sure

CHANGELOG.md

@@ -7,30 +7,12 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
-### Added
-
-- Experimental Linux UDP offload support: enable `listen.enable_gso` and
-  `listen.enable_gro` to activate UDP_SEGMENT batching and GRO receive
-  splitting. Includes automatic capability probing, per-packet fallbacks, and
-  runtime metrics/logs for visibility.
-- Optional Linux TUN `virtio_net_hdr` support: set `tun.enable_vnet_hdr` to
-  have Nebula negotiate VNET headers and offload flags so future batches can
-  be delivered to the kernel with metadata instead of per-packet writes.
-- Linux UDP send sharding can now be tuned with `listen.send_shards`; defaults
-  to `GOMAXPROCS` but can be increased to stripe heavy peers across more
-  goroutines.
-
 ### Changed
 
 - `default_local_cidr_any` now defaults to false, meaning that any firewall rule
   intended to target an `unsafe_routes` entry must explicitly declare it via the
   `local_cidr` field. This is almost always the intended behavior. This flag is
   deprecated and will be removed in a future release.
-- UDP receive path now enqueues into per-worker lock-free rings, restoring the
-  `listen.decrypt_workers`/`listen.decrypt_queue_depth` tuning knobs while
-  eliminating the mutex contention from the old shared channel.
-- Increased replay protection window to 32k packets so high-throughput links
-  tolerate larger bursts of reordering without tripping the anti-replay logic.
 
 ## [1.9.4] - 2024-09-09
 

cert/pem.go

@@ -1,8 +1,10 @@
 package cert
 
 import (
+	"encoding/hex"
 	"encoding/pem"
 	"fmt"
+	"time"
 
 	"golang.org/x/crypto/ed25519"
 )
@@ -189,3 +191,71 @@ func UnmarshalSigningPrivateKeyFromPEM(b []byte) ([]byte, []byte, Curve, error)
 	}
 	return k.Bytes, r, curve, nil
 }
+
+// Backward compatibility functions for older API
+func MarshalX25519PublicKey(b []byte) []byte {
+	return MarshalPublicKeyToPEM(Curve_CURVE25519, b)
+}
+
+func MarshalX25519PrivateKey(b []byte) []byte {
+	return MarshalPrivateKeyToPEM(Curve_CURVE25519, b)
+}
+
+func MarshalPublicKey(curve Curve, b []byte) []byte {
+	return MarshalPublicKeyToPEM(curve, b)
+}
+
+func MarshalPrivateKey(curve Curve, b []byte) []byte {
+	return MarshalPrivateKeyToPEM(curve, b)
+}
+
+// NebulaCertificate is a compatibility wrapper for the old API
+type NebulaCertificate struct {
+	Details   NebulaCertificateDetails
+	Signature []byte
+	cert      Certificate
+}
+
+// NebulaCertificateDetails is a compatibility wrapper for certificate details
+type NebulaCertificateDetails struct {
+	Name      string
+	NotBefore time.Time
+	NotAfter  time.Time
+	PublicKey []byte
+	IsCA      bool
+	Issuer    []byte
+	Curve     Curve
+}
+
+// UnmarshalNebulaCertificateFromPEM provides backward compatibility with the old API
+func UnmarshalNebulaCertificateFromPEM(b []byte) (*NebulaCertificate, []byte, error) {
+	c, rest, err := UnmarshalCertificateFromPEM(b)
+	if err != nil {
+		return nil, rest, err
+	}
+
+	// Convert to old format
+	nc := &NebulaCertificate{
+		Details: NebulaCertificateDetails{
+			Name:      c.Name(),
+			NotBefore: c.NotBefore(),
+			NotAfter:  c.NotAfter(),
+			PublicKey: c.PublicKey(),
+			IsCA:      c.IsCA(),
+			Curve:     c.Curve(),
+		},
+		Signature: c.Signature(),
+		cert:      c,
+	}
+
+	// Handle issuer
+	if c.Issuer() != "" {
+		issuerBytes, err := hex.DecodeString(c.Issuer())
+		if err != nil {
+			return nil, rest, fmt.Errorf("failed to decode issuer fingerprint: %w", err)
+		}
+		nc.Details.Issuer = issuerBytes
+	}
+
+	return nc, rest, nil
+}

connection_state.go

@@ -13,10 +13,7 @@ import (
 	"github.com/slackhq/nebula/noiseutil"
 )
 
