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endpoint.go
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endpoint.go
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// 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"
"slices"
"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
lastRecvWG mono.Time // last time there were incoming packets from this peer destined for wireguard-go (e.g. not disco)
lastRecvUDPAny mono.Time // last time there were incoming UDP packets from this peer of any kind
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
lastSendExt mono.Time // last time there were outgoing packets sent to this peer from an external trigger (e.g. wireguard-go or disco pingCLI)
lastSendAny mono.Time // last time there were outgoing packets sent this peer from any trigger, internal or external to magicsock
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; mutate via setBestAddrLocked()
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
probeUDPLifetime *probeUDPLifetime // UDP path lifetime probing; nil if disabled
expired bool // whether the node has expired
isWireguardOnly bool // whether the endpoint is WireGuard only
}
func (de *endpoint) setBestAddrLocked(v addrQuality) {
if v.AddrPort != de.bestAddr.AddrPort {
de.probeUDPLifetime.resetCycleEndpointLocked()
}
de.bestAddr = v
}
const (
// udpLifetimeProbeCliffSlack is how much slack to use relative to a
// ProbeUDPLifetimeConfig.Cliffs duration in order to account for RTT,
// scheduling jitter, buffers, etc. If the cliff is 10s, we attempt to probe
// after 10s - 2s (8s) amount of inactivity.
udpLifetimeProbeCliffSlack = time.Second * 2
// udpLifetimeProbeSchedulingTolerance is how much of a difference can be
// tolerated between a UDP lifetime probe scheduling target and when it
// actually fired. This must be some fraction of udpLifetimeProbeCliffSlack.
udpLifetimeProbeSchedulingTolerance = udpLifetimeProbeCliffSlack / 8
)
// probeUDPLifetime represents the configuration and state tied to probing UDP
// path lifetime. A probe "cycle" involves pinging the UDP path at various
// timeout cliffs, which are pre-defined durations of interest commonly used by
// NATs/firewalls as default stateful session timeout values. Cliffs are probed
// in ascending order. A "cycle" completes when all cliffs have received a pong,
// or when a ping times out. Cycles may extend across endpoint session lifetimes
// if they are disrupted by user traffic.
type probeUDPLifetime struct {
// All fields are guarded by endpoint.mu. probeUDPLifetime methods are for
// convenience.
// config holds the probing configuration.
config ProbeUDPLifetimeConfig
// timer is nil when idle. A non-nil timer indicates we intend to probe a
// timeout cliff in the future.
timer *time.Timer
// bestAddr contains the endpoint.bestAddr.AddrPort at the time a cycle was
// scheduled to start. A probing cycle is 1:1 with the current
// endpoint.bestAddr.AddrPort in the interest of simplicity. When
// endpoint.bestAddr.AddrPort changes, any active probing cycle will reset.
bestAddr netip.AddrPort
// cycleStartedAt contains the time at which the first cliff
// (ProbeUDPLifetimeConfig.Cliffs[0]) was pinged for the current/last cycle.
cycleStartedAt time.Time
// cycleActive is true if a probing cycle is active, otherwise false.
cycleActive bool
// currentCliff represents the index into ProbeUDPLifetimeConfig.Cliffs for
// the cliff that we are waiting to ping, or waiting on a pong/timeout.
currentCliff int
// lastTxID is the ID for the last ping that was sent.
lastTxID stun.TxID
}
func (p *probeUDPLifetime) currentCliffDurationEndpointLocked() time.Duration {
if p == nil {
return 0
}
return p.config.Cliffs[p.currentCliff]
}
// cycleCompleteMaxCliffEndpointLocked records the max cliff (as an index of
// ProbeUDPLifetimeConfig.Cliffs) a probing cycle reached, i.e. received a pong
// for. A value < 0 indicates no cliff was reached. It is a no-op if the active
// configuration does not equal defaultProbeUDPLifetimeConfig.
func (p *probeUDPLifetime) cycleCompleteMaxCliffEndpointLocked(cliff int) {
if !p.config.Equals(defaultProbeUDPLifetimeConfig) {
return
}
switch {
case cliff < 0:
metricUDPLifetimeCycleCompleteNoCliffReached.Add(1)
case cliff == 0:
metricUDPLifetimeCycleCompleteAt10sCliff.Add(1)
case cliff == 1:
metricUDPLifetimeCycleCompleteAt30sCliff.Add(1)
case cliff == 2:
metricUDPLifetimeCycleCompleteAt60sCliff.Add(1)
}
}
// resetCycleEndpointLocked resets the state contained in p to reflect an
// inactive cycle.
