Adding upstream version 7.0.14-dfsg.upstream/7.0.14-dfsg

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

4 files changed, 2803 insertions, 0 deletions

diff --git a/src/VBox/HostDrivers/VBoxNetFlt/linux/Makefile b/src/VBox/HostDrivers/VBoxNetFlt/linux/Makefile
new file mode 100644
index 00000000..9c5d5b80
--- /dev/null
+++ b/src/VBox/HostDrivers/VBoxNetFlt/linux/Makefile
@@ -0,0 +1,81 @@
+# $Id: Makefile $
+## @file
+# Makefile for the VirtualBox Linux Host Network Filter Driver.
+#
+
+#
+# Copyright (C) 2006-2023 Oracle and/or its affiliates.
+#
+# This file is part of VirtualBox base platform packages, as
+# available from https://www.virtualbox.org.
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License
+# as published by the Free Software Foundation, in version 3 of the
+# License.
+#
+# This program is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, see <https://www.gnu.org/licenses>.
+#
+# The contents of this file may alternatively be used under the terms
+# of the Common Development and Distribution License Version 1.0
+# (CDDL), a copy of it is provided in the "COPYING.CDDL" file included
+# in the VirtualBox distribution, in which case the provisions of the
+# CDDL are applicable instead of those of the GPL.
+#
+# You may elect to license modified versions of this file under the
+# terms and conditions of either the GPL or the CDDL or both.
+#
+# SPDX-License-Identifier: GPL-3.0-only OR CDDL-1.0
+#
+
+# Linux kbuild sets this to our source directory if we are called from there
+obj ?= $(CURDIR)
+include $(obj)/Makefile-header.gmk
+VBOXNETFLT_DIR := $(VBOX_MODULE_SRC_DIR)
+
+# Allow building directly from the subdirectory without assuming the toplevel
+# makefile has done the copying. Not the default use case, but can be handy.
+ifndef KBUILD_EXTRA_SYMBOLS
+KBUILD_EXTRA_SYMBOLS=$(abspath $(VBOXNETFLT_DIR)/../vboxdrv/Module.symvers)
+endif
+
+VBOXMOD_NAME = vboxnetflt
+VBOXMOD_OBJS = \
+	linux/VBoxNetFlt-linux.o \
+	VBoxNetFlt.o \
+	SUPR0IdcClient.o \
+	SUPR0IdcClientComponent.o \
+	linux/SUPR0IdcClient-linux.o
+ifeq ($(VBOX_KBUILD_TARGET_ARCH),x86)
+VBOXMOD_OBJS += \
+	math/gcc/divdi3.o \
+	math/gcc/moddi3.o \
+	math/gcc/qdivrem.o \
+	math/gcc/udivdi3.o \
+	math/gcc/udivmoddi4.o \
+	math/gcc/divdi3.o \
+	math/gcc/umoddi3.o
+endif
+VBOXMOD_INCL = \
+	$(VBOXNETFLT_DIR) \
+	$(VBOXNETFLT_DIR)include \
+	$(VBOXNETFLT_DIR)r0drv/linux
+VBOXMOD_DEFS = \
+	RT_OS_LINUX \
+	IN_RING0 \
+	IN_RT_R0 \
+	IN_SUP_R0 \
+	VBOX \
+	RT_WITH_VBOX \
+	VBOX_WITH_HARDENING \
+	VBOX_WITH_64_BITS_GUESTS # <-- must be consistent with Config.kmk!
+VBOXMOD_CFLAGS = -include $(VBOXNETFLT_DIR)include/VBox/SUPDrvMangling.h -fno-pie -Wno-declaration-after-statement
+
+include $(obj)/Makefile-footer.gmk
+
diff --git a/src/VBox/HostDrivers/VBoxNetFlt/linux/Makefile.kup b/src/VBox/HostDrivers/VBoxNetFlt/linux/Makefile.kup
new file mode 100644
index 00000000..e69de29b
--- /dev/null
+++ b/src/VBox/HostDrivers/VBoxNetFlt/linux/Makefile.kup
diff --git a/src/VBox/HostDrivers/VBoxNetFlt/linux/VBoxNetFlt-linux.c b/src/VBox/HostDrivers/VBoxNetFlt/linux/VBoxNetFlt-linux.c
new file mode 100644
index 00000000..eaf07e8c
--- /dev/null
+++ b/src/VBox/HostDrivers/VBoxNetFlt/linux/VBoxNetFlt-linux.c
@@ -0,0 +1,2609 @@
+/* $Id: VBoxNetFlt-linux.c $ */
+/** @file
+ * VBoxNetFlt - Network Filter Driver (Host), Linux Specific Code.
