remove the requirement for a cert-v2 certificate to have an IPv4 Network to have IPv4 UnsafeNetworks

CHANGELOG.md

@@ -7,17 +7,6 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
-## [1.10.2] - 2026-01-21
-
-### Fixed
-
-- Fix panic when using `use_system_route_table` that was introduced in v1.10.1. (#1580)
-
-### Changed
-
-- Fix some typos in comments. (#1582)
-- Dependency updates. (#1581)
-
 ## [1.10.1] - 2026-01-16
 
 See the [v1.10.1](https://github.com/slackhq/nebula/milestone/26?closed=1) milestone for a complete list of changes.
@@ -775,8 +764,7 @@ created.)
 
 - Initial public release.
 
-[Unreleased]: https://github.com/slackhq/nebula/compare/v1.10.2...HEAD
-[1.10.2]: https://github.com/slackhq/nebula/releases/tag/v1.10.2
+[Unreleased]: https://github.com/slackhq/nebula/compare/v1.10.1...HEAD
 [1.10.1]: https://github.com/slackhq/nebula/releases/tag/v1.10.1
 [1.10.0]: https://github.com/slackhq/nebula/releases/tag/v1.10.0
 [1.9.7]: https://github.com/slackhq/nebula/releases/tag/v1.9.7

cert/cert_v2.go

@@ -396,7 +396,6 @@ func (c *certificateV2) validate() error {
 		return NewErrInvalidCertificateProperties("non-CA certificate must contain at least 1 network")
 	}
 
-	hasV4Networks := false
 	hasV6Networks := false
 	for _, network := range c.details.networks {
 		if !network.IsValid() || !network.Addr().IsValid() {
@@ -415,7 +414,6 @@ func (c *certificateV2) validate() error {
 			return NewErrInvalidCertificateProperties("4in6 networks are not allowed: %s", network)
 		}
 
-		hasV4Networks = hasV4Networks || network.Addr().Is4()
 		hasV6Networks = hasV6Networks || network.Addr().Is6()
 	}
 
@@ -439,10 +437,6 @@ func (c *certificateV2) validate() error {
 				if !hasV6Networks {
 					return NewErrInvalidCertificateProperties("IPv6 unsafe networks require an IPv6 address assignment: %s", network)
 				}
-			} else if network.Addr().Is4() {
-				if !hasV4Networks {
-					return NewErrInvalidCertificateProperties("IPv4 unsafe networks require an IPv4 address assignment: %s", network)
-				}
 			}
 		}
 	}

inside.go

@@ -9,75 +9,8 @@ import (
 	"github.com/slackhq/nebula/iputil"
 	"github.com/slackhq/nebula/noiseutil"
 	"github.com/slackhq/nebula/routing"
-	"github.com/slackhq/nebula/udp"
 )
 
-// consumeInsidePacketBatched is a variant of consumeInsidePacket that queues
-// outgoing packets into pendingPackets instead of sending them immediately.
-// The caller is responsible for flushing pendingPackets with WriteBatch.
-func (f *Interface) consumeInsidePacketBatched(packet []byte, fwPacket *firewall.Packet, nb, out []byte, q int, localCache firewall.ConntrackCache, pendingPackets *[]udp.BatchPacket) {
-	err := newPacket(packet, false, fwPacket)
-	if err != nil {
-		if f.l.Level >= logrus.DebugLevel {
-			f.l.WithField("packet", packet).Debugf("Error while validating outbound packet: %s", err)
-		}
-		return
-	}
-
-	// Ignore local broadcast packets
-	if f.dropLocalBroadcast {
-		if f.myBroadcastAddrsTable.Contains(fwPacket.RemoteAddr) {
-			return
-		}
-	}
-
-	if f.myVpnAddrsTable.Contains(fwPacket.RemoteAddr) {
-		if immediatelyForwardToSelf {
-			_, err := f.readers[q].Write(packet)
-			if err != nil {
-				f.l.WithError(err).Error("Failed to forward to tun")
-			}
-		}
-		return
-	}
-
-	// Ignore multicast packets
-	if f.dropMulticast && fwPacket.RemoteAddr.IsMulticast() {
-		return
-	}
-
-	hostinfo, ready := f.getOrHandshakeConsiderRouting(fwPacket, func(hh *HandshakeHostInfo) {
-		hh.cachePacket(f.l, header.Message, 0, packet, f.sendMessageNow, f.cachedPacketMetrics)
-	})
-
-	if hostinfo == nil {
-		f.rejectInside(packet, out, q)
-		if f.l.Level >= logrus.DebugLevel {
-			f.l.WithField("vpnAddr", fwPacket.RemoteAddr).
-				WithField("fwPacket", fwPacket).
-				Debugln("dropping outbound packet, vpnAddr not in our vpn networks or in unsafe networks")
-		}
-		return
-	}
-
-	if !ready {
-		return
-	}
-
-	dropReason := f.firewall.Drop(*fwPacket, false, hostinfo, f.pki.GetCAPool(), localCache)
-	if dropReason == nil {
-		f.sendNoMetricsBatched(header.Message, 0, hostinfo.ConnectionState, hostinfo, netip.AddrPort{}, packet, nb, out, q, pendingPackets)
-	} else {
-		f.rejectInside(packet, out, q)
-		if f.l.Level >= logrus.DebugLevel {
-			hostinfo.logger(f.l).
-				WithField("fwPacket", fwPacket).
-				WithField("reason", dropReason).
-				Debugln("dropping outbound packet")
-		}
-	}
-}
-
 func (f *Interface) consumeInsidePacket(packet []byte, fwPacket *firewall.Packet, nb, out []byte, q int, localCache firewall.ConntrackCache) {
 	err := newPacket(packet, false, fwPacket)
 	if err != nil {
@@ -136,6 +69,7 @@ func (f *Interface) consumeInsidePacket(packet []byte, fwPacket *firewall.Packet
 	dropReason := f.firewall.Drop(*fwPacket, false, hostinfo, f.pki.GetCAPool(), localCache)
 	if dropReason == nil {
 		f.sendNoMetrics(header.Message, 0, hostinfo.ConnectionState, hostinfo, netip.AddrPort{}, packet, nb, out, q)
+
 	} else {
 		f.rejectInside(packet, out, q)
 		if f.l.Level >= logrus.DebugLevel {
@@ -476,75 +410,3 @@ func (f *Interface) sendNoMetrics(t header.MessageType, st header.MessageSubType
 		}
 	}
 }
-
-// sendNoMetricsBatched is like sendNoMetrics but queues the packet for batched sending
-// instead of sending immediately. The caller must flush pendingPackets with WriteBatch.
-func (f *Interface) sendNoMetricsBatched(t header.MessageType, st header.MessageSubType, ci *ConnectionState, hostinfo *HostInfo, remote netip.AddrPort, p, nb, out []byte, q int, pendingPackets *[]udp.BatchPacket) {
-	if ci.eKey == nil {
-		return
-	}
-	useRelay := !remote.IsValid() && !hostinfo.remote.IsValid()
-	fullOut := out
-
-	if useRelay {
-		if len(out) < header.Len {
-			out = out[:header.Len]
-		}
-		out = out[header.Len:]
-	}
-
-	if noiseutil.EncryptLockNeeded {
-		ci.writeLock.Lock()
-	}
-	c := ci.messageCounter.Add(1)
-
-	out = header.Encode(out, header.Version, t, st, hostinfo.remoteIndexId, c)
-	f.connectionManager.Out(hostinfo)
-
-	if t != header.CloseTunnel && hostinfo.lastRebindCount != f.rebindCount {
-		f.lightHouse.QueryServer(hostinfo.vpnAddrs[0])
-		hostinfo.lastRebindCount = f.rebindCount
-		if f.l.Level >= logrus.DebugLevel {
-			f.l.WithField("vpnAddrs", hostinfo.vpnAddrs).Debug("Lighthouse update triggered for punch due to rebind counter")
-		}
-	}
-
-	var err error
-	out, err = ci.eKey.EncryptDanger(out, out, p, c, nb)
-	if noiseutil.EncryptLockNeeded {
-		ci.writeLock.Unlock()
-	}
-	if err != nil {
-		hostinfo.logger(f.l).WithError(err).
-			WithField("udpAddr", remote).WithField("counter", c).
-			WithField("attemptedCounter", c).
-			Error("Failed to encrypt outgoing packet")
-		return
-	}
-
-	// Queue the packet for batched sending
-	var addr netip.AddrPort
-	if remote.IsValid() {
-		addr = remote
-	} else if hostinfo.remote.IsValid() {
-		addr = hostinfo.remote
-	} else {
-		// Relay path - send immediately, not batched
-		for _, relayIP := range hostinfo.relayState.CopyRelayIps() {
-			relayHostInfo, relay, err := f.hostMap.QueryVpnAddrsRelayFor(hostinfo.vpnAddrs, relayIP)
-			if err != nil {
-				hostinfo.relayState.DeleteRelay(relayIP)
-				hostinfo.logger(f.l).WithField("relay", relayIP).WithError(err).Info("sendNoMetricsBatched failed to find HostInfo")
-				continue
-			}
-			f.SendVia(relayHostInfo, relay, out, nb, fullOut[:header.Len+len(out)], true)
-			break
-		}
-		return
-	}
-
-	// Copy the payload since the buffer will be reused
-	payload := make([]byte, len(out))
-	copy(payload, out)
-	*pendingPackets = append(*pendingPackets, udp.BatchPacket{Payload: payload, Addr: addr})
-}

