write batching

interface.go

@@ -280,15 +280,20 @@ func (f *Interface) listenOut(i int) {
 	ctCache := firewall.NewConntrackCacheTicker(f.conntrackCacheTimeout)
 	lhh := f.lightHouse.NewRequestHandler()
 
-	// Allocate plaintext buffer with virtio header headroom to avoid copies on TUN write
-	plaintext := make([]byte, virtioNetHdrLen+udp.MTU)
+	// Pre-allocate output buffers for batch processing
+	batchSize := li.BatchSize()
+	outs := make([][]byte, batchSize)
+	for idx := range outs {
+		// Allocate full buffer with virtio header space
+		outs[idx] = make([]byte, virtioNetHdrLen, virtioNetHdrLen+udp.MTU)
+	}
 
 	h := &header.H{}
 	fwPacket := &firewall.Packet{}
 	nb := make([]byte, 12)
 
-	li.ListenOut(func(fromUdpAddr netip.AddrPort, payload []byte) {
-		f.readOutsidePackets(fromUdpAddr, nil, plaintext[:virtioNetHdrLen], payload, h, fwPacket, lhh, nb, i, ctCache.Get(f.l))
+	li.ListenOutBatch(func(addrs []netip.AddrPort, payloads [][]byte, count int) {
+		f.readOutsidePacketsBatch(addrs, payloads, count, outs[:count], nb, i, h, fwPacket, lhh, ctCache.Get(f.l))
 	})
 }
 

overlay/tun_linux.go

@@ -102,6 +102,11 @@ func (w *wgDeviceWrapper) Write(b []byte) (int, error) {
 	return len(b), nil
 }
 
+func (w *wgDeviceWrapper) WriteBatch(bufs [][]byte, offset int) (int, error) {
+	// Pass all buffers to WireGuard's batch write
+	return w.dev.Write(bufs, offset)
+}
+
 func (w *wgDeviceWrapper) Close() error {
 	return w.dev.Close()
 }
@@ -436,6 +441,22 @@ func (t *tun) Write(b []byte) (int, error) {
 	}
 }
 
+// WriteBatch writes multiple packets to the TUN device in a single syscall
+func (t *tun) WriteBatch(bufs [][]byte, offset int) (int, error) {
+	if t.wgDevice != nil {
+		return t.wgDevice.Write(bufs, offset)
+	}
+
+	// Fallback: write individually (shouldn't happen in normal operation)
+	for i, buf := range bufs {
+		_, err := t.Write(buf)
+		if err != nil {
+			return i, err
+		}
+	}
+	return len(bufs), nil
+}
+
 func (t *tun) deviceBytes() (o [16]byte) {
 	for i, c := range t.Device {
 		o[i] = byte(c)

udp/conn.go

@@ -13,13 +13,21 @@ type EncReader func(
 	payload []byte,
 )
 
+type EncBatchReader func(
+	addrs []netip.AddrPort,
+	payloads [][]byte,
+	count int,
+)
+
 type Conn interface {
 	Rebind() error
 	LocalAddr() (netip.AddrPort, error)
 	ListenOut(r EncReader)
+	ListenOutBatch(r EncBatchReader)
 	WriteTo(b []byte, addr netip.AddrPort) error
 	WriteMulti(packets [][]byte, addrs []netip.AddrPort) (int, error)
 	ReloadConfig(c *config.C)
+	BatchSize() int
 	Close() error
 }
 
@@ -34,6 +42,9 @@ func (NoopConn) LocalAddr() (netip.AddrPort, error) {
 func (NoopConn) ListenOut(_ EncReader) {
 	return
 }
+func (NoopConn) ListenOutBatch(_ EncBatchReader) {
+	return
+}
 func (NoopConn) WriteTo(_ []byte, _ netip.AddrPort) error {
 	return nil
 }
@@ -43,6 +54,9 @@ func (NoopConn) WriteMulti(_ [][]byte, _ []netip.AddrPort) (int, error) {
 func (NoopConn) ReloadConfig(_ *config.C) {
 	return
 }
+func (NoopConn) BatchSize() int {
+	return 1
+}
 func (NoopConn) Close() error {
 	return nil
 }

udp/udp_darwin.go

@@ -195,6 +195,34 @@ func (u *StdConn) ListenOut(r EncReader) {
 	}
 }
 
+// ListenOutBatch - fallback to single-packet reads for Darwin
+func (u *StdConn) ListenOutBatch(r EncBatchReader) {
+	buffer := make([]byte, MTU)
+	addrs := make([]netip.AddrPort, 1)
+	payloads := make([][]byte, 1)
+
+	for {
+		// Just read one packet at a time and call batch callback with count=1
+		n, rua, err := u.ReadFromUDPAddrPort(buffer)
+		if err != nil {
+			if errors.Is(err, net.ErrClosed) {
+				u.l.WithError(err).Debug("udp socket is closed, exiting read loop")
+				return
+			}
+
+			u.l.WithError(err).Error("unexpected udp socket receive error")
+		}
+
+		addrs[0] = netip.AddrPortFrom(rua.Addr().Unmap(), rua.Port())
+		payloads[0] = buffer[:n]
+		r(addrs, payloads, 1)
+	}
+}
+
+func (u *StdConn) BatchSize() int {
+	return 1
+}
+
 func (u *StdConn) Rebind() error {
 	var err error
 	if u.isV4 {

