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tailscale/net/tstun/wrap.go

1093 lines
32 KiB
Go

// 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"
"gvisor.dev/gvisor/pkg/tcpip/stack"
"tailscale.com/disco"
"tailscale.com/net/connstats"
"tailscale.com/net/packet"
"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/types/netmap"
"tailscale.com/types/views"
"tailscale.com/util/clientmetric"
"tailscale.com/util/mak"
"tailscale.com/wgengine/capture"
"tailscale.com/wgengine/filter"
)
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]
// 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
}
// 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[netip.Addr, netip.Addr] // dst -> masqAddr
// TODO(maisem/nyghtowl): add support for subnets and exit nodes and test them.
// Determine IP routing table algorithm to use - e.g. ART?
}
// 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
}
if eip, ok := c.dstMasqAddrs.GetOk(dst); ok {
return eip
}
return oldSrc
}
// natConfigFromNetMap generates a natV4Config from nm.
// If v4 NAT is not required, it returns nil.
func natConfigFromNetMap(nm *netmap.NetworkMap) *natV4Config {
if nm == nil || nm.SelfNode == nil {
return nil
}
nativeAddr := findV4(nm.SelfNode.Addresses)
if !nativeAddr.IsValid() {
return nil
}
var (
dstMasqAddrs map[netip.Addr]netip.Addr
listenAddrs map[netip.Addr]struct{}
)
for _, p := range nm.Peers {
if !p.SelfNodeV4MasqAddrForThisPeer.IsValid() {
continue
}
peerV4 := findV4(p.Addresses)
if !peerV4.IsValid() {
continue
}
mak.Set(&dstMasqAddrs, peerV4, p.SelfNodeV4MasqAddrForThisPeer)
mak.Set(&listenAddrs, p.SelfNodeV4MasqAddrForThisPeer, struct{}{})
}
if len(listenAddrs) == 0 || len(dstMasqAddrs) == 0 {
return nil
}
return &natV4Config{
nativeAddr: nativeAddr,
listenAddrs: views.MapOf(listenAddrs),
dstMasqAddrs: views.MapOf(dstMasqAddrs),
}
}
// SetNetMap is called when a new NetworkMap is received.
// It currently (2023-03-01) only updates the IPv4 NAT configuration.
func (t *Wrapper) SetNetMap(nm *netmap.NetworkMap) {
cfg := natConfigFromNetMap(nm)
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)
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 capt := t.captureHook.Load(); capt != nil {
capt(capture.FromLocal, time.Now(), p.Buffer())
}
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) filter.Response {
if capt := t.captureHook.Load(); capt != nil {
capt(capture.FromPeer, time.Now(), p.Buffer())
}
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)
for _, buff := range buffs {
p.Decode(buff[offset:])
t.dnatV4(p)
if !t.disableFilter {
if t.filterPacketInboundFromWireGuard(p) != 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:])
if capt := t.captureHook.Load(); capt != nil {
capt(capture.SynthesizedToLocal, time.Now(), p.Buffer())
}
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(packet []byte) error {
if len(packet) > MaxPacketSize {
return errPacketTooBig
}
if len(packet) == 0 {
return nil
}
t.injectOutbound(tunInjectedRead{data: packet})
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(packet stack.PacketBufferPtr) error {
size := packet.Size()
if size > MaxPacketSize {
packet.DecRef()
return errPacketTooBig
}
if size == 0 {
packet.DecRef()
return nil
}
if capt := t.captureHook.Load(); capt != nil {
b := packet.ToBuffer()
capt(capture.SynthesizedToPeer, time.Now(), b.Flatten())
}
t.injectOutbound(tunInjectedRead{packet: packet})
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)
}