interface.go

@@ -48,8 +48,6 @@ type InterfaceConfig struct {
 
 	ConntrackCacheTimeout time.Duration
 	l                     *logrus.Logger
-
-	tunBatchSize int // batch size for TUN read/write batching, 0 to disable
 }
 
 type Interface struct {
@@ -88,9 +86,8 @@ type Interface struct {
 
 	conntrackCacheTimeout time.Duration
 
-	writers      []udp.Conn
-	readers      []io.ReadWriteCloser
-	tunBatchSize int // batch size for TUN read/write batching
+	writers []udp.Conn
+	readers []io.ReadWriteCloser
 
 	metricHandshakes    metrics.Histogram
 	messageMetrics      *MessageMetrics
@@ -190,7 +187,6 @@ func NewInterface(ctx context.Context, c *InterfaceConfig) (*Interface, error) {
 		relayManager:          c.relayManager,
 		connectionManager:     c.connectionManager,
 		conntrackCacheTimeout: c.ConntrackCacheTimeout,
-		tunBatchSize:          c.tunBatchSize,
 
 		metricHandshakes: metrics.GetOrRegisterHistogram("handshakes", nil, metrics.NewExpDecaySample(1028, 0.015)),
 		messageMetrics:   c.MessageMetrics,
@@ -248,15 +244,6 @@ func (f *Interface) activate() {
 		f.readers[i] = reader
 	}
 
-	// Enable batch reading on all readers if batch size > 1
-	if f.tunBatchSize > 1 {
-		for i := 0; i < f.routines; i++ {
-			if err := overlay.EnableBatchReading(f.readers[i]); err != nil {
-				f.l.WithError(err).WithField("routine", i).Warn("Failed to enable batch reading, falling back to single reads")
-			}
-		}
-	}
-
 	if err := f.inside.Activate(); err != nil {
 		f.inside.Close()
 		f.l.Fatal(err)
@@ -300,21 +287,13 @@ func (f *Interface) listenOut(i int) {
 func (f *Interface) listenIn(reader io.ReadWriteCloser, i int) {
 	runtime.LockOSThread()
 
-	conntrackCache := firewall.NewConntrackCacheTicker(f.conntrackCacheTimeout)
-
-	// Check if batch reading is available and enabled
-	batchReader := overlay.AsBatchReader(reader)
-	if batchReader != nil && f.tunBatchSize > 1 {
-		f.listenInBatched(reader, batchReader, i, conntrackCache)
-		return
-	}
-
-	// Fallback to single-packet reading
 	packet := make([]byte, mtu)
 	out := make([]byte, mtu)
 	fwPacket := &firewall.Packet{}
 	nb := make([]byte, 12, 12)
 
+	conntrackCache := firewall.NewConntrackCacheTicker(f.conntrackCacheTimeout)
+
 	for {
 		n, err := reader.Read(packet)
 		if err != nil {
@@ -331,54 +310,6 @@ func (f *Interface) listenIn(reader io.ReadWriteCloser, i int) {
 	}
 }
 
-func (f *Interface) listenInBatched(reader io.ReadWriteCloser, batchReader overlay.BatchReader, i int, conntrackCache *firewall.ConntrackCacheTicker) {
-	batchSize := f.tunBatchSize
-
-	// Pre-allocate buffers for batch reading
-	packets := make([][]byte, batchSize)
-	for j := range packets {
-		packets[j] = make([]byte, mtu)
-	}
-	sizes := make([]int, batchSize)
-
-	// Pre-allocate buffers for packet processing
-	out := make([]byte, mtu)
-	fwPacket := &firewall.Packet{}
-	nb := make([]byte, 12, 12)
-
-	// Pre-allocate buffer for batched UDP writes
-	pendingPackets := make([]udp.BatchPacket, 0, batchSize)
-
-	for {
-		// Read a batch of packets from TUN
-		n, err := batchReader.ReadBatch(packets, sizes)
-		if err != nil {
-			if errors.Is(err, os.ErrClosed) && f.closed.Load() {
-				return
-			}
-
-			f.l.WithError(err).Error("Error while reading outbound packets")
-			os.Exit(2)
-		}
-
-		if n == 0 {
-			continue
-		}
-
-		// Process all packets in the batch
-		cache := conntrackCache.Get(f.l)
-		for j := 0; j < n; j++ {
-			f.consumeInsidePacketBatched(packets[j][:sizes[j]], fwPacket, nb, out, i, cache, &pendingPackets)
-		}
-
-		// Flush all pending UDP writes
-		if len(pendingPackets) > 0 {
-			f.writers[i].WriteBatch(pendingPackets)
-			pendingPackets = pendingPackets[:0]
-		}
-	}
-}
-
 func (f *Interface) RegisterConfigChangeCallbacks(c *config.C) {
 	c.RegisterReloadCallback(f.reloadFirewall)
 	c.RegisterReloadCallback(f.reloadSendRecvError)
@@ -559,14 +490,6 @@ func (f *Interface) Close() error {
 			f.l.WithError(err).Error("Error while closing udp socket")
 		}
 	}
-	for i, r := range f.readers {
-		if i == 0 {
-			continue // f.readers[0] is f.inside, which we want to save for last
-		}
-		if err := r.Close(); err != nil {
-			f.l.WithError(err).Error("Error while closing tun reader")
-		}
-	}
 
 	// Release the tun device
 	return f.inside.Close()

lighthouse_test.go

@@ -1,6 +1,7 @@
 package nebula
 
 import (
+	"context"
 	"encoding/binary"
 	"fmt"
 	"net/netip"
@@ -41,14 +42,14 @@ func Test_lhStaticMapping(t *testing.T) {
 	c := config.NewC(l)
 	c.Settings["lighthouse"] = map[string]any{"hosts": []any{lh1}}
 	c.Settings["static_host_map"] = map[string]any{lh1: []any{"1.1.1.1:4242"}}
-	_, err := NewLightHouseFromConfig(t.Context(), l, c, cs, nil, nil)
+	_, err := NewLightHouseFromConfig(context.Background(), l, c, cs, nil, nil)
 	require.NoError(t, err)
 
 	lh2 := "10.128.0.3"
 	c = config.NewC(l)
 	c.Settings["lighthouse"] = map[string]any{"hosts": []any{lh1, lh2}}
 	c.Settings["static_host_map"] = map[string]any{lh1: []any{"100.1.1.1:4242"}}
-	_, err = NewLightHouseFromConfig(t.Context(), l, c, cs, nil, nil)
+	_, err = NewLightHouseFromConfig(context.Background(), l, c, cs, nil, nil)
 	require.EqualError(t, err, "lighthouse 10.128.0.3 does not have a static_host_map entry")
 }
 