+ */
+
+/*
+ * Copyright (C) 2006-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * The contents of this file may alternatively be used under the terms
+ * of the Common Development and Distribution License Version 1.0
+ * (CDDL), a copy of it is provided in the "COPYING.CDDL" file included
+ * in the VirtualBox distribution, in which case the provisions of the
+ * CDDL are applicable instead of those of the GPL.
+ *
+ * You may elect to license modified versions of this file under the
+ * terms and conditions of either the GPL or the CDDL or both.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only OR CDDL-1.0
+ */
+
+
+/*********************************************************************************************************************************
+*   Header Files                                                                                                                 *
+*********************************************************************************************************************************/
+#define LOG_GROUP LOG_GROUP_NET_FLT_DRV
+#define VBOXNETFLT_LINUX_NO_XMIT_QUEUE
+#include "the-linux-kernel.h"
+#include "version-generated.h"
+#include "revision-generated.h"
+#include "product-generated.h"
+#if RTLNX_VER_MIN(2,6,24)
+# include <linux/nsproxy.h>
+#endif
+#if RTLNX_VER_MIN(6,4,10) || RTLNX_RHEL_RANGE(9,4, 9,99)
+# include <net/gso.h>
+#endif
+#include <linux/netdevice.h>
+#if RTLNX_VER_MAX(2,6,29) || RTLNX_VER_MIN(5,11,0)
+# include <linux/ethtool.h>
+#endif
+#include <linux/etherdevice.h>
+#include <linux/rtnetlink.h>
+#include <linux/miscdevice.h>
+#include <linux/inetdevice.h>
+#include <linux/in.h>
+#include <linux/ip.h>
+#include <linux/if_vlan.h>
+#if RTLNX_VER_MIN(4,5,0)
+# include <uapi/linux/pkt_cls.h>
+#endif
+#include <net/ipv6.h>
+#include <net/if_inet6.h>
+#include <net/addrconf.h>
+
+#include <VBox/log.h>
+#include <VBox/err.h>
+#include <VBox/intnetinline.h>
+#include <VBox/vmm/pdmnetinline.h>
+#include <VBox/param.h>
+#include <iprt/alloca.h>
+#include <iprt/assert.h>
+#include <iprt/spinlock.h>
+#include <iprt/semaphore.h>
+#include <iprt/initterm.h>
+#include <iprt/process.h>
+#include <iprt/mem.h>
+#include <iprt/net.h>
+#include <iprt/log.h>
+#include <iprt/mp.h>
+#include <iprt/mem.h>
+#include <iprt/time.h>
+
+#define VBOXNETFLT_OS_SPECFIC 1
+#include "../VBoxNetFltInternal.h"
+
+typedef struct VBOXNETFLTNOTIFIER {
+    struct notifier_block Notifier;
+    PVBOXNETFLTINS pThis;
+} VBOXNETFLTNOTIFIER;
+typedef struct VBOXNETFLTNOTIFIER *PVBOXNETFLTNOTIFIER;
+
+
+/*********************************************************************************************************************************
+*   Defined Constants And Macros                                                                                                 *
+*********************************************************************************************************************************/
+#define VBOX_FLT_NB_TO_INST(pNB)    RT_FROM_MEMBER(pNB, VBOXNETFLTINS, u.s.Notifier)
+#define VBOX_FLT_PT_TO_INST(pPT)    RT_FROM_MEMBER(pPT, VBOXNETFLTINS, u.s.PacketType)
