tailscale/net/netcheck/netcheck.go

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// Copyright (c) 2020 Tailscale Inc & AUTHORS All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Package netcheck checks the network conditions from the current host.
package netcheck
import (
"bufio"
"context"
"crypto/tls"
"errors"
"fmt"
"io"
"log"
"net"
"net/http"
"net/netip"
"runtime"
"sort"
"sync"
"time"
"github.com/tcnksm/go-httpstat"
"tailscale.com/derp/derphttp"
"tailscale.com/envknob"
"tailscale.com/net/interfaces"
"tailscale.com/net/netaddr"
"tailscale.com/net/neterror"
"tailscale.com/net/netns"
"tailscale.com/net/ping"
"tailscale.com/net/portmapper"
2020-05-25 16:15:50 +00:00
"tailscale.com/net/stun"
"tailscale.com/syncs"
"tailscale.com/tailcfg"
"tailscale.com/types/logger"
"tailscale.com/types/nettype"
"tailscale.com/types/opt"
"tailscale.com/util/clientmetric"
"tailscale.com/util/mak"
)
// Debugging and experimentation tweakables.
var (
debugNetcheck = envknob.RegisterBool("TS_DEBUG_NETCHECK")
)
// The various default timeouts for things.
const (
// overallProbeTimeout is the maximum amount of time netcheck will
// spend gathering a single report.
overallProbeTimeout = 5 * time.Second
// stunTimeout is the maximum amount of time netcheck will spend
// probing with STUN packets without getting a reply before
// switching to HTTP probing, on the assumption that outbound UDP
// is blocked.
stunProbeTimeout = 3 * time.Second
// icmpProbeTimeout is the maximum amount of time netcheck will spend
// probing with ICMP packets.
icmpProbeTimeout = 1 * time.Second
// hairpinCheckTimeout is the amount of time we wait for a
// hairpinned packet to come back.
hairpinCheckTimeout = 100 * time.Millisecond
// defaultActiveRetransmitTime is the retransmit interval we use
// for STUN probes when we're in steady state (not in start-up),
// but don't have previous latency information for a DERP
// node. This is a somewhat conservative guess because if we have
// no data, likely the DERP node is very far away and we have no
// data because we timed out the last time we probed it.
defaultActiveRetransmitTime = 200 * time.Millisecond
// defaultInitialRetransmitTime is the retransmit interval used
// when netcheck first runs. We have no past context to work with,
// and we want answers relatively quickly, so it's biased slightly
// more aggressive than defaultActiveRetransmitTime. A few extra
// packets at startup is fine.
defaultInitialRetransmitTime = 100 * time.Millisecond
)
type Report struct {
UDP bool // a UDP STUN round trip completed
IPv6 bool // an IPv6 STUN round trip completed
IPv4 bool // an IPv4 STUN round trip completed
IPv6CanSend bool // an IPv6 packet was able to be sent
IPv4CanSend bool // an IPv4 packet was able to be sent
OSHasIPv6 bool // could bind a socket to ::1
ICMPv4 bool // an ICMPv4 round trip completed
// MappingVariesByDestIP is whether STUN results depend which
// STUN server you're talking to (on IPv4).
MappingVariesByDestIP opt.Bool
// HairPinning is whether the router supports communicating
// between two local devices through the NATted public IP address
// (on IPv4).
HairPinning opt.Bool
// UPnP is whether UPnP appears present on the LAN.
// Empty means not checked.
UPnP opt.Bool
// PMP is whether NAT-PMP appears present on the LAN.
// Empty means not checked.
PMP opt.Bool
// PCP is whether PCP appears present on the LAN.
// Empty means not checked.
PCP opt.Bool
PreferredDERP int // or 0 for unknown
RegionLatency map[int]time.Duration // keyed by DERP Region ID
RegionV4Latency map[int]time.Duration // keyed by DERP Region ID
RegionV6Latency map[int]time.Duration // keyed by DERP Region ID
GlobalV4 string // ip:port of global IPv4
GlobalV6 string // [ip]:port of global IPv6
// TODO: update Clone when adding new fields
}
// AnyPortMappingChecked reports whether any of UPnP, PMP, or PCP are non-empty.
func (r *Report) AnyPortMappingChecked() bool {
return r.UPnP != "" || r.PMP != "" || r.PCP != ""
}
func (r *Report) Clone() *Report {
if r == nil {
return nil
}
r2 := *r
r2.RegionLatency = cloneDurationMap(r2.RegionLatency)
r2.RegionV4Latency = cloneDurationMap(r2.RegionV4Latency)
r2.RegionV6Latency = cloneDurationMap(r2.RegionV6Latency)
return &r2
}
func cloneDurationMap(m map[int]time.Duration) map[int]time.Duration {
if m == nil {
return nil
}
m2 := make(map[int]time.Duration, len(m))
for k, v := range m {
m2[k] = v
}
return m2
}
// Client generates a netcheck Report.
type Client struct {
// Verbose enables verbose logging.
Verbose bool
// Logf optionally specifies where to log to.
// If nil, log.Printf is used.
Logf logger.Logf
// TimeNow, if non-nil, is used instead of time.Now.
TimeNow func() time.Time
// GetSTUNConn4 optionally provides a func to return the
// connection to use for sending & receiving IPv4 packets. If
// nil, an emphemeral one is created as needed.
GetSTUNConn4 func() STUNConn
// GetSTUNConn6 is like GetSTUNConn4, but for IPv6.
GetSTUNConn6 func() STUNConn
// SkipExternalNetwork controls whether the client should not try
// to reach things other than localhost. This is set to true
// in tests to avoid probing the local LAN's router, etc.
SkipExternalNetwork bool
// UDPBindAddr, if non-empty, is the address to listen on for UDP.