func (p *probeUDPLifetime) resetCycleEndpointLocked() {
if p == nil {
return
}
if p.timer != nil {
p.timer.Stop()
p.timer = nil
}
p.cycleActive = false
p.currentCliff = 0
p.bestAddr = netip.AddrPort{}
}
// ProbeUDPLifetimeConfig represents the configuration for probing UDP path
// lifetime.
type ProbeUDPLifetimeConfig struct {
// The timeout cliffs to probe. Values are in ascending order. Ascending
// order is chosen over descending because we have limited opportunities to
// probe. With a descending order we are stuck waiting for a new UDP
// path/session if the first value times out. When that new path is
// established is anyone's guess.
Cliffs []time.Duration
// CycleCanStartEvery represents the min duration between cycles starting
// up.
CycleCanStartEvery time.Duration
}
var (
// defaultProbeUDPLifetimeConfig is the configuration that must be used
// for UDP path lifetime probing until it can be wholly disseminated (not
// just on/off) from upstream control components, and associated metrics
// (metricUDPLifetime*) have lifetime management.
//
// TODO(#10928): support dynamic config via tailcfg.PeerCapMap.
defaultProbeUDPLifetimeConfig = &ProbeUDPLifetimeConfig{
Cliffs: []time.Duration{
time.Second * 10,
time.Second * 30,
time.Second * 60,
},
CycleCanStartEvery: time.Hour * 24,
}
)
// Equals returns true if b equals p, otherwise false. If both sides are nil,
// Equals returns true. If only one side is nil, Equals returns false.
func (p *ProbeUDPLifetimeConfig) Equals(b *ProbeUDPLifetimeConfig) bool {
if p == b {
return true
}
if (p == nil && b != nil) || (b == nil && p != nil) {
return false
}
if !slices.Equal(p.Cliffs, b.Cliffs) {
return false
}
if p.CycleCanStartEvery != b.CycleCanStartEvery {
return false
}
return true
}
// Valid returns true if p is valid, otherwise false. p must be non-nil.
func (p *ProbeUDPLifetimeConfig) Valid() bool {
if len(p.Cliffs) < 1 {
// We need at least one cliff, otherwise there is nothing to probe.
return false
}
if p.CycleCanStartEvery < 1 {
// Probing must be constrained by a positive CycleCanStartEvery.
return false
}
for i, c := range p.Cliffs {
if c <= max(udpLifetimeProbeCliffSlack*2, heartbeatInterval) {
// A timeout cliff less than or equal to twice
// udpLifetimeProbeCliffSlack is invalid due to being effectively
// zero when the cliff slack is subtracted from the cliff value at
// scheduling time.
//
// A timeout cliff less or equal to the heartbeatInterval is also
// invalid, as we may attempt to schedule on the tail end of the
// last heartbeat tied to an active session.
//
// These values are constants, but max()'d in case they change in
// the future.
return false
}
if i == 0 {
continue
}
if c <= p.Cliffs[i-1] {
// Cliffs must be in ascending order.
return false
}
}
return true
}
// setProbeUDPLifetimeOn enables or disables probing of UDP path lifetime based
// on v. In the case of enablement defaultProbeUDPLifetimeConfig is used as the
// desired configuration.
func (de *endpoint) setProbeUDPLifetimeOn(v bool) {
de.mu.Lock()
if v {
de.setProbeUDPLifetimeConfigLocked(defaultProbeUDPLifetimeConfig)
} else {
de.setProbeUDPLifetimeConfigLocked(nil)
}
de.mu.Unlock()
}
// setProbeUDPLifetimeConfigLocked sets the desired configuration for probing
// UDP path lifetime. Ownership of desired is passed to endpoint, it must not be
// mutated once this call is made. A nil value disables the feature. If desired
// is non-nil but desired.Valid() returns false this is a no-op.
