tailscale/net/tsdial/tsdial.go

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// Copyright (c) 2021 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 tsdial provides a Dialer type that can dial out of tailscaled.
package tsdial
import (
"context"
"errors"
"fmt"
"net"
"net/http"
"runtime"
"strings"
"sync"
"sync/atomic"
"syscall"
"time"
"inet.af/netaddr"
"tailscale.com/net/dnscache"
"tailscale.com/net/netknob"
"tailscale.com/types/netmap"
"tailscale.com/wgengine/monitor"
)
// 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.
type Dialer struct {
// UseNetstackForIP if non-nil is whether NetstackDialTCP (if
// it's non-nil) should be used to dial the provided IP.
UseNetstackForIP func(netaddr.IP) bool
// NetstackDialTCP dials the provided IPPort using netstack.
// If nil, it's not used.
NetstackDialTCP func(context.Context, netaddr.IPPort) (net.Conn, error)
peerDialControlFuncAtomic atomic.Value // of func() func(network, address string, c syscall.RawConn) error
peerClientOnce sync.Once
peerClient *http.Client
peerDialerOnce sync.Once
peerDialer *net.Dialer
mu sync.Mutex
dns dnsMap
tunName string // tun device name
linkMon *monitor.Mon
exitDNSDoHBase string // non-empty if DoH-proxying exit node in use; base URL+path (without '?')
dnsCache *dnscache.MessageCache // nil until first first non-empty SetExitDNSDoH
}
// 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()
}
}
func (d *Dialer) SetLinkMonitor(mon *monitor.Mon) {
d.mu.Lock()
defer d.mu.Unlock()
d.linkMon = mon
}
func (d *Dialer) interfaceIndexLocked(ifName string) (index int, ok bool) {
if d.linkMon == nil {
return 0, false
}
st := d.linkMon.InterfaceState()
iface, ok := st.Interface[ifName]
if !ok {
return 0, false
}
return iface.Index, true
}
// 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
}
func (d *Dialer) userDialResolve(ctx context.Context, network, addr string) (netaddr.IPPort, error) {
d.mu.Lock()
dns := d.dns
exitDNSDoH := d.exitDNSDoHBase
d.mu.Unlock()
// MagicDNS or otherwise baked in to 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 netaddr.IPPort{}, 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 netaddr.IPPort{}, err
}
if len(ips) == 0 {
return netaddr.IPPort{}, fmt.Errorf("DNS lookup returned no results for %q", host)
}
ip, _ := netaddr.FromStdIP(ips[0])
return netaddr.IPPortFrom(ip, 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"
}
// 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.IP()) {
if d.NetstackDialTCP == nil {
return nil, errors.New("Dialer not initialized correctly")
}
return d.NetstackDialTCP(ctx, ipp)
}
// 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 := netaddr.ParseIPPort(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.IP()) {
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 to use
// peer API.
//
// 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
// withing 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
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)
}