@@ -70,7 +71,7 @@ func TestReloadLighthouseInterval(t *testing.T) {
 	}
 
 	c.Settings["static_host_map"] = map[string]any{lh1: []any{"1.1.1.1:4242"}}
-	lh, err := NewLightHouseFromConfig(t.Context(), l, c, cs, nil, nil)
+	lh, err := NewLightHouseFromConfig(context.Background(), l, c, cs, nil, nil)
 	require.NoError(t, err)
 	lh.ifce = &mockEncWriter{}
 
@@ -98,7 +99,7 @@ func BenchmarkLighthouseHandleRequest(b *testing.B) {
 	}
 
 	c := config.NewC(l)
-	lh, err := NewLightHouseFromConfig(b.Context(), l, c, cs, nil, nil)
+	lh, err := NewLightHouseFromConfig(context.Background(), l, c, cs, nil, nil)
 	require.NoError(b, err)
 
 	hAddr := netip.MustParseAddrPort("4.5.6.7:12345")
@@ -201,7 +202,7 @@ func TestLighthouse_Memory(t *testing.T) {
 		myVpnNetworks:      []netip.Prefix{myVpnNet},
 		myVpnNetworksTable: nt,
 	}
-	lh, err := NewLightHouseFromConfig(t.Context(), l, c, cs, nil, nil)
+	lh, err := NewLightHouseFromConfig(context.Background(), l, c, cs, nil, nil)
 	lh.ifce = &mockEncWriter{}
 	require.NoError(t, err)
 	lhh := lh.NewRequestHandler()
@@ -287,7 +288,7 @@ func TestLighthouse_reload(t *testing.T) {
 		myVpnNetworksTable: nt,
 	}
 
-	lh, err := NewLightHouseFromConfig(t.Context(), l, c, cs, nil, nil)
+	lh, err := NewLightHouseFromConfig(context.Background(), l, c, cs, nil, nil)
 	require.NoError(t, err)
 
 	nc := map[string]any{
@@ -522,7 +523,7 @@ func TestLighthouse_Dont_Delete_Static_Hosts(t *testing.T) {
 		myVpnNetworks:      []netip.Prefix{myVpnNet},
 		myVpnNetworksTable: nt,
 	}
-	lh, err := NewLightHouseFromConfig(t.Context(), l, c, cs, nil, nil)
+	lh, err := NewLightHouseFromConfig(context.Background(), l, c, cs, nil, nil)
 	require.NoError(t, err)
 	lh.ifce = &mockEncWriter{}
 
@@ -588,7 +589,7 @@ func TestLighthouse_DeletesWork(t *testing.T) {
 		myVpnNetworks:      []netip.Prefix{myVpnNet},
 		myVpnNetworksTable: nt,
 	}
-	lh, err := NewLightHouseFromConfig(t.Context(), l, c, cs, nil, nil)
+	lh, err := NewLightHouseFromConfig(context.Background(), l, c, cs, nil, nil)
 	require.NoError(t, err)
 	lh.ifce = &mockEncWriter{}
 

main.go

@@ -250,7 +250,6 @@ func Main(c *config.C, configTest bool, buildVersion string, logger *logrus.Logg
 		punchy:                punchy,
 		ConntrackCacheTimeout: conntrackCacheTimeout,
 		l:                     l,
-		tunBatchSize:          c.GetInt("listen.batch", 64),
 	}
 
 	var ifce *Interface

overlay/device.go

@@ -16,38 +16,3 @@ type Device interface {
 	SupportsMultiqueue() bool
 	NewMultiQueueReader() (io.ReadWriteCloser, error)
 }
-
-// BatchReader is an optional interface that devices can implement
-// to support reading multiple packets in a single batch operation.
-// This can significantly reduce syscall overhead under high load.
-type BatchReader interface {
-	// ReadBatch reads up to len(packets) packets into the provided buffers.
-	// Each packet is read into packets[i] and its length is stored in sizes[i].
-	// Returns the number of packets read, or an error.
-	// A return of (0, nil) indicates no packets were available (non-blocking).
-	ReadBatch(packets [][]byte, sizes []int) (int, error)
-}
-
-// AsBatchReader returns a BatchReader if the reader supports batch operations,
-// otherwise returns nil.
-func AsBatchReader(r io.ReadWriteCloser) BatchReader {
-	if br, ok := r.(BatchReader); ok {
-		return br
-	}
-	return nil
-}
-
-// BatchEnabler is an optional interface for devices that need explicit
-// enabling of batch read support (e.g., setting non-blocking mode).
-type BatchEnabler interface {
-	EnableBatchReading() error
-}
-
-// EnableBatchReading enables batch reading on the device if supported.
-// Returns nil if the device doesn't support or need explicit enabling.
-func EnableBatchReading(d interface{}) error {
-	if be, ok := d.(BatchEnabler); ok {
-		return be.EnableBatchReading()
-	}
-	return nil
-}

overlay/tun.go

@@ -12,15 +12,6 @@ import (
 
 const DefaultMTU = 1300
 
-type NameError struct {
-	Name       string
-	Underlying error
-}
-
-func (e *NameError) Error() string {
-	return fmt.Sprintf("could not set tun device name: %s because %s", e.Name, e.Underlying)
-}
-
 // TODO: We may be able to remove routines
 type DeviceFactory func(c *config.C, l *logrus.Logger, vpnNetworks []netip.Prefix, routines int) (Device, error)
 

overlay/tun_freebsd.go

@@ -266,7 +266,7 @@ func newTun(c *config.C, l *logrus.Logger, vpnNetworks []netip.Prefix, _ bool) (
 		}
 
 		// Set the device name
-		_ = ioctl(fd, syscall.SIOCSIFNAME, uintptr(unsafe.Pointer(&ifrr)))
+		ioctl(fd, syscall.SIOCSIFNAME, uintptr(unsafe.Pointer(&ifrr)))
 	}
 
 	t := &tun{

overlay/tun_linux.go

@@ -24,11 +24,6 @@ import (
 	"golang.org/x/sys/unix"
 )
 
-const (
-	// virtioNetHdrLen is the length of virtio_net_hdr (without mergeable buffers)
-	virtioNetHdrLen = 10
-)
-
 type tun struct {
 	io.ReadWriteCloser
 	fd          int
@@ -39,13 +34,6 @@ type tun struct {
 	TXQueueLen  int
 	deviceIndex int
 	ioctlFd     uintptr
-	nonBlocking bool // true if fd is in non-blocking mode
-	vnetHdr     bool // true if IFF_VNET_HDR is enabled on the TUN device
-
-	// readBuf is used when vnetHdr is enabled to read the full packet+header
-	// before stripping the header. This is needed because caller-provided
-	// buffers are sized for MTU but kernel writes MTU+10 with virtio header.
-	readBuf []byte
 
 	Routes                    atomic.Pointer[[]Route]
 	routeTree                 atomic.Pointer[bart.Table[routing.Gateways]]
@@ -65,23 +53,6 @@ func (t *tun) Networks() []netip.Prefix {
 	return t.vpnNetworks
 }
 
-// tunVnetHdrSupported checks if the kernel supports IFF_VNET_HDR on TUN devices
-func tunVnetHdrSupported() bool {
-	fd, err := unix.Open("/dev/net/tun", unix.O_RDONLY, 0)
-	if err != nil {
-		return false
-	}
-	defer unix.Close(fd)
-
-	var features uint32
-	err = ioctl(uintptr(fd), uintptr(unix.TUNGETFEATURES), uintptr(unsafe.Pointer(&features)))
-	if err != nil {
-		return false
-	}
-
-	return features&unix.IFF_VNET_HDR != 0
-}
-
 type ifReq struct {
 	Name  [16]byte
 	Flags uint16
@@ -136,35 +107,17 @@ func newTun(c *config.C, l *logrus.Logger, vpnNetworks []netip.Prefix, multiqueu
 		}
 	}
 
