}
}
de.noteActiveLocked()
}
var (
errExpired = errors.New("peer's node key has expired")
errNoUDPOrDERP = errors.New("no UDP or DERP addr")
errPingTooBig = errors.New("ping size too big")
)
func (de *endpoint) send(buffs [][]byte) error {
de.mu.Lock()
if de.expired {
de.mu.Unlock()
return errExpired
}
now := mono.Now()
udpAddr, derpAddr, startWGPing := de.addrForSendLocked(now)
if de.isWireguardOnly {
if startWGPing {
de.sendWireGuardOnlyPingsLocked(now)
}
} else if !udpAddr.IsValid() || now.After(de.trustBestAddrUntil) {
de.sendDiscoPingsLocked(now, true)
}
de.noteActiveLocked()
de.mu.Unlock()
if !udpAddr.IsValid() && !derpAddr.IsValid() {
return errNoUDPOrDERP
}
var err error
if udpAddr.IsValid() {
_, err = de.c.sendUDPBatch(udpAddr, buffs)
// If the error is known to indicate that the endpoint is no longer
// usable, clear the endpoint statistics so that the next send will
// re-evaluate the best endpoint.
if err != nil && isBadEndpointErr(err) {
de.noteBadEndpoint(udpAddr)
}
// TODO(raggi): needs updating for accuracy, as in error conditions we may have partial sends.
if stats := de.c.stats.Load(); err == nil && stats != nil {
var txBytes int
for _, b := range buffs {
txBytes += len(b)
}
stats.UpdateTxPhysical(de.nodeAddr, udpAddr, txBytes)
}
}
if derpAddr.IsValid() {
allOk := true
for _, buff := range buffs {
ok, _ := de.c.sendAddr(derpAddr, de.publicKey, buff)
if stats := de.c.stats.Load(); stats != nil {
stats.UpdateTxPhysical(de.nodeAddr, derpAddr, len(buff))
}
if !ok {
allOk = false
}
}
if allOk {
return nil
}
}
return err
}
func (de *endpoint) discoPingTimeout(txid stun.TxID) {
de.mu.Lock()
defer de.mu.Unlock()
sp, ok := de.sentPing[txid]
if !ok {
return
}
if debugDisco() || !de.bestAddr.IsValid() || mono.Now().After(de.trustBestAddrUntil) {
de.c.dlogf("[v1] magicsock: disco: timeout waiting for pong %x from %v (%v, %v)", txid[:6], sp.to, de.publicKey.ShortString(), de.discoShort())
}
de.removeSentDiscoPingLocked(txid, sp)
}
// forgetDiscoPing is called by a timer when a ping either fails to send or
// has taken too long to get a pong reply.
func (de *endpoint) forgetDiscoPing(txid stun.TxID) {
de.mu.Lock()
defer de.mu.Unlock()
if sp, ok := de.sentPing[txid]; ok {
de.removeSentDiscoPingLocked(txid, sp)
}
}
func (de *endpoint) removeSentDiscoPingLocked(txid stun.TxID, sp sentPing) {
// Stop the timer for the case where sendPing failed to write to UDP.
// In the case of a timer already having fired, this is a no-op:
sp.timer.Stop()
delete(de.sentPing, txid)
}
// discoPingSize is the size of a complete disco ping packet, without any padding.
const discoPingSize = len(disco.Magic) + key.DiscoPublicRawLen + disco.NonceLen +
poly1305.TagSize + disco.MessageHeaderLen + disco.PingLen
// sendDiscoPing sends a ping with the provided txid to ep using de's discoKey. size
// is the desired disco message size, including all disco headers but excluding IP/UDP
// headers.
//
// The caller (startDiscoPingLocked) should've already recorded the ping in
// sentPing and set up the timer.
//
// The caller should use de.discoKey as the discoKey argument.