// It defaults to ":0".
UDPBindAddr string
// PortMapper, if non-nil, is used for portmap queries.
// If nil, portmap discovery is not done.
PortMapper *portmapper.Client // lazily initialized on first use
mu sync.Mutex // guards following
nextFull bool // do a full region scan, even if last != nil
prev map[time.Time]*Report // some previous reports
last *Report // most recent report
lastFull time.Time // time of last full (non-incremental) report
curState *reportState // non-nil if we're in a call to GetReportn
}
// STUNConn is the interface required by the netcheck Client when
// reusing an existing UDP connection.
type STUNConn interface {
WriteToUDPAddrPort([]byte, netip.AddrPort) (int, error)
WriteTo([]byte, net.Addr) (int, error)
ReadFrom([]byte) (int, net.Addr, error)
}
func (c *Client) enoughRegions() int {
if c.Verbose {
// Abuse verbose a bit here so netcheck can show all region latencies
// in verbose mode.
return 100
}
return 3
}
func (c *Client) logf(format string, a ...any) {
if c.Logf != nil {
c.Logf(format, a...)
} else {
log.Printf(format, a...)
}
}
func (c *Client) vlogf(format string, a ...any) {
if c.Verbose || debugNetcheck() {
c.logf(format, a...)
}
}
// handleHairSTUN reports whether pkt (from src) was our magic hairpin
// probe packet that we sent to ourselves.
func (c *Client) handleHairSTUNLocked(pkt []byte, src netip.AddrPort) bool {
rs := c.curState
if rs == nil {
return false
}
if tx, err := stun.ParseBindingRequest(pkt); err == nil && tx == rs.hairTX {
select {
case rs.gotHairSTUN <- src:
default:
}
return true
}
return false
}
// MakeNextReportFull forces the next GetReport call to be a full
// (non-incremental) probe of all DERP regions.
func (c *Client) MakeNextReportFull() {
c.mu.Lock()
defer c.mu.Unlock()
c.nextFull = true
}
func (c *Client) ReceiveSTUNPacket(pkt []byte, src netip.AddrPort) {
c.vlogf("received STUN packet from %s", src)
if src.Addr().Is4() {
metricSTUNRecv4.Add(1)
} else if src.Addr().Is6() {
metricSTUNRecv6.Add(1)
}
c.mu.Lock()
if c.handleHairSTUNLocked(pkt, src) {
c.mu.Unlock()
return
}
rs := c.curState
c.mu.Unlock()
if rs == nil {
return
}
tx, addrPort, err := stun.ParseResponse(pkt)
if err != nil {
if _, err := stun.ParseBindingRequest(pkt); err == nil {
// This was probably our own netcheck hairpin
// check probe coming in late. Ignore.
return
}
c.logf("netcheck: received unexpected STUN message response from %v: %v", src, err)
return
}
rs.mu.Lock()
onDone, ok := rs.inFlight[tx]
if ok {
delete(rs.inFlight, tx)
}
rs.mu.Unlock()
if ok {
onDone(addrPort)
}
}
// probeProto is the protocol used to time a node's latency.
type probeProto uint8
const (
probeIPv4 probeProto = iota // STUN IPv4
probeIPv6 // STUN IPv6
probeHTTPS // HTTPS
)
type probe struct {
// delay is when the probe is started, relative to the time
// that GetReport is called. One probe in each probePlan
// should have a delay of 0. Non-zero values are for retries
// on UDP loss or timeout.
delay time.Duration
// node is the name of the node name. DERP node names are globally
// unique so there's no region ID.
node string
// proto is how the node should be probed.
proto probeProto
// wait is how long to wait until the probe is considered failed.
// 0 means to use a default value.
wait time.Duration
}
// probePlan is a set of node probes to run.
// The map key is a descriptive name, only used for tests.
//
// The values are logically an unordered set of tests to run concurrently.
// In practice there's some order to them based on their delay fields,
// but multiple probes can have the same delay time or be running concurrently
// both within and between sets.
//
// A set of probes is done once either one of the probes completes, or
// the next probe to run wouldn't yield any new information not
// already discovered by any previous probe in any set.
type probePlan map[string][]probe
// sortRegions returns the regions of dm first sorted
// from fastest to slowest (based on the 'last' report),
// end in regions that have no data.
func sortRegions(dm *tailcfg.DERPMap, last *Report) (prev []*tailcfg.DERPRegion) {
prev = make([]*tailcfg.DERPRegion, 0, len(dm.Regions))
for _, reg := range dm.Regions {
if reg.Avoid {
continue
}
prev = append(prev, reg)
}
sort.Slice(prev, func(i, j int) bool {
da, db := last.RegionLatency[prev[i].RegionID], last.RegionLatency[prev[j].RegionID]
if db == 0 && da != 0 {
// Non-zero sorts before zero.
return true
}
if da == 0 {
// Zero can't sort before anything else.
return false
}
return da < db
})
return prev
}
// numIncrementalRegions is the number of fastest regions to
// periodically re-query during incremental netcheck reports. (During
// a full report, all regions are scanned.)
const numIncrementalRegions = 3
// makeProbePlan generates the probe plan for a DERPMap, given the most
// recent report and whether IPv6 is configured on an interface.
func makeProbePlan(dm *tailcfg.DERPMap, ifState *interfaces.State, last *Report) (plan probePlan) {
if last == nil || len(last.RegionLatency) == 0 {
return makeProbePlanInitial(dm, ifState)
}
have6if := ifState.HaveV6
have4if := ifState.HaveV4
plan = make(probePlan)
if !have4if && !have6if {
return plan
}
had4 := len(last.RegionV4Latency) > 0
had6 := len(last.RegionV6Latency) > 0
hadBoth := have6if && had4 && had6
for ri, reg := range sortRegions(dm, last) {
if ri == numIncrementalRegions {
break
}
var p4, p6 []probe
do4 := have4if
do6 := have6if
// By default, each node only gets one STUN packet sent,
// except the fastest two from the previous round.
