// Copyright (c) Tailscale Inc & AUTHORS // SPDX-License-Identifier: BSD-3-Clause // Package tstun provides a TUN struct implementing the tun.Device interface // with additional features as required by wgengine. package tstun import ( "errors" "fmt" "io" "net/netip" "os" "reflect" "strings" "sync" "sync/atomic" "time" "github.com/tailscale/wireguard-go/device" "github.com/tailscale/wireguard-go/tun" "go4.org/mem" "golang.org/x/exp/slices" "gvisor.dev/gvisor/pkg/tcpip/stack" "tailscale.com/disco" "tailscale.com/net/connstats" "tailscale.com/net/packet" "tailscale.com/net/tsaddr" "tailscale.com/net/tstun/table" "tailscale.com/syncs" "tailscale.com/tstime/mono" "tailscale.com/types/ipproto" "tailscale.com/types/key" "tailscale.com/types/logger" "tailscale.com/types/views" "tailscale.com/util/clientmetric" "tailscale.com/util/mak" "tailscale.com/wgengine/capture" "tailscale.com/wgengine/filter" "tailscale.com/wgengine/wgcfg" ) const maxBufferSize = device.MaxMessageSize // PacketStartOffset is the minimal amount of leading space that must exist // before &packet[offset] in a packet passed to Read, Write, or InjectInboundDirect. // This is necessary to avoid reallocation in wireguard-go internals. const PacketStartOffset = device.MessageTransportHeaderSize // MaxPacketSize is the maximum size (in bytes) // of a packet that can be injected into a tstun.Wrapper. const MaxPacketSize = device.MaxContentSize const tapDebug = false // for super verbose TAP debugging var ( // ErrClosed is returned when attempting an operation on a closed Wrapper. ErrClosed = errors.New("device closed") // ErrFiltered is returned when the acted-on packet is rejected by a filter. ErrFiltered = errors.New("packet dropped by filter") ) var ( errPacketTooBig = errors.New("packet too big") errOffsetTooBig = errors.New("offset larger than buffer length") errOffsetTooSmall = errors.New("offset smaller than PacketStartOffset") ) // parsedPacketPool holds a pool of Parsed structs for use in filtering. // This is needed because escape analysis cannot see that parsed packets // do not escape through {Pre,Post}Filter{In,Out}. var parsedPacketPool = sync.Pool{New: func() any { return new(packet.Parsed) }} // FilterFunc is a packet-filtering function with access to the Wrapper device. // It must not hold onto the packet struct, as its backing storage will be reused. type FilterFunc func(*packet.Parsed, *Wrapper) filter.Response // Wrapper augments a tun.Device with packet filtering and injection. type Wrapper struct { logf logger.Logf limitedLogf logger.Logf // aggressively rate-limited logf used for potentially high volume errors // tdev is the underlying Wrapper device. tdev tun.Device isTAP bool // whether tdev is a TAP device closeOnce sync.Once // lastActivityAtomic is read/written atomically. // On 32 bit systems, if the fields above change, // you might need to add an align64 field here. lastActivityAtomic mono.Time // time of last send or receive destIPActivity syncs.AtomicValue[map[netip.Addr]func()] destMACAtomic syncs.AtomicValue[[6]byte] discoKey syncs.AtomicValue[key.DiscoPublic] // timeNow, if non-nil, will be used to obtain the current time. timeNow func() time.Time // natV4Config stores the current NAT configuration. natV4Config atomic.Pointer[natV4Config] // vectorBuffer stores the oldest unconsumed packet vector from tdev. It is // allocated in wrap() and the underlying arrays should never grow. vectorBuffer [][]byte // bufferConsumedMu protects bufferConsumed from concurrent sends, closes, // and send-after-close (by way of bufferConsumedClosed). bufferConsumedMu sync.Mutex // bufferConsumedClosed is true when bufferConsumed has been closed. This is // read by bufferConsumed writers to prevent send-after-close. bufferConsumedClosed bool // bufferConsumed synchronizes access to vectorBuffer (shared by Read() and // pollVector()). // // Close closes bufferConsumed and sets bufferConsumedClosed to true. bufferConsumed chan struct{} // closed signals poll (by closing) when the device is closed. closed chan struct{} // outboundMu protects outbound and vectorOutbound from concurrent