// It is passed in so that sendDiscoPing doesn't need to lock de.mu.
func (de *endpoint) sendDiscoPing(ep netip.AddrPort, discoKey key.DiscoPublic, txid stun.TxID, size int, logLevel discoLogLevel) {
size = min(size, MaxDiscoPingSize)
padding := max(size-discoPingSize, 0)
sent, _ := de.c.sendDiscoMessage(ep, de.publicKey, discoKey, &disco.Ping{
TxID: [12]byte(txid),
NodeKey: de.c.publicKeyAtomic.Load(),
Padding: padding,
}, logLevel)
if !sent {
de.forgetDiscoPing(txid)
return
}
if size != 0 {
metricSentDiscoPeerMTUProbes.Add(1)
metricSentDiscoPeerMTUProbeBytes.Add(int64(pingSizeToPktLen(size, ep.Addr().Is6())))
}
}
// discoPingPurpose is the reason why a discovery ping message was sent.
type discoPingPurpose int
//go:generate go run tailscale.com/cmd/addlicense -file discopingpurpose_string.go go run golang.org/x/tools/cmd/stringer -type=discoPingPurpose -trimprefix=ping
const (
// pingDiscovery means that purpose of a ping was to see if a
// path was valid.
pingDiscovery discoPingPurpose = iota
// pingHeartbeat means that purpose of a ping was whether a
// peer was still there.
pingHeartbeat
// pingCLI means that the user is running "tailscale ping"
// from the CLI. These types of pings can go over DERP.
pingCLI
)
// startDiscoPingLocked sends a disco ping to ep in a separate goroutine. resCB,
// if non-nil, means that a caller external to the magicsock package internals
// is interested in the result (such as a CLI "tailscale ping" or a c2n ping
// request, etc)
func (de *endpoint) startDiscoPingLocked(ep netip.AddrPort, now mono.Time, purpose discoPingPurpose, size int, resCB *pingResultAndCallback) {
if runtime.GOOS == "js" {
return
}
epDisco := de.disco.Load()
if epDisco == nil {
return
}
if purpose != pingCLI {
st, ok := de.endpointState[ep]
if !ok {
// Shouldn't happen. But don't ping an endpoint that's
// not active for us.
de.c.logf("magicsock: disco: [unexpected] attempt to ping no longer live endpoint %v", ep)
return
}
st.lastPing = now
}
// If we are doing a discovery ping or a CLI ping with no specified size
// to a non DERP address, then probe the MTU. Otherwise just send the
// one specified ping.
// Default to sending a single ping of the specified size
sizes := []int{size}
if de.c.PeerMTUEnabled() {
isDerp := ep.Addr() == tailcfg.DerpMagicIPAddr
if !isDerp && ((purpose == pingDiscovery) || (purpose == pingCLI && size == 0)) {
de.c.dlogf("[v1] magicsock: starting MTU probe")
sizes = mtuProbePingSizesV4
if ep.Addr().Is6() {
sizes = mtuProbePingSizesV6
}
}
}
logLevel := discoLog
if purpose == pingHeartbeat {
logLevel = discoVerboseLog
}
for _, s := range sizes {
txid := stun.NewTxID()
de.sentPing[txid] = sentPing{
to: ep,
at: now,
timer: time.AfterFunc(pingTimeoutDuration, func() { de.discoPingTimeout(txid) }),
purpose: purpose,
resCB: resCB,
size: s,
}
go de.sendDiscoPing(ep, epDisco.key, txid, s, logLevel)
}
}
// sendDiscoPingsLocked starts pinging all of ep's endpoints.
func (de *endpoint) sendDiscoPingsLocked(now mono.Time, sendCallMeMaybe bool) {
de.lastFullPing = now
var sentAny bool
for ep, st := range de.endpointState {
if st.shouldDeleteLocked() {
de.deleteEndpointLocked("sendPingsLocked", ep)
continue
}
if runtime.GOOS == "js" {
continue
}
if !st.lastPing.IsZero() && now.Sub(st.lastPing) < discoPingInterval {
continue
}
firstPing := !sentAny
sentAny = true
if firstPing && sendCallMeMaybe {
de.c.dlogf("[v1] magicsock: disco: send, starting discovery for %v (%v)", de.publicKey.ShortString(), de.discoShort())
}
de.startDiscoPingLocked(ep, now, pingDiscovery, 0, nil)
}
derpAddr := de.derpAddr
if sentAny && sendCallMeMaybe && derpAddr.IsValid() {
// Have our magicsock.Conn figure out its STUN endpoint (if
// it doesn't know already) and then send a CallMeMaybe
// message to our 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.
