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https://github.com/tailscale/tailscale.git
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net/tstun: provide exactly one buffer of readahead on tun
Signed-off-by: James Tucker <james@tailscale.com>
This commit is contained in:
parent
0c34fc7b5b
commit
7898bc9d56
@ -33,6 +33,7 @@
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"tailscale.com/wgengine/filter"
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"tailscale.com/wgengine/filter"
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)
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)
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const bufferPoolSize = 2
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const maxBufferSize = device.MaxMessageSize
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const maxBufferSize = device.MaxMessageSize
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// PacketStartOffset is the minimal amount of leading space that must exist
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// PacketStartOffset is the minimal amount of leading space that must exist
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@ -87,18 +88,9 @@ type Wrapper struct {
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destMACAtomic syncs.AtomicValue[[6]byte]
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destMACAtomic syncs.AtomicValue[[6]byte]
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discoKey syncs.AtomicValue[key.DiscoPublic]
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discoKey syncs.AtomicValue[key.DiscoPublic]
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// buffer stores the oldest unconsumed packet from tdev.
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// bufferPool contains a limited number of buffers for use pulling packets
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// It is made a static buffer in order to avoid allocations.
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// from the tun device.
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buffer [maxBufferSize]byte
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bufferPool chan []byte
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// bufferConsumedMu protects bufferConsumed from concurrent sends and closes.
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// It does not prevent send-after-close, only data races.
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bufferConsumedMu sync.Mutex
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// bufferConsumed synchronizes access to buffer (shared by Read and poll).
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//
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// Close closes bufferConsumed. There may be outstanding sends to bufferConsumed
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// when that happens; we catch any resulting panics.
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// This lets us avoid expensive multi-case selects.
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bufferConsumed chan struct{}
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// closed signals poll (by closing) when the device is closed.
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// closed signals poll (by closing) when the device is closed.
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closed chan struct{}
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closed chan struct{}
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@ -178,6 +170,10 @@ type tunReadResult struct {
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packet *stack.PacketBuffer
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packet *stack.PacketBuffer
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data []byte
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data []byte
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// If poolbuf is non-nil it should be returned to the tun buffer pool when
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// the read result is no longer being aliased.
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poolbuf []byte
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// injected is set if the read result was generated internally, and contained packets should not
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// injected is set if the read result was generated internally, and contained packets should not
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// pass through filters.
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// pass through filters.
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injected bool
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injected bool
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@ -198,9 +194,6 @@ func wrap(logf logger.Logf, tdev tun.Device, isTAP bool) *Wrapper {
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limitedLogf: logger.RateLimitedFn(logf, 1*time.Minute, 2, 10),
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limitedLogf: logger.RateLimitedFn(logf, 1*time.Minute, 2, 10),
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isTAP: isTAP,
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isTAP: isTAP,
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tdev: tdev,
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tdev: tdev,
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// bufferConsumed is conceptually a condition variable:
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// a goroutine should not block when setting it, even with no listeners.
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bufferConsumed: make(chan struct{}, 1),
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closed: make(chan struct{}),
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closed: make(chan struct{}),
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outbound: make(chan tunReadResult),
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outbound: make(chan tunReadResult),
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eventsUpDown: make(chan tun.Event),
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eventsUpDown: make(chan tun.Event),
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@ -209,10 +202,13 @@ func wrap(logf logger.Logf, tdev tun.Device, isTAP bool) *Wrapper {
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filterFlags: filter.LogAccepts | filter.LogDrops,
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filterFlags: filter.LogAccepts | filter.LogDrops,
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}
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}
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tun.bufferPool = make(chan []byte, bufferPoolSize)
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for i := 0; i < bufferPoolSize; i++ {
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tun.bufferPool <- make([]byte, maxBufferSize)
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}
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go tun.poll()
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go tun.poll()
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go tun.pumpEvents()
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go tun.pumpEvents()
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// The buffer starts out consumed.
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tun.bufferConsumed <- struct{}{}
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tun.noteActivity()
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tun.noteActivity()
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return tun
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return tun
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@ -255,9 +251,6 @@ func (t *Wrapper) Close() error {
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var err error
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var err error
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t.closeOnce.Do(func() {
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t.closeOnce.Do(func() {
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close(t.closed)
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close(t.closed)
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t.bufferConsumedMu.Lock()
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close(t.bufferConsumed)
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t.bufferConsumedMu.Unlock()
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t.outboundMu.Lock()
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t.outboundMu.Lock()
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close(t.outbound)
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close(t.outbound)
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t.outboundMu.Unlock()
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t.outboundMu.Unlock()
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@ -362,7 +355,7 @@ func allowSendOnClosedChannel() {
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// This is needed because t.tdev.Read in general may block (it does on Windows),
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// This is needed because t.tdev.Read in general may block (it does on Windows),
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// so packets may be stuck in t.outbound if t.Read called t.tdev.Read directly.