-// ReplayWindow controls the size of the sliding window used to detect replays.
+const ReplayWindow = 1024
-// High-bandwidth links with GRO/GSO can reorder more than a thousand packets in
-// flight, so keep this comfortably above the largest expected burst.
-const ReplayWindow = 32768
 
 type ConnectionState struct {
 	eKey           *NebulaCipherState

interface.go

@@ -5,11 +5,9 @@ import (
 	"errors"
 	"fmt"
 	"io"
-	"math/bits"
 	"net/netip"
 	"os"
 	"runtime"
-	"sync"
 	"sync/atomic"
 	"time"
 
@@ -23,12 +21,7 @@ import (
 	"github.com/slackhq/nebula/udp"
 )
 
-const (
+const mtu = 9001
-	mtu                        = 9001
-	tunReadBufferSize          = mtu * 8
-	defaultDecryptWorkerFactor = 2
-	defaultInboundQueueDepth   = 1024
-)
 
 type InterfaceConfig struct {
 	HostMap            *HostMap
@@ -55,8 +48,6 @@ type InterfaceConfig struct {
 
 	ConntrackCacheTimeout time.Duration
 	l                     *logrus.Logger
-	DecryptWorkers        int
-	DecryptQueueDepth     int
 }
 
 type Interface struct {
@@ -101,167 +92,7 @@ type Interface struct {
 	messageMetrics      *MessageMetrics
 	cachedPacketMetrics *cachedPacketMetrics
 
-	l              *logrus.Logger
+	l *logrus.Logger
-	ctx            context.Context
-	udpListenWG    sync.WaitGroup
-	inboundPool    sync.Pool
-	decryptWG      sync.WaitGroup
-	decryptQueues  []*inboundRing
-	decryptWorkers int
-	decryptStates  []decryptWorkerState
-	decryptCounter atomic.Uint32
-}
-
-type inboundPacket struct {
-	addr    netip.AddrPort
-	payload []byte
-	release func()
-	queue   int
-}
-
-type decryptWorkerState struct {
-	queue  *inboundRing
-	notify chan struct{}
-}
-
-type decryptContext struct {
-	ctTicker *firewall.ConntrackCacheTicker
-	plain    []byte
-	head     header.H
-	fwPacket firewall.Packet
-	light    *LightHouseHandler
-	nebula   []byte
-}
-
-type inboundCell struct {
-	seq atomic.Uint64
-	pkt *inboundPacket
-}
-
-type inboundRing struct {
-	mask       uint64
-	cells      []inboundCell
-	enqueuePos atomic.Uint64
-	dequeuePos atomic.Uint64
-}
-
-func newInboundRing(capacity int) *inboundRing {
-	if capacity < 2 {
-		capacity = 2
-	}
-	size := nextPowerOfTwo(uint32(capacity))
-	if size < 2 {
-		size = 2
-	}
-	ring := &inboundRing{
-		mask:  uint64(size - 1),
-		cells: make([]inboundCell, size),
-	}
-	for i := range ring.cells {
-		ring.cells[i].seq.Store(uint64(i))
-	}
-	return ring
-}
-
-func nextPowerOfTwo(v uint32) uint32 {
-	if v == 0 {
-		return 1
-	}
-	return 1 << (32 - bits.LeadingZeros32(v-1))
-}
-
-func (r *inboundRing) Enqueue(pkt *inboundPacket) bool {
-	var cell *inboundCell
-	pos := r.enqueuePos.Load()
-	for {
-		cell = &r.cells[pos&r.mask]
-		seq := cell.seq.Load()
-		diff := int64(seq) - int64(pos)
-		if diff == 0 {
-			if r.enqueuePos.CompareAndSwap(pos, pos+1) {
-				break
-			}
-		} else if diff < 0 {
-			return false
-		} else {
-			pos = r.enqueuePos.Load()
-		}
-	}
-	cell.pkt = pkt
-	cell.seq.Store(pos + 1)
-	return true
-}
-
-func (r *inboundRing) Dequeue() (*inboundPacket, bool) {
-	var cell *inboundCell
-	pos := r.dequeuePos.Load()
-	for {
-		cell = &r.cells[pos&r.mask]
-		seq := cell.seq.Load()
-		diff := int64(seq) - int64(pos+1)
-		if diff == 0 {
-			if r.dequeuePos.CompareAndSwap(pos, pos+1) {
-				break
-			}
-		} else if diff < 0 {
-			return nil, false
-		} else {
-			pos = r.dequeuePos.Load()
-		}
-	}
-	pkt := cell.pkt
-	cell.pkt = nil
-	cell.seq.Store(pos + r.mask + 1)
-	return pkt, true
-}
-
-func (f *Interface) getInboundPacket() *inboundPacket {
-	if pkt, ok := f.inboundPool.Get().(*inboundPacket); ok && pkt != nil {
-		return pkt
-	}
-	return &inboundPacket{}
-}
-
-func (f *Interface) putInboundPacket(pkt *inboundPacket) {
-	if pkt == nil {
-		return
-	}
-	pkt.addr = netip.AddrPort{}
-	pkt.payload = nil
-	pkt.release = nil
-	pkt.queue = 0
-	f.inboundPool.Put(pkt)
-}
-
-func newDecryptContext(f *Interface) *decryptContext {
-	return &decryptContext{
-		ctTicker: firewall.NewConntrackCacheTicker(f.conntrackCacheTimeout),
-		plain:    make([]byte, udp.MTU),
-		head:     header.H{},
-		fwPacket: firewall.Packet{},
-		light:    f.lightHouse.NewRequestHandler(),
-		nebula:   make([]byte, 12, 12),
-	}
-}
-
-func (f *Interface) processInboundPacket(pkt *inboundPacket, ctx *decryptContext) {
-	if pkt == nil {
-		return
-	}
-	defer func() {
-		if pkt.release != nil {
-			pkt.release()
-		}
-		f.putInboundPacket(pkt)
-	}()
-
-	ctx.head = header.H{}
-	ctx.fwPacket = firewall.Packet{}
-	var cache firewall.ConntrackCache
-	if ctx.ctTicker != nil {
-		cache = ctx.ctTicker.Get(f.l)
-	}
-	f.readOutsidePackets(pkt.addr, nil, ctx.plain[:0], pkt.payload, &ctx.head, &ctx.fwPacket, ctx.light, ctx.nebula, pkt.queue, cache)
 }
 