func (de *endpoint) setProbeUDPLifetimeConfigLocked(desired *ProbeUDPLifetimeConfig) {
if de.isWireguardOnly {
return
}
if desired == nil {
if de.probeUDPLifetime == nil {
// noop, not currently configured or desired
return
}
de.probeUDPLifetime.resetCycleEndpointLocked()
de.probeUDPLifetime = nil
return
}
if !desired.Valid() {
return
}
if de.probeUDPLifetime != nil {
if de.probeUDPLifetime.config.Equals(desired) {
// noop, current config equals desired
return
}
de.probeUDPLifetime.resetCycleEndpointLocked()
} else {
de.probeUDPLifetime = &probeUDPLifetime{}
}
p := de.probeUDPLifetime
p.config = *desired
p.resetCycleEndpointLocked()
}
// 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.setBestAddrLocked(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.Time) {
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.lastRecvWG.LoadAtomic())
if elapsed > 10*time.Second {
de.lastRecvWG.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
}
// maybeProbeUDPLifetimeLocked returns an afterInactivityFor duration and true
// if de is a candidate for UDP path lifetime probing in the future, otherwise
// false.
func (de *endpoint) maybeProbeUDPLifetimeLocked() (afterInactivityFor time.Duration, maybe bool) {
p := de.probeUDPLifetime
if p == nil {
return afterInactivityFor, false
}
if !de.bestAddr.IsValid() {
return afterInactivityFor, false
}
epDisco := de.disco.Load()
if epDisco == nil {
// peer does not support disco
return afterInactivityFor, false
}
// We compare disco keys, which may have a shorter lifetime than node keys
// since disco keys reset on startup. This has the desired side effect of
// shuffling probing probability where the local node ends up with a large
// key value lexicographically relative to the other nodes it tends to
// communicate with. If de's disco key changes, the cycle will reset.
if de.c.discoPublic.Compare(epDisco.key) >= 0 {
// lower disco pub key node probes higher
return afterInactivityFor, false
}
if !p.cycleActive && time.Since(p.cycleStartedAt) < p.config.CycleCanStartEvery {
// This is conservative as it doesn't account for afterInactivityFor use
// by the caller, potentially delaying the start of the next cycle. We
// assume the cycle could start immediately following
// maybeProbeUDPLifetimeLocked(), regardless of the value of
// afterInactivityFor relative to latest packets in/out time.
return afterInactivityFor, false
}
afterInactivityFor = p.currentCliffDurationEndpointLocked() - udpLifetimeProbeCliffSlack
if afterInactivityFor < 0 {
// shouldn't happen
return afterInactivityFor, false
}
return afterInactivityFor, true
}
// heartbeatForLifetimeVia represents the scheduling source of
// endpoint.heartbeatForLifetime().
type heartbeatForLifetimeVia string
const (
heartbeatForLifetimeViaSessionInactive heartbeatForLifetimeVia = "session-inactive"
heartbeatForLifetimeViaPongRx heartbeatForLifetimeVia = "pong-rx"
heartbeatForLifetimeViaSelf heartbeatForLifetimeVia = "self"
)
// scheduleHeartbeatForLifetimeLocked schedules de.heartbeatForLifetime to fire
// in the future (after). The caller must describe themselves in the via arg.
func (de *endpoint) scheduleHeartbeatForLifetimeLocked(after time.Duration, via heartbeatForLifetimeVia) {
p := de.probeUDPLifetime
if p == nil {
return
}
de.c.dlogf("[v1] magicsock: disco: scheduling UDP lifetime probe for cliff=%v via=%v to %v (%v)",
p.currentCliffDurationEndpointLocked(), via, de.publicKey.ShortString(), de.discoShort())
p.bestAddr = de.bestAddr.AddrPort
p.timer = time.AfterFunc(after, de.heartbeatForLifetime)
if via == heartbeatForLifetimeViaSelf {
metricUDPLifetimeCliffsRescheduled.Add(1)
} else {
metricUDPLifetimeCliffsScheduled.Add(1)
}
}
// heartbeatForLifetime sends a disco ping recorded locally with a purpose of
// pingHeartbeatForUDPLifetime to de if de.bestAddr has remained stable, and it
// has been inactive for a duration that is within the error bounds for current
// lifetime probing cliff. Alternatively it may reschedule itself into the
// future, which is one of three scheduling sources. The other scheduling
// sources are de.heartbeat() and de.probeUDPLifetimeCliffDoneLocked().
func (de *endpoint) heartbeatForLifetime() {
de.mu.Lock()
defer de.mu.Unlock()
p := de.probeUDPLifetime
if p == nil || p.timer == nil {
// We raced with a code path trying to p.timer.Stop() us. Give up early
// in the interest of simplicity. If p.timer.Stop() happened in
// de.heartbeat() presumably because of recent packets in/out we *could*
// still probe here, and it would be meaningful, but the time logic
// below would reschedule as-is.