go de.c.enqueueCallMeMaybe(derpAddr, de)
}
}
// sendWireGuardOnlyPingsLocked evaluates all available addresses for
// a WireGuard only endpoint and initates an ICMP ping for useable
// addresses.
func (de *endpoint) sendWireGuardOnlyPingsLocked(now mono.Time) {
if runtime.GOOS == "js" {
return
}
// Normally we only send pings at a low rate as the decision to start
// sending a ping sets bestAddrAtUntil with a reasonable time to keep trying
// that address, however, if that code changed we may want to be sure that
// we don't ever send excessive pings to avoid impact to the client/user.
if !now.After(de.lastFullPing.Add(10 * time.Second)) {
return
}
de.lastFullPing = now
for ipp := range de.endpointState {
if ipp.Addr().Is4() && de.c.noV4.Load() {
continue
}
if ipp.Addr().Is6() && de.c.noV6.Load() {
continue
}
go de.sendWireGuardOnlyPing(ipp, now)
}
}
// sendWireGuardOnlyPing sends a ICMP ping to a WireGuard only address to
// discover the latency.
func (de *endpoint) sendWireGuardOnlyPing(ipp netip.AddrPort, now mono.Time) {
ctx, cancel := context.WithTimeout(de.c.connCtx, 5*time.Second)
defer cancel()
de.setLastPing(ipp, now)
addr := &net.IPAddr{
IP: net.IP(ipp.Addr().AsSlice()),
Zone: ipp.Addr().Zone(),
}
p := de.c.getPinger()
if p == nil {
de.c.logf("[v2] magicsock: sendWireGuardOnlyPingLocked: pinger is nil")
return
}
latency, err := p.Send(ctx, addr, nil)
if err != nil {
de.c.logf("[v2] magicsock: sendWireGuardOnlyPingLocked: %s", err)
return
}
de.mu.Lock()
defer de.mu.Unlock()
state, ok := de.endpointState[ipp]
if !ok {
return
}
state.addPongReplyLocked(pongReply{
latency: latency,
pongAt: now,
from: ipp,
pongSrc: netip.AddrPort{}, // We don't know this.
})
}
// setLastPing sets lastPing on the endpointState to now.
func (de *endpoint) setLastPing(ipp netip.AddrPort, now mono.Time) {
de.mu.Lock()
defer de.mu.Unlock()
state, ok := de.endpointState[ipp]
if !ok {
return
}
state.lastPing = now
}
// updateFromNode updates the endpoint based on a tailcfg.Node from a NetMap
// update.
func (de *endpoint) updateFromNode(n tailcfg.NodeView, heartbeatDisabled bool) {
if !n.Valid() {
panic("nil node when updating endpoint")
}
de.mu.Lock()
defer de.mu.Unlock()
de.heartbeatDisabled = heartbeatDisabled
de.expired = n.Expired()
epDisco := de.disco.Load()
var discoKey key.DiscoPublic
if epDisco != nil {
discoKey = epDisco.key
}
if discoKey != n.DiscoKey() {
de.c.logf("[v1] magicsock: disco: node %s changed from %s to %s", de.publicKey.ShortString(), discoKey, n.DiscoKey())
de.disco.Store(&endpointDisco{
key: n.DiscoKey(),
short: n.DiscoKey().ShortString(),
})
de.debugUpdates.Add(EndpointChange{
When: time.Now(),
What: "updateFromNode-resetLocked",
})
de.resetLocked()
}
if n.DERP() == "" {
if de.derpAddr.IsValid() {
de.debugUpdates.Add(EndpointChange{
When: time.Now(),
What: "updateFromNode-remove-DERP",
From: de.derpAddr,
})
}
de.derpAddr = netip.AddrPort{}
} else {
newDerp, _ := netip.ParseAddrPort(n.DERP())
if de.derpAddr != newDerp {
de.debugUpdates.Add(EndpointChange{
When: time.Now(),
What: "updateFromNode-DERP",
From: de.derpAddr,
To: newDerp,
})
}
de.derpAddr = newDerp
}
de.setEndpointsLocked(n.Endpoints())
}
func (de *endpoint) setEndpointsLocked(eps interface {
LenIter() []struct{}
At(i int) netip.AddrPort
}) {
for _, st := range de.endpointState {
st.index = indexSentinelDeleted // assume deleted until updated in next loop
}
var newIpps []netip.AddrPort
for i := range eps.LenIter() {
if i > math.MaxInt16 {
// Seems unlikely.