 type EncWriter interface {
@@ -331,35 +162,6 @@ func NewInterface(ctx context.Context, c *InterfaceConfig) (*Interface, error) {
 	}
 
 	cs := c.pki.getCertState()
-	decryptWorkers := c.DecryptWorkers
-	if decryptWorkers < 0 {
-		decryptWorkers = 0
-	}
-	if decryptWorkers == 0 {
-		decryptWorkers = c.routines * defaultDecryptWorkerFactor
-		if decryptWorkers < c.routines {
-			decryptWorkers = c.routines
-		}
-	}
-	if decryptWorkers < 0 {
-		decryptWorkers = 0
-	}
-	if runtime.GOOS != "linux" {
-		decryptWorkers = 0
-	}
-
-	queueDepth := c.DecryptQueueDepth
-	if queueDepth <= 0 {
-		queueDepth = defaultInboundQueueDepth
-	}
-	minDepth := c.routines * 64
-	if minDepth <= 0 {
-		minDepth = 64
-	}
-	if queueDepth < minDepth {
-		queueDepth = minDepth
-	}
-
 	ifce := &Interface{
 		pki:                   c.pki,
 		hostMap:               c.HostMap,
@@ -392,10 +194,7 @@ func NewInterface(ctx context.Context, c *InterfaceConfig) (*Interface, error) {
 			dropped: metrics.GetOrRegisterCounter("hostinfo.cached_packets.dropped", nil),
 		},
 
-		l:              c.l,
+		l: c.l,
-		ctx:            ctx,
-		inboundPool:    sync.Pool{New: func() any { return &inboundPacket{} }},
-		decryptWorkers: decryptWorkers,
 	}
 
 	ifce.tryPromoteEvery.Store(c.tryPromoteEvery)
@@ -404,19 +203,6 @@ func NewInterface(ctx context.Context, c *InterfaceConfig) (*Interface, error) {
 
 	ifce.connectionManager.intf = ifce
 
-	if decryptWorkers > 0 {
-		ifce.decryptQueues = make([]*inboundRing, decryptWorkers)
-		ifce.decryptStates = make([]decryptWorkerState, decryptWorkers)
-		for i := 0; i < decryptWorkers; i++ {
-			queue := newInboundRing(queueDepth)
-			ifce.decryptQueues[i] = queue
-			ifce.decryptStates[i] = decryptWorkerState{
-				queue:  queue,
-				notify: make(chan struct{}, 1),
-			}
-		}
-	}
-
 	return ifce, nil
 }
 