sends, // closes, and send-after-close (by way of outboundClosed). outboundMu sync.Mutex // outboundClosed is true when outbound or vectorOutbound have been closed. // This is read by outbound and vectorOutbound writers to prevent // send-after-close. outboundClosed bool // vectorOutbound is the queue by which packets leave the TUN device. // // The directions are relative to the network, not the device: // inbound packets arrive via UDP and are written into the TUN device; // outbound packets are read from the TUN device and sent out via UDP. // This queue is needed because although inbound writes are synchronous, // the other direction must wait on a WireGuard goroutine to poll it. // // Empty reads are skipped by WireGuard, so it is always legal // to discard an empty packet instead of sending it through vectorOutbound. // // Close closes vectorOutbound and sets outboundClosed to true. vectorOutbound chan tunVectorReadResult // eventsUpDown yields up and down tun.Events that arrive on a Wrapper's events channel. eventsUpDown chan tun.Event // eventsOther yields non-up-and-down tun.Events that arrive on a Wrapper's events channel. eventsOther chan tun.Event // filter atomically stores the currently active packet filter filter atomic.Pointer[filter.Filter] // filterFlags control the verbosity of logging packet drops/accepts. filterFlags filter.RunFlags // PreFilterPacketInboundFromWireGuard is the inbound filter function that runs before the main filter // and therefore sees the packets that may be later dropped by it. PreFilterPacketInboundFromWireGuard FilterFunc // PostFilterPacketInboundFromWireGaurd is the inbound filter function that runs after the main filter. PostFilterPacketInboundFromWireGaurd FilterFunc // PreFilterPacketOutboundToWireGuardNetstackIntercept is a filter function that runs before the main filter // for packets from the local system. This filter is populated by netstack to hook // packets that should be handled by netstack. If set, this filter runs before // PreFilterFromTunToEngine. PreFilterPacketOutboundToWireGuardNetstackIntercept FilterFunc // PreFilterPacketOutboundToWireGuardEngineIntercept is a filter function that runs before the main filter // for packets from the local system. This filter is populated by wgengine to hook // packets which it handles internally. If both this and PreFilterFromTunToNetstack // filter functions are non-nil, this filter runs second. PreFilterPacketOutboundToWireGuardEngineIntercept FilterFunc // PostFilterPacketOutboundToWireGuard is the outbound filter function that runs after the main filter. PostFilterPacketOutboundToWireGuard FilterFunc // OnTSMPPongReceived, if non-nil, is called whenever a TSMP pong arrives. OnTSMPPongReceived func(packet.TSMPPongReply) // OnICMPEchoResponseReceived, if non-nil, is called whenever a ICMP echo response // arrives. If the packet is to be handled internally this returns true, // false otherwise. OnICMPEchoResponseReceived func(*packet.Parsed) bool // PeerAPIPort, if non-nil, returns the peerapi port that's // running for the given IP address. PeerAPIPort func(netip.Addr) (port uint16, ok bool) // disableFilter disables all filtering when set. This should only be used in tests. disableFilter bool // disableTSMPRejected disables TSMP rejected responses. For tests. disableTSMPRejected bool // stats maintains per-connection counters. stats atomic.Pointer[connstats.Statistics] captureHook syncs.AtomicValue[capture.Callback] } // tunInjectedRead is an injected packet pretending to be a tun.Read(). type tunInjectedRead struct { // Only one of packet or data should be set, and are read in that order of // precedence. packet stack.PacketBufferPtr data []byte } // tunVectorReadResult is the result of a tun.Read(), or an injected packet // pretending to be a tun.Read(). type tunVectorReadResult struct { // When err AND data are nil, injected will be set with meaningful data // (injected packet). If either err OR data is non-nil, injected should be // ignored (a "real" tun.Read). err error data [][]byte injected tunInjectedRead dataOffset int } type setWrapperer