tries := 1
isFastestTwo := ri < 2
if isFastestTwo {
tries = 2
} else if hadBoth {
// For dual stack machines, make the 3rd & slower nodes alternate
// between.
if ri%2 == 0 {
do4, do6 = true, false
} else {
do4, do6 = false, true
}
}
if !isFastestTwo && !had6 {
do6 = false
}
if reg.RegionID == last.PreferredDERP {
// But if we already had a DERP home, try extra hard to
// make sure it's there so we don't flip flop around.
tries = 4
}
for try := 0; try < tries; try++ {
if len(reg.Nodes) == 0 {
// Shouldn't be possible.
continue
}
if try != 0 && !had6 {
do6 = false
}
n := reg.Nodes[try%len(reg.Nodes)]
prevLatency := last.RegionLatency[reg.RegionID] * 120 / 100
if prevLatency == 0 {
prevLatency = defaultActiveRetransmitTime
}
delay := time.Duration(try) * prevLatency
if try > 1 {
delay += time.Duration(try) * 50 * time.Millisecond
}
if do4 {
p4 = append(p4, probe{delay: delay, node: n.Name, proto: probeIPv4})
}
if do6 {
p6 = append(p6, probe{delay: delay, node: n.Name, proto: probeIPv6})
}
}
if len(p4) > 0 {
plan[fmt.Sprintf("region-%d-v4", reg.RegionID)] = p4
}
if len(p6) > 0 {
plan[fmt.Sprintf("region-%d-v6", reg.RegionID)] = p6
}
}
return plan
}
func makeProbePlanInitial(dm *tailcfg.DERPMap, ifState *interfaces.State) (plan probePlan) {
plan = make(probePlan)
for _, reg := range dm.Regions {
var p4 []probe
var p6 []probe
for try := 0; try < 3; try++ {
n := reg.Nodes[try%len(reg.Nodes)]
delay := time.Duration(try) * defaultInitialRetransmitTime
if ifState.HaveV4 && nodeMight4(n) {
p4 = append(p4, probe{delay: delay, node: n.Name, proto: probeIPv4})
}
if ifState.HaveV6 && nodeMight6(n) {
p6 = append(p6, probe{delay: delay, node: n.Name, proto: probeIPv6})
}
}
if len(p4) > 0 {
plan[fmt.Sprintf("region-%d-v4", reg.RegionID)] = p4
}
if len(p6) > 0 {
plan[fmt.Sprintf("region-%d-v6", reg.RegionID)] = p6
}
}
return plan
}
// nodeMight6 reports whether n might reply to STUN over IPv6 based on
// its config alone, without DNS lookups. It only returns false if
// it's not explicitly disabled.
func nodeMight6(n *tailcfg.DERPNode) bool {
if n.IPv6 == "" {
return true
}
ip, _ := netip.ParseAddr(n.IPv6)
return ip.Is6()
}
// nodeMight4 reports whether n might reply to STUN over IPv4 based on
// its config alone, without DNS lookups. It only returns false if
// it's not explicitly disabled.
func nodeMight4(n *tailcfg.DERPNode) bool {
if n.IPv4 == "" {
return true
}
ip, _ := netip.ParseAddr(n.IPv4)
return ip.Is4()
}
// readPackets reads STUN packets from pc until there's an error or ctx is done.
// In either case, it closes pc.
func (c *Client) readPackets(ctx context.Context, pc net.PacketConn) {
done := make(chan struct{})
defer close(done)
go func() {
select {
case <-ctx.Done():
case <-done:
}
pc.Close()
}()
var buf [64 << 10]byte
for {
n, addr, err := pc.ReadFrom(buf[:])
if err != nil {
if ctx.Err() != nil {
return
}
c.logf("ReadFrom: %v", err)
return
}
ua, ok := addr.(*net.UDPAddr)
if !ok {
c.logf("ReadFrom: unexpected addr %T", addr)
continue
}
pkt := buf[:n]
if !stun.Is(pkt) {
continue
}
if ap := netaddr.Unmap(ua.AddrPort()); ap.IsValid() {
c.ReceiveSTUNPacket(pkt, ap)
}
}
}
// reportState holds the state for a single invocation of Client.GetReport.
type reportState struct {
c *Client
hairTX stun.TxID
gotHairSTUN chan netip.AddrPort
hairTimeout chan struct{} // closed on timeout
pc4 STUNConn
pc6 STUNConn
pc4Hair nettype.PacketConn
incremental bool // doing a lite, follow-up netcheck
stopProbeCh chan struct{}
waitPortMap sync.WaitGroup
mu sync.Mutex
sentHairCheck bool
report *Report // to be returned by GetReport
inFlight map[stun.TxID]func(netip.AddrPort) // called without c.mu held
gotEP4 string
timers []*time.Timer
}
func (rs *reportState) anyUDP() bool {
rs.mu.Lock()
defer rs.mu.Unlock()
return rs.report.UDP
}
func (rs *reportState) haveRegionLatency(regionID int) bool {
rs.mu.Lock()
defer rs.mu.Unlock()
_, ok := rs.report.RegionLatency[regionID]
return ok
}
// probeWouldHelp reports whether executing the given probe would
// yield any new information.