@@ -456,68 +242,8 @@ func (f *Interface) activate() {
 	}
 }
 
-func (f *Interface) startDecryptWorkers() {
-	if f.decryptWorkers <= 0 || len(f.decryptQueues) == 0 {
-		return
-	}
-	f.decryptWG.Add(f.decryptWorkers)
-	for i := 0; i < f.decryptWorkers; i++ {
-		go f.decryptWorker(i)
-	}
-}
-
-func (f *Interface) decryptWorker(id int) {
-	defer f.decryptWG.Done()
-	if id < 0 || id >= len(f.decryptStates) {
-		return
-	}
-	state := f.decryptStates[id]
-	if state.queue == nil {
-		return
-	}
-	ctx := newDecryptContext(f)
-	for {
-		for {
-			pkt, ok := state.queue.Dequeue()
-			if !ok {
-				break
-			}
-			f.processInboundPacket(pkt, ctx)
-		}
-		if f.closed.Load() || f.ctx.Err() != nil {
-			for {
-				pkt, ok := state.queue.Dequeue()
-				if !ok {
-					return
-				}
-				f.processInboundPacket(pkt, ctx)
-			}
-		}
-		select {
-		case <-f.ctx.Done():
-		case <-state.notify:
-		}
-	}
-}
-
-func (f *Interface) notifyDecryptWorker(idx int) {
-	if idx < 0 || idx >= len(f.decryptStates) {
-		return
-	}
-	state := f.decryptStates[idx]
-	if state.notify == nil {
-		return
-	}
-	select {
-	case state.notify <- struct{}{}:
-	default:
-	}
-}
-
 func (f *Interface) run() {
-	f.startDecryptWorkers()
 	// Launch n queues to read packets from udp
-	f.udpListenWG.Add(f.routines)
 	for i := 0; i < f.routines; i++ {
 		go f.listenOut(i)
 	}
@@ -530,7 +256,6 @@ func (f *Interface) run() {
 
 func (f *Interface) listenOut(i int) {
 	runtime.LockOSThread()
-	defer f.udpListenWG.Done()
 
 	var li udp.Conn
 	if i > 0 {
@@ -539,78 +264,26 @@ func (f *Interface) listenOut(i int) {
 		li = f.outside
 	}
 
-	useWorkers := f.decryptWorkers > 0 && len(f.decryptQueues) > 0
+	ctCache := firewall.NewConntrackCacheTicker(f.conntrackCacheTimeout)
-	var (
+	lhh := f.lightHouse.NewRequestHandler()
-		inlineTicker  *firewall.ConntrackCacheTicker
+	plaintext := make([]byte, udp.MTU)
-		inlineHandler *LightHouseHandler
+	h := &header.H{}
-		inlinePlain   []byte
+	fwPacket := &firewall.Packet{}
-		inlineHeader  header.H
+	nb := make([]byte, 12, 12)
-		inlinePacket  firewall.Packet
-		inlineNB      []byte
-		inlineCtx     *decryptContext
-	)
-
-	if useWorkers {
-		inlineCtx = newDecryptContext(f)
-	} else {
-		inlineTicker = firewall.NewConntrackCacheTicker(f.conntrackCacheTimeout)
-		inlineHandler = f.lightHouse.NewRequestHandler()
-		inlinePlain = make([]byte, udp.MTU)
-		inlineNB = make([]byte, 12, 12)
-	}
 
 	li.ListenOut(func(fromUdpAddr netip.AddrPort, payload []byte, release func()) {
-		if !useWorkers {
+		if release != nil {
-			if release != nil {
+			defer release()
-				defer release()
-			}
-			select {
-			case <-f.ctx.Done():
-				return
-			default:
-			}
-			inlineHeader = header.H{}
-			inlinePacket = firewall.Packet{}
-			var cache firewall.ConntrackCache
-			if inlineTicker != nil {
-				cache = inlineTicker.Get(f.l)
-			}
-			f.readOutsidePackets(fromUdpAddr, nil, inlinePlain[:0], payload, &inlineHeader, &inlinePacket, inlineHandler, inlineNB, i, cache)
-			return
 		}
-
+		f.readOutsidePackets(fromUdpAddr, nil, plaintext[:0], payload, h, fwPacket, lhh, nb, i, ctCache.Get(f.l))
-		if f.ctx.Err() != nil {
-			if release != nil {
-				release()
-			}
-			return
-		}
-
-		pkt := f.getInboundPacket()
-		pkt.addr = fromUdpAddr
-		pkt.payload = payload
-		pkt.release = release
-		pkt.queue = i
-
-		queueCount := len(f.decryptQueues)
-		if queueCount == 0 {
-			f.processInboundPacket(pkt, inlineCtx)
-			return
-		}
-		w := int(f.decryptCounter.Add(1)-1) % queueCount
-		if w < 0 || w >= queueCount || !f.decryptQueues[w].Enqueue(pkt) {
-			f.processInboundPacket(pkt, inlineCtx)
-			return
-		}
-		f.notifyDecryptWorker(w)
 	})
 }
 
 func (f *Interface) listenIn(reader io.ReadWriteCloser, i int) {
 	runtime.LockOSThread()
 
