mirror of
https://github.com/tailscale/tailscale.git
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6fb5d4080c
Fixes #1525. Signed-off-by: David Anderson <danderson@tailscale.com>
641 lines
17 KiB
Go
641 lines
17 KiB
Go
// Copyright (c) 2021 Tailscale Inc & AUTHORS All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Package portmapper is a UDP port mapping client. It currently only does
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// NAT-PMP, but will likely do UPnP and perhaps PCP later.
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package portmapper
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import (
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"context"
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"crypto/rand"
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"encoding/binary"
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"errors"
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"fmt"
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"io"
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"net"
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"sync"
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"time"
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"go4.org/mem"
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"inet.af/netaddr"
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"tailscale.com/net/interfaces"
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"tailscale.com/net/netns"
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"tailscale.com/types/logger"
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)
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// References:
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//
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// NAT-PMP: https://tools.ietf.org/html/rfc6886
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// PCP: https://tools.ietf.org/html/rfc6887
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// portMapServiceTimeout is the time we wait for port mapping
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// services (UPnP, NAT-PMP, PCP) to respond before we give up and
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// decide that they're not there. Since these services are on the
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// same LAN as this machine and a single L3 hop away, we don't
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// give them much time to respond.
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const portMapServiceTimeout = 250 * time.Millisecond
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// trustServiceStillAvailableDuration is how often we re-verify a port
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// mapping service is available.
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const trustServiceStillAvailableDuration = 10 * time.Minute
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// Client is a port mapping client.
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type Client struct {
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logf logger.Logf
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ipAndGateway func() (gw, ip netaddr.IP, ok bool)
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mu sync.Mutex // guards following, and all fields thereof
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lastMyIP netaddr.IP
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lastGW netaddr.IP
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closed bool
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lastProbe time.Time
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pmpPubIP netaddr.IP // non-zero if known
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pmpPubIPTime time.Time // time pmpPubIP last verified
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pmpLastEpoch uint32
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pcpSawTime time.Time // time we last saw PCP was available
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uPnPSawTime time.Time // time we last saw UPnP was available
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localPort uint16
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pmpMapping *pmpMapping // non-nil if we have a PMP mapping
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}
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// HaveMapping reports whether we have a current valid mapping.
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func (c *Client) HaveMapping() bool {
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c.mu.Lock()
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defer c.mu.Unlock()
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return c.pmpMapping != nil && c.pmpMapping.useUntil.After(time.Now())
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}
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// pmpMapping is an already-created PMP mapping.
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//
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// All fields are immutable once created.
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type pmpMapping struct {
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gw netaddr.IP
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external netaddr.IPPort
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internal netaddr.IPPort
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useUntil time.Time // the mapping's lifetime minus renewal interval
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epoch uint32
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}
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// externalValid reports whether m.external is valid, with both its IP and Port populated.
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func (m *pmpMapping) externalValid() bool {
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return !m.external.IP.IsZero() && m.external.Port != 0
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}
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// release does a best effort fire-and-forget release of the PMP mapping m.
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func (m *pmpMapping) release() {
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uc, err := netns.Listener().ListenPacket(context.Background(), "udp4", ":0")
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if err != nil {
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return
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}
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defer uc.Close()
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pkt := buildPMPRequestMappingPacket(m.internal.Port, m.external.Port, pmpMapLifetimeDelete)
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uc.WriteTo(pkt, netaddr.IPPort{IP: m.gw, Port: pmpPort}.UDPAddr())
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}
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// NewClient returns a new portmapping client.
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func NewClient(logf logger.Logf) *Client {
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return &Client{
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logf: logf,
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ipAndGateway: interfaces.LikelyHomeRouterIP,
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}
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}
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// SetGatewayLookupFunc set the func that returns the machine's default gateway IP, and
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// the primary IP address for that gateway. It must be called before the client is used.
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// If not called, interfaces.LikelyHomeRouterIP is used.