break
}
ipp := eps.At(i)
if !ipp.IsValid() {
de.c.logf("magicsock: bogus netmap endpoint from %v", eps)
continue
}
if st, ok := de.endpointState[ipp]; ok {
st.index = int16(i)
} else {
de.endpointState[ipp] = &endpointState{index: int16(i)}
newIpps = append(newIpps, ipp)
}
}
if len(newIpps) > 0 {
de.debugUpdates.Add(EndpointChange{
When: time.Now(),
What: "updateFromNode-new-Endpoints",
To: newIpps,
})
}
// Now delete anything unless it's still in the network map or
// was a recently discovered endpoint.
for ep, st := range de.endpointState {
if st.shouldDeleteLocked() {
de.deleteEndpointLocked("updateFromNode", ep)
}
}
}
// addCandidateEndpoint adds ep as an endpoint to which we should send
// future pings. If there is an existing endpointState for ep, and forRxPingTxID
// matches the last received ping TxID, this function reports true, otherwise
// false.
//
// This is called once we've already verified that we got a valid
// discovery message from de via ep.
func (de *endpoint) addCandidateEndpoint(ep netip.AddrPort, forRxPingTxID stun.TxID) (duplicatePing bool) {
de.mu.Lock()
defer de.mu.Unlock()
if st, ok := de.endpointState[ep]; ok {
duplicatePing = forRxPingTxID == st.lastGotPingTxID
if !duplicatePing {
st.lastGotPingTxID = forRxPingTxID
}
if st.lastGotPing.IsZero() {
// Already-known endpoint from the network map.
return duplicatePing
}
st.lastGotPing = time.Now()
return duplicatePing
}
// Newly discovered endpoint. Exciting!
de.c.dlogf("[v1] magicsock: disco: adding %v as candidate endpoint for %v (%s)", ep, de.discoShort(), de.publicKey.ShortString())
de.endpointState[ep] = &endpointState{
lastGotPing: time.Now(),
lastGotPingTxID: forRxPingTxID,
}
// If for some reason this gets very large, do some cleanup.
if size := len(de.endpointState); size > 100 {
for ep, st := range de.endpointState {
if st.shouldDeleteLocked() {
de.deleteEndpointLocked("addCandidateEndpoint", ep)
}
}
size2 := len(de.endpointState)
de.c.dlogf("[v1] magicsock: disco: addCandidateEndpoint pruned %v candidate set from %v to %v entries", size, size2)
}
return false
}
// clearBestAddrLocked clears the bestAddr and related fields such that future
// packets will re-evaluate the best address to send to next.
//
// de.mu must be held.
func (de *endpoint) clearBestAddrLocked() {
de.bestAddr = addrQuality{}
de.bestAddrAt = 0
de.trustBestAddrUntil = 0
}
// noteBadEndpoint marks ipp as a bad endpoint that would need to be
// re-evaluated before future use, this should be called for example if a send
// to ipp fails due to a host unreachable error or similar.
func (de *endpoint) noteBadEndpoint(ipp netip.AddrPort) {
de.mu.Lock()
defer de.mu.Unlock()
de.clearBestAddrLocked()
if st, ok := de.endpointState[ipp]; ok {
st.clear()
}
}
// noteConnectivityChange is called when connectivity changes enough
// that we should question our earlier assumptions about which paths
// work.