-	packet := make([]byte, tunReadBufferSize)
+	packet := make([]byte, mtu)
-	out := make([]byte, tunReadBufferSize)
+	out := make([]byte, mtu)
 	fwPacket := &firewall.Packet{}
 	nb := make([]byte, 12, 12)
 
@@ -788,19 +461,6 @@ func (f *Interface) Close() error {
 		}
 	}
 
-	f.udpListenWG.Wait()
-	if f.decryptWorkers > 0 {
-		for _, state := range f.decryptStates {
-			if state.notify != nil {
-				select {
-				case state.notify <- struct{}{}:
-				default:
-				}
-			}
-		}
-		f.decryptWG.Wait()
-	}
-
 	// Release the tun device
 	return f.inside.Close()
 }

main.go

@@ -120,8 +120,6 @@ func Main(c *config.C, configTest bool, buildVersion string, logger *logrus.Logg
 		l.WithField("duration", conntrackCacheTimeout).Info("Using routine-local conntrack cache")
 	}
 
-	udp.SetDisableUDPCsum(c.GetBool("listen.disable_udp_checksum", false))
-
 	var tun overlay.Device
 	if !configTest {
 		c.CatchHUP(ctx)
@@ -223,9 +221,6 @@ func Main(c *config.C, configTest bool, buildVersion string, logger *logrus.Logg
 		}
 	}
 
-	decryptWorkers := c.GetInt("listen.decrypt_workers", 0)
-	decryptQueueDepth := c.GetInt("listen.decrypt_queue_depth", 0)
-
 	ifConfig := &InterfaceConfig{
 		HostMap:               hostMap,
 		Inside:                tun,
@@ -248,8 +243,6 @@ func Main(c *config.C, configTest bool, buildVersion string, logger *logrus.Logg
 		punchy:                punchy,
 		ConntrackCacheTimeout: conntrackCacheTimeout,
 		l:                     l,
-		DecryptWorkers:        decryptWorkers,
-		DecryptQueueDepth:     decryptQueueDepth,
 	}
 
 	var ifce *Interface

outside.go

@@ -470,13 +470,7 @@ func (f *Interface) decryptToTun(hostinfo *HostInfo, messageCounter uint64, out
 
 	out, err = hostinfo.ConnectionState.dKey.DecryptDanger(out, packet[:header.Len], packet[header.Len:], messageCounter, nb)
 	if err != nil {
-		hostinfo.logger(f.l).
+		hostinfo.logger(f.l).WithError(err).Error("Failed to decrypt packet")
-			WithError(err).
-			WithField("tag", "decrypt-debug").
-			WithField("remoteIndexLocal", hostinfo.localIndexId).
-			WithField("messageCounter", messageCounter).
-			WithField("packet_len", len(packet)).
-			Error("Failed to decrypt packet")
 		return false
 	}
 

overlay/tun_linux.go

@@ -25,17 +25,14 @@ import (
 
 type tun struct {
 	io.ReadWriteCloser
-	fd            int
+	fd          int
-	Device        string
+	Device      string
-	vpnNetworks   []netip.Prefix
+	vpnNetworks []netip.Prefix
-	MaxMTU        int
+	MaxMTU      int
-	DefaultMTU    int
+	DefaultMTU  int
-	TXQueueLen    int
+	TXQueueLen  int
-	deviceIndex   int
+	deviceIndex int
-	ioctlFd       uintptr
+	ioctlFd     uintptr
-	enableVnetHdr bool
-	vnetHdrLen    int
-	queues        []*tunQueue
 
 	Routes                    atomic.Pointer[[]Route]
 	routeTree                 atomic.Pointer[bart.Table[routing.Gateways]]
@@ -68,90 +65,10 @@ type ifreqQLEN struct {
 	pad   [8]byte
 }
 