// The given node is provided just because the sole caller already has it
// and it saves a lookup.
func (rs *reportState) probeWouldHelp(probe probe, node *tailcfg.DERPNode) bool {
rs.mu.Lock()
defer rs.mu.Unlock()
// If the probe is for a region we don't yet know about, that
// would help.
if _, ok := rs.report.RegionLatency[node.RegionID]; !ok {
return true
}
// If the probe is for IPv6 and we don't yet have an IPv6
// report, that would help.
if probe.proto == probeIPv6 && len(rs.report.RegionV6Latency) == 0 {
return true
}
// For IPv4, we need at least two IPv4 results overall to
// determine whether we're behind a NAT that shows us as
// different source IPs and/or ports depending on who we're
// talking to. If we don't yet have two results yet
// (MappingVariesByDestIP is blank), then another IPv4 probe
// would be good.
if probe.proto == probeIPv4 && rs.report.MappingVariesByDestIP == "" {
return true
}
// Otherwise not interesting.
return false
}
func (rs *reportState) startHairCheckLocked(dst netip.AddrPort) {
if rs.sentHairCheck || rs.incremental {
return
}
rs.sentHairCheck = true
rs.pc4Hair.WriteToUDPAddrPort(stun.Request(rs.hairTX), dst)
rs.c.vlogf("sent haircheck to %v", dst)
time.AfterFunc(hairpinCheckTimeout, func() { close(rs.hairTimeout) })
}
func (rs *reportState) waitHairCheck(ctx context.Context) {
rs.mu.Lock()
defer rs.mu.Unlock()
ret := rs.report
if rs.incremental {
if rs.c.last != nil {
ret.HairPinning = rs.c.last.HairPinning
}
return
}
if !rs.sentHairCheck {
return
}
select {
case <-rs.gotHairSTUN:
ret.HairPinning.Set(true)
case <-rs.hairTimeout:
rs.c.vlogf("hairCheck timeout")
ret.HairPinning.Set(false)
default:
select {
case <-rs.gotHairSTUN:
ret.HairPinning.Set(true)
case <-rs.hairTimeout:
ret.HairPinning.Set(false)
case <-ctx.Done():
}
}
}
func (rs *reportState) stopTimers() {
rs.mu.Lock()
defer rs.mu.Unlock()
for _, t := range rs.timers {
t.Stop()
}
}
// addNodeLatency updates rs to note that node's latency is d. If ipp
// is non-zero (for all but HTTPS replies), it's recorded as our UDP
// IP:port.
func (rs *reportState) addNodeLatency(node *tailcfg.DERPNode, ipp netip.AddrPort, d time.Duration) {
var ipPortStr string
if ipp != (netip.AddrPort{}) {
ipPortStr = net.JoinHostPort(ipp.Addr().String(), fmt.Sprint(ipp.Port()))
}
rs.mu.Lock()
defer rs.mu.Unlock()
ret := rs.report
ret.UDP = true
updateLatency(ret.RegionLatency, node.RegionID, d)
// Once we've heard from enough regions (3), start a timer to
// give up on the other ones. The timer's duration is a
// function of whether this is our initial full probe or an
// incremental one. For incremental ones, wait for the
// duration of the slowest region. For initial ones, double
// that.
if len(ret.RegionLatency) == rs.c.enoughRegions() {
timeout := maxDurationValue(ret.RegionLatency)
if !rs.incremental {
timeout *= 2
}
rs.timers = append(rs.timers, time.AfterFunc(timeout, rs.stopProbes))
}
switch {
case ipp.Addr().Is6():
updateLatency(ret.RegionV6Latency, node.RegionID, d)
ret.IPv6 = true
ret.GlobalV6 = ipPortStr
// TODO: track MappingVariesByDestIP for IPv6
// too? Would be sad if so, but who knows.
case ipp.Addr().Is4():
updateLatency(ret.RegionV4Latency, node.RegionID, d)
ret.IPv4 = true
if rs.gotEP4 == "" {
rs.gotEP4 = ipPortStr
ret.GlobalV4 = ipPortStr
rs.startHairCheckLocked(ipp)
} else {
if rs.gotEP4 != ipPortStr {
ret.MappingVariesByDestIP.Set(true)
} else if ret.MappingVariesByDestIP == "" {
ret.MappingVariesByDestIP.Set(false)
}
}
}
}
func (rs *reportState) stopProbes() {
select {
case rs.stopProbeCh <- struct{}{}:
default:
}
}
func (rs *reportState) setOptBool(b *opt.Bool, v bool) {
rs.mu.Lock()
defer rs.mu.Unlock()
b.Set(v)
}
func (rs *reportState) probePortMapServices() {
defer rs.waitPortMap.Done()
rs.setOptBool(&rs.report.UPnP, false)
rs.setOptBool(&rs.report.PMP, false)
rs.setOptBool(&rs.report.PCP, false)
res, err := rs.c.PortMapper.Probe(context.Background())
if err != nil {
if !errors.Is(err, portmapper.ErrGatewayRange) {
// "skipping portmap; gateway range likely lacks support"
// is not very useful, and too spammy on cloud systems.
// If there are other errors, we want to log those.
rs.c.logf("probePortMapServices: %v", err)
}
return
}
rs.setOptBool(&rs.report.UPnP, res.UPnP)
rs.setOptBool(&rs.report.PMP, res.PMP)
rs.setOptBool(&rs.report.PCP, res.PCP)
}
func newReport() *Report {
return &Report{
RegionLatency: make(map[int]time.Duration),
RegionV4Latency: make(map[int]time.Duration),
RegionV6Latency: make(map[int]time.Duration),
}
}
func (c *Client) udpBindAddr() string {
if v := c.UDPBindAddr; v != "" {
return v
}
return ":0"
}
// GetReport gets a report.