+#ifndef VBOXNETFLT_LINUX_NO_XMIT_QUEUE
+# define VBOX_FLT_XT_TO_INST(pXT)   RT_FROM_MEMBER(pXT, VBOXNETFLTINS, u.s.XmitTask)
+#endif
+
+#if RTLNX_VER_MIN(3,11,0)
+# define VBOX_NETDEV_NOTIFIER_INFO_TO_DEV(ptr) netdev_notifier_info_to_dev(ptr)
+#else
+# define VBOX_NETDEV_NOTIFIER_INFO_TO_DEV(ptr) ((struct net_device *)ptr)
+#endif
+
+#if RTLNX_VER_MIN(3,5,0)
+# define VBOX_SKB_KMAP_FRAG(frag) kmap_atomic(skb_frag_page(frag))
+# define VBOX_SKB_KUNMAP_FRAG(vaddr) kunmap_atomic(vaddr)
+#else
+# if RTLNX_VER_MIN(3,2,0)
+#  define VBOX_SKB_KMAP_FRAG(frag) kmap_atomic(skb_frag_page(frag), KM_SKB_DATA_SOFTIRQ)
+#  define VBOX_SKB_KUNMAP_FRAG(vaddr) kunmap_atomic(vaddr, KM_SKB_DATA_SOFTIRQ)
+# else
+#  define VBOX_SKB_KMAP_FRAG(frag) kmap_atomic(frag->page, KM_SKB_DATA_SOFTIRQ)
+#  define VBOX_SKB_KUNMAP_FRAG(vaddr) kunmap_atomic(vaddr, KM_SKB_DATA_SOFTIRQ)
+# endif
+#endif
+
+#if RTLNX_VER_MIN(2,6,34)
+# define VBOX_NETDEV_NAME(dev)              netdev_name(dev)
+#else
+# define VBOX_NETDEV_NAME(dev)              ((dev)->reg_state != NETREG_REGISTERED ? "(unregistered net_device)" : (dev)->name)
+#endif
+
+#if RTLNX_VER_MIN(2,6,25)
+# define VBOX_IPV4_IS_LOOPBACK(addr)        ipv4_is_loopback(addr)
+# define VBOX_IPV4_IS_LINKLOCAL_169(addr)   ipv4_is_linklocal_169(addr)
+#else
+# define VBOX_IPV4_IS_LOOPBACK(addr)        ((addr & htonl(IN_CLASSA_NET)) == htonl(0x7f000000))
+# define VBOX_IPV4_IS_LINKLOCAL_169(addr)   ((addr & htonl(IN_CLASSB_NET)) == htonl(0xa9fe0000))
+#endif
+
+#if RTLNX_VER_MIN(2,6,22)
+# define VBOX_SKB_RESET_NETWORK_HDR(skb)    skb_reset_network_header(skb)
+# define VBOX_SKB_RESET_MAC_HDR(skb)        skb_reset_mac_header(skb)
+# define VBOX_SKB_CSUM_OFFSET(skb)          skb->csum_offset
+#else
+# define VBOX_SKB_RESET_NETWORK_HDR(skb)    skb->nh.raw = skb->data
+# define VBOX_SKB_RESET_MAC_HDR(skb)        skb->mac.raw = skb->data
+# define VBOX_SKB_CSUM_OFFSET(skb)          skb->csum
+#endif
+
+#if RTLNX_VER_MIN(2,6,19)
+# define VBOX_SKB_CHECKSUM_HELP(skb)        skb_checksum_help(skb)
+#else
+# define CHECKSUM_PARTIAL                   CHECKSUM_HW
+# if RTLNX_VER_MIN(2,6,10)
+#  define VBOX_SKB_CHECKSUM_HELP(skb)       skb_checksum_help(skb, 0)
+# else
+#  if RTLNX_VER_MIN(2,6,7)
+#   define VBOX_SKB_CHECKSUM_HELP(skb)      skb_checksum_help(&skb, 0)
+#  else
+#   define VBOX_SKB_CHECKSUM_HELP(skb)      (!skb_checksum_help(skb))
+#  endif
+/* Versions prior 2.6.10 use stats for both bstats and qstats */
+#  define bstats stats
+#  define qstats stats
+# endif
+#endif
+
+#if RTLNX_VER_MIN(3,20,0) || RTLNX_RHEL_RANGE(7,2,  8,0) || RTLNX_RHEL_RANGE(6,8,  7,0)
+# define VBOX_HAVE_SKB_VLAN
+#endif
+
+#ifdef VBOX_HAVE_SKB_VLAN
+# define vlan_tx_tag_get(skb)       skb_vlan_tag_get(skb)
+# define vlan_tx_tag_present(skb)   skb_vlan_tag_present(skb)
+#endif
+
+#ifndef NET_IP_ALIGN
+# define NET_IP_ALIGN 2
+#endif
+
+#if 1
+/** Create scatter / gather segments for fragments. When not used, we will
+ *  linearize the socket buffer before creating the internal networking SG. */
+# define VBOXNETFLT_SG_SUPPORT 1
+#endif
+
+#if RTLNX_VER_MIN(2,6,18)
+