func (de *endpoint) noteConnectivityChange() {
de.mu.Lock()
defer de.mu.Unlock()
de.clearBestAddrLocked()
for k := range de.endpointState {
de.endpointState[k].clear()
}
}
// pingSizeToPktLen calculates the minimum path MTU that would permit
// a disco ping message of length size to reach its target at
// addr. size is the length of the entire disco message including
// disco headers. If size is zero, assume it is the safe wire MTU.
func pingSizeToPktLen(size int, is6 bool) tstun.WireMTU {
if size == 0 {
return tstun.SafeWireMTU()
}
headerLen := ipv4.HeaderLen
if is6 {
headerLen = ipv6.HeaderLen
}
headerLen += 8 // UDP header length
return tstun.WireMTU(size + headerLen)
}
// pktLenToPingSize calculates the ping payload size that would
// create a disco ping message whose on-the-wire length is exactly mtu
// bytes long. If mtu is zero or less than the minimum ping size, then
// no MTU probe is desired and return zero for an unpadded ping.
func pktLenToPingSize(mtu tstun.WireMTU, is6 bool) int {
if mtu == 0 {
return 0
}
headerLen := ipv4.HeaderLen
if is6 {
headerLen = ipv6.HeaderLen
}
headerLen += 8 // UDP header length
if mtu < tstun.WireMTU(headerLen) {
return 0
}
return int(mtu) - headerLen
}
// handlePongConnLocked handles a Pong message (a reply to an earlier ping).
// It should be called with the Conn.mu held.
//
// It reports whether m.TxID corresponds to a ping that this endpoint sent.
func (de *endpoint) handlePongConnLocked(m *disco.Pong, di *discoInfo, src netip.AddrPort) (knownTxID bool) {
de.mu.Lock()
defer de.mu.Unlock()
isDerp := src.Addr() == tailcfg.DerpMagicIPAddr
sp, ok := de.sentPing[m.TxID]
if !ok {
// This is not a pong for a ping we sent.
return false
}
knownTxID = true // for naked returns below
de.removeSentDiscoPingLocked(m.TxID, sp)
pktLen := int(pingSizeToPktLen(sp.size, sp.to.Addr().Is6()))
if sp.size != 0 {
m := getPeerMTUsProbedMetric(tstun.WireMTU(pktLen))
m.Add(1)
if metricMaxPeerMTUProbed.Value() < int64(pktLen) {
metricMaxPeerMTUProbed.Set(int64(pktLen))
}
}
now := mono.Now()
latency := now.Sub(sp.at)
if !isDerp {
st, ok := de.endpointState[sp.to]
if !ok {
// This is no longer an endpoint we care about.
return
}
de.c.peerMap.setNodeKeyForIPPort(src, de.publicKey)
st.addPongReplyLocked(pongReply{
latency: latency,
pongAt: now,
from: src,
pongSrc: m.Src,
})
}
if sp.purpose != pingHeartbeat {
de.c.dlogf("[v1] magicsock: disco: %v<-%v (%v, %v) got pong tx=%x latency=%v pktlen=%v pong.src=%v%v", de.c.discoShort, de.discoShort(), de.publicKey.ShortString(), src, m.TxID[:6], latency.Round(time.Millisecond), pktLen, m.Src, logger.ArgWriter(func(bw *bufio.Writer) {
if sp.to != src {
fmt.Fprintf(bw, " ping.to=%v", sp.to)
}
}))
}
// Currently only CLI ping uses this callback.