return
}
p.timer = nil
if !p.bestAddr.IsValid() || de.bestAddr.AddrPort != p.bestAddr {
// best path changed
p.resetCycleEndpointLocked()
return
}
afterInactivityFor, ok := de.maybeProbeUDPLifetimeLocked()
if !ok {
p.resetCycleEndpointLocked()
return
}
inactiveFor := mono.Now().Sub(max(de.lastRecvUDPAny.LoadAtomic(), de.lastSendAny))
delta := afterInactivityFor - inactiveFor
if delta.Abs() > udpLifetimeProbeSchedulingTolerance {
if delta < 0 {
// We missed our opportunity. We can resume this cliff at the tail
// end of another session.
metricUDPLifetimeCliffsMissed.Add(1)
return
} else {
// We need to wait longer before sending a ping. This can happen for
// a number of reasons, which are described in more detail in
// de.heartbeat().
de.scheduleHeartbeatForLifetimeLocked(delta, heartbeatForLifetimeViaSelf)
return
}
}
if p.currentCliff == 0 {
p.cycleStartedAt = time.Now()
p.cycleActive = true
}
de.c.dlogf("[v1] magicsock: disco: sending disco ping for UDP lifetime probe cliff=%v to %v (%v)",
p.currentCliffDurationEndpointLocked(), de.publicKey.ShortString(), de.discoShort())
de.startDiscoPingLocked(de.bestAddr.AddrPort, mono.Now(), pingHeartbeatForUDPLifetime, 0, nil)
}
// heartbeat is called every heartbeatInterval to keep the best UDP path alive,
// kick off discovery of other paths, or schedule the probing of UDP path
// lifetime on the tail end of an active session.
func (de *endpoint) heartbeat() {
de.mu.Lock()
defer de.mu.Unlock()
if de.probeUDPLifetime != nil && de.probeUDPLifetime.timer != nil {
de.probeUDPLifetime.timer.Stop()
de.probeUDPLifetime.timer = nil
}
de.heartBeatTimer = nil
if de.heartbeatDisabled {
// If control override to disable heartBeatTimer set, return early.
return
}
if de.lastSendExt.IsZero() {
// Shouldn't happen.
return
}
now := mono.Now()
if now.Sub(de.lastSendExt) > 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())
if afterInactivityFor, ok := de.maybeProbeUDPLifetimeLocked(); ok {
// This is the best place to best effort schedule a probe of UDP
// path lifetime in the future as it loosely translates to "UDP path
// is inactive".
//
// Note: wireguard-go schedules a WireGuard keepalive packet (by
// default, not tied to persistent keepalive feature) 10 seconds in
// the future after receiving an authenticated data packet. It's
// typically only sent by one side based on how the WireGuard state
// machine controls the timer. So, if we are on the receiving end of
// that keepalive, de.lastSendExt won't move, assuming there is no
// other user-generated traffic. This is one reason why we perform
// a more granular check of the last packets in/out time, below, as
// a WireGuard keepalive may have fallen somewhere within the
// sessionActiveTimeout window. heartbeatForLifetime will also
// perform a similar check, and reschedule as necessary.
inactiveFor := now.Sub(max(de.lastSendAny, de.lastRecvUDPAny.LoadAtomic()))
after := afterInactivityFor - inactiveFor
if after < 0 {
// shouldn't happen
return
}
de.scheduleHeartbeatForLifetimeLocked(after, heartbeatForLifetimeViaSessionInactive)
}
return
}
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) noteTxActivityExtTriggerLocked(now mono.Time) {
de.lastSendExt = 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)
}
}
}
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.noteTxActivityExtTriggerLocked(now)
de.lastSendAny = now
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
}
// probeUDPLifetimeCliffDoneLocked is called when a disco
// pingHeartbeatForUDPLifetime is being cleaned up. result contains the reason
// for the cleanup, txid contains the ping's txid.
// probeUDPLifetimeCliffDoneLocked may schedule another
// pingHeartbeatForUDPLifetime in the future if there is another cliff remaining
// for the current probing cycle.
func (de *endpoint) probeUDPLifetimeCliffDoneLocked(result discoPingResult, txid stun.TxID) {
p := de.probeUDPLifetime
if p == nil || !p.cycleActive || de.probeUDPLifetime.timer != nil || txid != p.lastTxID {
// Probing may have been disabled while heartbeats were in flight. This