tailscale/net/tsdial/tsdial.go

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// Copyright (c) Tailscale Inc & AUTHORS
// SPDX-License-Identifier: BSD-3-Clause
// Package tsdial provides a Dialer type that can dial out of tailscaled.
package tsdial
import (
"context"
"errors"
"fmt"
"net"
"net/http"
"net/netip"
"runtime"
"strings"
"sync"
"sync/atomic"
"syscall"
"time"
"github.com/gaissmai/bart"
"tailscale.com/net/dnscache"
"tailscale.com/net/netknob"
"tailscale.com/net/netmon"
"tailscale.com/net/netns"
"tailscale.com/net/tsaddr"
"tailscale.com/types/logger"
"tailscale.com/types/netmap"
"tailscale.com/util/clientmetric"
"tailscale.com/util/mak"
"tailscale.com/util/testenv"
"tailscale.com/version"
)
// NewDialer returns a new Dialer that can dial out of tailscaled.
// Its exported fields should be set before use, if any.
func NewDialer(netMon *netmon.Monitor) *Dialer {
if netMon == nil {
panic("NewDialer: netMon is nil")
}
d := &Dialer{}
d.SetNetMon(netMon)
return d
}
// Dialer dials out of tailscaled, while taking care of details while
// handling the dozens of edge cases depending on the server mode
// (TUN, netstack), the OS network sandboxing style (macOS/iOS
// Extension, none), user-selected route acceptance prefs, etc.
//
// Before use, SetNetMon should be called with a netmon.Monitor.
type Dialer struct {
Logf logger.Logf
// UseNetstackForIP if non-nil is whether NetstackDialTCP (if
// it's non-nil) should be used to dial the provided IP.
UseNetstackForIP func(netip.Addr) bool
// NetstackDialTCP dials the provided IPPort using netstack.
// If nil, it's not used.
NetstackDialTCP func(context.Context, netip.AddrPort) (net.Conn, error)
// NetstackDialUDP dials the provided IPPort using netstack.
// If nil, it's not used.
NetstackDialUDP func(context.Context, netip.AddrPort) (net.Conn, error)
peerClientOnce sync.Once
peerClient *http.Client
peerDialerOnce sync.Once
peerDialer *net.Dialer
netnsDialerOnce sync.Once
netnsDialer netns.Dialer
routes atomic.Pointer[bart.Table[bool]] // or nil if UserDial should not use routes. `true` indicates routes that point into the Tailscale interface
mu sync.Mutex
closed bool
dns dnsMap
tunName string // tun device name
netMon *netmon.Monitor
netMonUnregister func()
exitDNSDoHBase string // non-empty if DoH-proxying exit node in use; base URL+path (without '?')
dnsCache *dnscache.MessageCache // nil until first non-empty SetExitDNSDoH
nextSysConnID int
activeSysConns map[int]net.Conn // active connections not yet closed
}
// sysConn wraps a net.Conn that was created using d.SystemDial.
// It exists to track which connections are still open, and should be
// closed on major link changes.
type sysConn struct {
net.Conn
id int
d *Dialer
}
func (c sysConn) Close() error {
c.d.closeSysConn(c.id)
return nil
}
// SetTUNName sets the name of the tun device in use ("tailscale0", "utun6",
// etc). This is needed on some platforms to set sockopts to bind
// to the same interface index.
func (d *Dialer) SetTUNName(name string) {
d.mu.Lock()
defer d.mu.Unlock()
d.tunName = name
}
// TUNName returns the name of the tun device in use, if any.
// Example format ("tailscale0", "utun6").
func (d *Dialer) TUNName() string {
d.mu.Lock()
defer d.mu.Unlock()
return d.tunName
}
// SetExitDNSDoH sets (or clears) the exit node DNS DoH server base URL to use.
// The doh URL should contain the scheme, authority, and path, but without
// a '?' and/or query parameters.