if sp.resCB.reply() {
if sp.purpose == pingCLI {
de.c.populateCLIPingResponseLocked(sp.resCB.res, latency, sp.to)
}
go sp.resCB.cb(sp.resCB.res)
}
// 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 !isDerp {
thisPong := addrQuality{sp.to, latency, tstun.WireMTU(pingSizeToPktLen(sp.size, sp.to.Addr().Is6()))}
if betterAddr(thisPong, de.bestAddr) {
de.c.logf("magicsock: disco: node %v %v now using %v mtu=%v tx=%x", de.publicKey.ShortString(), de.discoShort(), sp.to, thisPong.wireMTU, m.TxID[:6])
de.debugUpdates.Add(EndpointChange{
When: time.Now(),
What: "handlePingLocked-bestAddr-update",
From: de.bestAddr,
To: thisPong,
})
de.bestAddr = thisPong
}
if de.bestAddr.AddrPort == thisPong.AddrPort {
de.debugUpdates.Add(EndpointChange{
When: time.Now(),
What: "handlePingLocked-bestAddr-latency",
From: de.bestAddr,
To: thisPong,
})
de.bestAddr.latency = latency
de.bestAddrAt = now
de.trustBestAddrUntil = now.Add(trustUDPAddrDuration)
}
}
return
}
// addrQuality is an IPPort with an associated latency and path mtu.
type addrQuality struct {
netip.AddrPort
latency time.Duration
wireMTU tstun.WireMTU
}
func (a addrQuality) String() string {
return fmt.Sprintf("%v@%v+%v", a.AddrPort, a.latency, a.wireMTU)
}
// betterAddr reports whether a is a better addr to use than b.
func betterAddr(a, b addrQuality) bool {
if a.AddrPort == b.AddrPort {
if a.wireMTU > b.wireMTU {
// TODO(val): Think harder about the case of lower
// latency and smaller or unknown MTU, and higher
// latency but larger MTU. Probably in most cases the
// largest MTU will also be the lowest latency but we
// can't depend on that.
return true
}
return false
}
if !b.IsValid() {
return true
}
if !a.IsValid() {
return false
}
// Each address starts with a set of points (from 0 to 100) that
// represents how much faster they are than the highest-latency
// endpoint. For example, if a has latency 200ms and b has latency
// 190ms, then a starts with 0 points and b starts with 5 points since
// it's 5% faster.
var aPoints, bPoints int
if a.latency > b.latency && a.latency > 0 {
bPoints = int(100 - ((b.latency * 100) / a.latency))
} else if b.latency > 0 {
aPoints = int(100 - ((a.latency * 100) / b.latency))
}
// Prefer private IPs over public IPs as long as the latencies are
// roughly equivalent, since it's less likely that a user will have to
// pay for the bandwidth in a cloud environment.
//
// Additionally, prefer any loopback address strongly over non-loopback
// addresses.
if a.Addr().IsLoopback() {
aPoints += 50
} else if a.Addr().IsPrivate() {
aPoints += 20
}
if b.Addr().IsLoopback() {
bPoints += 50
} else if b.Addr().IsPrivate() {
bPoints += 20
}
// Prefer IPv6 for being a bit more robust, as long as
// the latencies are roughly equivalent.
if a.Addr().Is6() {
aPoints += 10
}
if b.Addr().Is6() {
bPoints += 10
}
// Don't change anything if the latency improvement is less than 1%; we
// want a bit of "stickiness" (a.k.a. hysteresis) to avoid flapping if
// there's two roughly-equivalent endpoints.
//
// Points are essentially the percentage improvement of latency vs. the
// slower endpoint; absent any boosts from private IPs, IPv6, etc., a
// will be a better address than b by a fraction of 1% or less if
// aPoints <= 1 and bPoints == 0.
if aPoints <= 1 && bPoints == 0 {
return false
}
return aPoints > bPoints
}
// handleCallMeMaybe handles a CallMeMaybe discovery message via
// DERP. The contract for use of this message is that the peer has
// already sent to us via UDP, so their stateful firewall should be
// open. Now we can Ping back and make it through.
func (de *endpoint) handleCallMeMaybe(m *disco.CallMeMaybe) {
if runtime.GOOS == "js" {
// Nothing to do on js/wasm if we can't send UDP packets anyway.
return
}
de.mu.Lock()
defer de.mu.Unlock()
now := time.Now()
for ep := range de.isCallMeMaybeEP {
de.isCallMeMaybeEP[ep] = false // mark for deletion
}
var newEPs []netip.AddrPort
for _, ep := range m.MyNumber {
if ep.Addr().Is6() && ep.Addr().IsLinkLocalUnicast() {
// We send these out, but ignore them for now.
