hrm

overlay/tun_linux.go

@@ -66,6 +66,78 @@ type ifreqQLEN struct {
 	pad   [8]byte
 }
 
+const (
+	virtioNetHdrLen = 10 // Size of virtio_net_hdr structure
+)
+
+// tunVirtioReader wraps a file descriptor that has IFF_VNET_HDR enabled
+// and strips the virtio header on reads, adds it on writes
+type tunVirtioReader struct {
+	f   *os.File
+	buf [virtioNetHdrLen + 65535]byte // Space for header + max packet
+}
+
+func (r *tunVirtioReader) Read(b []byte) (int, error) {
+	// Read into our buffer which has space for the virtio header
+	n, err := r.f.Read(r.buf[:])
+	if err != nil {
+		return 0, err
+	}
+
+	// Strip the virtio header (first 10 bytes)
+	if n < virtioNetHdrLen {
+		return 0, fmt.Errorf("packet too short: %d bytes", n)
+	}
+
+	// Copy payload (after header) to destination
+	copy(b, r.buf[virtioNetHdrLen:n])
+	return n - virtioNetHdrLen, nil
+}
+
+func (r *tunVirtioReader) Write(b []byte) (int, error) {
+	// Zero out the virtio header (no offload from userspace write)
+	for i := 0; i < virtioNetHdrLen; i++ {
+		r.buf[i] = 0
+	}
+
+	// Copy packet data after header
+	copy(r.buf[virtioNetHdrLen:], b)
+
+	// Write with header prepended
+	n, err := r.f.Write(r.buf[:virtioNetHdrLen+len(b)])
+	if err != nil {
+		return 0, err
+	}
+
+	// Return payload size (excluding header)
+	return n - virtioNetHdrLen, nil
+}
+
+func (r *tunVirtioReader) Close() error {
+	return r.f.Close()
+}
+
+// BatchRead reads multiple packets at once for performance
+// This is not used for multiqueue readers as they use direct file I/O
+// Returns number of packets read
+func (r *tunVirtioReader) BatchRead(bufs [][]byte, sizes []int) (int, error) {
+	// For multiqueue file descriptors, we don't have the wireguard Device interface
+	// Fall back to single packet reads
+	// TODO: Could implement proper batching with unix.Recvmmsg
+	n, err := r.Read(bufs[0])
+	if err != nil {
+		return 0, err
+	}
+	sizes[0] = n
+	return 1, nil
+}
+
+// BatchSize returns the batch size for multiqueue readers
+func (r *tunVirtioReader) BatchSize() int {
+	// Multiqueue readers use single packet mode for now
+	return 1
+}
+
 func newTunFromFd(c *config.C, l *logrus.Logger, deviceFd int, vpnNetworks []netip.Prefix) (*tun, error) {
 	wgDev, name, err := wgtun.CreateUnmonitoredTUNFromFD(deviceFd)
 	if err != nil {
@@ -106,7 +178,7 @@ func newTun(c *config.C, l *logrus.Logger, vpnNetworks []netip.Prefix, multiqueu
 	}
 
 	var req ifReq
-	req.Flags = uint16(unix.IFF_TUN | unix.IFF_NO_PI)
+	req.Flags = uint16(unix.IFF_TUN | unix.IFF_NO_PI | unix.IFF_VNET_HDR)
 	if multiqueue {
 		req.Flags |= unix.IFF_MULTI_QUEUE
 	}
@@ -122,6 +194,18 @@ func newTun(c *config.C, l *logrus.Logger, vpnNetworks []netip.Prefix, multiqueu
 		return nil, err
 	}
 