//
// For example, "http://100.68.82.120:47830/dns-query".
func (d *Dialer) SetExitDNSDoH(doh string) {
d.mu.Lock()
defer d.mu.Unlock()
if d.exitDNSDoHBase == doh {
return
}
d.exitDNSDoHBase = doh
if doh != "" && d.dnsCache == nil {
d.dnsCache = new(dnscache.MessageCache)
}
if d.dnsCache != nil {
d.dnsCache.Flush()
}
}
// SetRoutes configures the dialer to dial the specified routes via Tailscale,
// and the specified localRoutes using the default interface.
func (d *Dialer) SetRoutes(routes, localRoutes []netip.Prefix) {
var rt *bart.Table[bool]
if len(routes) > 0 || len(localRoutes) > 0 {
rt = &bart.Table[bool]{}
for _, r := range routes {
rt.Insert(r, true)
}
for _, r := range localRoutes {
rt.Insert(r, false)
}
}
d.routes.Store(rt)
}
func (d *Dialer) Close() error {
d.mu.Lock()
defer d.mu.Unlock()
d.closed = true
if d.netMonUnregister != nil {
d.netMonUnregister()
d.netMonUnregister = nil
}
for _, c := range d.activeSysConns {
c.Close()
}
d.activeSysConns = nil
return nil
}
// SetNetMon sets d's network monitor to netMon.
// It is a no-op to call SetNetMon with the same netMon as the current one.
func (d *Dialer) SetNetMon(netMon *netmon.Monitor) {
d.mu.Lock()
defer d.mu.Unlock()
if d.netMon == netMon {
return
}
if d.netMonUnregister != nil {
go d.netMonUnregister()
d.netMonUnregister = nil
}
d.netMon = netMon
d.netMonUnregister = d.netMon.RegisterChangeCallback(d.linkChanged)
}
// NetMon returns the Dialer's network monitor.
// It returns nil if SetNetMon has not been called.
func (d *Dialer) NetMon() *netmon.Monitor {
d.mu.Lock()
defer d.mu.Unlock()
return d.netMon
}
var (
metricLinkChangeConnClosed = clientmetric.NewCounter("tsdial_linkchange_closes")
metricChangeDeltaNoDefaultRoute = clientmetric.NewCounter("tsdial_changedelta_no_default_route")
)
func (d *Dialer) linkChanged(delta *netmon.ChangeDelta) {
// Track how often we see ChangeDeltas with no DefaultRouteInterface.
if delta.New.DefaultRouteInterface == "" {
metricChangeDeltaNoDefaultRoute.Add(1)
}
d.mu.Lock()
defer d.mu.Unlock()
var anyClosed bool
for id, c := range d.activeSysConns {
if changeAffectsConn(delta, c) {
anyClosed = true
d.logf("tsdial: closing system connection %v->%v due to link change", c.LocalAddr(), c.RemoteAddr())
go c.Close()
delete(d.activeSysConns, id)
}
}
if anyClosed {
metricLinkChangeConnClosed.Add(1)
}
}
// changeAffectsConn reports whether the network change delta affects
// the provided connection.
func changeAffectsConn(delta *netmon.ChangeDelta, conn net.Conn) bool {
la, _ := conn.LocalAddr().(*net.TCPAddr)
ra, _ := conn.RemoteAddr().(*net.TCPAddr)
if la == nil || ra == nil {
return false // not TCP
}
lip, rip := la.AddrPort().Addr(), ra.AddrPort().Addr()
if delta.Old == nil {
return false
}
if delta.Old.DefaultRouteInterface != delta.New.DefaultRouteInterface ||
delta.Old.HTTPProxy != delta.New.HTTPProxy {
return true
}
// In a few cases, we don't have a new DefaultRouteInterface (e.g. on
// Android; see tailscale/corp#19124); if so, pessimistically assume
// that all connections are affected.
if delta.New.DefaultRouteInterface == "" {
return true
}
if !delta.New.HasIP(lip) && delta.Old.HasIP(lip) {
// Our interface with this source IP went away.
return true
}
_ = rip // TODO(bradfitz): use the remote IP?
return false
}
func (d *Dialer) closeSysConn(id int) {
d.mu.Lock()
defer d.mu.Unlock()
c, ok := d.activeSysConns[id]
if !ok {
return
}
delete(d.activeSysConns, id)
go c.Close() // ignore the error
}
// peerDialControlFunc is non-nil on platforms that require a way to
// bind to dial out to other peers.
var peerDialControlFunc func(*Dialer) func(network, address string, c syscall.RawConn) error
// PeerDialControlFunc returns a function
// that can assigned to net.Dialer.Control to set sockopts or whatnot
// to make a dial escape the current platform's network sandbox.