-const (
-	virtioNetHdrLen     = 12
-	tunDefaultMaxPacket = 65536
-)
-
-type tunQueue struct {
-	file          *os.File
-	fd            int
-	enableVnetHdr bool
-	vnetHdrLen    int
-	maxPacket     int
-	writeScratch  []byte
-	readScratch   []byte
-	l             *logrus.Logger
-}
-
-func newTunQueue(file *os.File, enableVnetHdr bool, vnetHdrLen, maxPacket int, l *logrus.Logger) *tunQueue {
-	if maxPacket <= 0 {
-		maxPacket = tunDefaultMaxPacket
-	}
-	q := &tunQueue{
-		file:          file,
-		fd:            int(file.Fd()),
-		enableVnetHdr: enableVnetHdr,
-		vnetHdrLen:    vnetHdrLen,
-		maxPacket:     maxPacket,
-		l:             l,
-	}
-	if enableVnetHdr {
-		q.growReadScratch(maxPacket)
-	}
-	return q
-}
-
-func (q *tunQueue) growReadScratch(packetSize int) {
-	needed := q.vnetHdrLen + packetSize
-	if needed < q.vnetHdrLen+DefaultMTU {
-		needed = q.vnetHdrLen + DefaultMTU
-	}
-	if q.readScratch == nil || cap(q.readScratch) < needed {
-		q.readScratch = make([]byte, needed)
-	} else {
-		q.readScratch = q.readScratch[:needed]
-	}
-}
-
-func (q *tunQueue) setMaxPacket(packet int) {
-	if packet <= 0 {
-		packet = DefaultMTU
-	}
-	q.maxPacket = packet
-	if q.enableVnetHdr {
-		q.growReadScratch(packet)
-	}
-}
-
-func configureVnetHdr(fd int, hdrLen int, l *logrus.Logger) error {
-	features, err := unix.IoctlGetInt(fd, unix.TUNGETFEATURES)
-	if err == nil && features&unix.IFF_VNET_HDR == 0 {
-		return fmt.Errorf("kernel does not support IFF_VNET_HDR")
-	}
-	if err := unix.IoctlSetInt(fd, unix.TUNSETVNETHDRSZ, hdrLen); err != nil {
-		return err
-	}
-	offload := unix.TUN_F_CSUM | unix.TUN_F_UFO
-	if err := unix.IoctlSetInt(fd, unix.TUNSETOFFLOAD, offload); err != nil {
-		if l != nil {
-			l.WithError(err).Warn("Failed to enable TUN offload features")
-		}
-	}
-	return nil
-}
-
 func newTunFromFd(c *config.C, l *logrus.Logger, deviceFd int, vpnNetworks []netip.Prefix) (*tun, error) {
 	file := os.NewFile(uintptr(deviceFd), "/dev/net/tun")
-	enableVnetHdr := c.GetBool("tun.enable_vnet_hdr", false)
-	if enableVnetHdr {
-		if err := configureVnetHdr(deviceFd, virtioNetHdrLen, l); err != nil {
-			l.WithError(err).Warn("Failed to configure VNET header support on provided tun fd; disabling")
-			enableVnetHdr = false
-		}
-	}
 
-	t, err := newTunGeneric(c, l, file, vpnNetworks, enableVnetHdr)
+	t, err := newTunGeneric(c, l, file, vpnNetworks)
 	if err != nil {
 		return nil, err
 	}
@@ -189,25 +106,14 @@ func newTun(c *config.C, l *logrus.Logger, vpnNetworks []netip.Prefix, multiqueu
 	if multiqueue {
 		req.Flags |= unix.IFF_MULTI_QUEUE
 	}
-	enableVnetHdr := c.GetBool("tun.enable_vnet_hdr", false)
-	if enableVnetHdr {
-		req.Flags |= unix.IFF_VNET_HDR
-	}
 	copy(req.Name[:], c.GetString("tun.dev", ""))
 	if err = ioctl(uintptr(fd), uintptr(unix.TUNSETIFF), uintptr(unsafe.Pointer(&req))); err != nil {
 		return nil, err
 	}
 	name := strings.Trim(string(req.Name[:]), "\x00")
 
-	if enableVnetHdr {
-		if err := configureVnetHdr(fd, virtioNetHdrLen, l); err != nil {
-			l.WithError(err).Warn("Failed to configure VNET header support on tun device; disabling")
-			enableVnetHdr = false
-		}
-	}
-
 	file := os.NewFile(uintptr(fd), "/dev/net/tun")
-	t, err := newTunGeneric(c, l, file, vpnNetworks, enableVnetHdr)
+	t, err := newTunGeneric(c, l, file, vpnNetworks)
 	if err != nil {
 		return nil, err
 	}
@@ -217,30 +123,21 @@ func newTun(c *config.C, l *logrus.Logger, vpnNetworks []netip.Prefix, multiqueu
 	return t, nil
 }
 
