// Copyright (c) Tailscale Inc & AUTHORS // SPDX-License-Identifier: BSD-3-Clause package tstun import ( "errors" "fmt" "io" "net/netip" "os" "reflect" "runtime" "slices" "strings" "sync" "sync/atomic" "time" "github.com/gaissmai/bart" "github.com/tailscale/wireguard-go/conn" "github.com/tailscale/wireguard-go/device" "github.com/tailscale/wireguard-go/tun" "go4.org/mem" "gvisor.dev/gvisor/pkg/tcpip/stack" "tailscale.com/disco" tsmetrics "tailscale.com/metrics" "tailscale.com/net/connstats" "tailscale.com/net/packet" "tailscale.com/net/packet/checksum" "tailscale.com/net/tsaddr" "tailscale.com/syncs" "tailscale.com/tstime/mono" "tailscale.com/types/ipproto" "tailscale.com/types/key" "tailscale.com/types/logger" "tailscale.com/util/clientmetric" "tailscale.com/util/usermetric" "tailscale.com/wgengine/capture" "tailscale.com/wgengine/filter" "tailscale.com/wgengine/netstack/gro" "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 // GROFilterFunc is a FilterFunc extended with a *gro.GRO, enabling increased // throughput where GRO is supported by a packet.Parsed interceptor, e.g. // netstack/gVisor, and we are handling a vector of packets. Callers must pass a // nil g for the first packet in a given vector, and continue passing the // returned *gro.GRO for all remaining packets in said vector. If the returned // *gro.GRO is non-nil after the last packet for a given vector is passed // through the GROFilterFunc, the caller must also call Flush() on it to deliver // any previously Enqueue()'d packets. type GROFilterFunc func(p *packet.Parsed, w *Wrapper, g *gro.GRO) (filter.Response, *gro.GRO) // Wrapper augments a tun.Device with packet filtering and injection. // // A Wrapper starts in a "corked" mode where Read calls are blocked // until the Wrapper's Start method is called. 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 started atomic.Bool // whether Start has been called startCh chan struct{} // closed in Start 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()] //lint:ignore U1000 used in tap_linux.go 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 // peerConfig stores the current NAT configuration. peerConfig atomic.Pointer[peerConfigTable] // 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 // jailedFilter is the packet filter for jailed nodes. // Can be nil, which means drop all packets. jailedFilter atomic.Pointer[filter.Filter] // 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 // PostFilterPacketInboundFromWireGuard is the inbound filter function that runs after the main filter. PostFilterPacketInboundFromWireGuard GROFilterFunc // 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 GROFilterFunc // 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] metrics *metrics } type metrics struct { inboundDroppedPacketsTotal *tsmetrics.MultiLabelMap[dropPacketLabel] outboundDroppedPacketsTotal *tsmetrics.MultiLabelMap[dropPacketLabel] } func registerMetrics(reg *usermetric.Registry) *metrics { return &metrics{ inboundDroppedPacketsTotal: usermetric.NewMultiLabelMapWithRegistry[dropPacketLabel]( reg, "tailscaled_inbound_dropped_packets_total", "counter", "Counts the number of dropped packets received by the node from other peers", ), outboundDroppedPacketsTotal: usermetric.NewMultiLabelMapWithRegistry[dropPacketLabel]( reg, "tailscaled_outbound_dropped_packets_total", "counter", "Counts the number of packets dropped while being sent to other peers", ), } } // 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.PacketBuffer 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) } // Start unblocks any Wrapper.Read calls that have already started // and makes the Wrapper functional. // // Start must be