//
// On many platforms the returned func will be nil.
//
// Notably, this is non-nil on iOS and macOS when run as a Network or
// System Extension (the GUI variants).
func (d *Dialer) PeerDialControlFunc() func(network, address string, c syscall.RawConn) error {
if peerDialControlFunc == nil {
return nil
}
return peerDialControlFunc(d)
}
// SetNetMap sets the current network map and notably, the DNS names
// in its DNS configuration.
func (d *Dialer) SetNetMap(nm *netmap.NetworkMap) {
m := dnsMapFromNetworkMap(nm)
d.mu.Lock()
defer d.mu.Unlock()
d.dns = m
}
// userDialResolve resolves addr as if a user initiating the dial. (e.g. from a
// SOCKS or HTTP outbound proxy)
func (d *Dialer) userDialResolve(ctx context.Context, network, addr string) (netip.AddrPort, error) {
d.mu.Lock()
dns := d.dns
exitDNSDoH := d.exitDNSDoHBase
d.mu.Unlock()
// MagicDNS or otherwise baked into the NetworkMap? Try that first.
ipp, err := dns.resolveMemory(ctx, network, addr)
if err != errUnresolved {
return ipp, err
}
// Otherwise, hit the network.
// TODO(bradfitz): wire up net/dnscache too.
host, port, err := splitHostPort(addr)
if err != nil {
// addr is malformed.
return netip.AddrPort{}, err
}
var r net.Resolver
if exitDNSDoH != "" && runtime.GOOS != "windows" { // Windows: https://github.com/golang/go/issues/33097
r.PreferGo = true
r.Dial = func(ctx context.Context, network, address string) (net.Conn, error) {
return &dohConn{
ctx: ctx,
baseURL: exitDNSDoH,
hc: d.PeerAPIHTTPClient(),
dnsCache: d.dnsCache,
}, nil
}
}
ips, err := r.LookupIP(ctx, ipNetOfNetwork(network), host)
if err != nil {
return netip.AddrPort{}, err
}
if len(ips) == 0 {
return netip.AddrPort{}, fmt.Errorf("DNS lookup returned no results for %q", host)
}
ip, _ := netip.AddrFromSlice(ips[0])
return netip.AddrPortFrom(ip.Unmap(), port), nil
}
// ipNetOfNetwork returns "ip", "ip4", or "ip6" corresponding
// to the input value of "tcp", "tcp4", "udp6" etc network
// names.
func ipNetOfNetwork(n string) string {
if strings.HasSuffix(n, "4") {
return "ip4"
}
if strings.HasSuffix(n, "6") {
return "ip6"
}
return "ip"
}
func (d *Dialer) logf(format string, args ...any) {
if d.Logf != nil {
d.Logf(format, args...)
}
}
// SystemDial connects to the provided network address without going over
// Tailscale. It prefers going over the default interface and closes existing
// connections if the default interface changes. It is used to connect to
// Control and (in the future, as of 2022-04-27) DERPs..
