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tailscale/net/portmapper/upnp.go

326 lines
9.5 KiB
Go

// 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.
//go:build !ios
// +build !ios
// (https://github.com/tailscale/tailscale/issues/2495)
package portmapper
import (
"bufio"
"bytes"
"context"
"fmt"
"math/rand"
"net/http"
"net/url"
"strings"
"time"
"github.com/tailscale/goupnp"
"github.com/tailscale/goupnp/dcps/internetgateway2"
"inet.af/netaddr"
"tailscale.com/control/controlknobs"
"tailscale.com/net/netns"
"tailscale.com/types/logger"
)
// References:
//
// WANIP Connection v2: http://upnp.org/specs/gw/UPnP-gw-WANIPConnection-v2-Service.pdf
// upnpMapping is a port mapping over the upnp protocol. After being created it is immutable,
// but the client field may be shared across mapping instances.
type upnpMapping struct {
gw netaddr.IP
external netaddr.IPPort
internal netaddr.IPPort
goodUntil time.Time
renewAfter time.Time
// client is a connection to a upnp device, and may be reused across different UPnP mappings.
client upnpClient
}
func (u *upnpMapping) GoodUntil() time.Time { return u.goodUntil }
func (u *upnpMapping) RenewAfter() time.Time { return u.renewAfter }
func (u *upnpMapping) External() netaddr.IPPort { return u.external }
func (u *upnpMapping) Release(ctx context.Context) {
u.client.DeletePortMapping(ctx, "", u.external.Port(), "udp")
}
// upnpClient is an interface over the multiple different clients exported by goupnp,
// exposing the functions we need for portmapping. Those clients are auto-generated from XML-specs,
// which is why they're not very idiomatic.
type upnpClient interface {
AddPortMapping(
ctx context.Context,
// remoteHost is the remote device sending packets to this device, in the format of x.x.x.x.
// The empty string, "", means any host out on the internet can send packets in.
remoteHost string,
// externalPort is the exposed port of this port mapping. Visible during NAT operations.
// 0 will let the router select the port, but there is an additional call,
// `AddAnyPortMapping`, which is available on 1 of the 3 possible protocols,
// which should be used if available. See `addAnyPortMapping` below, which calls this if
// `AddAnyPortMapping` is not supported.
externalPort uint16,
// protocol is whether this is over TCP or UDP. Either "tcp" or "udp".
protocol string,
// internalPort is the port that the gateway device forwards the traffic to.
internalPort uint16,
// internalClient is the IP address that packets will be forwarded to for this mapping.
// Internal client is of the form "x.x.x.x".
internalClient string,
// enabled is whether this portmapping should be enabled or disabled.
enabled bool,
// portMappingDescription is a user-readable description of this portmapping.
portMappingDescription string,
// leaseDurationSec is the duration of this portmapping. The value of this argument must be
// greater than 0. From the spec, it appears if it is set to 0, it will switch to using
// 604800 seconds, but not sure why this is desired. The recommended time is 3600 seconds.
leaseDurationSec uint32,
) error
DeletePortMapping(ctx context.Context, remoteHost string, externalPort uint16, protocol string) error
GetExternalIPAddress(ctx context.Context) (externalIPAddress string, err error)
}
// tsPortMappingDesc gets sent to UPnP clients as a human-readable label for the portmapping.
// It is not used for anything other than labelling.
const tsPortMappingDesc = "tailscale-portmap"
// addAnyPortMapping abstracts over different UPnP client connections, calling the available
// AddAnyPortMapping call if available for WAN IP connection v2, otherwise defaulting to the old
// behavior of calling AddPortMapping with port = 0 to specify a wildcard port.
// It returns the new external port (which may not be identical to the external port specified),
// or an error.
//
// TODO(bradfitz): also returned the actual lease duration obtained. and check it regularly.
func addAnyPortMapping(
ctx context.Context,
upnp upnpClient,
externalPort uint16,
internalPort uint16,
internalClient string,
leaseDuration time.Duration,
) (newPort uint16, err error) {
if upnp, ok := upnp.(*internetgateway2.WANIPConnection2); ok {
return upnp.AddAnyPortMapping(
ctx,
"",
externalPort,
"udp",
internalPort,
internalClient,
true,
tsPortMappingDesc,
uint32(leaseDuration.Seconds()),
)
}
for externalPort == 0 {
externalPort = uint16(rand.Intn(65535))
}
err = upnp.AddPortMapping(
ctx,
"",
externalPort,
"udp",
internalPort,
internalClient,
true,
tsPortMappingDesc,
uint32(leaseDuration.Seconds()),
)
return externalPort, err
}
// getUPnPClient gets a client for interfacing with UPnP, ignoring the underlying protocol for
// now.
// Adapted from https://github.com/huin/goupnp/blob/master/GUIDE.md.
//
// The gw is the detected gateway.
//
// The meta is the most recently parsed UDP discovery packet response
// from the Internet Gateway Device.