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func (c *Client) SetGatewayLookupFunc(f func() (gw, myIP netaddr.IP, ok bool)) {
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c.ipAndGateway = f
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}
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// NoteNetworkDown should be called when the network has transitioned to a down state.
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// It's too late to release port mappings at this point (the user might've just turned off
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// their wifi), but we can make sure we invalidate mappings for later when the network
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// comes back.
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func (c *Client) NoteNetworkDown() {
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c.mu.Lock()
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defer c.mu.Unlock()
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c.invalidateMappingsLocked(false)
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}
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func (c *Client) Close() error {
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c.mu.Lock()
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defer c.mu.Unlock()
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if c.closed {
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return nil
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}
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c.closed = true
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c.invalidateMappingsLocked(true)
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// TODO: close some future ever-listening UDP socket(s),
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// waiting for multicast announcements from router.
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return nil
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}
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// SetLocalPort updates the local port number to which we want to port
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// map UDP traffic.
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func (c *Client) SetLocalPort(localPort uint16) {
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c.mu.Lock()
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defer c.mu.Unlock()
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if c.localPort == localPort {
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return
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}
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c.localPort = localPort
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c.invalidateMappingsLocked(true)
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}
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func (c *Client) gatewayAndSelfIP() (gw, myIP netaddr.IP, ok bool) {
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gw, myIP, ok = c.ipAndGateway()
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if !ok {
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gw = netaddr.IP{}
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myIP = netaddr.IP{}
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}
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c.mu.Lock()
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defer c.mu.Unlock()
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if gw != c.lastGW || myIP != c.lastMyIP || !ok {
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c.lastMyIP = myIP
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c.lastGW = gw
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c.invalidateMappingsLocked(true)
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}
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return
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}
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func (c *Client) invalidateMappingsLocked(releaseOld bool) {
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if c.pmpMapping != nil {
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if releaseOld {
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c.pmpMapping.release()
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}
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c.pmpMapping = nil
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}
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c.pmpPubIP = netaddr.IP{}
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c.pmpPubIPTime = time.Time{}
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c.pcpSawTime = time.Time{}
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c.uPnPSawTime = time.Time{}
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}
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func (c *Client) sawPMPRecently() bool {
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c.mu.Lock()
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defer c.mu.Unlock()
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return c.sawPMPRecentlyLocked()
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}
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func (c *Client) sawPMPRecentlyLocked() bool {
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return !c.pmpPubIP.IsZero() && c.pmpPubIPTime.After(time.Now().Add(-trustServiceStillAvailableDuration))
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}
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func (c *Client) sawPCPRecently() bool {
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c.mu.Lock()
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defer c.mu.Unlock()
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return c.pcpSawTime.After(time.Now().Add(-trustServiceStillAvailableDuration))
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}
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func (c *Client) sawUPnPRecently() bool {
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c.mu.Lock()
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defer c.mu.Unlock()
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return c.uPnPSawTime.After(time.Now().Add(-trustServiceStillAvailableDuration))
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}
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// closeCloserOnContextDone starts a new goroutine to call c.Close
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// if/when ctx becomes done.
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// To stop the goroutine, call the returned stop func.
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func closeCloserOnContextDone(ctx context.Context, c io.Closer) (stop func()) {
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// Close uc on ctx being done.
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ctxDone := ctx.Done()
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if ctxDone == nil {
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return func() {}
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}
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stopWaitDone := make(chan struct{})
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go func() {
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select {
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case <-stopWaitDone:
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case <-ctxDone:
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c.Close()
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}
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}()
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return func() { close(stopWaitDone) }
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}
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// NoMappingError is returned by CreateOrGetMapping when no NAT
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// mapping could be returned.
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type NoMappingError struct {
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err error
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}
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func (nme NoMappingError) Unwrap() error { return nme.err }
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func (nme NoMappingError) Error() string { return fmt.Sprintf("no NAT mapping available: %v", nme.err) }
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// IsNoMappingError reports whether err is of type NoMappingError.