//
// It may not be called concurrently with itself.
func (c *Client) GetReport(ctx context.Context, dm *tailcfg.DERPMap) (_ *Report, reterr error) {
defer func() {
if reterr != nil {
metricNumGetReportError.Add(1)
}
}()
metricNumGetReport.Add(1)
// Mask user context with ours that we guarantee to cancel so
// we can depend on it being closed in goroutines later.
// (User ctx might be context.Background, etc)
ctx, cancel := context.WithTimeout(ctx, overallProbeTimeout)
defer cancel()
if dm == nil {
return nil, errors.New("netcheck: GetReport: DERP map is nil")
}
c.mu.Lock()
if c.curState != nil {
c.mu.Unlock()
return nil, errors.New("invalid concurrent call to GetReport")
}
rs := &reportState{
c: c,
report: newReport(),
inFlight: map[stun.TxID]func(netip.AddrPort){},
hairTX: stun.NewTxID(), // random payload
gotHairSTUN: make(chan netip.AddrPort, 1),
hairTimeout: make(chan struct{}),
stopProbeCh: make(chan struct{}, 1),
}
c.curState = rs
last := c.last
now := c.timeNow()
if c.nextFull || now.Sub(c.lastFull) > 5*time.Minute {
last = nil // causes makeProbePlan below to do a full (initial) plan
c.nextFull = false
c.lastFull = now
metricNumGetReportFull.Add(1)
}
rs.incremental = last != nil
c.mu.Unlock()
defer func() {
c.mu.Lock()
defer c.mu.Unlock()
c.curState = nil
}()
if runtime.GOOS == "js" {
if err := c.runHTTPOnlyChecks(ctx, last, rs, dm); err != nil {
return nil, err
}
return c.finishAndStoreReport(rs, dm), nil
}
ifState, err := interfaces.GetState()
if err != nil {
c.logf("[v1] interfaces: %v", err)
return nil, err
}
// See if IPv6 works at all, or if it's been hard disabled at the
// OS level.
v6udp, err := nettype.MakePacketListenerWithNetIP(netns.Listener(c.logf)).ListenPacket(ctx, "udp6", "[::1]:0")
if err == nil {
rs.report.OSHasIPv6 = true
v6udp.Close()
}
// Create a UDP4 socket used for sending to our discovered IPv4 address.
rs.pc4Hair, err = nettype.MakePacketListenerWithNetIP(netns.Listener(c.logf)).ListenPacket(ctx, "udp4", ":0")
if err != nil {
c.logf("udp4: %v", err)
return nil, err
}
defer rs.pc4Hair.Close()
if !c.SkipExternalNetwork && c.PortMapper != nil {
rs.waitPortMap.Add(1)
go rs.probePortMapServices()
}
// At least the Apple Airport Extreme doesn't allow hairpin
// sends from a private socket until it's seen traffic from
// that src IP:port to something else out on the internet.
//
// See https://github.com/tailscale/tailscale/issues/188#issuecomment-600728643
//
// And it seems that even sending to a likely-filtered RFC 5737
// documentation-only IPv4 range is enough to set up the mapping.
// So do that for now. In the future we might want to classify networks
// that do and don't require this separately. But for now help it.
const documentationIP = "203.0.113.1"
rs.pc4Hair.WriteTo([]byte("tailscale netcheck; see https://github.com/tailscale/tailscale/issues/188"), &net.UDPAddr{IP: net.ParseIP(documentationIP), Port: 12345})
if f := c.GetSTUNConn4; f != nil {
rs.pc4 = f()
} else {
u4, err := nettype.MakePacketListenerWithNetIP(netns.Listener(c.logf)).ListenPacket(ctx, "udp4", c.udpBindAddr())
if err != nil {
c.logf("udp4: %v", err)
return nil, err
}
rs.pc4 = u4
go c.readPackets(ctx, u4)
}
if ifState.HaveV6 {
if f := c.GetSTUNConn6; f != nil {
rs.pc6 = f()
} else {
u6, err := nettype.MakePacketListenerWithNetIP(netns.Listener(c.logf)).ListenPacket(ctx, "udp6", c.udpBindAddr())
if err != nil {
c.logf("udp6: %v", err)
} else {
rs.pc6 = u6
go c.readPackets(ctx, u6)
}
}
}
plan := makeProbePlan(dm, ifState, last)
wg := syncs.NewWaitGroupChan()
wg.Add(len(plan))
for _, probeSet := range plan {
setCtx, cancelSet := context.WithCancel(ctx)
go func(probeSet []probe) {
for _, probe := range probeSet {
go rs.runProbe(setCtx, dm, probe, cancelSet)
}
<-setCtx.Done()
wg.Decr()
}(probeSet)
}
stunTimer := time.NewTimer(stunProbeTimeout)
defer stunTimer.Stop()
select {
case <-stunTimer.C:
case <-ctx.Done():
case <-wg.DoneChan():
case <-rs.stopProbeCh:
// Saw enough regions.
c.vlogf("saw enough regions; not waiting for rest")
}
rs.waitHairCheck(ctx)
c.vlogf("hairCheck done")
if !c.SkipExternalNetwork && c.PortMapper != nil {
rs.waitPortMap.Wait()
c.vlogf("portMap done")
}
rs.stopTimers()
// Try HTTPS and ICMP latency check if all STUN probes failed due to
// UDP presumably being blocked.