-	// Check if VNET_HDR is supported before trying to use it
-	useVnetHdr := tunVnetHdrSupported()
-
 	var req ifReq
 	req.Flags = uint16(unix.IFF_TUN | unix.IFF_NO_PI)
 	if multiqueue {
 		req.Flags |= unix.IFF_MULTI_QUEUE
 	}
-	if useVnetHdr {
-		req.Flags |= unix.IFF_VNET_HDR
-	}
-
-	nameStr := c.GetString("tun.dev", "")
-	copy(req.Name[:], nameStr)
+	copy(req.Name[:], c.GetString("tun.dev", ""))
 	if err = ioctl(uintptr(fd), uintptr(unix.TUNSETIFF), uintptr(unsafe.Pointer(&req))); err != nil {
-		return nil, &NameError{
-			Name:       nameStr,
-			Underlying: err,
-		}
+		return nil, err
 	}
 	name := strings.Trim(string(req.Name[:]), "\x00")
 
-	// Track if VNET_HDR is in use
-	// Note: We don't call TUNSETOFFLOAD - just handle the headers manually
-	vnetHdrEnabled := useVnetHdr
-	if vnetHdrEnabled {
-		l.Info("TUN VNET_HDR enabled")
-	}
-
 	file := os.NewFile(uintptr(fd), "/dev/net/tun")
 	t, err := newTunGeneric(c, l, file, vpnNetworks)
 	if err != nil {
@@ -172,13 +125,6 @@ func newTun(c *config.C, l *logrus.Logger, vpnNetworks []netip.Prefix, multiqueu
 	}
 
 	t.Device = name
-	t.vnetHdr = vnetHdrEnabled
-
-	// Allocate read buffer for virtio header handling
-	// Buffer needs to be large enough for virtio header + max packet
-	if t.vnetHdr {
-		t.readBuf = make([]byte, t.MaxMTU+virtioNetHdrLen)
-	}
 
 	return t, nil
 }
@@ -191,7 +137,6 @@ func newTunGeneric(c *config.C, l *logrus.Logger, file *os.File, vpnNetworks []n
 		TXQueueLen:                c.GetInt("tun.tx_queue", 500),
 		useSystemRoutes:           c.GetBool("tun.use_system_route_table", false),
 		useSystemRoutesBufferSize: c.GetInt("tun.use_system_route_table_buffer_size", 0),
-		routesFromSystem:          map[netip.Prefix]routing.Gateways{},
 		l:                         l,
 	}
 
@@ -289,172 +234,21 @@ func (t *tun) SupportsMultiqueue() bool {
 }
 
 func (t *tun) NewMultiQueueReader() (io.ReadWriteCloser, error) {
-	fd, err := unix.Open("/dev/net/tun", os.O_RDWR|unix.O_NONBLOCK, 0)
+	fd, err := unix.Open("/dev/net/tun", os.O_RDWR, 0)
 	if err != nil {
 		return nil, err
 	}
 
 	var req ifReq
 	req.Flags = uint16(unix.IFF_TUN | unix.IFF_NO_PI | unix.IFF_MULTI_QUEUE)
-	if t.vnetHdr {
-		req.Flags |= unix.IFF_VNET_HDR
-	}
 	copy(req.Name[:], t.Device)
 	if err = ioctl(uintptr(fd), uintptr(unix.TUNSETIFF), uintptr(unsafe.Pointer(&req))); err != nil {
 		return nil, err
 	}
 
-	reader := &tunBatchReader{fd: fd, device: t.Device, vnetHdr: t.vnetHdr}
-	if t.vnetHdr {
-		reader.readBuf = make([]byte, t.MaxMTU+virtioNetHdrLen)
-	}
-	return reader, nil
-}
+	file := os.NewFile(uintptr(fd), "/dev/net/tun")
 
-// tunBatchReader implements BatchReader for efficient batch packet reading
-type tunBatchReader struct {
-	fd      int
-	device  string
-	vnetHdr bool
-	readBuf []byte // internal buffer for virtio header handling
-}
-
-func (r *tunBatchReader) Read(b []byte) (int, error) {
-	// Choose buffer: use internal buffer for vnetHdr, caller's buffer otherwise
-	readBuf := b
-	if r.vnetHdr {
-		readBuf = r.readBuf
-	}
-
-	// Use poll to wait for data, then read
-	for {
-		n, err := unix.Read(r.fd, readBuf)
-		if err == nil {
-			if r.vnetHdr && n > virtioNetHdrLen {
-				packetLen := n - virtioNetHdrLen
-				copy(b, readBuf[virtioNetHdrLen:n])
-				return packetLen, nil
-			}
-			if r.vnetHdr {
-				return 0, nil // No packet data
-			}
-			return n, nil
-		}
-		if err == unix.EAGAIN || err == unix.EWOULDBLOCK {
-			// Wait for data
-			pfds := []unix.PollFd{{Fd: int32(r.fd), Events: unix.POLLIN}}
-			_, err = unix.Poll(pfds, -1)
-			if err != nil {
-				if err == unix.EINTR {
-					continue
-				}
-				return 0, err
-			}
-			continue
-		}
-		return n, err
-	}
-}
-
-func (r *tunBatchReader) Write(b []byte) (int, error) {
-	if !r.vnetHdr {
-		return unix.Write(r.fd, b)
-	}
-
-	// Use writev to prepend virtio header without copying the packet data
-	// Header is all zeros = no GSO, no checksum offload
-	var hdr [virtioNetHdrLen]byte
-	bufs := [][]byte{hdr[:], b}
-
-	n, err := unix.Writev(r.fd, bufs)
-	if err != nil {
-		return 0, err
-	}
-	// Return only the packet bytes written (exclude header)
-	if n > virtioNetHdrLen {
-		return n - virtioNetHdrLen, nil
-	}
-	return 0, nil
-}
-
-func (r *tunBatchReader) Close() error {
-	return unix.Close(r.fd)
-}
-
-// ReadBatch reads up to len(packets) packets from the TUN device.
-// It drains all available packets without blocking, using poll() only
-// when no packets have been read yet.
-func (r *tunBatchReader) ReadBatch(packets [][]byte, sizes []int) (int, error) {
-	count := 0
-	maxPackets := len(packets)
-	if len(sizes) < maxPackets {
-		maxPackets = len(sizes)
-	}
-
-	// Choose read buffer based on vnetHdr
-	readBuf := packets[0] // Will be updated in loop for non-vnetHdr
-	if r.vnetHdr {
-		readBuf = r.readBuf
-	}
-
-	for count < maxPackets {
-		if !r.vnetHdr {
-			readBuf = packets[count]
-		}
-
-		n, err := unix.Read(r.fd, readBuf)
-		if err == nil && n > 0 {
-			if r.vnetHdr {
-				if n > virtioNetHdrLen {
-					packetLen := n - virtioNetHdrLen
-					copy(packets[count], readBuf[virtioNetHdrLen:n])
-					sizes[count] = packetLen
-				} else {
-					// Malformed packet (no data after header), skip
-					continue
-				}
-			} else {
-				sizes[count] = n
-			}
-			count++
-			continue
-		}
-
-		if err == unix.EAGAIN || err == unix.EWOULDBLOCK {
-			// No more packets available
-			if count > 0 {
-				// We have some packets, return them
-				return count, nil
-			}
-			// No packets yet, wait for at least one
-			pfds := []unix.PollFd{{Fd: int32(r.fd), Events: unix.POLLIN}}
-			_, err = unix.Poll(pfds, -1)
-			if err != nil {
-				if err == unix.EINTR {
-					continue
-				}
-				return 0, err
-			}
-			continue
-		}
-
-		if err != nil {
-			if count > 0 {
-				// Return what we have
-				return count, nil
-			}
-			return 0, err
-		}
-
-		if n == 0 {
-			if count > 0 {
-				return count, nil
-			}
-			return 0, io.EOF
-		}
-	}
-
-	return count, nil
+	return file, nil
 }
 
 func (t *tun) RoutesFor(ip netip.Addr) routing.Gateways {
@@ -463,27 +257,6 @@ func (t *tun) RoutesFor(ip netip.Addr) routing.Gateways {
 }
 
 func (t *tun) Write(b []byte) (int, error) {
-	if !t.vnetHdr {
-		return t.writeSimple(b)
-	}
-
-	// Use writev to prepend virtio header without copying the packet data
-	// Header is all zeros = no GSO, no checksum offload
-	var hdr [virtioNetHdrLen]byte
-	bufs := [][]byte{hdr[:], b}
-
-	n, err := unix.Writev(t.fd, bufs)
-	if err != nil {
-		return 0, err
-	}
-	// Return only the packet bytes written (exclude header)
-	if n > virtioNetHdrLen {
-		return n - virtioNetHdrLen, nil
-	}
-	return 0, nil
-}
-
-func (t *tun) writeSimple(b []byte) (int, error) {
 	var nn int
 	maximum := len(b)
 