// TODO: teach the ping code to ping on all interfaces
// for these.
continue
}
mak.Set(&de.isCallMeMaybeEP, ep, true)
if es, ok := de.endpointState[ep]; ok {
es.callMeMaybeTime = now
} else {
de.endpointState[ep] = &endpointState{callMeMaybeTime: now}
newEPs = append(newEPs, ep)
}
}
if len(newEPs) > 0 {
de.debugUpdates.Add(EndpointChange{
When: time.Now(),
What: "handleCallMeMaybe-new-endpoints",
To: newEPs,
})
de.c.dlogf("[v1] magicsock: disco: call-me-maybe from %v %v added new endpoints: %v",
de.publicKey.ShortString(), de.discoShort(),
logger.ArgWriter(func(w *bufio.Writer) {
for i, ep := range newEPs {
if i > 0 {
w.WriteString(", ")
}
w.WriteString(ep.String())
}
}))
}
// Delete any prior CallMeMaybe endpoints that weren't included
// in this message.
for ep, want := range de.isCallMeMaybeEP {
if !want {
delete(de.isCallMeMaybeEP, ep)
de.deleteEndpointLocked("handleCallMeMaybe", ep)
}
}
// Zero out all the lastPing times to force sendPingsLocked to send new ones,
// even if it's been less than 5 seconds ago.
for _, st := range de.endpointState {
st.lastPing = 0
}
de.sendDiscoPingsLocked(mono.Now(), false)
}
func (de *endpoint) populatePeerStatus(ps *ipnstate.PeerStatus) {
de.mu.Lock()
defer de.mu.Unlock()
ps.Relay = de.c.derpRegionCodeOfIDLocked(int(de.derpAddr.Port()))
if de.lastSend.IsZero() {
return
}
now := mono.Now()
ps.LastWrite = de.lastSend.WallTime()
ps.Active = now.Sub(de.lastSend) < sessionActiveTimeout
if udpAddr, derpAddr, _ := de.addrForSendLocked(now); udpAddr.IsValid() && !derpAddr.IsValid() {
ps.CurAddr = udpAddr.String()
}
}
// stopAndReset stops timers associated with de and resets its state back to zero.
// It's called when a discovery endpoint is no longer present in the
// NetworkMap, or when magicsock is transitioning from running to
// stopped state (via SetPrivateKey(zero))
func (de *endpoint) stopAndReset() {
atomic.AddInt64(&de.numStopAndResetAtomic, 1)
de.mu.Lock()
defer de.mu.Unlock()
if closing := de.c.closing.Load(); !closing {
if de.isWireguardOnly {
de.c.logf("[v1] magicsock: doing cleanup for wireguard key %s", de.publicKey.ShortString())
} else {
de.c.logf("[v1] magicsock: doing cleanup for discovery key %s", de.discoShort())
}
}
de.debugUpdates.Add(EndpointChange{
When: time.Now(),
What: "stopAndReset-resetLocked",
})
de.resetLocked()
if de.heartBeatTimer != nil {
de.heartBeatTimer.Stop()
de.heartBeatTimer = nil
}
}
// resetLocked clears all the endpoint's p2p state, reverting it to a
// DERP-only endpoint. It does not stop the endpoint's heartbeat
// timer, if one is running.
func (de *endpoint) resetLocked() {
de.lastSend = 0
de.lastFullPing = 0
de.clearBestAddrLocked()
for _, es := range de.endpointState {
es.lastPing = 0
}
if !de.isWireguardOnly {
for txid, sp := range de.sentPing {
de.removeSentDiscoPingLocked(txid, sp)
}
}
}
func (de *endpoint) numStopAndReset() int64 {
return atomic.LoadInt64(&de.numStopAndResetAtomic)
}
func (de *endpoint) setDERPHome(regionID uint16) {
de.mu.Lock()
defer de.mu.Unlock()
de.derpAddr = netip.AddrPortFrom(tailcfg.DerpMagicIPAddr, uint16(regionID))
}