interface { // setWrapper enables the underlying TUN/TAP to have access to the Wrapper. // It MUST be called only once during initialization, other usage is unsafe. setWrapper(*Wrapper) } func WrapTAP(logf logger.Logf, tdev tun.Device) *Wrapper { return wrap(logf, tdev, true) } func Wrap(logf logger.Logf, tdev tun.Device) *Wrapper { return wrap(logf, tdev, false) } func wrap(logf logger.Logf, tdev tun.Device, isTAP bool) *Wrapper { logf = logger.WithPrefix(logf, "tstun: ") w := &Wrapper{ logf: logf, limitedLogf: logger.RateLimitedFn(logf, 1*time.Minute, 2, 10), isTAP: isTAP, tdev: tdev, // bufferConsumed is conceptually a condition variable: // a goroutine should not block when setting it, even with no listeners. bufferConsumed: make(chan struct{}, 1), closed: make(chan struct{}), // vectorOutbound can be unbuffered; the buffer is an optimization. vectorOutbound: make(chan tunVectorReadResult, 1), eventsUpDown: make(chan tun.Event), eventsOther: make(chan tun.Event), // TODO(dmytro): (highly rate-limited) hexdumps should happen on unknown packets. filterFlags: filter.LogAccepts | filter.LogDrops, } w.vectorBuffer = make([][]byte, tdev.BatchSize()) for i := range w.vectorBuffer { w.vectorBuffer[i] = make([]byte, maxBufferSize) } go w.pollVector() go w.pumpEvents() // The buffer starts out consumed. w.bufferConsumed <- struct{}{} w.noteActivity() if sw, ok := w.tdev.(setWrapperer); ok { sw.setWrapper(w) } return w } // now returns the current time, either by calling t.timeNow if set or time.Now // if not. func (t *Wrapper) now() time.Time { if t.timeNow != nil { return t.timeNow() } return time.Now() } // SetDestIPActivityFuncs sets a map of funcs to run per packet // destination (the map keys). // // The map ownership passes to the Wrapper. It must be non-nil. func (t *Wrapper) SetDestIPActivityFuncs(m map[netip.Addr]func()) { t.destIPActivity.Store(m) } // SetDiscoKey sets the current discovery key. // // It is only used for filtering out bogus traffic when network // stack(s) get confused; see Issue 1526. func (t *Wrapper) SetDiscoKey(k key.DiscoPublic) { t.discoKey.Store(k) } // isSelfDisco reports whether packet p // looks like a Disco packet from ourselves. // See Issue 1526. func (t *Wrapper) isSelfDisco(p *packet.Parsed) bool { if p.IPProto != ipproto.UDP { return false } pkt := p.Payload() discobs, ok := disco.Source(pkt) if !ok { return false } discoSrc := key.DiscoPublicFromRaw32(mem.B(discobs)) selfDiscoPub := t.discoKey.Load() return selfDiscoPub == discoSrc } func (t *Wrapper) Close() error { var err error t.closeOnce.Do(func() { close(t.closed) t.bufferConsumedMu.Lock() t.bufferConsumedClosed = true close(t.bufferConsumed) t.bufferConsumedMu.Unlock() t.outboundMu.Lock() t.outboundClosed = true close(t.vectorOutbound) t.outboundMu.Unlock() err = t.tdev.Close() }) return err } // isClosed reports whether t is closed. func (t *Wrapper) isClosed() bool { select { case <-t.closed: return true default: return false } } // pumpEvents copies events from t.tdev to t.eventsUpDown and t.eventsOther. // pumpEvents exits when t.tdev.events or t.closed is closed. // pumpEvents closes t.eventsUpDown and t.eventsOther when it exits. func (t *Wrapper) pumpEvents() { defer close(t.eventsUpDown) defer close(t.eventsOther) src := t.tdev.Events() for { // Retrieve an event from the TUN device. var event tun.Event var ok bool select { case <-t.closed: return case event, ok = <-src: if !ok { return } } // Pass along event to the correct recipient. // Though event is a bitmask, in practice there is only ever one bit set at a time. dst := t.eventsOther if event&(tun.EventUp|tun.EventDown) != 0 { dst = t.eventsUpDown } select { case <-t.closed: return case dst <- event: } } } // EventsUpDown returns a TUN event channel that contains all Up and Down events. func (t *Wrapper) EventsUpDown() chan tun.Event { return t.eventsUpDown } // Events returns a TUN event channel that contains all non-Up, non-Down events. // It is named Events because it is the set of events that we want to expose to wireguard-go, // and Events is the name specified by the wireguard-go tun.Device