@@ -506,177 +279,6 @@ func (t *tun) writeSimple(b []byte) (int, error) {
 	}
 }
 
-// EnableBatchReading sets the TUN fd to non-blocking mode to enable batch reading.
-// This should be called before using ReadBatch.
-func (t *tun) EnableBatchReading() error {
-	if t.nonBlocking {
-		return nil
-	}
-	err := unix.SetNonblock(t.fd, true)
-	if err != nil {
-		return err
-	}
-	t.nonBlocking = true
-	return nil
-}
-
-// Read overrides the default Read to handle non-blocking mode and virtio headers
-func (t *tun) Read(b []byte) (int, error) {
-	if !t.vnetHdr {
-		return t.readSimple(b)
-	}
-
-	// With VNET_HDR, read into internal buffer (which has space for header)
-	// then copy packet data to caller's buffer
-	if !t.nonBlocking {
-		n, err := t.ReadWriteCloser.Read(t.readBuf)
-		if err != nil {
-			return 0, err
-		}
-		if n <= virtioNetHdrLen {
-			return 0, nil // No packet data
-		}
-		packetLen := n - virtioNetHdrLen
-		copy(b, t.readBuf[virtioNetHdrLen:n])
-		return packetLen, nil
-	}
-
-	// Non-blocking read with poll
-	for {
-		n, err := unix.Read(t.fd, t.readBuf)
-		if err == nil {
-			if n <= virtioNetHdrLen {
-				return 0, nil // No packet data
-			}
-			packetLen := n - virtioNetHdrLen
-			copy(b, t.readBuf[virtioNetHdrLen:n])
-			return packetLen, nil
-		}
-		if err == unix.EAGAIN || err == unix.EWOULDBLOCK {
-			pfds := []unix.PollFd{{Fd: int32(t.fd), Events: unix.POLLIN}}
-			_, err = unix.Poll(pfds, -1)
-			if err != nil {
-				if err == unix.EINTR {
-					continue
-				}
-				return 0, err
-			}
-			continue
-		}
-		return n, err
-	}
-}
-
-func (t *tun) readSimple(b []byte) (int, error) {
-	if !t.nonBlocking {
-		return t.ReadWriteCloser.Read(b)
-	}
-
-	for {
-		n, err := unix.Read(t.fd, b)
-		if err == nil {
-			return n, nil
-		}
-		if err == unix.EAGAIN || err == unix.EWOULDBLOCK {
-			pfds := []unix.PollFd{{Fd: int32(t.fd), Events: unix.POLLIN}}
-			_, err = unix.Poll(pfds, -1)
-			if err != nil {
-				if err == unix.EINTR {
-					continue
-				}
-				return 0, err
-			}
-			continue
-		}
-		return n, err
-	}
-}
-
-// ReadBatch reads up to len(packets) packets from the TUN device.
-// EnableBatchReading must be called first.
-func (t *tun) ReadBatch(packets [][]byte, sizes []int) (int, error) {
-	if !t.nonBlocking {
-		// Fallback to single read if non-blocking not enabled
-		n, err := t.Read(packets[0])
-		if err != nil {
-			return 0, err
-		}
-		sizes[0] = n
-		return 1, nil
-	}
-
-	count := 0
-	maxPackets := len(packets)
-	if len(sizes) < maxPackets {
-		maxPackets = len(sizes)
-	}
-
-	// Choose read buffer based on vnetHdr
-	// With vnetHdr, we need to read into internal buffer (has space for header)
-	// then copy packet data to caller's buffer
-	readBuf := packets[0] // Will be updated in the loop
-	if t.vnetHdr {
-		readBuf = t.readBuf
-	}
-
-	for count < maxPackets {
-		if !t.vnetHdr {
-			readBuf = packets[count]
-		}
-
-		n, err := unix.Read(t.fd, readBuf)
-		if err == nil && n > 0 {
-			if t.vnetHdr {
-				if n > virtioNetHdrLen {
-					packetLen := n - virtioNetHdrLen
-					copy(packets[count], readBuf[virtioNetHdrLen:n])
-					sizes[count] = packetLen
-				} else {
-					// Malformed packet (no data after header), skip
-					continue
-				}
-			} else {
-				sizes[count] = n
-			}
-			count++
-			continue
-		}
-
-		if err == unix.EAGAIN || err == unix.EWOULDBLOCK {
-			// No more packets available
-			if count > 0 {
-				return count, nil
-			}
-			// No packets yet, wait for at least one
-			pfds := []unix.PollFd{{Fd: int32(t.fd), Events: unix.POLLIN}}
-			_, err = unix.Poll(pfds, -1)
-			if err != nil {
-				if err == unix.EINTR {
-					continue
-				}
-				return 0, err
-			}
-			continue
-		}
-
-		if err != nil {
-			if count > 0 {
-				return count, nil
-			}
-			return 0, err
-		}
-
-		if n == 0 {
-			if count > 0 {
-				return count, nil
-			}
-			return 0, io.EOF
-		}
-	}
-
-	return count, nil
-}
-
 func (t *tun) deviceBytes() (o [16]byte) {
 	for i, c := range t.Device {
 		o[i] = byte(c)
@@ -1110,7 +712,6 @@ func (t *tun) Close() error {
 
 	if t.ioctlFd > 0 {
 		_ = os.NewFile(t.ioctlFd, "ioctlFd").Close()
-		t.ioctlFd = 0
 	}
 
 	return nil

overlay/tun_windows.go

@@ -74,10 +74,7 @@ func newTun(c *config.C, l *logrus.Logger, vpnNetworks []netip.Prefix, _ bool) (
 		l.WithError(err).Debug("Failed to create wintun device, retrying")
 		tunDevice, err = wintun.CreateTUNWithRequestedGUID(deviceName, guid, t.MTU)
 		if err != nil {
-			return nil, &NameError{
-				Name:       deviceName,
-				Underlying: fmt.Errorf("create TUN device failed: %w", err),
-			}
+			return nil, fmt.Errorf("create TUN device failed: %w", err)
 		}
 	}
 	t.tun = tunDevice.(*wintun.NativeTun)

udp/conn.go

@@ -13,22 +13,13 @@ type EncReader func(
 	payload []byte,
 )
 
-// BatchPacket represents a single packet in a batch write operation
-type BatchPacket struct {
-	Payload []byte
-	Addr    netip.AddrPort
-}
-
 type Conn interface {
 	Rebind() error
 	LocalAddr() (netip.AddrPort, error)
 	ListenOut(r EncReader)
 	WriteTo(b []byte, addr netip.AddrPort) error
-	WriteBatch(pkts []BatchPacket) (int, error)
 	ReloadConfig(c *config.C)
 	SupportsMultipleReaders() bool
-	SupportsGSO() bool
-	SupportsGRO() bool
 	Close() error
 }
 
@@ -46,18 +37,9 @@ func (NoopConn) ListenOut(_ EncReader) {
 func (NoopConn) SupportsMultipleReaders() bool {
 	return false
 }
-func (NoopConn) SupportsGSO() bool {
-	return false
-}
-func (NoopConn) SupportsGRO() bool {
-	return false
-}
 func (NoopConn) WriteTo(_ []byte, _ netip.AddrPort) error {
 	return nil
 }
-func (NoopConn) WriteBatch(pkts []BatchPacket) (int, error) {
-	return len(pkts), nil
-}
 func (NoopConn) ReloadConfig(_ *config.C) {
 	return
 }

udp/udp_darwin.go

@@ -188,14 +188,6 @@ func (u *StdConn) SupportsMultipleReaders() bool {
 	return false
 }
 
