// Copyright (c) Tailscale Inc & AUTHORS // SPDX-License-Identifier: BSD-3-Clause // Package portmapper is a UDP port mapping client. It currently allows for mapping over // NAT-PMP, UPnP, and PCP. package portmapper import ( "context" "encoding/binary" "errors" "fmt" "io" "net" "net/http" "net/netip" "slices" "sync" "sync/atomic" "time" "go4.org/mem" "tailscale.com/control/controlknobs" "tailscale.com/net/interfaces" "tailscale.com/net/netaddr" "tailscale.com/net/neterror" "tailscale.com/net/netmon" "tailscale.com/net/netns" "tailscale.com/net/sockstats" "tailscale.com/syncs" "tailscale.com/types/logger" "tailscale.com/types/nettype" "tailscale.com/util/clientmetric" ) // DebugKnobs contains debug configuration that can be provided when creating a // Client. The zero value is valid for use. type DebugKnobs struct { // VerboseLogs tells the Client to print additional debug information // to its logger. VerboseLogs bool // LogHTTP tells the Client to print the raw HTTP logs (from UPnP) to // its logger. This is useful when debugging buggy UPnP // implementations. LogHTTP bool // Disable* disables a specific service from mapping. DisableUPnP bool DisablePMP bool DisablePCP bool // DisableAll, if non-nil, is a func that reports whether all port // mapping attempts should be disabled. DisableAll func() bool } func (k *DebugKnobs) disableAll() bool { if k.DisableAll != nil { return k.DisableAll() } return false } // References: // // NAT-PMP: https://tools.ietf.org/html/rfc6886 // portMapServiceTimeout is the time we wait for port mapping // services (UPnP, NAT-PMP, PCP) to respond before we give up and // decide that they're not there. Since these services are on the // same LAN as this machine and a single L3 hop away, we don't // give them much time to respond. const portMapServiceTimeout = 250 * time.Millisecond // trustServiceStillAvailableDuration is how often we re-verify a port // mapping service is available. const trustServiceStillAvailableDuration = 10 * time.Minute // Client is a port mapping client. type Client struct { logf logger.Logf netMon *netmon.Monitor // optional; nil means interfaces will be looked up on-demand controlKnobs *controlknobs.Knobs ipAndGateway func() (gw, ip netip.Addr, ok bool) onChange func() // or nil debug DebugKnobs testPxPPort uint16 // if non-zero, pxpPort to use for tests testUPnPPort uint16 // if non-zero, uPnPPort to use for tests mu sync.Mutex // guards following, and all fields thereof // runningCreate is whether we're currently working on creating // a port mapping (whether GetCachedMappingOrStartCreatingOne kicked // off a createMapping goroutine). runningCreate bool lastMyIP netip.Addr lastGW netip.Addr closed bool lastProbe time.Time // The following PMP fields are populated during Probe pmpPubIP netip.Addr // non-zero if known pmpPubIPTime time.Time // time pmpPubIP last verified pmpLastEpoch uint32 // The following PCP fields are populated during Probe pcpSawTime time.Time // time we last saw PCP was available pcpLastEpoch uint32 uPnPSawTime time.Time // time we last saw UPnP was available uPnPMetas []uPnPDiscoResponse // UPnP UDP discovery responses uPnPHTTPClient *http.Client // netns-configured HTTP client for UPnP; nil until needed localPort uint16 mapping mapping // non-nil if we have a mapping } func (c *Client) vlogf(format string, args ...any) { if c.debug.VerboseLogs { c.logf(format, args...) } } // mapping represents a created port-mapping over some protocol. It specifies a lease duration, // how to release the mapping, and whether the map is still valid. // // After a mapping is created, it should be immutable, and thus reads should be safe across // concurrent goroutines. type mapping interface { // Release will attempt to unmap the established port mapping. It will block until completion, // but can be called asynchronously. Release should be idempotent, and thus even if called // multiple times should not cause additional side-effects. Release(context.Context) // GoodUntil will return the lease time that the mapping is valid for. GoodUntil() time.Time // RenewAfter returns the earliest time that the mapping should be renewed. RenewAfter() time.Time // External indicates what port the mapping can be reached from on the outside. External() netip.AddrPort // MappingType returns a descriptive string for this type of mapping. MappingType() string // MappingDebug returns a debug string for this mapping, for use when // printing verbose logs. MappingDebug() string } // HaveMapping reports whether we have a current valid mapping. func (c *Client) HaveMapping() bool { c.mu.Lock() defer c.mu.Unlock() return c.mapping != nil && c.mapping.GoodUntil().After(time.Now()) } // pmpMapping is an already-created PMP mapping. // // All fields are immutable once created. type pmpMapping struct { c *Client gw netip.AddrPort external netip.AddrPort internal netip.AddrPort renewAfter