+	// Enable TCP and UDP offload (TSO/GRO) for performance
+	// This allows the kernel to handle segmentation/coalescing
+	const (
+		tunTCPOffloads = unix.TUN_F_CSUM | unix.TUN_F_TSO4 | unix.TUN_F_TSO6
+		tunUDPOffloads = unix.TUN_F_USO4 | unix.TUN_F_USO6
+	)
+	offloads := tunTCPOffloads | tunUDPOffloads
+	if err = unix.IoctlSetInt(fd, unix.TUNSETOFFLOAD, offloads); err != nil {
+		// Log warning but don't fail - offload is optional
+		l.WithError(err).Warn("Failed to enable TUN offload (TSO/GRO), performance may be reduced")
+	}
+
 	file := os.NewFile(uintptr(fd), "/dev/net/tun")
 
 	// Create wireguard device from file descriptor
@@ -251,16 +335,18 @@ func (t *tun) NewMultiQueueReader() (io.ReadWriteCloser, error) {
 	}
 
 	var req ifReq
-	// MUST match the flags used in newTun
-	req.Flags = uint16(unix.IFF_TUN | unix.IFF_NO_PI | unix.IFF_MULTI_QUEUE)
+	// MUST match the flags used in newTun - includes IFF_VNET_HDR
+	req.Flags = uint16(unix.IFF_TUN | unix.IFF_NO_PI | unix.IFF_VNET_HDR | unix.IFF_MULTI_QUEUE)
 	copy(req.Name[:], t.Device)
 	if err = ioctl(uintptr(fd), uintptr(unix.TUNSETIFF), uintptr(unsafe.Pointer(&req))); err != nil {
+		unix.Close(fd)
 		return nil, err
 	}
 
 	file := os.NewFile(uintptr(fd), "/dev/net/tun")
 
-	return file, nil
+	// Wrap in virtio header handler
+	return &tunVirtioReader{f: file}, nil
 }
 
 func (t *tun) RoutesFor(ip netip.Addr) routing.Gateways {
@@ -268,7 +354,70 @@ func (t *tun) RoutesFor(ip netip.Addr) routing.Gateways {
 	return r
 }
 
+func (t *tun) Read(b []byte) (int, error) {
+	if t.wgDevice != nil {
+		// Use wireguard device which handles virtio headers internally
+		bufs := [][]byte{b}
+		sizes := make([]int, 1)
+		n, err := t.wgDevice.Read(bufs, sizes, 0)
+		if err != nil {
+			return 0, err
+		}
+		if n == 0 {
+			return 0, io.EOF
+		}
+		return sizes[0], nil
+	}
+
+	// Fallback: direct read from file (shouldn't happen in normal operation)
+	return t.ReadWriteCloser.Read(b)
+}
+
+// BatchRead reads multiple packets at once for improved performance
+// bufs: slice of buffers to read into
+// sizes: slice that will be filled with packet sizes
+// Returns number of packets read
+func (t *tun) BatchRead(bufs [][]byte, sizes []int) (int, error) {
+	if t.wgDevice != nil {
+		return t.wgDevice.Read(bufs, sizes, 0)
+	}
+
+	// Fallback: single packet read
+	n, err := t.ReadWriteCloser.Read(bufs[0])
+	if err != nil {
+		return 0, err
+	}
+	sizes[0] = n
+	return 1, nil
+}
+
+// BatchSize returns the optimal number of packets to read/write in a batch
+func (t *tun) BatchSize() int {
+	if t.wgDevice != nil {
+		return t.wgDevice.BatchSize()
+	}
+	return 1
+}
+
 func (t *tun) Write(b []byte) (int, error) {
+	if t.wgDevice != nil {
+		// Use wireguard device which handles virtio headers internally
+		// Allocate buffer with space for virtio header
+		buf := make([]byte, virtioNetHdrLen+len(b))
+		copy(buf[virtioNetHdrLen:], b)
+
+		bufs := [][]byte{buf}
+		n, err := t.wgDevice.Write(bufs, virtioNetHdrLen)
+		if err != nil {
+			return 0, err
+		}
+		if n == 0 {
+			return 0, io.ErrShortWrite
+		}
+		return len(b), nil
+	}
+
+	// Fallback: direct write (shouldn't happen in normal operation)
 	var nn int
 	maximum := len(b)