// TODO: this should be moved into the probePlan, using probeProto probeHTTPS.
if !rs.anyUDP() && ctx.Err() == nil {
var wg sync.WaitGroup
var need []*tailcfg.DERPRegion
for rid, reg := range dm.Regions {
if !rs.haveRegionLatency(rid) && regionHasDERPNode(reg) {
need = append(need, reg)
}
}
if len(need) > 0 {
// Kick off ICMP in parallel to HTTPS checks; we don't
// reuse the same WaitGroup for those probes because we
// need to close the underlying Pinger after a timeout
// or when all ICMP probes are done, regardless of
// whether the HTTPS probes have finished.
wg.Add(1)
go func() {
defer wg.Done()
if err := c.measureAllICMPLatency(ctx, rs, need); err != nil {
c.logf("[v1] measureAllICMPLatency: %v", err)
}
}()
wg.Add(len(need))
c.logf("netcheck: UDP is blocked, trying HTTPS")
}
for _, reg := range need {
go func(reg *tailcfg.DERPRegion) {
defer wg.Done()
if d, ip, err := c.measureHTTPSLatency(ctx, reg); err != nil {
c.logf("[v1] netcheck: measuring HTTPS latency of %v (%d): %v", reg.RegionCode, reg.RegionID, err)
} else {
rs.mu.Lock()
if l, ok := rs.report.RegionLatency[reg.RegionID]; !ok {
mak.Set(&rs.report.RegionLatency, reg.RegionID, d)
} else if l >= d {
rs.report.RegionLatency[reg.RegionID] = d
}
// We set these IPv4 and IPv6 but they're not really used
// and we don't necessarily set them both. If UDP is blocked
// and both IPv4 and IPv6 are available over TCP, it's basically
// random which fields end up getting set here.
// Since they're not needed, that's fine for now.
if ip.Is4() {
rs.report.IPv4 = true
}
if ip.Is6() {
rs.report.IPv6 = true
}
rs.mu.Unlock()
}
}(reg)
}
wg.Wait()
}
return c.finishAndStoreReport(rs, dm), nil
}
func (c *Client) finishAndStoreReport(rs *reportState, dm *tailcfg.DERPMap) *Report {
rs.mu.Lock()
report := rs.report.Clone()
rs.mu.Unlock()
c.addReportHistoryAndSetPreferredDERP(report)
c.logConciseReport(report, dm)
return report
}
// runHTTPOnlyChecks is the netcheck done by environments that can
// only do HTTP requests, such as ws/wasm.
func (c *Client) runHTTPOnlyChecks(ctx context.Context, last *Report, rs *reportState, dm *tailcfg.DERPMap) error {
var regions []*tailcfg.DERPRegion
if rs.incremental && last != nil {
for rid := range last.RegionLatency {
if dr, ok := dm.Regions[rid]; ok {
regions = append(regions, dr)
}
}
}
if len(regions) == 0 {
for _, dr := range dm.Regions {
regions = append(regions, dr)
}
}
c.logf("running HTTP-only netcheck against %v regions", len(regions))
var wg sync.WaitGroup
for _, rg := range regions {
if len(rg.Nodes) == 0 {
continue
}
wg.Add(1)
rg := rg
go func() {
defer wg.Done()
node := rg.Nodes[0]
req, _ := http.NewRequestWithContext(ctx, "HEAD", "https://"+node.HostName+"/derp/probe", nil)
// One warm-up one to get HTTP connection set
// up and get a connection from the browser's
// pool.
if r, err := http.DefaultClient.Do(req); err != nil || r.StatusCode > 299 {
if err != nil {
c.logf("probing %s: %v", node.HostName, err)
} else {
c.logf("probing %s: unexpected status %s", node.HostName, r.Status)
}
return
}
t0 := c.timeNow()
if r, err := http.DefaultClient.Do(req); err != nil || r.StatusCode > 299 {
if err != nil {
c.logf("probing %s: %v", node.HostName, err)
} else {
c.logf("probing %s: unexpected status %s", node.HostName, r.Status)
}
return
}
d := c.timeNow().Sub(t0)
rs.addNodeLatency(node, netip.AddrPort{}, d)
}()
}
wg.Wait()
return nil
}
func (c *Client) measureHTTPSLatency(ctx context.Context, reg *tailcfg.DERPRegion) (time.Duration, netip.Addr, error) {
metricHTTPSend.Add(1)
var result httpstat.Result
ctx, cancel := context.WithTimeout(httpstat.WithHTTPStat(ctx, &result), overallProbeTimeout)
defer cancel()
var ip netip.Addr
dc := derphttp.NewNetcheckClient(c.logf)
tlsConn, tcpConn, node, err := dc.DialRegionTLS(ctx, reg)
if err != nil {
return 0, ip, err
}
defer tcpConn.Close()
if ta, ok := tlsConn.RemoteAddr().(*net.TCPAddr); ok {
ip, _ = netip.AddrFromSlice(ta.IP)
ip = ip.Unmap()
}
if ip == (netip.Addr{}) {
return 0, ip, fmt.Errorf("no unexpected RemoteAddr %#v", tlsConn.RemoteAddr())
}
connc := make(chan *tls.Conn, 1)
connc <- tlsConn
tr := &http.Transport{
DialContext: func(ctx context.Context, network, addr string) (net.Conn, error) {
return nil, errors.New("unexpected DialContext dial")
},
DialTLSContext: func(ctx context.Context, network, addr string) (net.Conn, error) {
select {
case nc := <-connc:
return nc, nil
default:
return nil, errors.New("only one conn expected")
}
},
}
hc := &http.Client{Transport: tr}
req, err := http.NewRequestWithContext(ctx, "GET", "https://"+node.HostName+"/derp/latency-check", nil)
if err != nil {
return 0, ip, err
}
resp, err := hc.Do(req)
if err != nil {
return 0, ip, err
}
defer resp.Body.Close()
// DERPs should give us a nominal status code, so anything else is probably
// an access denied by a MITM proxy (or at the very least a signal not to
// trust this latency check).
if resp.StatusCode > 299 {
return 0, ip, fmt.Errorf("unexpected status code: %d (%s)", resp.StatusCode, resp.Status)
}
_, err = io.Copy(io.Discard, io.LimitReader(resp.Body, 8<<10))
if err != nil {
return 0, ip, err
}
result.End(c.timeNow())
// TODO: decide best timing heuristic here.