time.Time // the time at which we want to renew the mapping goodUntil time.Time // the mapping's total lifetime epoch uint32 } // externalValid reports whether m.external is valid, with both its IP and Port populated. func (m *pmpMapping) externalValid() bool { return m.external.Addr().IsValid() && m.external.Port() != 0 } func (p *pmpMapping) MappingType() string { return "pmp" } func (p *pmpMapping) GoodUntil() time.Time { return p.goodUntil } func (p *pmpMapping) RenewAfter() time.Time { return p.renewAfter } func (p *pmpMapping) External() netip.AddrPort { return p.external } func (p *pmpMapping) MappingDebug() string { return fmt.Sprintf("pmpMapping{gw:%v, external:%v, internal:%v, renewAfter:%d, goodUntil:%d, epoch:%v}", p.gw, p.external, p.internal, p.renewAfter.Unix(), p.goodUntil.Unix(), p.epoch) } // Release does a best effort fire-and-forget release of the PMP mapping m. func (m *pmpMapping) Release(ctx context.Context) { uc, err := m.c.listenPacket(ctx, "udp4", ":0") if err != nil { return } defer uc.Close() pkt := buildPMPRequestMappingPacket(m.internal.Port(), m.external.Port(), pmpMapLifetimeDelete) uc.WriteToUDPAddrPort(pkt, m.gw) } // NewClient returns a new portmapping client. // // The netMon parameter is optional; if non-nil it's used to do faster interface // lookups. // // The debug argument allows configuring the behaviour of the portmapper for // debugging; if nil, a sensible set of defaults will be used. // // The controlKnobs, if non-nil, specifies the control knobs from the control // plane that might disable portmapping. // // The optional onChange argument specifies a func to run in a new goroutine // whenever the port mapping status has changed. If nil, it doesn't make a // callback. func NewClient(logf logger.Logf, netMon *netmon.Monitor, debug *DebugKnobs, controlKnobs *controlknobs.Knobs, onChange func()) *Client { ret := &Client{ logf: logf, netMon: netMon, ipAndGateway: interfaces.LikelyHomeRouterIP, onChange: onChange, controlKnobs: controlKnobs, } if debug != nil { ret.debug = *debug } return ret } // SetGatewayLookupFunc set the func that returns the machine's default gateway IP, and // the primary IP address for that gateway. It must be called before the client is used. // If not called, interfaces.LikelyHomeRouterIP is used. func (c *Client) SetGatewayLookupFunc(f func() (gw, myIP netip.Addr, ok bool)) { c.ipAndGateway = f } // NoteNetworkDown should be called when the network has transitioned to a down state. // It's too late to release port mappings at this point (the user might've just turned off // their wifi), but we can make sure we invalidate mappings for later when the network // comes back. func (c *Client) NoteNetworkDown() { c.mu.Lock() defer c.mu.Unlock() c.invalidateMappingsLocked(false) } func (c *Client) Close() error { c.mu.Lock() defer c.mu.Unlock() if c.closed { return nil } c.closed = true c.invalidateMappingsLocked(true) // TODO: close some future ever-listening UDP socket(s), // waiting for multicast announcements from router. return nil } // SetLocalPort updates the local port number to which we want to port // map UDP traffic. func (c *Client) SetLocalPort(localPort uint16) { c.mu.Lock() defer c.mu.Unlock() if c.localPort == localPort { return } c.localPort = localPort c.invalidateMappingsLocked(true) } func (c *Client) gatewayAndSelfIP() (gw, myIP netip.Addr, ok bool) { gw, myIP, ok = c.ipAndGateway() if !ok { gw = netip.Addr{} myIP = netip.Addr{} } c.mu.Lock() defer c.mu.Unlock() if gw != c.lastGW || myIP != c.lastMyIP || !ok { c.lastMyIP = myIP c.lastGW = gw c.invalidateMappingsLocked(true) } return } // pxpPort returns the NAT-PMP and PCP port number. // It returns 5351, except for in tests where it varies by run. func (c *Client) pxpPort() uint16 { if c.testPxPPort != 0 { return c.testPxPPort } return pmpDefaultPort } // upnpPort returns the UPnP discovery port number. // It returns 1900, except for in tests where it varies by run. func (c *Client) upnpPort() uint16 { if c.testUPnPPort != 0 { return c.testUPnPPort } return upnpDefaultPort } func (c *Client) listenPacket(ctx context.Context, network, addr string) (nettype.PacketConn, error) { ctx = sockstats.WithSockStats(ctx, sockstats.LabelPortmapperClient, c.logf) // When running under testing conditions, we bind the IGD server // to localhost, and may be running in an environment where our // netns code would decide that binding the portmapper client // socket to the default route interface is the correct way to // ensure connectivity. This can result in us trying to send // packets for 127.0.0.1 out the machine's LAN interface, which // obviously gets dropped on the floor. // // So, under those testing conditions, do _not_ use netns to // create listening sockets. Such sockets are vulnerable to // routing loops, but it's tests that don't set up routing loops, // so we don't care. if c.testPxPPort != 0 || c.testUPnPPort != 0 { var lc net.ListenConfig pc, err := lc.ListenPacket(ctx, network, addr) if err != nil { return nil, err } return pc.