func (d *Dialer) SystemDial(ctx context.Context, network, addr string) (net.Conn, error) {
d.mu.Lock()
if d.netMon == nil {
d.mu.Unlock()
if testenv.InTest() {
panic("SystemDial requires a netmon.Monitor; call SetNetMon first")
}
return nil, errors.New("SystemDial requires a netmon.Monitor; call SetNetMon first")
}
closed := d.closed
d.mu.Unlock()
if closed {
return nil, net.ErrClosed
}
d.netnsDialerOnce.Do(func() {
d.netnsDialer = netns.NewDialer(d.logf, d.netMon)
})
c, err := d.netnsDialer.DialContext(ctx, network, addr)
if err != nil {
return nil, err
}
d.mu.Lock()
defer d.mu.Unlock()
id := d.nextSysConnID
d.nextSysConnID++
mak.Set(&d.activeSysConns, id, c)
return sysConn{
id: id,
d: d,
Conn: c,
}, nil
}
// UserDial connects to the provided network address as if a user were
// initiating the dial. (e.g. from a SOCKS or HTTP outbound proxy)
func (d *Dialer) UserDial(ctx context.Context, network, addr string) (net.Conn, error) {
ipp, err := d.userDialResolve(ctx, network, addr)
if err != nil {
return nil, err
}
if d.UseNetstackForIP != nil && d.UseNetstackForIP(ipp.Addr()) {
if d.NetstackDialTCP == nil || d.NetstackDialUDP == nil {
return nil, errors.New("Dialer not initialized correctly")
}
if strings.HasPrefix(network, "udp") {
return d.NetstackDialUDP(ctx, ipp)
}
return d.NetstackDialTCP(ctx, ipp)
}
if routes := d.routes.Load(); routes != nil {
if isTailscaleRoute, _ := routes.Lookup(ipp.Addr()); isTailscaleRoute {
return d.getPeerDialer().DialContext(ctx, network, ipp.String())
}
return d.SystemDial(ctx, network, ipp.String())
}
// Workaround for macOS for now: dial Tailscale IPs with peer dialer.
// TODO(bradfitz): fix dialing subnet routers, public IPs via exit nodes,
// etc. This is a temporary partial for macOS. We need to plumb ART tables &
// prefs & host routing table updates around in more places. We just don't
// know from the limited context here how to dial properly.
if version.IsMacGUIVariant() && tsaddr.IsTailscaleIP(ipp.Addr()) {
return d.getPeerDialer().DialContext(ctx, network, ipp.String())
}
// TODO(bradfitz): netns, etc
var stdDialer net.Dialer
return stdDialer.DialContext(ctx, network, ipp.String())
}
// dialPeerAPI connects to a Tailscale peer's peerapi over TCP.
//
// network must a "tcp" type, and addr must be an ip:port. Name resolution
// is not supported.
func (d *Dialer) dialPeerAPI(ctx context.Context, network, addr string) (net.Conn, error) {
switch network {
case "tcp", "tcp6", "tcp4":
default:
return nil, fmt.Errorf("peerAPI dial requires tcp; %q not supported", network)
}
ipp, err := netip.ParseAddrPort(addr)
if err != nil {
return nil, fmt.Errorf("peerAPI dial requires ip:port, not name resolution: %w", err)
}
if d.UseNetstackForIP != nil && d.UseNetstackForIP(ipp.Addr()) {
if d.NetstackDialTCP == nil {
return nil, errors.New("Dialer not initialized correctly")
}
return d.NetstackDialTCP(ctx, ipp)
}
return d.getPeerDialer().DialContext(ctx, network, addr)
}
// getPeerDialer returns the *net.Dialer to use to dial peers (e.g. for peerapi,
// "tailscale nc", or querying internal DNS servers over Tailscale)
//
// This is not used in netstack mode.
//
// The primary function of this is to work on macOS & iOS's in the
// Network/System Extension so it can mark the dialer as staying within the
// network namespace/sandbox.
func (d *Dialer) getPeerDialer() *net.Dialer {
d.peerDialerOnce.Do(func() {
d.peerDialer = &net.Dialer{
Timeout: 30 * time.Second,
KeepAlive: netknob.PlatformTCPKeepAlive(),
Control: d.PeerDialControlFunc(),
}
})
return d.peerDialer
}
// PeerAPIHTTPClient returns an HTTP Client to call peers' peerapi
// endpoints. //
// The returned Client must not be mutated; it's owned by the Dialer
// and shared by callers.
func (d *Dialer) PeerAPIHTTPClient() *http.Client {
d.peerClientOnce.Do(func() {
t := http.DefaultTransport.(*http.Transport).Clone()
t.Dial = nil
t.DialContext = d.dialPeerAPI
// Do not use the environment proxy for PeerAPI.
t.Proxy = nil
d.peerClient = &http.Client{Transport: t}
})
return d.peerClient
}
// PeerAPITransport returns a Transport to call peers' peerapi
// endpoints.
//
// The returned value must not be mutated; it's owned by the Dialer
// and shared by callers.
func (d *Dialer) PeerAPITransport() *http.Transport {
return d.PeerAPIHTTPClient().Transport.(*http.Transport)
}