// Maybe the server should return the tcpinfo_rtt?
return result.ServerProcessing, ip, nil
}
func (c *Client) measureAllICMPLatency(ctx context.Context, rs *reportState, need []*tailcfg.DERPRegion) error {
if len(need) == 0 {
return nil
}
ctx, done := context.WithTimeout(ctx, icmpProbeTimeout)
defer done()
p, err := ping.New(ctx, c.logf)
if err != nil {
return err
}
defer p.Close()
c.logf("UDP is blocked, trying ICMP")
var wg sync.WaitGroup
wg.Add(len(need))
for _, reg := range need {
go func(reg *tailcfg.DERPRegion) {
defer wg.Done()
if d, err := c.measureICMPLatency(ctx, reg, p); err != nil {
c.logf("[v1] measuring ICMP latency of %v (%d): %v", reg.RegionCode, reg.RegionID, err)
} else {
c.logf("[v1] ICMP latency of %v (%d): %v", reg.RegionCode, reg.RegionID, d)
rs.mu.Lock()
if l, ok := rs.report.RegionLatency[reg.RegionID]; !ok {
mak.Set(&rs.report.RegionLatency, reg.RegionID, d)
} else if l >= d {
rs.report.RegionLatency[reg.RegionID] = d
}
// We only send IPv4 ICMP right now
rs.report.IPv4 = true
rs.report.ICMPv4 = true
rs.mu.Unlock()
}
}(reg)
}
wg.Wait()
return nil
}
func (c *Client) measureICMPLatency(ctx context.Context, reg *tailcfg.DERPRegion, p *ping.Pinger) (time.Duration, error) {
if len(reg.Nodes) == 0 {
return 0, fmt.Errorf("no nodes for region %d (%v)", reg.RegionID, reg.RegionCode)
}
// Try pinging the first node in the region
node := reg.Nodes[0]
// Get the IPAddr by asking for the UDP address that we would use for
// STUN and then using that IP.
//
// TODO(andrew-d): this is a bit ugly
nodeAddr := c.nodeAddr(ctx, node, probeIPv4)
if !nodeAddr.IsValid() {
return 0, fmt.Errorf("no address for node %v", node.Name)
}
addr := &net.IPAddr{
IP: net.IP(nodeAddr.Addr().AsSlice()),
Zone: nodeAddr.Addr().Zone(),
}
// Use the unique node.Name field as the packet data to reduce the
// likelihood that we get a mismatched echo response.
return p.Send(ctx, addr, []byte(node.Name))
}
func (c *Client) logConciseReport(r *Report, dm *tailcfg.DERPMap) {
c.logf("[v1] report: %v", logger.ArgWriter(func(w *bufio.Writer) {
fmt.Fprintf(w, "udp=%v", r.UDP)
if !r.IPv4 {
fmt.Fprintf(w, " v4=%v", r.IPv4)
}
if !r.UDP {
fmt.Fprintf(w, " icmpv4=%v", r.ICMPv4)
}
fmt.Fprintf(w, " v6=%v", r.IPv6)
fmt.Fprintf(w, " mapvarydest=%v", r.MappingVariesByDestIP)
fmt.Fprintf(w, " hair=%v", r.HairPinning)
if r.AnyPortMappingChecked() {
fmt.Fprintf(w, " portmap=%v%v%v", conciseOptBool(r.UPnP, "U"), conciseOptBool(r.PMP, "M"), conciseOptBool(r.PCP, "C"))
} else {
fmt.Fprintf(w, " portmap=?")
}
if r.GlobalV4 != "" {
fmt.Fprintf(w, " v4a=%v", r.GlobalV4)
}
if r.GlobalV6 != "" {
fmt.Fprintf(w, " v6a=%v", r.GlobalV6)
}
fmt.Fprintf(w, " derp=%v", r.PreferredDERP)
if r.PreferredDERP != 0 {
fmt.Fprintf(w, " derpdist=")
needComma := false
for _, rid := range dm.RegionIDs() {
if d := r.RegionV4Latency[rid]; d != 0 {
if needComma {
w.WriteByte(',')
}
fmt.Fprintf(w, "%dv4:%v", rid, d.Round(time.Millisecond))
needComma = true
}
if d := r.RegionV6Latency[rid]; d != 0 {
if needComma {
w.WriteByte(',')
}
fmt.Fprintf(w, "%dv6:%v", rid, d.Round(time.Millisecond))
needComma = true
}
}
}
}))
}
func (c *Client) timeNow() time.Time {
if c.TimeNow != nil {
return c.TimeNow()
}
return time.Now()
}
// addReportHistoryAndSetPreferredDERP adds r to the set of recent Reports
// and mutates r.PreferredDERP to contain the best recent one.
func (c *Client) addReportHistoryAndSetPreferredDERP(r *Report) {
c.mu.Lock()
defer c.mu.Unlock()
var prevDERP int
if c.last != nil {
prevDERP = c.last.PreferredDERP
}
if c.prev == nil {
c.prev = map[time.Time]*Report{}
}
now := c.timeNow()
c.prev[now] = r
c.last = r
const maxAge = 5 * time.Minute
// region ID => its best recent latency in last maxAge
bestRecent := map[int]time.Duration{}
for t, pr := range c.prev {
if now.Sub(t) > maxAge {
delete(c.prev, t)
continue
}
for regionID, d := range pr.RegionLatency {
if bd, ok := bestRecent[regionID]; !ok || d < bd {
bestRecent[regionID] = d
}
}
}
// Then, pick which currently-alive DERP server from the
// current report has the best latency over the past maxAge.