(*net.UDPConn), nil } pc, err := netns.Listener(c.logf, c.netMon).ListenPacket(ctx, network, addr) if err != nil { return nil, err } return pc.(*net.UDPConn), nil } func (c *Client) invalidateMappingsLocked(releaseOld bool) { if c.mapping != nil { if releaseOld { c.mapping.Release(context.Background()) } c.mapping = nil } c.pmpPubIP = netip.Addr{} c.pmpPubIPTime = time.Time{} c.pmpLastEpoch = 0 c.pcpSawTime = time.Time{} c.pcpLastEpoch = 0 c.uPnPSawTime = time.Time{} c.uPnPMetas = nil } func (c *Client) sawPMPRecently() bool { c.mu.Lock() defer c.mu.Unlock() return c.sawPMPRecentlyLocked() } func (c *Client) sawPMPRecentlyLocked() bool { return c.pmpPubIP.IsValid() && c.pmpPubIPTime.After(time.Now().Add(-trustServiceStillAvailableDuration)) } func (c *Client) sawPCPRecently() bool { c.mu.Lock() defer c.mu.Unlock() return c.sawPCPRecentlyLocked() } func (c *Client) sawPCPRecentlyLocked() bool { return c.pcpSawTime.After(time.Now().Add(-trustServiceStillAvailableDuration)) } func (c *Client) sawUPnPRecently() bool { c.mu.Lock() defer c.mu.Unlock() return c.uPnPSawTime.After(time.Now().Add(-trustServiceStillAvailableDuration)) } // closeCloserOnContextDone starts a new goroutine to call c.Close // if/when ctx becomes done. // To stop the goroutine, call the returned stop func. func closeCloserOnContextDone(ctx context.Context, c io.Closer) (stop func()) { // Close uc on ctx being done. ctxDone := ctx.Done() if ctxDone == nil { return func() {} } stopWaitDone := make(chan struct{}) go func() { select { case <-stopWaitDone: case <-ctxDone: c.Close() } }() return func() { close(stopWaitDone) } } // NoMappingError is returned when no NAT mapping could be done. type NoMappingError struct { err error } func (nme NoMappingError) Unwrap() error { return nme.err } func (nme NoMappingError) Error() string { return fmt.Sprintf("no NAT mapping available: %v", nme.err) } // IsNoMappingError reports whether err is of type NoMappingError. func IsNoMappingError(err error) bool { _, ok := err.(NoMappingError) return ok } var ( ErrNoPortMappingServices = errors.New("no port mapping services were found") ErrGatewayRange = errors.New("skipping portmap; gateway range likely lacks support") ErrGatewayIPv6 = errors.New("skipping portmap; no IPv6 support for portmapping") ErrPortMappingDisabled = errors.New("port mapping is disabled") ) // GetCachedMappingOrStartCreatingOne quickly returns with our current cached portmapping, if any. // If there's not one, it starts up a background goroutine to create one. // If the background goroutine ends up creating one, the onChange hook registered with the // NewClient constructor (if any) will fire. func (c *Client) GetCachedMappingOrStartCreatingOne() (external netip.AddrPort, ok bool) { c.mu.Lock() defer c.mu.Unlock() // Do we have an existing mapping that's valid? now := time.Now() if m := c.mapping; m != nil { if now.Before(m.GoodUntil()) { if now.After(m.RenewAfter()) { c.maybeStartMappingLocked() } return m.External(), true } } c.maybeStartMappingLocked() return netip.AddrPort{}, false } // maybeStartMappingLocked starts a createMapping goroutine up, if one isn't already running. // // c.mu must be held. func (c *Client) maybeStartMappingLocked() { if !c.runningCreate { c.runningCreate = true go c.createMapping() } } func (c *Client) createMapping() { ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second) defer cancel() defer func() { c.mu.Lock() defer c.mu.Unlock() c.runningCreate = false }() if _, err := c.createOrGetMapping(ctx); err == nil && c.onChange != nil { go c.onChange() } else if err != nil && !IsNoMappingError(err) { c.logf("createOrGetMapping: %v", err) } } // wildcardIP is used when the previous external IP is not known for PCP port mapping. var wildcardIP = netip.MustParseAddr("0.0.0.0") // createOrGetMapping either creates a new mapping or returns a cached // valid one. // // If no mapping is available, the error will be of type // NoMappingError; see IsNoMappingError. func (c *Client) createOrGetMapping(ctx context.Context) (external netip.AddrPort, err error) { if c.debug.disableAll() { return netip.AddrPort{}, NoMappingError{ErrPortMappingDisabled} } if c.debug.DisableUPnP && c.debug.DisablePCP && c.debug.DisablePMP { return netip.AddrPort{}, NoMappingError{ErrNoPortMappingServices} } gw, myIP, ok := c.gatewayAndSelfIP() if !ok { return netip.AddrPort{}, NoMappingError{ErrGatewayRange} } if gw.Is6() { return netip.AddrPort{}, NoMappingError{ErrGatewayIPv6} } now := time.Now() // Log what kind of portmap we obtained reusedExisting := false defer func() { if err != nil { return } c.mu.Lock() defer c.mu.Unlock() portmapType := "none" if c.mapping != nil { portmapType = c.mapping.MappingType() } if reusedExisting { portmapType = "existing-" + portmapType } if c.mapping == nil { c.logf("[unexpected] no error but no stored mapping: now=%d external=%v type=%s", now.Unix(), external, portmapType) return } // Print the internal details of each mapping if we're being verbose. if c.debug.VerboseLogs { c.logf("successfully obtained mapping: now=%d external=%v type=%s mapping=%s", now.Unix(), external, portmapType, c.mapping.MappingDebug()) return } c.logf("[v1] successfully obtained mapping: now=%d external=%v type=%s goodUntil=%d renewAfter=%d", now.Unix(), external, portmapType, c.mapping.GoodUntil().Unix(), c.mapping.RenewAfter().Unix()) }() c.mu.Lock() localPort := c.localPort internalAddr := netip.AddrPortFrom(myIP, localPort) // prevPort is the port we had most previously, if any. We try // to ask for the same port. 0 means to give us any port. var prevPort uint16 // Do we have an existing mapping that's valid? if m := c.mapping; m != nil { if now.Before(m.RenewAfter()) { defer c.mu.Unlock() reusedExisting = true return m.External(), nil } // The mapping might still be valid, so just try to renew it. prevPort = m.External().Port() } if c.debug.DisablePCP && c.debug.DisablePMP { c.mu.Unlock() if external, ok := c.getUPnPPortMapping(ctx, gw, internalAddr, prevPort); ok { return external, nil } c.vlogf("fallback to UPnP due to PCP and PMP being disabled failed") return netip.AddrPort{}, NoMappingError{ErrNoPortMappingServices} } // If we just did a Probe (e.g. via netchecker) but didn't // find a PMP service, bail out early rather than probing // again. Cuts down latency for most clients. haveRecentPMP := c.sawPMPRecentlyLocked() haveRecentPCP := c.sawPCPRecentlyLocked() // Since PMP mapping may require multiple calls, and it's not clear from the outset // whether we're doing a PCP or PMP call, initialize the PMP mapping here, // and only return it once completed. // // PCP returns all the information necessary for a mapping in a single packet, so we can // construct it upon receiving that packet. m := &pmpMapping{ c: c, gw: netip.AddrPortFrom(gw, c.pxpPort()), internal: internalAddr, } if haveRecentPMP { m.external = netip.AddrPortFrom(c.pmpPubIP, m.external.Port()) } if c.lastProbe.After(now.Add(-5*time.Second)) && !haveRecentPMP && !haveRecentPCP { c.mu.Unlock() // fallback to UPnP portmapping if external, ok := c.getUPnPPortMapping(ctx, gw, internalAddr, prevPort); ok { return external, nil } c.vlogf("fallback to UPnP due to no PCP and PMP failed") return netip.AddrPort{}, NoMappingError{ErrNoPortMappingServices} } c.mu.Unlock() uc, err := c.listenPacket(ctx, "udp4", ":0") if err != nil { return netip.AddrPort{}, err } defer uc.Close() uc.SetReadDeadline(time.Now().Add(portMapServiceTimeout)) defer closeCloserOnContextDone(ctx, uc)() pxpAddr := netip.AddrPortFrom(gw, c.pxpPort()) preferPCP := !c.debug.DisablePCP && (c.debug.DisablePMP || (!haveRecentPMP && haveRecentPCP)) // Create a mapping, defaulting to PMP unless only PCP was seen recently. if preferPCP { // TODO replace wildcardIP here with previous external if known. // Only do PCP mapping in the case when PMP did not appear to be available recently. pkt := buildPCPRequestMappingPacket(myIP, localPort, prevPort, pcpMapLifetimeSec, wildcardIP) if _, err := uc.WriteToUDPAddrPort(pkt, pxpAddr); err != nil { if neterror.TreatAsLostUDP(err) { err = NoMappingError{ErrNoPortMappingServices} } return netip.AddrPort{}, err } } else { // Ask for our external address if needed. if !m.external.Addr().IsValid() { if _, err := uc.WriteToUDPAddrPort(pmpReqExternalAddrPacket, pxpAddr); err != nil { if neterror.TreatAsLostUDP(err) { err = NoMappingError{ErrNoPortMappingServices} } return netip.AddrPort{}, err } } pkt := buildPMPRequestMappingPacket(localPort, prevPort, pmpMapLifetimeSec) if _, err := uc.WriteToUDPAddrPort(pkt, pxpAddr); err != nil { if neterror.TreatAsLostUDP(err) { err = NoMappingError{ErrNoPortMappingServices} } return netip.AddrPort{}, err } } res := make([]byte, 1500) for { n, src, err := uc.ReadFromUDPAddrPort(res) if err != nil { if ctx.Err() == context.Canceled { return netip.AddrPort{}, err } // fallback to UPnP portmapping if mapping, ok := c.getUPnPPortMapping(ctx, gw, internalAddr, prevPort); ok { return mapping, nil } return netip.AddrPort{}, NoMappingError{ErrNoPortMappingServices} } src = netaddr.Unmap(src) if !src.IsValid() { continue } if src == pxpAddr { version := res[0] switch version { case pmpVersion: pres, ok := parsePMPResponse(res[:n]) if !ok { c.logf("unexpected PMP response: % 02x", res[:n]) continue } if pres.ResultCode != 0 { return netip.AddrPort{}, NoMappingError{fmt.Errorf("PMP response Op=0x%x,Res=0x%x", pres.OpCode, pres.ResultCode)} } if pres.OpCode == pmpOpReply|pmpOpMapPublicAddr { m.external = netip.AddrPortFrom(pres.PublicAddr, m.external.Port()) } if pres.OpCode == pmpOpReply|pmpOpMapUDP { m.external = netip.AddrPortFrom(m.external.Addr(), pres.ExternalPort) d := time.Duration(pres.MappingValidSeconds) * time.Second now := time.Now() m.goodUntil = now.Add(d) m.renewAfter = now.Add(d / 2) // renew in half the time m.epoch = pres.SecondsSinceEpoch } case pcpVersion: pcpMapping, err := parsePCPMapResponse(res[:n]) if err != nil { c.logf("failed to get PCP mapping: %v", err) // PCP should only have a single packet response return netip.AddrPort{}, NoMappingError{ErrNoPortMappingServices} } pcpMapping.c = c pcpMapping.internal = m.internal pcpMapping.gw = netip.AddrPortFrom(gw, c.pxpPort()) c.mu.Lock() defer c.mu.Unlock() c.mapping = pcpMapping return pcpMapping.external, nil default: c.logf("unknown PMP/PCP version number: %d %v", version, res[:n]) return netip.AddrPort{}, NoMappingError{ErrNoPortMappingServices} } } if m.externalValid() { c.mu.Lock() defer c.mu.Unlock() c.mapping = m return m.external, nil } } } //go:generate go run tailscale.com/cmd/addlicense -file pmpresultcode_string.go go run golang.org/x/tools/cmd/stringer -type=pmpResultCode -trimprefix=pmpCode type pmpResultCode uint16 // NAT-PMP constants. const ( pmpDefaultPort = 5351 pmpMapLifetimeSec = 7200 // RFC recommended 2 hour map duration pmpMapLifetimeDelete = 0 // 0 second lifetime deletes pmpVersion = 0 pmpOpMapPublicAddr = 0 pmpOpMapUDP = 1 pmpOpReply = 0x80 // OR'd into request's op code on response pmpCodeOK pmpResultCode = 0 pmpCodeUnsupportedVersion pmpResultCode = 1 pmpCodeNotAuthorized pmpResultCode = 2 // "e.g., box supports mapping, but user has turned feature off" pmpCodeNetworkFailure pmpResultCode = 3 // "e.g., NAT box itself has not obtained a DHCP lease" pmpCodeOutOfResources pmpResultCode = 4 pmpCodeUnsupportedOpcode pmpResultCode = 5 ) func buildPMPRequestMappingPacket(localPort, prevPort uint16, lifetimeSec uint32) (pkt []byte) { pkt = make([]byte, 12) pkt[1] = pmpOpMapUDP binary.BigEndian.PutUint16(pkt[4:], localPort) binary.BigEndian.PutUint16(pkt[6:], prevPort) binary.BigEndian.PutUint32(pkt[8:], lifetimeSec) return pkt } type pmpResponse struct { OpCode uint8 ResultCode pmpResultCode SecondsSinceEpoch uint32 // For Map ops: MappingValidSeconds uint32 InternalPort uint16 ExternalPort uint16 // For public addr ops: PublicAddr netip.Addr } func parsePMPResponse(pkt []byte) (res pmpResponse, ok bool) { if len(pkt) < 12 { return } ver := pkt[0] if ver != 0 { return } res.OpCode = pkt[1] res.ResultCode = pmpResultCode(binary.BigEndian.Uint16(pkt[2:])) res.SecondsSinceEpoch = binary.BigEndian.Uint32(pkt[4:]) if res.OpCode == pmpOpReply|pmpOpMapUDP { if len(pkt) != 16 { return res, false } res.InternalPort = binary.BigEndian.Uint16(pkt[8:]) res.ExternalPort = binary.BigEndian.Uint16(pkt[10:]) res.MappingValidSeconds = binary.BigEndian.Uint32(pkt[12:]) } if res.OpCode == pmpOpReply|pmpOpMapPublicAddr { if len(pkt) != 12 { return res, false } res.PublicAddr = netaddr.IPv4(pkt[8], pkt[9], pkt[10], pkt[11]) } return res, true } type ProbeResult struct { PCP bool PMP bool UPnP bool } // Probe returns a summary of which port mapping services are // available on the network. // // If a probe has run recently and there haven't been any network changes since, // the returned result might be server from the Client's cache, without // sending any network traffic. func (c *Client) Probe(ctx context.Context) (res ProbeResult, err error) { if c.debug.disableAll() { return res, ErrPortMappingDisabled } gw, myIP, ok := c.gatewayAndSelfIP() if !ok { return res, ErrGatewayRange } defer func() { if err == nil { c.mu.Lock() defer c.mu.Unlock() c.lastProbe = time.Now() } }() uc, err := c.listenPacket(context.Background(), "udp4", ":0") if err != nil { c.logf("ProbePCP: %v", err) return res, err } defer uc.Close() ctx, cancel := context.WithTimeout(ctx, 250*time.Millisecond) defer cancel() defer closeCloserOnContextDone(ctx, uc)() pxpAddr := netip.AddrPortFrom(gw, c.pxpPort()) upnpAddr := netip.AddrPortFrom(gw, c.upnpPort()) upnpMulticastAddr := netip.AddrPortFrom(netaddr.IPv4(239, 255, 255, 250), c.upnpPort()) // Don't send probes to services that we recently learned (for // the same gw/myIP) are available. See // https://github.com/tailscale/tailscale/issues/1001 if c.sawPMPRecently() { res.PMP = true } else if !c.debug.DisablePMP { metricPMPSent.Add(1) uc.WriteToUDPAddrPort(pmpReqExternalAddrPacket, pxpAddr) } if c.sawPCPRecently() { res.PCP = true } else if !c.debug.DisablePCP { metricPCPSent.Add(1) uc.WriteToUDPAddrPort(pcpAnnounceRequest(myIP), pxpAddr) } if c.sawUPnPRecently() { res.UPnP = true } else if !c.debug.DisableUPnP { // Strictly speaking, you discover UPnP services by sending an // SSDP query (which uPnPPacket is) to udp/1900 on the SSDP // multicast address, and then get a flood of responses back // from everything on your network. // // Empirically, many home routers also respond to SSDP queries // directed at udp/1900 on their LAN unicast IP // (e.g. 192.168.1.1). This is handy because