udp/udp_generic.go

@@ -85,3 +85,42 @@ func (u *GenericConn) ListenOut(r EncReader) {
 		r(netip.AddrPortFrom(rua.Addr().Unmap(), rua.Port()), buffer[:n])
 	}
 }
+
+// ListenOutBatch - fallback to single-packet reads for generic platforms
+func (u *GenericConn) ListenOutBatch(r EncBatchReader) {
+	buffer := make([]byte, MTU)
+	addrs := make([]netip.AddrPort, 1)
+	payloads := make([][]byte, 1)
+
+	for {
+		// Just read one packet at a time and call batch callback with count=1
+		n, rua, err := u.ReadFromUDPAddrPort(buffer)
+		if err != nil {
+			u.l.WithError(err).Debug("udp socket is closed, exiting read loop")
+			return
+		}
+
+		addrs[0] = netip.AddrPortFrom(rua.Addr().Unmap(), rua.Port())
+		payloads[0] = buffer[:n]
+		r(addrs, payloads, 1)
+	}
+}
+
+// WriteMulti sends multiple packets - fallback implementation
+func (u *GenericConn) WriteMulti(packets [][]byte, addrs []netip.AddrPort) (int, error) {
+	for i := range packets {
+		err := u.WriteTo(packets[i], addrs[i])
+		if err != nil {
+			return i, err
+		}
+	}
+	return len(packets), nil
+}
+
+func (u *GenericConn) BatchSize() int {
+	return 1
+}
+
+func (u *GenericConn) Rebind() error {
+	return nil
+}

udp/udp_linux.go

@@ -174,6 +174,46 @@ func (u *StdConn) ListenOut(r EncReader) {
 	}
 }
 
+func (u *StdConn) ListenOutBatch(r EncBatchReader) {
+	var ip netip.Addr
+
+	msgs, buffers, names := u.PrepareRawMessages(u.batch)
+	read := u.ReadMulti
+	if u.batch == 1 {
+		read = u.ReadSingle
+	}
+
+	udpBatchHist := metrics.GetOrRegisterHistogram("batch.udp_read_size", nil, metrics.NewUniformSample(1024))
+
+	// Pre-allocate slices for batch callback
+	addrs := make([]netip.AddrPort, u.batch)
+	payloads := make([][]byte, u.batch)
+
+	for {
+		n, err := read(msgs)
+		if err != nil {
+			u.l.WithError(err).Debug("udp socket is closed, exiting read loop")
+			return
+		}
+
+		udpBatchHist.Update(int64(n))
+
+		// Prepare batch data
+		for i := 0; i < n; i++ {
+			if u.isV4 {
+				ip, _ = netip.AddrFromSlice(names[i][4:8])
+			} else {
+				ip, _ = netip.AddrFromSlice(names[i][8:24])
+			}
+			addrs[i] = netip.AddrPortFrom(ip.Unmap(), binary.BigEndian.Uint16(names[i][2:4]))
+			payloads[i] = buffers[i][:msgs[i].Len]
+		}
+
+		// Call batch callback with all packets
+		r(addrs, payloads, n)
+	}
+}
+
 func (u *StdConn) ReadSingle(msgs []rawMessage) (int, error) {
 	for {
 		n, _, err := unix.Syscall6(
@@ -463,6 +503,10 @@ func (u *StdConn) getMemInfo(meminfo *[unix.SK_MEMINFO_VARS]uint32) error {
 	return nil
 }
 
+func (u *StdConn) BatchSize() int {
+	return u.batch
+}
+
 func (u *StdConn) Close() error {
 	return syscall.Close(u.sysFd)
 }

udp/udp_tester.go

@@ -116,6 +116,31 @@ func (u *TesterConn) ListenOut(r EncReader) {
 	}
 }
 
+func (u *TesterConn) ListenOutBatch(r EncBatchReader) {
+	addrs := make([]netip.AddrPort, 1)
+	payloads := make([][]byte, 1)
+
+	for {
+		p, ok := <-u.RxPackets
+		if !ok {
+			return
+		}
+		addrs[0] = p.From
+		payloads[0] = p.Data
+		r(addrs, payloads, 1)
+	}
+}
+
+func (u *TesterConn) WriteMulti(packets [][]byte, addrs []netip.AddrPort) (int, error) {
+	for i := range packets {
+		err := u.WriteTo(packets[i], addrs[i])
+		if err != nil {
+			return i, err
+		}
+	}
+	return len(packets), nil
+}
+
 func (u *TesterConn) ReloadConfig(*config.C) {}
 
 func NewUDPStatsEmitter(_ []Conn) func() {
@@ -127,6 +152,10 @@ func (u *TesterConn) LocalAddr() (netip.AddrPort, error) {
 	return u.Addr, nil
 }
 
+func (u *TesterConn) BatchSize() int {
+	return 1
+}
+
 func (u *TesterConn) Rebind() error {
 	return nil
 }