+/** Indicates that the linux kernel may send us GSO frames. */
+# define VBOXNETFLT_WITH_GSO                1
+
+/** This enables or disables the transmitting of GSO frame from the internal
+ *  network and to the host.  */
+# define VBOXNETFLT_WITH_GSO_XMIT_HOST      1
+
+# if 0 /** @todo This is currently disable because it causes performance loss of 5-10%.  */
+/** This enables or disables the transmitting of GSO frame from the internal
+ *  network and to the wire. */
+#  define VBOXNETFLT_WITH_GSO_XMIT_WIRE     1
+# endif
+
+/** This enables or disables the forwarding/flooding of GSO frame from the host
+ *  to the internal network.  */
+# define VBOXNETFLT_WITH_GSO_RECV           1
+
+#endif /* RTLNX_VER_MIN(2,6,18) */
+
+#if RTLNX_VER_MIN(2,6,29)
+/** This enables or disables handling of GSO frames coming from the wire (GRO). */
+# define VBOXNETFLT_WITH_GRO                1
+#endif
+
+/*
+ * GRO support was backported to RHEL 5.4
+ */
+#if RTLNX_RHEL_MAJ_PREREQ(5, 4)
+# define VBOXNETFLT_WITH_GRO                1
+#endif
+
+
+/*********************************************************************************************************************************
+*   Internal Functions                                                                                                           *
+*********************************************************************************************************************************/
+static int      __init VBoxNetFltLinuxInit(void);
+static void     __exit VBoxNetFltLinuxUnload(void);
+static void     vboxNetFltLinuxForwardToIntNet(PVBOXNETFLTINS pThis, struct sk_buff *pBuf);
+
+
+/*********************************************************************************************************************************
+*   Global Variables                                                                                                             *
+*********************************************************************************************************************************/
+/**
+ * The (common) global data.
+ */
+static VBOXNETFLTGLOBALS g_VBoxNetFltGlobals;
+
+module_init(VBoxNetFltLinuxInit);
+module_exit(VBoxNetFltLinuxUnload);
+
+MODULE_AUTHOR(VBOX_VENDOR);
+MODULE_DESCRIPTION(VBOX_PRODUCT " Network Filter Driver");
+MODULE_LICENSE("GPL");
+#ifdef MODULE_VERSION
+MODULE_VERSION(VBOX_VERSION_STRING " r" RT_XSTR(VBOX_SVN_REV) " (" RT_XSTR(INTNETTRUNKIFPORT_VERSION) ")");
+#endif
+
+
+#if RTLNX_VER_MAX(2,6,12) && defined(LOG_ENABLED)
+unsigned dev_get_flags(const struct net_device *dev)
+{
+    unsigned flags;
+
+    flags = (dev->flags & ~(IFF_PROMISC |
+                            IFF_ALLMULTI |
+                            IFF_RUNNING)) |
+            (dev->gflags & (IFF_PROMISC |
+                            IFF_ALLMULTI));
+
+    if (netif_running(dev) && netif_carrier_ok(dev))
+        flags |= IFF_RUNNING;
+
+    return flags;
+}
+#endif /* RTLNX_VER_MAX(2,6,12) */
+
+
+/**
+ * Initialize module.
+ *
+ * @returns appropriate status code.
+ */
+static int __init VBoxNetFltLinuxInit(void)
+{
+    int rc;
+    /*
+     * Initialize IPRT.