called exactly once after the various Tailscale // subsystems have been wired up to each other. func (w *Wrapper) Start() { w.started.Store(true) close(w.startCh) } func WrapTAP(logf logger.Logf, tdev tun.Device, m *usermetric.Registry) *Wrapper { return wrap(logf, tdev, true, m) } func Wrap(logf logger.Logf, tdev tun.Device, m *usermetric.Registry) *Wrapper { return wrap(logf, tdev, false, m) } func wrap(logf logger.Logf, tdev tun.Device, isTAP bool, m *usermetric.Registry) *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, startCh: make(chan struct{}), metrics: registerMetrics(m), } 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() { if t.started.CompareAndSwap(false, true) { close(t.startCh) } 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 } // snat does SNAT on p if the destination address requires a different source address. func (pc *peerConfigTable) snat(p *packet.Parsed) { oldSrc := p.Src.Addr() newSrc := pc.selectSrcIP(oldSrc, p.Dst.Addr()) if oldSrc != newSrc { checksum.UpdateSrcAddr(p, newSrc) } } // dnat does destination NAT on p. func (pc *peerConfigTable) dnat(p *packet.Parsed) { oldDst := p.Dst.Addr() newDst := pc.mapDstIP(p.Src.Addr(), oldDst) if newDst != oldDst { checksum.UpdateDstAddr(p, 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{} } // findV6 returns the first Tailscale IPv6 address in addrs. func findV6(addrs []netip.Prefix) netip.Addr { for _, ap := range addrs { a := ap.Addr() if a.Is6() && tsaddr.IsTailscaleIP(a) { return a } } return netip.Addr{} } // peerConfigTable contains configuration for individual peers and related // information necessary to perform peer-specific operations. It should be // treated as immutable. // // The nil value is a valid configuration. type peerConfigTable struct { // nativeAddr4 and nativeAddr6 are the IPv4/IPv6 Tailscale Addresses of // the current node. // // These are implicitly used as the address to rewrite to in the DNAT // path (as configured by listenAddrs, below). The IPv4 address will be // used if the inbound packet is IPv4, and the IPv6 address if the // inbound packet is IPv6. nativeAddr4, nativeAddr6 netip.Addr // byIP contains configuration for each peer, indexed by a peer's IP // address(es). byIP bart.Table[*peerConfig] // masqAddrCounts is a count of peers by MasqueradeAsIP. // TODO? for logging masqAddrCounts map[netip.Addr]int } // peerConfig is the configuration for a single peer. type peerConfig struct { // dstMasqAddr{4,6} are the addresses that should be used as the // source address when masquerading packets to this peer (i.e. // SNAT). If an address is not valid, the packet should not be // masqueraded for that address family. dstMasqAddr4 netip.Addr dstMasqAddr6 netip.Addr // jailed is whether this peer is "jailed" (i.e. is restricted from being // able to initiate connections to this node). This is the case for shared // nodes. jailed bool } func (c *peerConfigTable) String() string { if c == nil { return "peerConfigTable(nil)" } var b strings.Builder b.WriteString("peerConfigTable{") fmt.Fprintf(&b, "nativeAddr4: %v, ", c.nativeAddr4) fmt.Fprintf(&b, "nativeAddr6: %v, ", c.nativeAddr6) // TODO: figure out how to iterate/debug/print c.byIP b.WriteString("}") return b.String() } func (c *peerConfig) String() string { if c == nil { return "peerConfig(nil)" } var b strings.Builder b.WriteString("peerConfig{") fmt.Fprintf(&b, "dstMasqAddr4: %v, ", c.dstMasqAddr4) fmt.Fprintf(&b, "dstMasqAddr6: %v, ", c.dstMasqAddr6) fmt.Fprintf(&b, "jailed: %v}", c.jailed) return b.String() } // 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 (pc *peerConfigTable) mapDstIP(src, oldDst netip.Addr) netip.Addr { if pc == nil { return oldDst } // The packet we're processing is inbound from WireGuard, received from // a peer. The 'src' of the packet is the remote peer's IP address, // possibly the masqueraded address (if the peer is shared/etc.). // // The 'dst' of the packet is the address for this local node. It could // be a masquerade address that we told other nodes to use, or one of // our local node's Addresses. c, ok := pc.byIP.Lookup(src) if !ok { return oldDst } if oldDst.Is4() && pc.nativeAddr4.IsValid() && c.dstMasqAddr4 == oldDst { return pc.nativeAddr4 } if oldDst.Is6() && pc.nativeAddr6.IsValid() && c.dstMasqAddr6 == oldDst { return pc.nativeAddr6 } 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 (pc *peerConfigTable) selectSrcIP(oldSrc, dst netip.Addr) netip.Addr { if pc == nil { return oldSrc } // If this packet doesn't originate from this Tailscale node, don't // SNAT it (e.g. if we're a subnet router). if oldSrc.Is4() && oldSrc != pc.nativeAddr4 { return oldSrc } if oldSrc.Is6() && oldSrc != pc.nativeAddr6 { return oldSrc } // Look up the configuration for the destination c, ok := pc.byIP.Lookup(dst) if !ok { return oldSrc } // Perform SNAT based on the address family and whether we have a valid // addr. if oldSrc.Is4() && c.dstMasqAddr4.IsValid() { return c.dstMasqAddr4 } if oldSrc.Is6() && c.dstMasqAddr6.IsValid() { return c.dstMasqAddr6 } // No SNAT; use old src return oldSrc } // peerConfigTableFromWGConfig generates a peerConfigTable from nm. If NAT is // not required, and no additional configuration is present, it returns nil. func peerConfigTableFromWGConfig(wcfg *wgcfg.Config) *peerConfigTable { if wcfg == nil { return nil } nativeAddr4 := findV4(wcfg.Addresses) nativeAddr6 := findV6(wcfg.Addresses) if !nativeAddr4.IsValid() && !nativeAddr6.IsValid() { return nil } ret := &peerConfigTable{ nativeAddr4: nativeAddr4, nativeAddr6: nativeAddr6, masqAddrCounts: make(map[netip.Addr]int), } // 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 { hasMasqAddr := false || (p.V4MasqAddr != nil && p.V4MasqAddr.IsValid()) || (p.V6MasqAddr != nil && p.V6MasqAddr.IsValid()) if hasMasqAddr { exitNodeRequiresMasq = true } break } } byIPSize := 0 for i := range wcfg.Peers { p := &wcfg.Peers[i] // Build a routing table that configures DNAT (i.e. changing // the V4MasqAddr/V6MasqAddr for a given peer to the current // peer's v4/v6 IP). var addrToUse4, addrToUse6 netip.Addr if p.V4MasqAddr != nil && p.V4MasqAddr.IsValid() { addrToUse4 = *p.V4MasqAddr ret.masqAddrCounts[addrToUse4]++ } if p.V6MasqAddr != nil && p.V6MasqAddr.IsValid() { addrToUse6 = *p.V6MasqAddr ret.masqAddrCounts[addrToUse6]++ } // If the exit node requires masquerading, set the masquerade // addresses to our native addresses. if exitNodeRequiresMasq { if !addrToUse4.IsValid() && nativeAddr4.IsValid() { addrToUse4 = nativeAddr4 } if !addrToUse6.IsValid() && nativeAddr6.IsValid() { addrToUse6 = nativeAddr6 } } if !addrToUse4.IsValid() && !addrToUse6.IsValid() && !p.IsJailed { // NAT not required for this peer. continue } // Use the same peer configuration for each address of the peer. pc := &peerConfig{ dstMasqAddr4: addrToUse4, dstMasqAddr6: addrToUse6, jailed: p.IsJailed, } // Insert an entry into our routing table for each allowed IP. for _, ip := range p.AllowedIPs { ret.byIP.Insert(ip, pc) byIPSize++ } } if byIPSize == 0 && len(ret.masqAddrCounts) == 0 { return nil } return ret } func (pc *peerConfigTable) inboundPacketIsJailed(p *packet.Parsed) bool { if pc == nil { return false } c, ok := pc.byIP.Lookup(p.Src.Addr()) if !ok { return false } return c.jailed } func (pc *peerConfigTable) outboundPacketIsJailed(p *packet.Parsed) bool { if pc == nil { return false } c, ok := pc.byIP.Lookup(p.Dst.Addr()) if !ok { return false } return c.jailed } // SetWGConfig is called when a new NetworkMap is received. func (t *Wrapper) SetWGConfig(wcfg *wgcfg.Config) { cfg := peerConfigTableFromWGConfig(wcfg) old := t.peerConfig.Swap(cfg) if !reflect.DeepEqual(old, cfg) { t.logf("peer 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, pc *peerConfigTable, gro *gro.GRO) (filter.Response, *gro.GRO) { // 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, gro // 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, gro // 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, gro } if t.PreFilterPacketOutboundToWireGuardNetstackIntercept != nil { var res filter.Response res, gro = t.PreFilterPacketOutboundToWireGuardNetstackIntercept(p, t, gro) if res.IsDrop() { // Handled by netstack.Impl.handleLocalPackets (quad-100 DNS primarily) return res, gro } } 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, gro } } // If the outbound packet is to a jailed peer, use our jailed peer // packet filter. var filt *filter.Filter if pc.outboundPacketIsJailed(p) { filt = t.jailedFilter.Load() } else { filt = t.filter.Load() } if filt == nil { return filter.Drop, gro } if filt.RunOut(p, t.filterFlags) != filter.Accept { metricPacketOutDropFilter.Add(1) t.metrics.outboundDroppedPacketsTotal.Add(dropPacketLabel{ Reason: DropReasonACL, }, 1) return filter.Drop, gro } if t.PostFilterPacketOutboundToWireGuard != nil { if res := t.PostFilterPacketOutboundToWireGuard(p, t); res.IsDrop() { return res, gro } } return filter.Accept, gro } // 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) { if !t.started.Load() { <-t.startCh } // 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 { return t.injectedRead(res.injected, buffs, sizes, offset) } metricPacketOut.Add(int64(len(res.data))) var buffsPos int p := parsedPacketPool.Get().(*packet.Parsed) defer parsedPacketPool.Put(p) captHook := t.captureHook.Load() pc := t.peerConfig.Load() var buffsGRO *gro.GRO for _, data := range res.data { p.Decode(data[res.dataOffset:]) 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 { var response filter.Response response, buffsGRO = t.filterPacketOutboundToWireGuard(p, pc, buffsGRO) if response != filter.Accept { metricPacketOutDrop.Add(1) continue } } // Make sure to do SNAT after filtering, so that any flow tracking in // the filter sees the original source address. See #12133. pc.snat(p) 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++ } if buffsGRO != nil { buffsGRO.Flush() } // 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 } const ( minTCPHeaderSize = 20 ) func stackGSOToTunGSO(pkt []byte, gso stack.GSO) (tun.GSOOptions, error) { options := tun.GSOOptions{ CsumStart: gso.L3HdrLen, CsumOffset: gso.CsumOffset, GSOSize: gso.MSS, NeedsCsum: gso.NeedsCsum, } switch gso.Type { case stack.GSONone: options.GSOType = tun.GSONone return options, nil case stack.GSOTCPv4: options.GSOType = tun.GSOTCPv4 case stack.GSOTCPv6: options.GSOType = tun.GSOTCPv6 default: return tun.GSOOptions{}, fmt.Errorf("unsupported gVisor GSOType: %v", gso.Type) } // options.HdrLen is both layer 3 and 4 together, whereas gVisor only // gives us layer 3 length. We have to gather TCP header length // ourselves. if len(pkt) < int(gso.L3HdrLen)+minTCPHeaderSize { return tun.GSOOptions{}, errors.New("gVisor GSOTCP packet length too short") } tcphLen := uint16(pkt[int(gso.L3HdrLen)+12] >> 4 * 4) options.HdrLen = gso.L3HdrLen + tcphLen return options, nil } // invertGSOChecksum inverts the transport layer checksum in pkt if gVisor // handed us a segment with a partial checksum. A partial checksum is not a // ones' complement of the sum, and incremental checksum updating is not yet // partial checksum aware. This may be called twice for a single packet, // both before and after partial checksum updates where later checksum // offloading still expects a partial checksum. // TODO(jwhited): plumb partial checksum awareness into net/packet/checksum. func invertGSOChecksum(pkt []byte, gso stack.GSO) { if gso.NeedsCsum != true { return } at := int(gso.L3HdrLen + gso.CsumOffset) if at+1 > len(pkt)-1 { return } pkt[at] = ^pkt[at] pkt[at+1] = ^pkt[at+1] } // injectedRead handles injected reads, which bypass filters. func (t *Wrapper) injectedRead(res tunInjectedRead, outBuffs [][]byte, sizes []int, offset int) (n int, err error) { var gso stack.GSO pkt := outBuffs[0][offset:] if res.packet != nil { bufN := copy(pkt, res.packet.NetworkHeader().Slice()) bufN += copy(pkt[bufN:], res.packet.TransportHeader().Slice()) bufN += copy(pkt[bufN:], res.packet.Data().AsRange().ToSlice()) gso = res.packet.GSOOptions pkt = pkt[:bufN] defer res.packet.DecRef() // defer DecRef so we may continue to reference it } else { sizes[0] = copy(pkt, res.data) pkt = pkt[:sizes[0]] n = 1 } pc := t.peerConfig.Load() p := parsedPacketPool.Get().(*packet.Parsed) defer parsedPacketPool.Put(p) p.Decode(pkt) invertGSOChecksum(pkt, gso) pc.snat(p) invertGSOChecksum(pkt, gso) if m := t.destIPActivity.Load(); m != nil { if fn := m[p.Dst.Addr()]; fn != nil { fn() } } if res.packet != nil { var gsoOptions tun.GSOOptions gsoOptions, err = stackGSOToTunGSO(pkt, gso) if err != nil { return 0, err } n, err = tun.GSOSplit(pkt, gsoOptions, outBuffs, sizes, offset) } if stats := t.stats.Load(); stats != nil { for i := 0; i < n; i++ { stats.UpdateTxVirtual(outBuffs[i][offset : offset+sizes[i]]) } } t.noteActivity() metricPacketOut.Add(int64(n)) return n, err } func (t *Wrapper) filterPacketInboundFromWireGuard(p *packet.Parsed, captHook capture.Callback, pc *peerConfigTable, gro *gro.GRO) (filter.Response, *gro.GRO) { 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, gro } 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, gro } } // 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, gro } if t.PreFilterPacketInboundFromWireGuard != nil { if res := t.PreFilterPacketInboundFromWireGuard(p, t); res.IsDrop() { return res, gro } } var filt *filter.Filter if pc.inboundPacketIsJailed(p) { filt = t.jailedFilter.Load() } else { filt = t.filter.Load() } if filt == nil { return filter.Drop, gro } 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) t.metrics.inboundDroppedPacketsTotal.Add(dropPacketLabel{ Reason: DropReasonACL, }, 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, gro } if t.PostFilterPacketInboundFromWireGuard != nil { var res filter.Response res, gro = t.PostFilterPacketInboundFromWireGuard(p, t, gro) if res.IsDrop() { return res, gro } } return filter.Accept, gro } // Write accepts incoming packets. The packets begin at buffs[:][offset:], // like wireguard-go/tun.Device.Write. Write is called per-peer via // wireguard-go/device.Peer.RoutineSequentialReceiver, so it MUST be // thread-safe. 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() pc := t.peerConfig.Load() var buffsGRO *gro.GRO for _, buff := range buffs { p.Decode(buff[offset:]) pc.dnat(p) if !t.disableFilter { var res filter.Response // TODO(jwhited): name and document this filter code path // appropriately. It is not only responsible for filtering, it // also routes packets towards gVisor/netstack. res, buffsGRO = t.filterPacketInboundFromWireGuard(p, captHook, pc, buffsGRO) if res != filter.Accept { metricPacketInDrop.Add(1) } else { buffs[i] = buff i++ } } } if buffsGRO != nil { buffsGRO.Flush() } if t.disableFilter { i = len(buffs) } buffs = buffs[:i] if len(buffs) > 0 { t.noteActivity() _, err := t.tdevWrite(buffs, offset) if err != nil { t.metrics.inboundDroppedPacketsTotal.Add(dropPacketLabel{ Reason: DropReasonError, }, int64(len(buffs))) } 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) } func (t *Wrapper) GetJailedFilter() *filter.Filter { return t.jailedFilter.Load() } func (t *Wrapper) SetJailedFilter(filt *filter.Filter) { t.jailedFilter.Store(filt) } // InjectInboundPacketBuffer makes the Wrapper device behave as if a packet // (pkt) with the given contents was received from the network. // It takes ownership of one reference count on pkt. The injected // packet will not pass through inbound filters. // // pkt will be copied into buffs before writing to the underlying tun.Device. // Therefore, callers must allocate and pass a buffs slice that is sized // appropriately for holding pkt.Size() + PacketStartOffset as a single // element (buffs[0]) and split across multiple elements if the originating // stack supports GSO. sizes must be sized with similar consideration, // len(buffs) should be equal to len(sizes). If any len(buffs[]) was // mutated by InjectInboundPacketBuffer it will be reset to cap(buffs[]) // before returning. // // This path is typically used to deliver synthesized packets to the // host networking stack. func (t *Wrapper) InjectInboundPacketBuffer(pkt *stack.PacketBuffer, buffs [][]byte, sizes []int) error { buf := buffs[0][PacketStartOffset:] bufN := copy(buf, pkt.NetworkHeader().Slice()) bufN += copy(buf[bufN:], pkt.TransportHeader().Slice()) bufN += copy(buf[bufN:], pkt.Data().AsRange().ToSlice()) if bufN != pkt.Size() { panic("unexpected packet size after copy") } buf = buf[:bufN] defer pkt.DecRef() pc := t.peerConfig.Load() p := parsedPacketPool.Get().(*packet.Parsed) defer parsedPacketPool.Put(p) p.Decode(buf) captHook := t.captureHook.Load() if captHook != nil { captHook(capture.SynthesizedToLocal, t.now(), p.Buffer(), p.CaptureMeta) } invertGSOChecksum(buf, pkt.GSOOptions) pc.dnat(p) invertGSOChecksum(buf, pkt.GSOOptions) gso, err := stackGSOToTunGSO(buf, pkt.GSOOptions) if err != nil { return err } // TODO(jwhited): support GSO passthrough to t.tdev. If t.tdev supports // GSO we don't need to split here and coalesce inside wireguard-go, // we can pass a coalesced segment all the way through. n, err := tun.GSOSplit(buf, gso, buffs, sizes, PacketStartOffset) if err != nil { if errors.Is(err, tun.ErrTooManySegments) { t.limitedLogf("InjectInboundPacketBuffer: GSO split overflows buffs") } else { return err } } for i := 0; i < n; i++ { buffs[i] = buffs[i][:PacketStartOffset+sizes[i]] } defer func() { for i := 0; i < n; i++ { buffs[i] = buffs[i][:cap(buffs[i])] } }() _, err = t.tdevWrite(buffs[:n], PacketStartOffset) return err } // 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.PacketBuffer) 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 { if runtime.GOOS == "linux" { // Always setup Linux to handle vectors, even in the very rare case that // the underlying t.tdev returns 1. gVisor GSO is always enabled for // Linux, and we cannot make a determination on gVisor usage at // wireguard-go.Device startup, which is when this value matters for // packet memory init. return conn.IdealBatchSize } 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") ) type DropReason string const ( DropReasonACL DropReason = "acl" DropReasonError DropReason = "error" ) type dropPacketLabel struct { // Reason indicates what we have done with the packet, and has the following values: // - acl (rejected packets because of ACL) // - error (rejected packets because of an error) Reason DropReason } func (t *Wrapper) InstallCaptureHook(cb capture.Callback) { t.captureHook.Store(cb) }