var bestAny time.Duration
var oldRegionCurLatency time.Duration
for regionID, d := range r.RegionLatency {
if regionID == prevDERP {
oldRegionCurLatency = d
}
best := bestRecent[regionID]
if r.PreferredDERP == 0 || best < bestAny {
bestAny = best
r.PreferredDERP = regionID
}
}
// If we're changing our preferred DERP but the old one's still
// accessible and the new one's not much better, just stick with
// where we are.
if prevDERP != 0 &&
r.PreferredDERP != prevDERP &&
oldRegionCurLatency != 0 &&
bestAny > oldRegionCurLatency/3*2 {
r.PreferredDERP = prevDERP
}
}
func updateLatency(m map[int]time.Duration, regionID int, d time.Duration) {
if prev, ok := m[regionID]; !ok || d < prev {
m[regionID] = d
}
}
func namedNode(dm *tailcfg.DERPMap, nodeName string) *tailcfg.DERPNode {
if dm == nil {
return nil
}
for _, r := range dm.Regions {
for _, n := range r.Nodes {
if n.Name == nodeName {
return n
}
}
}
return nil
}
func (rs *reportState) runProbe(ctx context.Context, dm *tailcfg.DERPMap, probe probe, cancelSet func()) {
c := rs.c
node := namedNode(dm, probe.node)
if node == nil {
c.logf("netcheck.runProbe: named node %q not found", probe.node)
return
}
if probe.delay > 0 {
delayTimer := time.NewTimer(probe.delay)
select {
case <-delayTimer.C:
case <-ctx.Done():
delayTimer.Stop()
return
}
}
if !rs.probeWouldHelp(probe, node) {
cancelSet()
return
}
addr := c.nodeAddr(ctx, node, probe.proto)
if !addr.IsValid() {
return
}
txID := stun.NewTxID()
req := stun.Request(txID)
sent := time.Now() // after DNS lookup above
rs.mu.Lock()
rs.inFlight[txID] = func(ipp netip.AddrPort) {
rs.addNodeLatency(node, ipp, time.Since(sent))
cancelSet() // abort other nodes in this set
}
rs.mu.Unlock()
switch probe.proto {
case probeIPv4:
metricSTUNSend4.Add(1)
n, err := rs.pc4.WriteToUDPAddrPort(req, addr)
if n == len(req) && err == nil || neterror.TreatAsLostUDP(err) {
rs.mu.Lock()
rs.report.IPv4CanSend = true
rs.mu.Unlock()
}
case probeIPv6:
metricSTUNSend6.Add(1)
n, err := rs.pc6.WriteToUDPAddrPort(req, addr)
if n == len(req) && err == nil || neterror.TreatAsLostUDP(err) {
rs.mu.Lock()
rs.report.IPv6CanSend = true
rs.mu.Unlock()
}
default:
panic("bad probe proto " + fmt.Sprint(probe.proto))
}
c.vlogf("sent to %v", addr)
}
// proto is 4 or 6
// If it returns nil, the node is skipped.
func (c *Client) nodeAddr(ctx context.Context, n *tailcfg.DERPNode, proto probeProto) (ap netip.AddrPort) {
port := n.STUNPort
if port == 0 {
port = 3478
}
if port < 0 || port > 1<<16-1 {
return
}
if n.STUNTestIP != "" {
ip, err := netip.ParseAddr(n.STUNTestIP)
if err != nil {
return
}
if proto == probeIPv4 && ip.Is6() {
return
}
if proto == probeIPv6 && ip.Is4() {
return
}
return netip.AddrPortFrom(ip, uint16(port))
}
switch proto {
case probeIPv4:
if n.IPv4 != "" {
ip, _ := netip.ParseAddr(n.IPv4)
if !ip.Is4() {
return
}
return netip.AddrPortFrom(ip, uint16(port))
}
case probeIPv6:
if n.IPv6 != "" {
ip, _ := netip.ParseAddr(n.IPv6)
if !ip.Is6() {
return
}
return netip.AddrPortFrom(ip, uint16(port))
}
default:
return
}
// TODO(bradfitz): add singleflight+dnscache here.
addrs, _ := net.DefaultResolver.LookupIPAddr(ctx, n.HostName)
for _, a := range addrs {
if (a.IP.To4() != nil) == (proto == probeIPv4) {
na, _ := netip.AddrFromSlice(a.IP.To4())
return netip.AddrPortFrom(na.Unmap(), uint16(port))
}
}
return
}
func regionHasDERPNode(r *tailcfg.DERPRegion) bool {
for _, n := range r.Nodes {
if !n.STUNOnly {
return true
}
}
return false
}
func maxDurationValue(m map[int]time.Duration) (max time.Duration) {
for _, v := range m {
if v > max {
max = v
}
}
return max
}
func conciseOptBool(b opt.Bool, trueVal string) string {
if b == "" {
return "_"
}
v, ok := b.Get()
if !ok {
return "x"
}
if v {
return trueVal
}
return ""
}
var (
metricNumGetReport = clientmetric.NewCounter("netcheck_report")
metricNumGetReportFull = clientmetric.NewCounter("netcheck_report_full")
metricNumGetReportError = clientmetric.NewCounter("netcheck_report_error")
metricSTUNSend4 = clientmetric.NewCounter("netcheck_stun_send_ipv4")
metricSTUNSend6 = clientmetric.NewCounter("netcheck_stun_send_ipv6")
metricSTUNRecv4 = clientmetric.NewCounter("netcheck_stun_recv_ipv4")
metricSTUNRecv6 = clientmetric.NewCounter("netcheck_stun_recv_ipv6")
metricHTTPSend = clientmetric.NewCounter("netcheck_https_measure")
)