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func IsNoMappingError(err error) bool {
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_, ok := err.(NoMappingError)
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return ok
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}
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var (
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ErrNoPortMappingServices = errors.New("no port mapping services were found")
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ErrGatewayNotFound = errors.New("failed to look up gateway address")
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)
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// CreateOrGetMapping either creates a new mapping or returns a cached
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// valid one.
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//
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// If no mapping is available, the error will be of type
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// NoMappingError; see IsNoMappingError.
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func (c *Client) CreateOrGetMapping(ctx context.Context) (external netaddr.IPPort, err error) {
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gw, myIP, ok := c.gatewayAndSelfIP()
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if !ok {
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return netaddr.IPPort{}, NoMappingError{ErrGatewayNotFound}
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}
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c.mu.Lock()
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localPort := c.localPort
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m := &pmpMapping{
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gw: gw,
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internal: netaddr.IPPort{IP: myIP, Port: localPort},
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}
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// prevPort is the port we had most previously, if any. We try
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// to ask for the same port. 0 means to give us any port.
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var prevPort uint16
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// Do we have an existing mapping that's valid?
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now := time.Now()
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if m := c.pmpMapping; m != nil {
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if now.Before(m.useUntil) {
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defer c.mu.Unlock()
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return m.external, nil
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}
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// The mapping might still be valid, so just try to renew it.
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prevPort = m.external.Port
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}
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// If we just did a Probe (e.g. via netchecker) but didn't
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// find a PMP service, bail out early rather than probing
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// again. Cuts down latency for most clients.
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haveRecentPMP := c.sawPMPRecentlyLocked()
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if haveRecentPMP {
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m.external.IP = c.pmpPubIP
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}
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if c.lastProbe.After(now.Add(-5*time.Second)) && !haveRecentPMP {
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c.mu.Unlock()
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return netaddr.IPPort{}, NoMappingError{ErrNoPortMappingServices}
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}
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c.mu.Unlock()
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uc, err := netns.Listener().ListenPacket(ctx, "udp4", ":0")
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if err != nil {
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return netaddr.IPPort{}, err
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}
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defer uc.Close()
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uc.SetReadDeadline(time.Now().Add(portMapServiceTimeout))
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defer closeCloserOnContextDone(ctx, uc)()
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pmpAddr := netaddr.IPPort{IP: gw, Port: pmpPort}
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pmpAddru := pmpAddr.UDPAddr()
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// Ask for our external address if needed.
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if m.external.IP.IsZero() {
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if _, err := uc.WriteTo(pmpReqExternalAddrPacket, pmpAddru); err != nil {
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return netaddr.IPPort{}, err
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}
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}
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// And ask for a mapping.
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pmpReqMapping := buildPMPRequestMappingPacket(localPort, prevPort, pmpMapLifetimeSec)
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if _, err := uc.WriteTo(pmpReqMapping, pmpAddru); err != nil {
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return netaddr.IPPort{}, err
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}
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res := make([]byte, 1500)
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for {
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n, srci, err := uc.ReadFrom(res)
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if err != nil {
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if ctx.Err() == context.Canceled {
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return netaddr.IPPort{}, err
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}
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return netaddr.IPPort{}, NoMappingError{ErrNoPortMappingServices}
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}
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srcu := srci.(*net.UDPAddr)
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src, ok := netaddr.FromStdAddr(srcu.IP, srcu.Port, srcu.Zone)
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if !ok {
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continue
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}
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if src == pmpAddr {
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pres, ok := parsePMPResponse(res[:n])
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if !ok {
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c.logf("unexpected PMP response: % 02x", res[:n])
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continue
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}
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if pres.ResultCode != 0 {
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return netaddr.IPPort{}, NoMappingError{fmt.Errorf("PMP response Op=0x%x,Res=0x%x", pres.OpCode, pres.ResultCode)}
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}
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if pres.OpCode == pmpOpReply|pmpOpMapPublicAddr {
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m.external.IP = pres.PublicAddr
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}
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if pres.OpCode == pmpOpReply|pmpOpMapUDP {
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m.external.Port = pres.ExternalPort
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d := time.Duration(pres.MappingValidSeconds) * time.Second
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d /= 2 // renew in half the time
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m.useUntil = time.Now().Add(d)
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m.epoch = pres.SecondsSinceEpoch
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}
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}
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if m.externalValid() {
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c.mu.Lock()
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defer c.mu.Unlock()
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c.pmpMapping = m
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return m.external, nil
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}
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}
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}
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type pmpResultCode uint16
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// NAT-PMP constants.