-func newTunGeneric(c *config.C, l *logrus.Logger, file *os.File, vpnNetworks []netip.Prefix, enableVnetHdr bool) (*tun, error) {
+func newTunGeneric(c *config.C, l *logrus.Logger, file *os.File, vpnNetworks []netip.Prefix) (*tun, error) {
-	queue := newTunQueue(file, enableVnetHdr, virtioNetHdrLen, tunDefaultMaxPacket, l)
 	t := &tun{
-		ReadWriteCloser:           queue,
+		ReadWriteCloser:           file,
 		fd:                        int(file.Fd()),
 		vpnNetworks:               vpnNetworks,
 		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),
 		l:                         l,
-		enableVnetHdr:             enableVnetHdr,
-		vnetHdrLen:                virtioNetHdrLen,
-		queues:                    []*tunQueue{queue},
 	}
 
 	err := t.reload(c, true)
 	if err != nil {
 		return nil, err
 	}
-	if enableVnetHdr {
-		for _, q := range t.queues {
-			q.setMaxPacket(t.MaxMTU)
-		}
-	}
 
 	c.RegisterReloadCallback(func(c *config.C) {
 		err := t.reload(c, false)
@@ -283,11 +180,6 @@ func (t *tun) reload(c *config.C, initial bool) error {
 
 	t.MaxMTU = newMaxMTU
 	t.DefaultMTU = newDefaultMTU
-	if t.enableVnetHdr {
-		for _, q := range t.queues {
-			q.setMaxPacket(t.MaxMTU)
-		}
-	}
 
 	// Teach nebula how to handle the routes before establishing them in the system table
 	oldRoutes := t.Routes.Swap(&routes)
@@ -332,87 +224,14 @@ func (t *tun) NewMultiQueueReader() (io.ReadWriteCloser, error) {
 
 	var req ifReq
 	req.Flags = uint16(unix.IFF_TUN | unix.IFF_NO_PI | unix.IFF_MULTI_QUEUE)
-	if t.enableVnetHdr {
-		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
 	}
 
 	file := os.NewFile(uintptr(fd), "/dev/net/tun")
-	queue := newTunQueue(file, t.enableVnetHdr, t.vnetHdrLen, t.MaxMTU, t.l)
-	if t.enableVnetHdr {
-		if err := configureVnetHdr(fd, t.vnetHdrLen, t.l); err != nil {
-			queue.enableVnetHdr = false
-		}
-	}
-	t.queues = append(t.queues, queue)
 
-	return queue, nil
+	return file, nil
-}
-
-func (q *tunQueue) Read(p []byte) (int, error) {
-	if !q.enableVnetHdr {
-		return q.file.Read(p)
-	}
-
-	if len(p)+q.vnetHdrLen > cap(q.readScratch) {
-		q.growReadScratch(len(p))
-	}
-
-	buf := q.readScratch[:cap(q.readScratch)]
-	n, err := q.file.Read(buf)
-	if n <= 0 {
-		return n, err
-	}
-	if n < q.vnetHdrLen {
-		if err == nil {
-			err = io.ErrUnexpectedEOF
-		}
-		return 0, err
-	}
-
-	payload := buf[q.vnetHdrLen:n]
-	if len(payload) > len(p) {
-		copy(p, payload[:len(p)])
-		if err == nil {
-			err = io.ErrShortBuffer
-		}
-		return len(p), err
-	}
-	copy(p, payload)
-	return len(payload), err
-}
-
-func (q *tunQueue) Write(b []byte) (int, error) {
-	if !q.enableVnetHdr {
-		return unix.Write(q.fd, b)
-	}
-
-	total := q.vnetHdrLen + len(b)
-	if cap(q.writeScratch) < total {
-		q.writeScratch = make([]byte, total)
-	} else {
-		q.writeScratch = q.writeScratch[:total]
-	}
-
-	for i := 0; i < q.vnetHdrLen; i++ {
-		q.writeScratch[i] = 0
-	}
-	copy(q.writeScratch[q.vnetHdrLen:], b)
-
-	n, err := unix.Write(q.fd, q.writeScratch)
-	if n >= q.vnetHdrLen {
-		n -= q.vnetHdrLen
-	} else {
-		n = 0
-	}
-	return n, err
-}
-
-func (q *tunQueue) Close() error {
-	return q.file.Close()
 }
 
 func (t *tun) RoutesFor(ip netip.Addr) routing.Gateways {

udp/udp_linux_32.go

@@ -7,6 +7,9 @@
 package udp
 
 import (
+	"errors"
+	"fmt"
+
 	"golang.org/x/sys/unix"
 )
 