it means we can // probe the router directly and likely get a reply. However, // the specs do not _require_ UPnP devices to respond to // unicast SSDP queries, so some conformant UPnP // implementations only respond to multicast queries. // // In theory, we could send just the multicast query and get // all compliant devices to respond. However, we instead send // to both a unicast and a multicast addresses, for a couple // of reasons: // // First, some LANs and OSes have broken multicast in one way // or another, so it's possible for the multicast query to be // lost while the unicast query gets through. But we still // have to send the multicast query to also get a response // from strict-UPnP devices on multicast-working networks. // // Second, SSDP's packet dynamics are a bit weird: you send // the SSDP query from your unicast IP to the SSDP multicast // IP, but responses are from the UPnP devices's _unicast_ IP // to your unicast IP. This can confuse some less-intelligent // stateful host firewalls, who might block the responses. To // work around this, we send the unicast query first, to teach // the firewall to expect a unicast response from the router, // and then send our multicast query. That way, even if the // device doesn't respond to the unicast query, we've set the // stage for the host firewall to accept the response to the // multicast query. // // See https://github.com/tailscale/tailscale/issues/3197 for // an example of a device that strictly implements UPnP, and // only responds to multicast queries. // // Then we send a discovery packet looking for // urn:schemas-upnp-org:device:InternetGatewayDevice:1 specifically, not // just ssdp:all, because there appear to be devices which only send // their first descriptor (like urn:schemas-wifialliance-org:device:WFADevice:1) // in response to ssdp:all. https://github.com/tailscale/tailscale/issues/3557 metricUPnPSent.Add(1) uc.WriteToUDPAddrPort(uPnPPacket, upnpAddr) uc.WriteToUDPAddrPort(uPnPPacket, upnpMulticastAddr) uc.WriteToUDPAddrPort(uPnPIGDPacket, upnpMulticastAddr) } // We can see multiple UPnP responses from LANs with multiple // UPnP-capable routers. Rather than randomly picking whichever arrives // first, let's collect all UPnP responses and choose at the end. // // We do this by starting a 50ms timer from when the first UDP packet // is received, and waiting at least that long for more UPnP responses // to arrive before returning (as long as the first packet is seen // within the first 200ms of the context creation, which is likely in // the common case). // // This 50ms timer is distinct from the context timeout; it is used to // delay an early return in the case where we see all three portmapping // responses (PCP, PMP, UPnP), whereas the context timeout causes the // loop to exit regardless of what portmapping responses we've seen. // // We use an atomic value to signal that the timer has finished. var ( upnpTimer *time.Timer upnpTimerDone atomic.Bool ) defer func() { if upnpTimer != nil { upnpTimer.Stop() } }() // Store all returned UPnP responses until we're done, at which point // we select from all available options. var upnpResponses []uPnPDiscoResponse defer func() { if !res.UPnP || len(upnpResponses) == 0 { // Either we didn't discover any UPnP responses or // c.sawUPnPRecently() is true; don't change anything. return } // Deduplicate and sort responses upnpResponses = processUPnPResponses(upnpResponses) c.mu.Lock() c.uPnPSawTime = time.Now() if !slices.Equal(c.uPnPMetas, upnpResponses) { c.logf("UPnP meta changed: %+v", upnpResponses) c.uPnPMetas = upnpResponses metricUPnPUpdatedMeta.Add(1) } c.mu.Unlock() }() // This is the main loop that receives UDP packets and parses them into // PCP, PMP, or UPnP responses, updates our ProbeResult, and stores // data for use in GetCachedMappingOrStartCreatingOne. buf := make([]byte, 1500) pcpHeard := false // true when we get any PCP response for { if pcpHeard && res.PMP && res.UPnP { if upnpTimerDone.Load() { // Nothing more to discover. return res, nil } // UPnP timer still running; fall through and keep // receiving packets. } n, src, err := uc.ReadFromUDPAddrPort(buf) if err != nil { if ctx.Err() == context.DeadlineExceeded { err = nil } return res, err } // Start timer after we get the first response. if upnpTimer == nil { upnpTimer = time.AfterFunc(50*time.Millisecond, func() { upnpTimerDone.Store(true) }) } ip := src.Addr().Unmap() handleUPnPResponse := func() { metricUPnPResponse.Add(1) if ip != gw { // https://github.com/tailscale/tailscale/issues/5502 c.logf("UPnP discovery response from %v, but gateway IP is %v", ip, gw) } meta, err := parseUPnPDiscoResponse(buf[:n]) if err != nil { metricUPnPParseErr.Add(1) c.logf("unrecognized UPnP discovery response; ignoring: %v", err) return } metricUPnPOK.Add(1) c.logf("[v1] UPnP reply %+v, %q", meta, buf[:n]) // Store the UPnP response for later