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const (
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pmpPort = 5351
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pmpMapLifetimeSec = 7200 // RFC recommended 2 hour map duration
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pmpMapLifetimeDelete = 0 // 0 second lifetime deletes
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pmpOpMapPublicAddr = 0
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pmpOpMapUDP = 1
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pmpOpReply = 0x80 // OR'd into request's op code on response
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pmpCodeOK pmpResultCode = 0
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pmpCodeUnsupportedVersion pmpResultCode = 1
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pmpCodeNotAuthorized pmpResultCode = 2 // "e.g., box supports mapping, but user has turned feature off"
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pmpCodeNetworkFailure pmpResultCode = 3 // "e.g., NAT box itself has not obtained a DHCP lease"
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pmpCodeOutOfResources pmpResultCode = 4
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pmpCodeUnsupportedOpcode pmpResultCode = 5
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)
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func buildPMPRequestMappingPacket(localPort, prevPort uint16, lifetimeSec uint32) (pkt []byte) {
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pkt = make([]byte, 12)
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pkt[1] = pmpOpMapUDP
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binary.BigEndian.PutUint16(pkt[4:], localPort)
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binary.BigEndian.PutUint16(pkt[6:], prevPort)
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binary.BigEndian.PutUint32(pkt[8:], lifetimeSec)
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return pkt
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}
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type pmpResponse struct {
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OpCode uint8
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ResultCode pmpResultCode
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SecondsSinceEpoch uint32
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// For Map ops:
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MappingValidSeconds uint32
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InternalPort uint16
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ExternalPort uint16
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// For public addr ops:
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PublicAddr netaddr.IP
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}
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func parsePMPResponse(pkt []byte) (res pmpResponse, ok bool) {
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if len(pkt) < 12 {
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return
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}
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ver := pkt[0]
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if ver != 0 {
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return
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}
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res.OpCode = pkt[1]
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res.ResultCode = pmpResultCode(binary.BigEndian.Uint16(pkt[2:]))
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res.SecondsSinceEpoch = binary.BigEndian.Uint32(pkt[4:])
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if res.OpCode == pmpOpReply|pmpOpMapUDP {
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if len(pkt) != 16 {
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return res, false
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}
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res.InternalPort = binary.BigEndian.Uint16(pkt[8:])
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res.ExternalPort = binary.BigEndian.Uint16(pkt[10:])
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res.MappingValidSeconds = binary.BigEndian.Uint32(pkt[12:])
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}
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if res.OpCode == pmpOpReply|pmpOpMapPublicAddr {
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if len(pkt) != 12 {
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return res, false
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}
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res.PublicAddr = netaddr.IPv4(pkt[8], pkt[9], pkt[10], pkt[11])
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}
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return res, true
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}
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type ProbeResult struct {
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PCP bool
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PMP bool
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UPnP bool
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}
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// Probe returns a summary of which port mapping services are
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// available on the network.
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//
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// If a probe has run recently and there haven't been any network changes since,
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// the returned result might be server from the Client's cache, without
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// sending any network traffic.