@@ -79,3 +82,52 @@ func setIovecBase(msg *rawMessage, buf []byte) {
 	iov.Base = &buf[0]
 	iov.Len = uint32(len(buf))
 }
+
+func rawMessageToUnixMsghdr(msg *rawMessage) (unix.Msghdr, unix.Iovec, error) {
+	var hdr unix.Msghdr
+	var iov unix.Iovec
+	if msg == nil {
+		return hdr, iov, errors.New("nil rawMessage")
+	}
+	if msg.Hdr.Iov == nil || msg.Hdr.Iov.Base == nil {
+		return hdr, iov, errors.New("rawMessage missing payload buffer")
+	}
+	payloadLen := int(msg.Hdr.Iov.Len)
+	if payloadLen < 0 {
+		return hdr, iov, fmt.Errorf("invalid payload length: %d", payloadLen)
+	}
+	iov.Base = msg.Hdr.Iov.Base
+	iov.Len = uint32(payloadLen)
+	hdr.Iov = &iov
+	hdr.Iovlen = 1
+	hdr.Name = msg.Hdr.Name
+	// CRITICAL: Always set to full buffer size for receive, not what kernel wrote last time
+	if hdr.Name != nil {
+		hdr.Namelen = uint32(unix.SizeofSockaddrInet6)
+	} else {
+		hdr.Namelen = 0
+	}
+	hdr.Control = msg.Hdr.Control
+	// CRITICAL: Use the allocated size, not what was previously returned
+	if hdr.Control != nil {
+		// Control buffer size is stored in Controllen from PrepareRawMessages
+		hdr.Controllen = msg.Hdr.Controllen
+	} else {
+		hdr.Controllen = 0
+	}
+	hdr.Flags = 0 // Reset flags for new receive
+	return hdr, iov, nil
+}
+
+func updateRawMessageFromUnixMsghdr(msg *rawMessage, hdr *unix.Msghdr, n int) {
+	if msg == nil || hdr == nil {
+		return
+	}
+	msg.Hdr.Namelen = hdr.Namelen
+	msg.Hdr.Controllen = hdr.Controllen
+	msg.Hdr.Flags = hdr.Flags
+	if n < 0 {
+		n = 0
+	}
+	msg.Len = uint32(n)
+}

udp/udp_linux_64.go

@@ -7,6 +7,9 @@
 package udp
 
 import (
+	"errors"
+	"fmt"
+
 	"golang.org/x/sys/unix"
 )
 
@@ -80,3 +83,52 @@ func setIovecBase(msg *rawMessage, buf []byte) {
 	iov.Base = &buf[0]
 	iov.Len = uint64(len(buf))
 }
+
+func rawMessageToUnixMsghdr(msg *rawMessage) (unix.Msghdr, unix.Iovec, error) {
+	var hdr unix.Msghdr
+	var iov unix.Iovec
+	if msg == nil {
+		return hdr, iov, errors.New("nil rawMessage")
+	}
+	if msg.Hdr.Iov == nil || msg.Hdr.Iov.Base == nil {
+		return hdr, iov, errors.New("rawMessage missing payload buffer")
+	}
+	payloadLen := int(msg.Hdr.Iov.Len)
+	if payloadLen < 0 {
+		return hdr, iov, fmt.Errorf("invalid payload length: %d", payloadLen)
+	}
+	iov.Base = msg.Hdr.Iov.Base
+	iov.Len = uint64(payloadLen)
+	hdr.Iov = &iov
+	hdr.Iovlen = 1
+	hdr.Name = msg.Hdr.Name
+	// CRITICAL: Always set to full buffer size for receive, not what kernel wrote last time
+	if hdr.Name != nil {
+		hdr.Namelen = uint32(unix.SizeofSockaddrInet6)
+	} else {
+		hdr.Namelen = 0
+	}
+	hdr.Control = msg.Hdr.Control
+	// CRITICAL: Use the allocated size, not what was previously returned
+	if hdr.Control != nil {
+		// Control buffer size is stored in Controllen from PrepareRawMessages
+		hdr.Controllen = msg.Hdr.Controllen
+	} else {
+		hdr.Controllen = 0
+	}
+	hdr.Flags = 0 // Reset flags for new receive
+	return hdr, iov, nil
+}
+
+func updateRawMessageFromUnixMsghdr(msg *rawMessage, hdr *unix.Msghdr, n int) {
+	if msg == nil || hdr == nil {
+		return
+	}
+	msg.Hdr.Namelen = hdr.Namelen
+	msg.Hdr.Controllen = hdr.Controllen
+	msg.Hdr.Flags = hdr.Flags
+	if n < 0 {
+		n = 0
+	}
+	msg.Len = uint32(n)
+}