interface. func (t *Wrapper) Events() <-chan tun.Event { return t.eventsOther } func (t *Wrapper) File() *os.File { return t.tdev.File() } func (t *Wrapper) MTU() (int, error) { return t.tdev.MTU() } func (t *Wrapper) Name() (string, error) { return t.tdev.Name() } const ethernetFrameSize = 14 // 2 six byte MACs, 2 bytes ethertype // pollVector polls t.tdev.Read(), placing the oldest unconsumed packet vector // into t.vectorBuffer. This is needed because t.tdev.Read() in general may // block (it does on Windows), so packets may be stuck in t.vectorOutbound if // t.Read() called t.tdev.Read() directly. func (t *Wrapper) pollVector() { sizes := make([]int, len(t.vectorBuffer)) readOffset := PacketStartOffset if t.isTAP { readOffset = PacketStartOffset - ethernetFrameSize } for range t.bufferConsumed { DoRead: for i := range t.vectorBuffer { t.vectorBuffer[i] = t.vectorBuffer[i][:cap(t.vectorBuffer[i])] } var n int var err error for n == 0 && err == nil { if t.isClosed() { return } n, err = t.tdev.Read(t.vectorBuffer[:], sizes, readOffset) if t.isTAP && tapDebug { s := fmt.Sprintf("% x", t.vectorBuffer[0][:]) for strings.HasSuffix(s, " 00") { s = strings.TrimSuffix(s, " 00") } t.logf("TAP read %v, %v: %s", n, err, s) } } for i := range sizes[:n] { t.vectorBuffer[i] = t.vectorBuffer[i][:readOffset+sizes[i]] } if t.isTAP { if err == nil { ethernetFrame := t.vectorBuffer[0][readOffset:] if t.handleTAPFrame(ethernetFrame) { goto DoRead } } // Fall through. We got an IP packet. if sizes[0] >= ethernetFrameSize { t.vectorBuffer[0] = t.vectorBuffer[0][:readOffset+sizes[0]-ethernetFrameSize] } if tapDebug { t.logf("tap regular frame: %x", t.vectorBuffer[0][PacketStartOffset:PacketStartOffset+sizes[0]]) } } t.sendVectorOutbound(tunVectorReadResult{ data: t.vectorBuffer[:n], dataOffset: PacketStartOffset, err: err, }) } } // sendBufferConsumed does t.bufferConsumed <- struct{}{}. func (t *Wrapper) sendBufferConsumed() { t.bufferConsumedMu.Lock() defer t.bufferConsumedMu.Unlock() if t.bufferConsumedClosed { return } t.bufferConsumed <- struct{}{} } // injectOutbound does t.vectorOutbound <- r func (t *Wrapper) injectOutbound(r tunInjectedRead) { t.outboundMu.Lock() defer t.outboundMu.Unlock() if t.outboundClosed { return } t.vectorOutbound <- tunVectorReadResult{ injected: r, } } // sendVectorOutbound does t.vectorOutbound <- r. func (t *Wrapper) sendVectorOutbound(r tunVectorReadResult) { t.outboundMu.Lock() defer t.outboundMu.Unlock() if t.outboundClosed { return } t.vectorOutbound <- r } // snatV4 does SNAT on p if it's an IPv4 packet and the destination // address requires a different source address. func (t *Wrapper) snatV4(p *packet.Parsed) { if p.IPVersion != 4 { return } nc := t.natV4Config.Load() oldSrc := p.Src.Addr() newSrc := nc.selectSrcIP(oldSrc, p.Dst.Addr()) if oldSrc != newSrc { p.UpdateSrcAddr(newSrc) } } // dnatV4 does destination NAT on p if it's an IPv4 packet. func (t *Wrapper) dnatV4(p *packet.Parsed) { if p.IPVersion != 4 { return } nc := t.natV4Config.Load() oldDst := p.Dst.Addr() newDst := nc.mapDstIP(oldDst) if newDst != oldDst { p.UpdateDstAddr(newDst) } } // findV4 returns the first Tailscale IPv4 address in addrs. func findV4(addrs []netip.Prefix) netip.Addr { for _, ap := range addrs { a := ap.Addr() if a.Is4() && tsaddr.IsTailscaleIP(a) { return a } } return netip.Addr{} } // natV4Config is the configuration for IPv4 NAT. // It should be treated as immutable. // // The nil value is a valid configuration. type natV4Config struct { // nativeAddr is the IPv4 Tailscale Address of the current node. nativeAddr netip.Addr // listenAddrs is the set of IPv4 addresses that should be // mapped to the native address. These are the addresses that // peers will use to connect to this node. listenAddrs views.Map[netip.Addr, struct{}] // masqAddr -> struct{} // dstMasqAddrs is map of dst addresses to their respective MasqueradeAsIP // addresses. The MasqueradeAsIP address is the address that should be used // as the source address for packets to dst. dstMasqAddrs views.Map[key.NodePublic, netip.Addr] // dst -> masqAddr // dstAddrToPeerKeyMapper is the