-func (u *StdConn) SupportsGSO() bool {
-	return false
-}
-
-func (u *StdConn) SupportsGRO() bool {
-	return false
-}
-
 func (u *StdConn) Rebind() error {
 	var err error
 	if u.isV4 {
@@ -210,12 +202,3 @@ func (u *StdConn) Rebind() error {
 
 	return nil
 }
-
-func (u *StdConn) WriteBatch(pkts []BatchPacket) (int, error) {
-	for i := range pkts {
-		if err := u.WriteTo(pkts[i].Payload, pkts[i].Addr); err != nil {
-			return i, err
-		}
-	}
-	return len(pkts), nil
-}

udp/udp_generic.go

@@ -101,20 +101,3 @@ func (u *GenericConn) ListenOut(r EncReader) {
 func (u *GenericConn) SupportsMultipleReaders() bool {
 	return false
 }
-
-func (u *GenericConn) SupportsGSO() bool {
-	return false
-}
-
-func (u *GenericConn) SupportsGRO() bool {
-	return false
-}
-
-func (u *GenericConn) WriteBatch(pkts []BatchPacket) (int, error) {
-	for i := range pkts {
-		if err := u.WriteTo(pkts[i].Payload, pkts[i].Addr); err != nil {
-			return i, err
-		}
-	}
-	return len(pkts), nil
-}

udp/udp_linux.go

@@ -5,7 +5,6 @@ package udp
 
 import (
 	"encoding/binary"
-	"errors"
 	"fmt"
 	"net"
 	"net/netip"
@@ -19,12 +18,10 @@ import (
 )
 
 type StdConn struct {
-	sysFd        int
-	isV4         bool
-	l            *logrus.Logger
-	batch        int
-	gsoSupported bool
-	groSupported bool
+	sysFd int
+	isV4  bool
+	l     *logrus.Logger
+	batch int
 }
 
 func maybeIPV4(ip net.IP) (net.IP, bool) {
@@ -35,78 +32,6 @@ func maybeIPV4(ip net.IP) (net.IP, bool) {
 	return ip, false
 }
 
-// supportsUDPOffload checks if the kernel supports UDP GSO (Generic Segmentation Offload)
-// by attempting to get the UDP_SEGMENT socket option.
-func supportsUDPOffload(fd int) bool {
-	_, err := unix.GetsockoptInt(fd, unix.IPPROTO_UDP, unix.UDP_SEGMENT)
-	return err == nil
-}
-
-// supportsUDPGRO checks if the kernel supports UDP GRO (Generic Receive Offload)
-// and attempts to enable it on the socket.
-func supportsUDPGRO(fd int) bool {
-	// Try to enable UDP_GRO
-	err := unix.SetsockoptInt(fd, unix.IPPROTO_UDP, unix.UDP_GRO, 1)
-	return err == nil
-}
-
-const (
-	// Maximum number of datagrams that can be coalesced with GSO/GRO
-	udpSegmentMaxDatagrams = 64
-
-	// Maximum size of a GRO coalesced packet (64KB is the practical limit)
-	// This is udpSegmentMaxDatagrams * MTU but capped at 65535
-	groMaxPacketSize = 65535
-)
-
-// setGSOSize writes a UDP_SEGMENT control message to the provided buffer
-// with the given segment size. Returns the actual control message length.
-func setGSOSize(control []byte, gsoSize uint16) int {
-	// Build the cmsghdr structure
-	cmsgLen := unix.CmsgLen(2) // 2 bytes for uint16 segment size
-	cmsg := (*unix.Cmsghdr)(unsafe.Pointer(&control[0]))
-	cmsg.Level = unix.IPPROTO_UDP
-	cmsg.Type = unix.UDP_SEGMENT
-	cmsg.SetLen(cmsgLen)
-
-	// Write the segment size after the header (after cmsghdr)
-	binary.NativeEndian.PutUint16(control[unix.SizeofCmsghdr:], gsoSize)
-
-	return unix.CmsgSpace(2) // aligned size
-}
-
-// getGROSize parses a control message buffer to extract the UDP_GRO segment size.
-// Returns 0 if no GRO control message is present (meaning the packet is not coalesced).
-func getGROSize(control []byte, controlLen int) uint16 {
-	if controlLen < unix.SizeofCmsghdr {
-		return 0
-	}
-
-	// Parse control messages
-	for offset := 0; offset < controlLen; {
-		if offset+unix.SizeofCmsghdr > controlLen {
-			break
-		}
-
-		cmsg := (*unix.Cmsghdr)(unsafe.Pointer(&control[offset]))
-		cmsgDataLen := int(cmsg.Len) - unix.SizeofCmsghdr
-		if cmsgDataLen < 0 {
-			break
-		}
-
-		if cmsg.Level == unix.IPPROTO_UDP && cmsg.Type == unix.UDP_GRO {
-			if cmsgDataLen >= 2 {
-				return binary.NativeEndian.Uint16(control[offset+unix.SizeofCmsghdr:])
-			}
-		}
-
-		// Move to next control message (aligned)
-		offset += unix.CmsgSpace(cmsgDataLen)
-	}
-
-	return 0
-}
-
 func NewListener(l *logrus.Logger, ip netip.Addr, port int, multi bool, batch int) (Conn, error) {
 	af := unix.AF_INET6
 	if ip.Is4() {
@@ -144,31 +69,13 @@ func NewListener(l *logrus.Logger, ip netip.Addr, port int, multi bool, batch in
 		return nil, fmt.Errorf("unable to bind to socket: %s", err)
 	}
 
-	gsoSupported := supportsUDPOffload(fd)
-	if gsoSupported {
-		l.Info("UDP GSO offload is supported")
-	}
-
-	groSupported := supportsUDPGRO(fd)
-	if groSupported {
-		l.Info("UDP GRO offload is supported and enabled")
-	}
-
-	return &StdConn{sysFd: fd, isV4: ip.Is4(), l: l, batch: batch, gsoSupported: gsoSupported, groSupported: groSupported}, err
+	return &StdConn{sysFd: fd, isV4: ip.Is4(), l: l, batch: batch}, err
 }
 
 func (u *StdConn) SupportsMultipleReaders() bool {
 	return true
 }
 
-func (u *StdConn) SupportsGSO() bool {
-	return u.gsoSupported
-}
-
-func (u *StdConn) SupportsGRO() bool {
-	return u.groSupported
-}
-
 func (u *StdConn) Rebind() error {
 	return nil
 }
@@ -218,27 +125,13 @@ func (u *StdConn) LocalAddr() (netip.AddrPort, error) {
 func (u *StdConn) ListenOut(r EncReader) {
 	var ip netip.Addr
 
-	msgs, buffers, names, controls := u.PrepareRawMessages(u.batch)
+	msgs, buffers, names := u.PrepareRawMessages(u.batch)
 	read := u.ReadMulti
 	if u.batch == 1 {
 		read = u.ReadSingle
 	}
 