//
// The provided ctx is not retained in the returned upnpClient, but
// its associated HTTP client is (if set via goupnp.WithHTTPClient).
func getUPnPClient(ctx context.Context, logf logger.Logf, gw netaddr.IP, meta uPnPDiscoResponse) (client upnpClient, err error) {
if controlknobs.DisableUPnP() || DisableUPnP {
return nil, nil
}
if meta.Location == "" {
return nil, nil
}
if VerboseLogs {
logf("fetching %v", meta.Location)
}
u, err := url.Parse(meta.Location)
if err != nil {
return nil, err
}
ipp, err := netaddr.ParseIPPort(u.Host)
if err != nil {
return nil, fmt.Errorf("unexpected host %q in %q", u.Host, meta.Location)
}
if ipp.IP() != gw {
return nil, fmt.Errorf("UPnP discovered root %q does not match gateway IP %v; ignoring UPnP",
meta.Location, gw)
}
// We're fetching a smallish XML document over plain HTTP
// across the local LAN, without using DNS. There should be
// very few round trips and low latency, so one second is a
// long time.
ctx, cancel := context.WithTimeout(ctx, time.Second)
defer cancel()
// This part does a network fetch.
root, err := goupnp.DeviceByURL(ctx, u)
if err != nil {
return nil, err
}
defer func() {
if client == nil {
return
}
logf("saw UPnP type %v at %v; %v (%v)",
strings.TrimPrefix(fmt.Sprintf("%T", client), "*internetgateway2."),
meta.Location, root.Device.FriendlyName, root.Device.Manufacturer)
}()
// These parts don't do a network fetch.
// Pick the best service type available.
if cc, _ := internetgateway2.NewWANIPConnection2ClientsFromRootDevice(ctx, root, u); len(cc) > 0 {
return cc[0], nil
}
if cc, _ := internetgateway2.NewWANIPConnection1ClientsFromRootDevice(ctx, root, u); len(cc) > 0 {
return cc[0], nil
}
if cc, _ := internetgateway2.NewWANPPPConnection1ClientsFromRootDevice(ctx, root, u); len(cc) > 0 {
return cc[0], nil
}
return nil, nil
}
func (c *Client) upnpHTTPClientLocked() *http.Client {
if c.uPnPHTTPClient == nil {
c.uPnPHTTPClient = &http.Client{
Transport: &http.Transport{
DialContext: netns.NewDialer().DialContext,
IdleConnTimeout: 2 * time.Second, // LAN is cheap
},
}
}
return c.uPnPHTTPClient
}
// getUPnPPortMapping attempts to create a port-mapping over the UPnP protocol. On success,
// it will return the externally exposed IP and port. Otherwise, it will return a zeroed IP and
// port and an error.
func (c *Client) getUPnPPortMapping(
ctx context.Context,
gw netaddr.IP,
internal netaddr.IPPort,
prevPort uint16,
) (external netaddr.IPPort, ok bool) {
if controlknobs.DisableUPnP() || DisableUPnP {
return netaddr.IPPort{}, false
}
now := time.Now()
upnp := &upnpMapping{
gw: gw,
internal: internal,
}
var client upnpClient
var err error
c.mu.Lock()
oldMapping, ok := c.mapping.(*upnpMapping)
meta := c.uPnPMeta
httpClient := c.upnpHTTPClientLocked()
c.mu.Unlock()
if ok && oldMapping != nil {
client = oldMapping.client
} else {
ctx := goupnp.WithHTTPClient(ctx, httpClient)
client, err = getUPnPClient(ctx, c.logf, gw, meta)
if VerboseLogs {
c.logf("getUPnPClient: %T, %v", client, err)
}
if err != nil {
return netaddr.IPPort{}, false
}
}
if client == nil {
return netaddr.IPPort{}, false
}
var newPort uint16
newPort, err = addAnyPortMapping(
ctx,
client,
prevPort,
internal.Port(),
internal.IP().String(),
time.Second*pmpMapLifetimeSec,
)
if VerboseLogs {
c.logf("addAnyPortMapping: %v, %v", newPort, err)
}
if err != nil {
return netaddr.IPPort{}, false
}
// TODO cache this ip somewhere?
extIP, err := client.GetExternalIPAddress(ctx)
if VerboseLogs {
c.logf("client.GetExternalIPAddress: %v, %v", extIP, err)
}
if err != nil {
// TODO this doesn't seem right
return netaddr.IPPort{}, false
}
externalIP, err := netaddr.ParseIP(extIP)
if err != nil {
return netaddr.IPPort{}, false
}
upnp.external = netaddr.IPPortFrom(externalIP, newPort)
d := time.Duration(pmpMapLifetimeSec) * time.Second
upnp.goodUntil = now.Add(d)
upnp.renewAfter = now.Add(d / 2)
upnp.client = client
c.mu.Lock()
defer c.mu.Unlock()
c.mapping = upnp
c.localPort = newPort
return upnp.external, true
}
type uPnPDiscoResponse struct {
Location string
}
// parseUPnPDiscoResponse parses a UPnP HTTP-over-UDP discovery response.
func parseUPnPDiscoResponse(body []byte) (uPnPDiscoResponse, error) {
var r uPnPDiscoResponse
res, err := http.ReadResponse(bufio.NewReaderSize(bytes.NewReader(body), 128), nil)
if err != nil {
return r, err
}
r.Location = res.Header.Get("Location")
return r, nil
}