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func (c *Client) Probe(ctx context.Context) (res ProbeResult, err error) {
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gw, myIP, ok := c.gatewayAndSelfIP()
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if !ok {
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return res, ErrGatewayNotFound
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}
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defer func() {
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if err == nil {
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c.mu.Lock()
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defer c.mu.Unlock()
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c.lastProbe = time.Now()
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}
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}()
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uc, err := netns.Listener().ListenPacket(context.Background(), "udp4", ":0")
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if err != nil {
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c.logf("ProbePCP: %v", err)
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return res, err
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}
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defer uc.Close()
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ctx, cancel := context.WithTimeout(ctx, 250*time.Millisecond)
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defer cancel()
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defer closeCloserOnContextDone(ctx, uc)()
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pcpAddr := netaddr.IPPort{IP: gw, Port: pcpPort}.UDPAddr()
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pmpAddr := netaddr.IPPort{IP: gw, Port: pmpPort}.UDPAddr()
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upnpAddr := netaddr.IPPort{IP: gw, Port: upnpPort}.UDPAddr()
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// Don't send probes to services that we recently learned (for
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// the same gw/myIP) are available. See
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// https://github.com/tailscale/tailscale/issues/1001
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if c.sawPMPRecently() {
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res.PMP = true
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} else {
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uc.WriteTo(pmpReqExternalAddrPacket, pmpAddr)
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}
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if c.sawPCPRecently() {
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res.PCP = true
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} else {
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uc.WriteTo(pcpAnnounceRequest(myIP), pcpAddr)
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}
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if c.sawUPnPRecently() {
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res.UPnP = true
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} else {
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uc.WriteTo(uPnPPacket, upnpAddr)
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}
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buf := make([]byte, 1500)
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pcpHeard := false // true when we get any PCP response
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for {
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if pcpHeard && res.PMP && res.UPnP {
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// Nothing more to discover.
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return res, nil
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}
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n, addr, err := uc.ReadFrom(buf)
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if err != nil {
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if ctx.Err() == context.DeadlineExceeded {
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err = nil
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}
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return res, err
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}
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port := addr.(*net.UDPAddr).Port
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switch port {
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case upnpPort:
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if mem.Contains(mem.B(buf[:n]), mem.S(":InternetGatewayDevice:")) {
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res.UPnP = true
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c.mu.Lock()
|
|
c.uPnPSawTime = time.Now()
|
|
c.mu.Unlock()
|
|
}
|
|
case pcpPort: // same as pmpPort
|
|
if pres, ok := parsePCPResponse(buf[:n]); ok {
|
|
if pres.OpCode == pcpOpReply|pcpOpAnnounce {
|
|
pcpHeard = true
|
|
c.mu.Lock()
|
|
c.pcpSawTime = time.Now()
|
|
c.mu.Unlock()
|
|
switch pres.ResultCode {
|
|
case pcpCodeOK:
|
|
c.logf("Got PCP response: epoch: %v", pres.Epoch)
|
|
res.PCP = true
|
|
continue
|
|
case pcpCodeNotAuthorized:
|
|
// A PCP service is running, but refuses to
|
|
// provide port mapping services.
|
|
res.PCP = false
|
|
continue
|
|
default:
|
|
// Fall through to unexpected log line.
|
|
}
|
|
}
|
|
c.logf("unexpected PCP probe response: %+v", pres)
|
|
}
|
|
if pres, ok := parsePMPResponse(buf[:n]); ok {
|
|
if pres.OpCode == pmpOpReply|pmpOpMapPublicAddr && pres.ResultCode == pmpCodeOK {
|
|
c.logf("Got PMP response; IP: %v, epoch: %v", pres.PublicAddr, pres.SecondsSinceEpoch)
|
|
res.PMP = true
|
|
c.mu.Lock()
|
|
c.pmpPubIP = pres.PublicAddr
|
|
c.pmpPubIPTime = time.Now()
|
|
c.pmpLastEpoch = pres.SecondsSinceEpoch
|
|
c.mu.Unlock()
|
|
continue
|
|
}
|
|
c.logf("unexpected PMP probe response: %+v", pres)
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
const (
|
|
pcpVersion = 2
|
|
pcpPort = 5351
|
|
|
|
pcpCodeOK = 0
|
|
pcpCodeNotAuthorized = 2
|
|
|
|
pcpOpReply = 0x80 // OR'd into request's op code on response
|
|
pcpOpAnnounce = 0
|
|
pcpOpMap = 1
|
|
)
|
|
|
|
// pcpAnnounceRequest generates a PCP packet with an ANNOUNCE opcode.