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// so packets may be stuck in t.outbound if t.Read called t.tdev.Read directly.
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func (t *Wrapper) poll() {
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func (t *Wrapper) poll() {
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for range t.bufferConsumed {
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for buffer := range t.bufferPool {
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DoRead:
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DoRead:
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var n int
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var n int
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var err error
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var err error
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@ -379,21 +372,21 @@ func (t *Wrapper) poll() {
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return
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return
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}
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}
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if t.isTAP {
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if t.isTAP {
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n, err = t.tdev.Read(t.buffer[:], PacketStartOffset-ethernetFrameSize)
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n, err = t.tdev.Read(buffer[:], PacketStartOffset-ethernetFrameSize)
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if tapDebug {
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if tapDebug {
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s := fmt.Sprintf("% x", t.buffer[:])
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s := fmt.Sprintf("% x", buffer[:])
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for strings.HasSuffix(s, " 00") {
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for strings.HasSuffix(s, " 00") {
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s = strings.TrimSuffix(s, " 00")
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s = strings.TrimSuffix(s, " 00")
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}
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}
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t.logf("TAP read %v, %v: %s", n, err, s)
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t.logf("TAP read %v, %v: %s", n, err, s)
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}
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}
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} else {
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} else {
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n, err = t.tdev.Read(t.buffer[:], PacketStartOffset)
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n, err = t.tdev.Read(buffer[:], PacketStartOffset)
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}
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}
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}
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}
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if t.isTAP {
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if t.isTAP {
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if err == nil {
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if err == nil {
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ethernetFrame := t.buffer[PacketStartOffset-ethernetFrameSize:][:n]
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ethernetFrame := buffer[PacketStartOffset-ethernetFrameSize:][:n]
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if t.handleTAPFrame(ethernetFrame) {
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if t.handleTAPFrame(ethernetFrame) {
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goto DoRead
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goto DoRead
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}
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}
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@ -403,20 +396,17 @@ func (t *Wrapper) poll() {
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n -= ethernetFrameSize
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n -= ethernetFrameSize
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}
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}
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if tapDebug {
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if tapDebug {
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t.logf("tap regular frame: %x", t.buffer[PacketStartOffset:PacketStartOffset+n])
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t.logf("tap regular frame: %x", buffer[PacketStartOffset:PacketStartOffset+n])
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}
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}
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}
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}
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t.sendOutbound(tunReadResult{data: t.buffer[PacketStartOffset : PacketStartOffset+n], err: err})
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t.sendOutbound(tunReadResult{data: buffer[PacketStartOffset : PacketStartOffset+n], poolbuf: buffer, err: err})
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}
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}
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}
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}
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// sendBufferConsumed does t.bufferConsumed <- struct{}{}.
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// sendBufferConsumed does t.bufferConsumed <- struct{}{}.
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// It protects against any panics or data races that that send could cause.
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// It protects against any panics or data races that that send could cause.
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func (t *Wrapper) sendBufferConsumed() {
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func (t *Wrapper) sendBufferConsumed(buffer []byte) {
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defer allowSendOnClosedChannel()
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t.bufferPool <- buffer
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t.bufferConsumedMu.Lock()
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defer t.bufferConsumedMu.Unlock()
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t.bufferConsumed <- struct{}{}
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}
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}
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// sendOutbound does t.outboundMu <- r.
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// sendOutbound does t.outboundMu <- r.
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@ -515,6 +505,9 @@ func (t *Wrapper) Read(buf []byte, offset int) (int, error) {
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// Wrapper is closed.
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// Wrapper is closed.
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return 0, io.EOF
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return 0, io.EOF
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}
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}
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if res.poolbuf != nil {
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defer t.sendBufferConsumed(res.poolbuf)
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}
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if res.err != nil {
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if res.err != nil {
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return 0, res.err
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return 0, res.err
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}
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}
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@ -531,12 +524,6 @@ func (t *Wrapper) Read(buf []byte, offset int) (int, error) {
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res.packet.DecRef()
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res.packet.DecRef()
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} else {
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} else {
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n = copy(buf[offset:], res.data)
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n = copy(buf[offset:], res.data)
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// t.buffer has a fixed location in memory.
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if &res.data[0] == &t.buffer[PacketStartOffset] {
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// We are done with t.buffer. Let poll re-use it.
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t.sendBufferConsumed()
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}
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}
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}
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p := parsedPacketPool.Get().(*packet.Parsed)
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p := parsedPacketPool.Get().(*packet.Parsed)
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