-	// Store the original control buffer size for resetting after each read
-	controlLen := 0
-	if u.groSupported && len(controls) > 0 && len(controls[0]) > 0 {
-		controlLen = len(controls[0])
-	}
-
 	for {
-		// Reset Controllen before each read - the kernel updates this field
-		// after recvmsg to indicate actual received control data length
-		if controlLen > 0 {
-			for i := range msgs {
-				setMsghdrControllen(&msgs[i].Hdr, controlLen)
-			}
-		}
-
 		n, err := read(msgs)
 		if err != nil {
 			u.l.WithError(err).Debug("udp socket is closed, exiting read loop")
@@ -246,36 +139,13 @@ func (u *StdConn) ListenOut(r EncReader) {
 		}
 
 		for i := 0; i < n; i++ {
-			// Extract source address
+			// Its ok to skip the ok check here, the slicing is the only error that can occur and it will panic
 			if u.isV4 {
 				ip, _ = netip.AddrFromSlice(names[i][4:8])
 			} else {
 				ip, _ = netip.AddrFromSlice(names[i][8:24])
 			}
-			srcAddr := netip.AddrPortFrom(ip.Unmap(), binary.BigEndian.Uint16(names[i][2:4]))
-
-			// Check for GRO coalesced packet
-			totalLen := int(msgs[i].Len)
-			segmentSize := uint16(0)
-			if controlLen > 0 {
-				segmentSize = getGROSize(controls[i], getMsghdrControllen(&msgs[i].Hdr))
-			}
-
-			if segmentSize > 0 && totalLen > int(segmentSize) {
-				// This is a GRO coalesced packet - split it into individual datagrams
-				for offset := 0; offset < totalLen; {
-					packetLen := int(segmentSize)
-					if offset+packetLen > totalLen {
-						// Last packet may be smaller
-						packetLen = totalLen - offset
-					}
-					r(srcAddr, buffers[i][offset:offset+packetLen])
-					offset += packetLen
-				}
-			} else {
-				// Single packet, no coalescing
-				r(srcAddr, buffers[i][:totalLen])
-			}
+			r(netip.AddrPortFrom(ip.Unmap(), binary.BigEndian.Uint16(names[i][2:4])), buffers[i][:msgs[i].Len])
 		}
 	}
 }
@@ -443,226 +313,6 @@ func (u *StdConn) Close() error {
 	return syscall.Close(u.sysFd)
 }
 
-func (u *StdConn) WriteBatch(pkts []BatchPacket) (int, error) {
-	if len(pkts) == 0 {
-		return 0, nil
-	}
-
-	// If GSO is supported, try to coalesce packets to the same destination
-	if u.gsoSupported {
-		return u.writeBatchGSO(pkts)
-	}
-
-	return u.writeBatchSendmmsg(pkts)
-}
-
-// writeBatchSendmmsg sends packets using sendmmsg without GSO coalescing
-func (u *StdConn) writeBatchSendmmsg(pkts []BatchPacket) (int, error) {
-	msgs := make([]rawMessage, len(pkts))
-	iovecs := make([]iovec, len(pkts))
-	var names4 []unix.RawSockaddrInet4
-	var names6 []unix.RawSockaddrInet6
-
-	if u.isV4 {
-		names4 = make([]unix.RawSockaddrInet4, len(pkts))
-	} else {
-		names6 = make([]unix.RawSockaddrInet6, len(pkts))
-	}
-
-	for i := range pkts {
-		setIovecBase(&iovecs[i], &pkts[i].Payload[0])
-		setIovecLen(&iovecs[i], len(pkts[i].Payload))
-		msgs[i].Hdr.Iov = &iovecs[i]
-		setMsghdrIovlen(&msgs[i].Hdr, 1)
-
-		if u.isV4 {
-			names4[i].Family = unix.AF_INET
-			names4[i].Addr = pkts[i].Addr.Addr().As4()
-			binary.BigEndian.PutUint16((*[2]byte)(unsafe.Pointer(&names4[i].Port))[:], pkts[i].Addr.Port())
-			msgs[i].Hdr.Name = (*byte)(unsafe.Pointer(&names4[i]))
-			msgs[i].Hdr.Namelen = unix.SizeofSockaddrInet4
-		} else {
-			names6[i].Family = unix.AF_INET6
-			names6[i].Addr = pkts[i].Addr.Addr().As16()
-			binary.BigEndian.PutUint16((*[2]byte)(unsafe.Pointer(&names6[i].Port))[:], pkts[i].Addr.Port())
-			msgs[i].Hdr.Name = (*byte)(unsafe.Pointer(&names6[i]))
-			msgs[i].Hdr.Namelen = unix.SizeofSockaddrInet6
-		}
-	}
-
-	var sent int
-	for sent < len(msgs) {
-		n, _, errno := unix.Syscall6(
-			unix.SYS_SENDMMSG,
-			uintptr(u.sysFd),
-			uintptr(unsafe.Pointer(&msgs[sent])),
-			uintptr(len(msgs)-sent),
-			0,
-			0,
-			0,
-		)
-
-		if errno == unix.EINTR {
-			continue
-		}
-
-		if errno != 0 {
-			return sent, &net.OpError{Op: "sendmmsg", Err: errno}
-		}
-
-		sent += int(n)
-	}
-
-	return sent, nil
-}
-
-// writeBatchGSO sends packets using GSO coalescing when possible.
-// Packets to the same destination with the same size are coalesced into a single
-// GSO message. Mixed destinations or sizes fall back to individual sendmmsg calls.
-func (u *StdConn) writeBatchGSO(pkts []BatchPacket) (int, error) {
-	// Group packets by destination and try to coalesce
-	totalSent := 0
-	i := 0
-
-	for i < len(pkts) {
-		// Find a run of packets to the same destination with compatible sizes
-		startIdx := i
-		dst := pkts[i].Addr
-		segmentSize := len(pkts[i].Payload)
-
-		// Count how many packets we can coalesce (same destination, same size except possibly last)
-		coalescedCount := 1
-		totalSize := segmentSize
-		for i+coalescedCount < len(pkts) && coalescedCount < udpSegmentMaxDatagrams {
-			next := pkts[i+coalescedCount]
-			if next.Addr != dst {
-				break
-			}
-			nextSize := len(next.Payload)
-			// For GSO, all packets except the last must have the same size
-			// The last packet can be smaller (but not larger)
-			if nextSize != segmentSize {
-				// Check if this could be the last packet (smaller is ok)
-				if nextSize < segmentSize && i+coalescedCount == len(pkts)-1 {
-					coalescedCount++
-					totalSize += nextSize
-				}
-				break
-			}
-			coalescedCount++
-			totalSize += nextSize
-		}
-
-		// If we have multiple packets to coalesce, use GSO
-		if coalescedCount > 1 {
-			err := u.sendGSO(pkts[startIdx:startIdx+coalescedCount], dst, segmentSize, totalSize)
-			if err != nil {
-				// If GSO fails (e.g., EIO due to NIC not supporting checksum offload),
-				// disable GSO and fall back to sendmmsg for the rest
-				if isGSOError(err) {
-					u.l.WithError(err).Warn("GSO send failed, disabling GSO for this connection")
-					u.gsoSupported = false
-					// Send remaining packets with sendmmsg
-					remaining, rerr := u.writeBatchSendmmsg(pkts[startIdx:])
-					return totalSent + remaining, rerr
-				}
-				return totalSent, err
-			}
-			totalSent += coalescedCount
-			i += coalescedCount
-		} else {
-			// Single packet, send without GSO overhead
-			err := u.WriteTo(pkts[i].Payload, pkts[i].Addr)
-			if err != nil {
-				return totalSent, err
-			}
-			totalSent++
-			i++
-		}
-	}
-
-	return totalSent, nil
-}
-
-// sendGSO sends coalesced packets using UDP GSO
-func (u *StdConn) sendGSO(pkts []BatchPacket, dst netip.AddrPort, segmentSize, totalSize int) error {
-	// Allocate a buffer large enough for all packet payloads
-	coalescedBuf := make([]byte, totalSize)
-	offset := 0
-	for _, pkt := range pkts {
-		copy(coalescedBuf[offset:], pkt.Payload)
-		offset += len(pkt.Payload)
-	}
-
-	// Prepare control message with GSO segment size
-	control := make([]byte, unix.CmsgSpace(2))
-	controlLen := setGSOSize(control, uint16(segmentSize))
-
-	// Prepare the iovec
-	iov := iovec{}
-	setIovecBase(&iov, &coalescedBuf[0])
-	setIovecLen(&iov, totalSize)
-
-	// Prepare the msghdr
-	var hdr msghdr
-	hdr.Iov = &iov
-	setMsghdrIovlen(&hdr, 1)
-	hdr.Control = &control[0]
-	setMsghdrControllen(&hdr, controlLen)
-
-	// Declare sockaddr at function scope so it remains valid for the syscall
-	// (must not go out of scope before the syscall is made)
-	var rsa4 unix.RawSockaddrInet4
-	var rsa6 unix.RawSockaddrInet6
-
-	// Set destination address
-	if u.isV4 {
-		rsa4.Family = unix.AF_INET
-		rsa4.Addr = dst.Addr().As4()
-		binary.BigEndian.PutUint16((*[2]byte)(unsafe.Pointer(&rsa4.Port))[:], dst.Port())
-		hdr.Name = (*byte)(unsafe.Pointer(&rsa4))
-		hdr.Namelen = unix.SizeofSockaddrInet4
-	} else {
-		rsa6.Family = unix.AF_INET6
-		rsa6.Addr = dst.Addr().As16()
-		binary.BigEndian.PutUint16((*[2]byte)(unsafe.Pointer(&rsa6.Port))[:], dst.Port())
-		hdr.Name = (*byte)(unsafe.Pointer(&rsa6))
-		hdr.Namelen = unix.SizeofSockaddrInet6
-	}
-
-	for {
-		_, _, errno := unix.Syscall6(
-			unix.SYS_SENDMSG,
-			uintptr(u.sysFd),
-			uintptr(unsafe.Pointer(&hdr)),
-			0,
-			0,
-			0,
-			0,
-		)
-
-		if errno == unix.EINTR {
-			continue
-		}
-
-		if errno != 0 {
-			return &net.OpError{Op: "sendmsg", Err: errno}
-		}
-
-		return nil
-	}
-}
-
-// isGSOError returns true if the error indicates GSO is not supported by the NIC
-func isGSOError(err error) bool {
-	var opErr *net.OpError
-	if !errors.As(err, &opErr) {
-		return false
-	}
-	// EIO typically means the NIC doesn't support checksum offload required for GSO
-	return errors.Is(opErr.Err, unix.EIO)
-}
-
 func NewUDPStatsEmitter(udpConns []Conn) func() {
 	// Check if our kernel supports SO_MEMINFO before registering the gauges
 	var udpGauges [][unix.SK_MEMINFO_VARS]metrics.Gauge