routing table used to map a given dst IP to // the peer key responsible for that IP. // It only contains peers that require a MasqueradeAsIP address. dstAddrToPeerKeyMapper *table.RoutingTable } // mapDstIP returns the destination IP to use for a packet to dst. // If dst is not one of the listen addresses, it is returned as-is, // otherwise the native address is returned. func (c *natV4Config) mapDstIP(oldDst netip.Addr) netip.Addr { if c == nil { return oldDst } if _, ok := c.listenAddrs.GetOk(oldDst); ok { return c.nativeAddr } return oldDst } // selectSrcIP returns the source IP to use for a packet to dst. // If the packet is not from the native address, it is returned as-is. func (c *natV4Config) selectSrcIP(oldSrc, dst netip.Addr) netip.Addr { if c == nil { return oldSrc } if oldSrc != c.nativeAddr { return oldSrc } p, ok := c.dstAddrToPeerKeyMapper.Lookup(dst) if !ok { return oldSrc } if eip, ok := c.dstMasqAddrs.GetOk(p); ok { return eip } return oldSrc } // natConfigFromWireGuardConfig generates a natV4Config from nm. // If v4 NAT is not required, it returns nil. func natConfigFromWGConfig(wcfg *wgcfg.Config) *natV4Config { if wcfg == nil { return nil } nativeAddr := findV4(wcfg.Addresses) if !nativeAddr.IsValid() { return nil } var ( rt table.RoutingTableBuilder dstMasqAddrs map[key.NodePublic]netip.Addr listenAddrs map[netip.Addr]struct{} ) // When using an exit node that requires masquerading, we need to // fill out the routing table with all peers not just the ones that // require masquerading. exitNodeRequiresMasq := false // true if using an exit node and it requires masquerading for _, p := range wcfg.Peers { isExitNode := slices.Contains(p.AllowedIPs, tsaddr.AllIPv4()) || slices.Contains(p.AllowedIPs, tsaddr.AllIPv6()) if isExitNode && p.V4MasqAddr != nil && p.V4MasqAddr.IsValid() { exitNodeRequiresMasq = true break } } for i := range wcfg.Peers { p := &wcfg.Peers[i] var addrToUse netip.Addr if p.V4MasqAddr != nil && p.V4MasqAddr.IsValid() { addrToUse = *p.V4MasqAddr mak.Set(&listenAddrs, addrToUse, struct{}{}) } else if exitNodeRequiresMasq { addrToUse = nativeAddr } else { continue } rt.InsertOrReplace(p.PublicKey, p.AllowedIPs...) mak.Set(&dstMasqAddrs, p.PublicKey, addrToUse) } if len(listenAddrs) == 0 && len(dstMasqAddrs) == 0 { return nil } return &natV4Config{ nativeAddr: nativeAddr, listenAddrs: views.MapOf(listenAddrs), dstMasqAddrs: views.MapOf(dstMasqAddrs), dstAddrToPeerKeyMapper: rt.Build(), } } // SetNetMap is called when a new NetworkMap is received. // It currently (2023-03-01) only updates the IPv4 NAT configuration. func (t *Wrapper) SetWGConfig(wcfg *wgcfg.Config) { cfg := natConfigFromWGConfig(wcfg) old := t.natV4Config.Swap(cfg) if !reflect.DeepEqual(old, cfg) { t.logf("nat config: %+v", cfg) } } var ( magicDNSIPPort = netip.AddrPortFrom(tsaddr.TailscaleServiceIP(), 0) // 100.100.100.100:0 magicDNSIPPortv6 = netip.AddrPortFrom(tsaddr.TailscaleServiceIPv6(), 0) ) func (t *Wrapper) filterPacketOutboundToWireGuard(p *packet.Parsed) filter.Response { // Fake ICMP echo responses to MagicDNS (100.100.100.100). if p.IsEchoRequest() { switch p.Dst { case magicDNSIPPort: header := p.ICMP4Header() header.ToResponse() outp := packet.Generate(&header, p.Payload()) t.InjectInboundCopy(outp) return filter.DropSilently // don't pass on to OS; already handled case magicDNSIPPortv6: header := p.ICMP6Header() header.ToResponse() outp := packet.Generate(&header, p.Payload()) t.InjectInboundCopy(outp) return filter.DropSilently // don't pass on to OS; already handled } } // Issue 1526 workaround: if we sent disco packets over // Tailscale from ourselves, then drop them, as that shouldn't // happen unless a networking stack is confused, as it seems // macOS in Network Extension mode might be. if p.IPProto == ipproto.UDP && // disco is over UDP; avoid isSelfDisco call for TCP/etc t.isSelfDisco(p) { t.limitedLogf("[unexpected] received self disco out packet over tstun; dropping") metricPacketOutDropSelfDisco.Add(1) return filter.DropSilently } if t.PreFilterPacketOutboundToWireGuardNetstackIntercept != nil { if res := t.PreFilterPacketOutboundToWireGuardNetstackIntercept(p, t); res.IsDrop() { // Handled by netstack.Impl.handleLocalPackets (quad-100 DNS primarily) return res } } if t.PreFilterPacketOutboundToWireGuardEngineIntercept != nil { if res := t.PreFilterPacketOutboundToWireGuardEngineIntercept(p, t); res.IsDrop() { // Handled by userspaceEngine.handleLocalPackets (primarily handles // quad-100 if netstack is not installed). return res } } filt := t.filter.Load() if filt == nil { return filter.Drop } if filt.RunOut(p, t.filterFlags) != filter.Accept { metricPacketOutDropFilter.Add(1) return filter.Drop } if t.PostFilterPacketOutboundToWireGuard != nil { if res := t.PostFilterPacketOutboundToWireGuard(p, t); res.IsDrop() { return res } } return filter.Accept } // noteActivity records that there was a read or write at the current time. func (t *Wrapper) noteActivity() { t.lastActivityAtomic.StoreAtomic(mono.Now()) } // IdleDuration reports how long it's been since the last read or write to this device. // // Its value should only be presumed accurate to roughly 10ms granularity. // If there's never been activity, the duration is since the wrapper was created. func (t *Wrapper) IdleDuration() time.Duration { return mono.Since(t.lastActivityAtomic.LoadAtomic()) } func (t *Wrapper) Read(buffs [][]byte, sizes []int, offset int) (int, error) { // packet from OS read and sent to WG res, ok := <-t.vectorOutbound if !ok { return 0, io.EOF } if res.err != nil && len(res.data) == 0 { return 0, res.err } if res.data == nil { n, err := t.injectedRead(res.injected, buffs[0], offset) sizes[0] = n if err != nil && n == 0 { return 0, err } return 1, err } metricPacketOut.Add(int64(len(res.data))) var buffsPos int p := parsedPacketPool.Get().(*packet.Parsed) defer parsedPacketPool.Put(p) captHook := t.captureHook.Load() for _, data := range res.data { p.Decode(data[res.dataOffset:]) t.snatV4(p) if m := t.destIPActivity.Load(); m != nil { if fn := m[p.Dst.Addr()]; fn != nil { fn() } } if captHook != nil { captHook(capture.FromLocal, t.now(), p.Buffer(), p.CaptureMeta) } if !t.disableFilter { response := t.filterPacketOutboundToWireGuard(p) if response != filter.Accept { metricPacketOutDrop.Add(1) continue } } n := copy(buffs[buffsPos][offset:], p.Buffer()) if n != len(data)-res.dataOffset { panic(fmt.Sprintf("short copy: %d != %d", n, len(data)-res.dataOffset)) } sizes[buffsPos] = n if stats := t.stats.Load(); stats != nil { stats.UpdateTxVirtual(p.Buffer()) } buffsPos++ } // t.vectorBuffer has a fixed location in memory. // TODO(raggi): add an explicit field and possibly method to the tunVectorReadResult // to signal when sendBufferConsumed should be called. if &res.data[0] == &t.vectorBuffer[0] { // We are done with t.buffer. Let poll() re-use it. t.sendBufferConsumed() } t.noteActivity() return buffsPos, res.err } // injectedRead handles injected reads, which bypass filters. func (t *Wrapper) injectedRead(res tunInjectedRead, buf []byte, offset int) (int, error) { metricPacketOut.Add(1) var n int if !res.packet.IsNil() { n = copy(buf[offset:], res.packet.NetworkHeader().Slice()) n += copy(buf[offset+n:], res.packet.TransportHeader().Slice()) n += copy(buf[offset+n:], res.packet.Data().AsRange().ToSlice()) res.packet.DecRef() } else { n = copy(buf[offset:], res.data) } p := parsedPacketPool.Get().(*packet.Parsed) defer parsedPacketPool.Put(p) p.Decode(buf[offset : offset+n]) t.snatV4(p) if m := t.destIPActivity.Load(); m != nil { if fn := m[p.Dst.Addr()]; fn != nil { fn() } } if stats := t.stats.Load(); stats != nil { stats.UpdateTxVirtual(buf[offset:][:n]) } t.noteActivity() return n, nil } func (t *Wrapper) filterPacketInboundFromWireGuard(p *packet.Parsed, captHook capture.Callback) filter.Response { if captHook != nil { captHook(capture.FromPeer, t.now(), p.Buffer(), p.CaptureMeta) } if p.IPProto == ipproto.TSMP { if pingReq, ok := p.AsTSMPPing(); ok { t.noteActivity() t.injectOutboundPong(p, pingReq) return filter.DropSilently } else if data, ok := p.AsTSMPPong(); ok { if f := t.OnTSMPPongReceived; f != nil { f(data) } } } if p.IsEchoResponse() { if f := t.OnICMPEchoResponseReceived; f != nil && f(p) { // Note: this looks dropped in metrics, even though it was // handled internally. return filter.DropSilently } } // Issue 1526 workaround: if we see disco packets over // Tailscale from ourselves, then drop them, as that shouldn't // happen unless a networking stack is confused, as it seems // macOS in Network Extension mode might be. if p.IPProto == ipproto.UDP && // disco is over UDP; avoid isSelfDisco call for TCP/etc t.isSelfDisco(p) { t.limitedLogf("[unexpected] received self disco in packet over tstun; dropping") metricPacketInDropSelfDisco.Add(1) return filter.DropSilently } if t.PreFilterPacketInboundFromWireGuard != nil { if res := t.PreFilterPacketInboundFromWireGuard(p, t); res.IsDrop() { return res } } filt := t.filter.Load() if filt == nil { return filter.Drop } outcome := filt.RunIn(p, t.filterFlags) // Let peerapi through the filter; its ACLs are handled at L7, // not at the packet level. if outcome != filter.Accept && p.IPProto == ipproto.TCP && p.TCPFlags&packet.TCPSyn != 0 && t.PeerAPIPort != nil { if port, ok := t.PeerAPIPort(p.Dst.Addr()); ok && port == p.Dst.Port() { outcome = filter.Accept } } if outcome != filter.Accept { metricPacketInDropFilter.Add(1) // Tell them, via TSMP, we're dropping them due to the ACL. // Their host networking stack can translate this into ICMP // or whatnot as required. But notably, their GUI or tailscale CLI // can show them a rejection history with reasons. if p.IPVersion == 4 && p.IPProto == ipproto.TCP && p.TCPFlags&packet.TCPSyn != 0 && !t.disableTSMPRejected { rj := packet.TailscaleRejectedHeader{ IPSrc: p.Dst.Addr(), IPDst: p.Src.Addr(), Src: p.Src, Dst: p.Dst, Proto: p.IPProto, Reason: packet.RejectedDueToACLs, } if filt.ShieldsUp() { rj.Reason = packet.RejectedDueToShieldsUp } pkt := packet.Generate(rj, nil) t.InjectOutbound(pkt) // TODO(bradfitz): also send a TCP RST, after the TSMP message. } return filter.Drop } if t.PostFilterPacketInboundFromWireGaurd != nil { if res := t.PostFilterPacketInboundFromWireGaurd(p, t); res.IsDrop() { return res } } return filter.Accept } // Write accepts incoming packets. The packets begins at buffs[:][offset:], // like wireguard-go/tun.Device.Write. func (t *Wrapper) Write(buffs [][]byte, offset int) (int, error) { metricPacketIn.Add(int64(len(buffs))) i := 0 p := parsedPacketPool.Get().(*packet.Parsed) defer parsedPacketPool.Put(p) captHook := t.captureHook.Load() for _, buff := range buffs { p.Decode(buff[offset:]) t.dnatV4(p) if !t.disableFilter { if t.filterPacketInboundFromWireGuard(p, captHook) != filter.Accept { metricPacketInDrop.Add(1) } else { buffs[i] = buff i++ } } } if t.disableFilter { i = len(buffs) } buffs = buffs[:i] if len(buffs) > 0 { t.noteActivity() _, err := t.tdevWrite(buffs, offset) return len(buffs), err } return 0, nil } func (t *Wrapper) tdevWrite(buffs [][]byte, offset int) (int, error) { if stats := t.stats.Load(); stats != nil { for i := range buffs { stats.UpdateRxVirtual((buffs)[i][offset:]) } } return t.tdev.Write(buffs, offset) } func (t *Wrapper) GetFilter() *filter.Filter { return t.filter.Load() } func (t *Wrapper) SetFilter(filt *filter.Filter) { t.filter.Store(filt) } // InjectInboundPacketBuffer makes the Wrapper device behave as if a packet // with the given contents was received from the network. // It takes ownership of one reference count on the packet. The injected // packet will not pass through inbound filters. // // This path is typically used to deliver synthesized packets to the // host networking stack. func (t *Wrapper) InjectInboundPacketBuffer(pkt stack.PacketBufferPtr) error { buf := make([]byte, PacketStartOffset+pkt.Size()) n := copy(buf[PacketStartOffset:], pkt.NetworkHeader().Slice()) n += copy(buf[PacketStartOffset+n:], pkt.TransportHeader().Slice()) n += copy(buf[PacketStartOffset+n:], pkt.Data().AsRange().ToSlice()) if n != pkt.Size() { panic("unexpected packet size after copy") } pkt.DecRef() p := parsedPacketPool.Get().