|
|
func pcpAnnounceRequest(myIP netaddr.IP) []byte {
|
|
// See https://tools.ietf.org/html/rfc6887#section-7.1
|
|
pkt := make([]byte, 24)
|
|
pkt[0] = pcpVersion // version
|
|
pkt[1] = pcpOpAnnounce
|
|
myIP16 := myIP.As16()
|
|
copy(pkt[8:], myIP16[:])
|
|
return pkt
|
|
}
|
|
|
|
//lint:ignore U1000 moved this code from netcheck's old PCP probing; will be needed when we add PCP mapping
|
|
|
|
// pcpMapRequest generates a PCP packet with a MAP opcode.
|
|
func pcpMapRequest(myIP netaddr.IP, mapToLocalPort int, delete bool) []byte {
|
|
const udpProtoNumber = 17
|
|
lifetimeSeconds := uint32(1)
|
|
if delete {
|
|
lifetimeSeconds = 0
|
|
}
|
|
const opMap = 1
|
|
|
|
// 24 byte header + 36 byte map opcode
|
|
pkt := make([]byte, (32+32+128)/8+(96+8+24+16+16+128)/8)
|
|
|
|
// The header (https://tools.ietf.org/html/rfc6887#section-7.1)
|
|
pkt[0] = 2 // version
|
|
pkt[1] = opMap
|
|
binary.BigEndian.PutUint32(pkt[4:8], lifetimeSeconds)
|
|
myIP16 := myIP.As16()
|
|
copy(pkt[8:], myIP16[:])
|
|
|
|
// The map opcode body (https://tools.ietf.org/html/rfc6887#section-11.1)
|
|
mapOp := pkt[24:]
|
|
rand.Read(mapOp[:12]) // 96 bit mappping nonce
|
|
mapOp[12] = udpProtoNumber
|
|
binary.BigEndian.PutUint16(mapOp[16:], uint16(mapToLocalPort))
|
|
v4unspec := netaddr.MustParseIP("0.0.0.0")
|
|
v4unspec16 := v4unspec.As16()
|
|
copy(mapOp[20:], v4unspec16[:])
|
|
return pkt
|
|
}
|
|
|
|
type pcpResponse struct {
|
|
OpCode uint8
|
|
ResultCode uint8
|
|
Lifetime uint32
|
|
Epoch uint32
|
|
}
|
|
|
|
func parsePCPResponse(b []byte) (res pcpResponse, ok bool) {
|
|
if len(b) < 24 || b[0] != pcpVersion {
|
|
return
|
|
}
|
|
res.OpCode = b[1]
|
|
res.ResultCode = b[3]
|
|
res.Lifetime = binary.BigEndian.Uint32(b[4:])
|
|
res.Epoch = binary.BigEndian.Uint32(b[8:])
|
|
return res, true
|
|
}
|
|
|
|
const (
|
|
upnpPort = 1900
|
|
)
|
|
|
|
var uPnPPacket = []byte("M-SEARCH * HTTP/1.1\r\n" +
|
|
"HOST: 239.255.255.250:1900\r\n" +
|
|
"ST: ssdp:all\r\n" +
|
|
"MAN: \"ssdp:discover\"\r\n" +
|
|
"MX: 2\r\n\r\n")
|
|
|
|
var pmpReqExternalAddrPacket = []byte{0, 0} // version 0, opcode 0 = "Public address request"
|