udp/udp_linux_32.go

@@ -30,26 +30,13 @@ type rawMessage struct {
 	Len uint32
 }
 
-func (u *StdConn) PrepareRawMessages(n int) ([]rawMessage, [][]byte, [][]byte, [][]byte) {
+func (u *StdConn) PrepareRawMessages(n int) ([]rawMessage, [][]byte, [][]byte) {
 	msgs := make([]rawMessage, n)
 	buffers := make([][]byte, n)
 	names := make([][]byte, n)
-	controls := make([][]byte, n)
-
-	// Use larger buffers if GRO is enabled to hold coalesced packets
-	bufSize := MTU
-	if u.groSupported {
-		bufSize = groMaxPacketSize
-	}
-
-	// Control buffer size for receiving UDP_GRO segment size
-	controlSize := 0
-	if u.groSupported {
-		controlSize = unix.CmsgSpace(2) // space for uint16 segment size
-	}
 
 	for i := range msgs {
-		buffers[i] = make([]byte, bufSize)
+		buffers[i] = make([]byte, MTU)
 		names[i] = make([]byte, unix.SizeofSockaddrInet6)
 
 		vs := []iovec{
@@ -61,34 +48,7 @@ func (u *StdConn) PrepareRawMessages(n int) ([]rawMessage, [][]byte, [][]byte, [
 
 		msgs[i].Hdr.Name = &names[i][0]
 		msgs[i].Hdr.Namelen = uint32(len(names[i]))
-
-		// Set up control message buffer for GRO
-		if controlSize > 0 {
-			controls[i] = make([]byte, controlSize)
-			msgs[i].Hdr.Control = &controls[i][0]
-			msgs[i].Hdr.Controllen = uint32(controlSize)
-		}
 	}
 
-	return msgs, buffers, names, controls
-}
-
-func setIovecBase(iov *iovec, base *byte) {
-	iov.Base = base
-}
-
-func setIovecLen(iov *iovec, l int) {
-	iov.Len = uint32(l)
-}
-
-func setMsghdrIovlen(hdr *msghdr, l int) {
-	hdr.Iovlen = uint32(l)
-}
-
-func setMsghdrControllen(hdr *msghdr, l int) {
-	hdr.Controllen = uint32(l)
-}
-
-func getMsghdrControllen(hdr *msghdr) int {
-	return int(hdr.Controllen)
+	return msgs, buffers, names
 }

udp/udp_linux_64.go

@@ -33,26 +33,13 @@ type rawMessage struct {
 	Pad0 [4]byte
 }
 
-func (u *StdConn) PrepareRawMessages(n int) ([]rawMessage, [][]byte, [][]byte, [][]byte) {
+func (u *StdConn) PrepareRawMessages(n int) ([]rawMessage, [][]byte, [][]byte) {
 	msgs := make([]rawMessage, n)
 	buffers := make([][]byte, n)
 	names := make([][]byte, n)
-	controls := make([][]byte, n)
-
-	// Use larger buffers if GRO is enabled to hold coalesced packets
-	bufSize := MTU
-	if u.groSupported {
-		bufSize = groMaxPacketSize
-	}
-
-	// Control buffer size for receiving UDP_GRO segment size
-	controlSize := 0
-	if u.groSupported {
-		controlSize = unix.CmsgSpace(2) // space for uint16 segment size
-	}
 
 	for i := range msgs {
-		buffers[i] = make([]byte, bufSize)
+		buffers[i] = make([]byte, MTU)
 		names[i] = make([]byte, unix.SizeofSockaddrInet6)
 
 		vs := []iovec{
@@ -64,34 +51,7 @@ func (u *StdConn) PrepareRawMessages(n int) ([]rawMessage, [][]byte, [][]byte, [
 
 		msgs[i].Hdr.Name = &names[i][0]
 		msgs[i].Hdr.Namelen = uint32(len(names[i]))
-
-		// Set up control message buffer for GRO
-		if controlSize > 0 {
-			controls[i] = make([]byte, controlSize)
-			msgs[i].Hdr.Control = &controls[i][0]
-			msgs[i].Hdr.Controllen = uint64(controlSize)
-		}
 	}
 
-	return msgs, buffers, names, controls
-}
-
-func setIovecBase(iov *iovec, base *byte) {
-	iov.Base = base
-}
-
-func setIovecLen(iov *iovec, l int) {
-	iov.Len = uint64(l)
-}
-
-func setMsghdrIovlen(hdr *msghdr, l int) {
-	hdr.Iovlen = uint64(l)
-}
-
-func setMsghdrControllen(hdr *msghdr, l int) {
-	hdr.Controllen = uint64(l)
-}
-
-func getMsghdrControllen(hdr *msghdr) int {
-	return int(hdr.Controllen)
+	return msgs, buffers, names
 }

udp/udp_rio_windows.go

@@ -332,29 +332,12 @@ func (u *RIOConn) SupportsMultipleReaders() bool {
 	return false
 }
 
-func (u *RIOConn) SupportsGSO() bool {
-	return false
-}
-
-func (u *RIOConn) SupportsGRO() bool {
-	return false
-}
-
 func (u *RIOConn) Rebind() error {
 	return nil
 }
 
 func (u *RIOConn) ReloadConfig(*config.C) {}
 
-func (u *RIOConn) WriteBatch(pkts []BatchPacket) (int, error) {
-	for i := range pkts {
-		if err := u.WriteTo(pkts[i].Payload, pkts[i].Addr); err != nil {
-			return i, err
-		}
-	}
-	return len(pkts), nil
-}
-
 func (u *RIOConn) Close() error {
 	if !u.isOpen.CompareAndSwap(true, false) {
 		return nil

udp/udp_tester.go

@@ -131,14 +131,6 @@ func (u *TesterConn) SupportsMultipleReaders() bool {
 	return false
 }
 
-func (u *TesterConn) SupportsGSO() bool {
-	return false
-}
-
-func (u *TesterConn) SupportsGRO() bool {
-	return false
-}
-
 func (u *TesterConn) Rebind() error {
 	return nil
 }
@@ -150,12 +142,3 @@ func (u *TesterConn) Close() error {
 	}
 	return nil
 }
-
-func (u *TesterConn) WriteBatch(pkts []BatchPacket) (int, error) {
-	for i := range pkts {
-		if err := u.WriteTo(pkts[i].Payload, pkts[i].Addr); err != nil {
-			return i, err
-		}
-	}
-	return len(pkts), nil
-}