selection res.UPnP = true if len(upnpResponses) > 10 { c.logf("too many UPnP responses: skipping") } else { upnpResponses = append(upnpResponses, meta) } } port := src.Port() switch port { case c.upnpPort(): if mem.Contains(mem.B(buf[:n]), mem.S(":InternetGatewayDevice:")) { handleUPnPResponse() } default: // https://github.com/tailscale/tailscale/issues/7377 if mem.Contains(mem.B(buf[:n]), mem.S(":InternetGatewayDevice:")) { c.logf("UPnP discovery response from non-UPnP port %d", port) metricUPnPResponseAlternatePort.Add(1) handleUPnPResponse() } case c.pxpPort(): // same value for PMP and PCP metricPXPResponse.Add(1) if pres, ok := parsePCPResponse(buf[:n]); ok { if pres.OpCode == pcpOpReply|pcpOpAnnounce { pcpHeard = true c.mu.Lock() c.maybeInvalidatePCPMappingLocked(pres.Epoch) // must be before we write to c.pcp* c.pcpSawTime = time.Now() c.pcpLastEpoch = pres.Epoch c.mu.Unlock() switch pres.ResultCode { case pcpCodeOK: c.logf("[v1] Got PCP response: epoch: %v", pres.Epoch) res.PCP = true metricPCPOK.Add(1) continue case pcpCodeNotAuthorized: // A PCP service is running, but refuses to // provide port mapping services. res.PCP = false metricPCPNotAuthorized.Add(1) continue case pcpCodeAddressMismatch: // A PCP service is running, but it is behind a NAT, so it can't help us. res.PCP = false metricPCPAddressMismatch.Add(1) continue default: // Fall through to unexpected log line. } } metricPCPUnhandledResponseCode.Add(1) c.logf("unexpected PCP probe response: %+v", pres) } if pres, ok := parsePMPResponse(buf[:n]); ok { if pres.OpCode != pmpOpReply|pmpOpMapPublicAddr { c.logf("unexpected PMP probe response opcode: %+v", pres) metricPMPUnhandledOpcode.Add(1) continue } switch pres.ResultCode { case pmpCodeOK: metricPMPOK.Add(1) c.logf("[v1] Got PMP response; IP: %v, epoch: %v", pres.PublicAddr, pres.SecondsSinceEpoch) res.PMP = true c.mu.Lock() c.maybeInvalidatePMPMappingLocked(pres.SecondsSinceEpoch) // must be before we write to c.pmp* c.pmpPubIP = pres.PublicAddr c.pmpPubIPTime = time.Now() c.pmpLastEpoch = pres.SecondsSinceEpoch c.mu.Unlock() continue case pmpCodeNotAuthorized: metricPMPNotAuthorized.Add(1) c.logf("PMP probe failed due result code: %+v", pres) continue case pmpCodeNetworkFailure: metricPMPNetworkFailure.Add(1) c.logf("PMP probe failed due result code: %+v", pres) continue case pmpCodeOutOfResources: metricPMPOutOfResources.Add(1) c.logf("PMP probe failed due result code: %+v", pres) continue } metricPMPUnhandledResponseCode.Add(1) c.logf("unexpected PMP probe response: %+v", pres) } } } } func (c *Client) maybeInvalidatePMPMappingLocked(epoch uint32) { if epoch == 0 || c.mapping == nil { return } m, ok := c.mapping.(*pmpMapping) if !ok { return } if epoch >= m.epoch { // Epoch increased, which is fine. // // TODO: we should more closely follow RFC6887 § 8.5 which also // requires us to check the current time and the time that this // epoch was received at. return } // Epoch decreased, so invalidate the mapping and clear PMP fields. c.logf("invalidating PMP mappings since returned epoch %d < stored epoch %d", epoch, m.epoch) c.mapping = nil c.pmpPubIP = netip.Addr{} c.pmpPubIPTime = time.Time{} c.pmpLastEpoch = 0 } func (c *Client) maybeInvalidatePCPMappingLocked(epoch uint32) { if epoch == 0 || c.mapping == nil { return } m, ok := c.mapping.(*pcpMapping) if !ok { return } if epoch >= m.epoch { // Epoch increased, which is fine. // // TODO: we should more closely follow RFC6887 § 8.5 which also // requires us to check the current time and the time that this // epoch was received at. return } // Epoch decreased, so invalidate the mapping and clear PCP fields. c.logf("invalidating PCP mappings since returned epoch %d < stored epoch %d", epoch, m.epoch) c.mapping = nil c.pcpSawTime = time.Time{} c.pcpLastEpoch = 0 } var pmpReqExternalAddrPacket = []byte{pmpVersion, pmpOpMapPublicAddr} // 0, 0 const ( upnpDefaultPort = 1900 // for UDP discovery only; TCP port discovered later ) // uPnPPacket is the UPnP UDP discovery packet's request body. 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") // Send a discovery frame for InternetGatewayDevice, since some devices respond // to ssdp:all with only their first descriptor (which is often not IGD). // https://github.com/tailscale/tailscale/issues/3557 var uPnPIGDPacket = []byte("M-SEARCH * HTTP/1.1\r\n" + "HOST: 239.255.255.250:1900\r\n" + "ST: urn:schemas-upnp-org:device:InternetGatewayDevice:1\r\n" + "MAN: \"ssdp:discover\"\r\n" + "MX: 2\r\n\r\n") // PCP/PMP metrics var ( // metricPXPResponse counts the number of times we received a PMP/PCP response. metricPXPResponse = clientmetric.NewCounter("portmap_pxp_response") // metricPCPSent counts the number of times we sent a PCP request. metricPCPSent = clientmetric.NewCounter("portmap_pcp_sent") // metricPCPOK counts the number of times // we received a successful PCP response. metricPCPOK = clientmetric.NewCounter("portmap_pcp_ok") // metricPCPAddressMismatch counts the number of times // we received a PCP address mismatch result code. metricPCPAddressMismatch = clientmetric.NewCounter("portmap_pcp_address_mismatch") // metricPCPNotAuthorized counts the number of times // we received a PCP not authorized result code. metricPCPNotAuthorized = clientmetric.NewCounter("portmap_pcp_not_authorized") // metricPCPUnhandledResponseCode counts the number of times // we received an (as yet) unhandled PCP result code. metricPCPUnhandledResponseCode = clientmetric.NewCounter("portmap_pcp_unhandled_response_code") // metricPMPSent counts the number of times we sent a PMP request. metricPMPSent = clientmetric.NewCounter("portmap_pmp_sent") // metricPMPOK counts the number of times // we received a successful PMP response. metricPMPOK = clientmetric.NewCounter("portmap_pmp_ok") // metricPMPUnhandledOpcode counts the number of times // we received an unhandled PMP opcode. metricPMPUnhandledOpcode = clientmetric.NewCounter("portmap_pmp_unhandled_opcode") // metricPMPUnhandledResponseCode counts the number of times // we received an unhandled PMP result code. metricPMPUnhandledResponseCode = clientmetric.NewCounter("portmap_pmp_unhandled_response_code") // metricPMPOutOfResources counts the number of times // we received a PCP out of resources result code. metricPMPOutOfResources = clientmetric.NewCounter("portmap_pmp_out_of_resources") // metricPMPNetworkFailure counts the number of times // we received a PCP network failure result code. metricPMPNetworkFailure = clientmetric.NewCounter("portmap_pmp_network_failure") // metricPMPNotAuthorized counts the number of times // we received a PCP not authorized result code. metricPMPNotAuthorized = clientmetric.NewCounter("portmap_pmp_not_authorized") ) // UPnP metrics var ( // metricUPnPSent counts the number of times we sent a UPnP request. metricUPnPSent = clientmetric.NewCounter("portmap_upnp_sent") // metricUPnPResponse counts the number of times we received a UPnP response. metricUPnPResponse = clientmetric.NewCounter("portmap_upnp_response") // metricUPnPResponseAlternatePort counts the number of times we // received a UPnP response from a port other than the UPnP port. metricUPnPResponseAlternatePort = clientmetric.NewCounter("portmap_upnp_response_alternate_port") // metricUPnPSelectLegacy counts the number of times that a legacy // service was found in a UPnP response. metricUPnPSelectLegacy = clientmetric.NewCounter("portmap_upnp_select_legacy") // metricUPnPSelectSingle counts the number of times that only a single // UPnP device was available in selectBestService. metricUPnPSelectSingle = clientmetric.NewCounter("portmap_upnp_select_single") // metricUPnPSelectMultiple counts the number of times that we need to // select from among multiple UPnP devices in selectBestService. metricUPnPSelectMultiple = clientmetric.NewCounter("portmap_upnp_select_multiple") // metricUPnPSelectExternalPublic counts the number of times that // selectBestService picked a UPnP device with an external public IP. metricUPnPSelectExternalPublic = clientmetric.NewCounter("portmap_upnp_select_external_public") // metricUPnPSelectExternalPrivate counts the number of times that // selectBestService picked a UPnP device with an external private IP. metricUPnPSelectExternalPrivate = clientmetric.NewCounter("portmap_upnp_select_external_private") // metricUPnPSelectUp counts the number of times that selectBestService // picked a UPnP device that was up but with no external IP. metricUPnPSelectUp = clientmetric.NewCounter("portmap_upnp_select_up") // metricUPnPSelectNone counts the number of times that selectBestService // picked a UPnP device that is not up. metricUPnPSelectNone = clientmetric.NewCounter("portmap_upnp_select_none") // metricUPnPParseErr counts the number of times we failed to parse a UPnP response. metricUPnPParseErr = clientmetric.NewCounter("portmap_upnp_parse_err") // metricUPnPOK counts the number of times we received a usable UPnP response. metricUPnPOK = clientmetric.NewCounter("portmap_upnp_ok") // metricUPnPUpdatedMeta counts the number of times // we received a UPnP response with a new meta. metricUPnPUpdatedMeta = clientmetric.NewCounter("portmap_upnp_updated_meta") ) // UPnP error metric that's keyed by code; lazily registered on first read var ( metricUPnPErrorsByCode syncs.Map[int, *clientmetric.Metric] ) func getUPnPErrorsMetric(code int) *clientmetric.Metric { mm, _ := metricUPnPErrorsByCode.LoadOrInit(code, func() *clientmetric.Metric { // Metric names cannot contain a hyphen, so we handle negative // numbers by prefixing the name with a "minus_". var codeStr string if code < 0 { codeStr = fmt.Sprintf("portmap_upnp_errors_with_code_minus_%d", -code) } else { codeStr = fmt.Sprintf("portmap_upnp_errors_with_code_%d", code) } return clientmetric.NewCounter(codeStr) }) return mm }