(*packet.Parsed) defer parsedPacketPool.Put(p) p.Decode(buf[PacketStartOffset:]) captHook := t.captureHook.Load() if captHook != nil { captHook(capture.SynthesizedToLocal, t.now(), p.Buffer(), p.CaptureMeta) } t.dnatV4(p) return t.InjectInboundDirect(buf, PacketStartOffset) } // InjectInboundDirect makes the Wrapper device behave as if a packet // with the given contents was received from the network. // It blocks and does not take ownership of the packet. // The injected packet will not pass through inbound filters. // // The packet contents are to start at &buf[offset]. // offset must be greater or equal to PacketStartOffset. // The space before &buf[offset] will be used by WireGuard. func (t *Wrapper) InjectInboundDirect(buf []byte, offset int) error { if len(buf) > MaxPacketSize { return errPacketTooBig } if len(buf) < offset { return errOffsetTooBig } if offset < PacketStartOffset { return errOffsetTooSmall } // Write to the underlying device to skip filters. _, err := t.tdevWrite([][]byte{buf}, offset) // TODO(jwhited): alloc? return err } // InjectInboundCopy takes a packet without leading space, // reallocates it to conform to the InjectInboundDirect interface // and calls InjectInboundDirect on it. Injecting a nil packet is a no-op. func (t *Wrapper) InjectInboundCopy(packet []byte) error { // We duplicate this check from InjectInboundDirect here // to avoid wasting an allocation on an oversized packet. if len(packet) > MaxPacketSize { return errPacketTooBig } if len(packet) == 0 { return nil } buf := make([]byte, PacketStartOffset+len(packet)) copy(buf[PacketStartOffset:], packet) return t.InjectInboundDirect(buf, PacketStartOffset) } func (t *Wrapper) injectOutboundPong(pp *packet.Parsed, req packet.TSMPPingRequest) { pong := packet.TSMPPongReply{ Data: req.Data, } if t.PeerAPIPort != nil { pong.PeerAPIPort, _ = t.PeerAPIPort(pp.Dst.Addr()) } switch pp.IPVersion { case 4: h4 := pp.IP4Header() h4.ToResponse() pong.IPHeader = h4 case 6: h6 := pp.IP6Header() h6.ToResponse() pong.IPHeader = h6 default: return } t.InjectOutbound(packet.Generate(pong, nil)) } // InjectOutbound makes the Wrapper device behave as if a packet // with the given contents was sent to the network. // It does not block, but takes ownership of the packet. // The injected packet will not pass through outbound filters. // Injecting an empty packet is a no-op. func (t *Wrapper) InjectOutbound(pkt []byte) error { if len(pkt) > MaxPacketSize { return errPacketTooBig } if len(pkt) == 0 { return nil } t.injectOutbound(tunInjectedRead{data: pkt}) return nil } // InjectOutboundPacketBuffer logically behaves as InjectOutbound. It takes ownership of one // reference count on the packet, and the packet may be mutated. The packet refcount will be // decremented after the injected buffer has been read. func (t *Wrapper) InjectOutboundPacketBuffer(pkt stack.PacketBufferPtr) error { size := pkt.Size() if size > MaxPacketSize { pkt.DecRef() return errPacketTooBig } if size == 0 { pkt.DecRef() return nil } if capt := t.captureHook.Load(); capt != nil { b := pkt.ToBuffer() capt(capture.SynthesizedToPeer, t.now(), b.Flatten(), packet.CaptureMeta{}) } t.injectOutbound(tunInjectedRead{packet: pkt}) return nil } func (t *Wrapper) BatchSize() int { return t.tdev.BatchSize() } // Unwrap returns the underlying tun.Device. func (t *Wrapper) Unwrap() tun.Device { return t.tdev } // SetStatistics specifies a per-connection statistics aggregator. // Nil may be specified to disable statistics gathering. func (t *Wrapper) SetStatistics(stats *connstats.Statistics) { t.stats.Store(stats) } var ( metricPacketIn = clientmetric.NewCounter("tstun_in_from_wg") metricPacketInDrop = clientmetric.NewCounter("tstun_in_from_wg_drop") metricPacketInDropFilter = clientmetric.NewCounter("tstun_in_from_wg_drop_filter") metricPacketInDropSelfDisco = clientmetric.NewCounter("tstun_in_from_wg_drop_self_disco") metricPacketOut = clientmetric.NewCounter("tstun_out_to_wg") metricPacketOutDrop = clientmetric.NewCounter("tstun_out_to_wg_drop") metricPacketOutDropFilter = clientmetric.NewCounter("tstun_out_to_wg_drop_filter") metricPacketOutDropSelfDisco = clientmetric.NewCounter("tstun_out_to_wg_drop_self_disco") ) func (t *Wrapper) InstallCaptureHook(cb capture.Callback) { t.captureHook.Store(cb) }