+     */
+    rc = RTR0Init(0);
+    if (RT_SUCCESS(rc))
+    {
+        Log(("VBoxNetFltLinuxInit\n"));
+
+        /*
+         * Initialize the globals and connect to the support driver.
+         *
+         * This will call back vboxNetFltOsOpenSupDrv (and maybe vboxNetFltOsCloseSupDrv)
+         * for establishing the connect to the support driver.
+         */
+        memset(&g_VBoxNetFltGlobals, 0, sizeof(g_VBoxNetFltGlobals));
+        rc = vboxNetFltInitGlobalsAndIdc(&g_VBoxNetFltGlobals);
+        if (RT_SUCCESS(rc))
+        {
+            LogRel(("VBoxNetFlt: Successfully started.\n"));
+            return 0;
+        }
+
+        LogRel(("VBoxNetFlt: failed to initialize device extension (rc=%d)\n", rc));
+        RTR0Term();
+    }
+    else
+        LogRel(("VBoxNetFlt: failed to initialize IPRT (rc=%d)\n", rc));
+
+    memset(&g_VBoxNetFltGlobals, 0, sizeof(g_VBoxNetFltGlobals));
+    return -RTErrConvertToErrno(rc);
+}
+
+
+/**
+ * Unload the module.
+ *
+ * @todo We have to prevent this if we're busy!
+ */
+static void __exit VBoxNetFltLinuxUnload(void)
+{
+    int rc;
+    Log(("VBoxNetFltLinuxUnload\n"));
+    Assert(vboxNetFltCanUnload(&g_VBoxNetFltGlobals));
+
+    /*
+     * Undo the work done during start (in reverse order).
+     */
+    rc = vboxNetFltTryDeleteIdcAndGlobals(&g_VBoxNetFltGlobals);
+    AssertRC(rc); NOREF(rc);
+
+    RTR0Term();
+
+    memset(&g_VBoxNetFltGlobals, 0, sizeof(g_VBoxNetFltGlobals));
+
+    Log(("VBoxNetFltLinuxUnload - done\n"));
+}
+
+
+/**
+ * We filter traffic from the host to the internal network
+ * before it reaches the NIC driver.
+ *
+ * The current code uses a very ugly hack overriding hard_start_xmit
+ * callback in the device structure, but it has been shown to give us a
+ * performance boost of 60-100% though. Eventually we have to find some
+ * less hacky way of getting this job done.
+ */
+#define VBOXNETFLT_WITH_HOST2WIRE_FILTER
+
+#ifdef VBOXNETFLT_WITH_HOST2WIRE_FILTER
+
+# if RTLNX_VER_MAX(2,6,29)
+
+typedef struct ethtool_ops OVR_OPSTYPE;
+# define OVR_OPS  ethtool_ops
+# define OVR_XMIT pfnStartXmit
+
+# else /* RTLNX_VER_MIN(2,6,29) */
+
+typedef struct net_device_ops OVR_OPSTYPE;
+# define OVR_OPS  netdev_ops
+# define OVR_XMIT pOrgOps->ndo_start_xmit
+
+# endif /* RTLNX_VER_MIN(2,6,29) */
+
+/**
+ * The overridden net_device_ops of the device we're attached to.
+ *
+ * As there is no net_device_ops structure in pre-2.6.29 kernels we override
+ * ethtool_ops instead along with hard_start_xmit callback in net_device
+ * structure.
+ *
+ * This is a very dirty hack that was created to explore how much we can improve
+ * the host to guest transfers by not CC'ing the NIC. It turns out to be
+ * the only way to filter outgoing packets for devices without TX queue.
+ */
+typedef struct VBoxNetDeviceOpsOverride
+{
+    /** Our overridden ops. */
+    OVR_OPSTYPE                     Ops;
+    /** Magic word. */
+    uint32_t                        u32Magic;
+    /** Pointer to the original ops. */
+    OVR_OPSTYPE const              *pOrgOps;
+# if RTLNX_VER_MAX(2,6,29)
+    /** Pointer to the original hard_start_xmit function. */
+    int (*pfnStartXmit)(struct sk_buff *pSkb, struct net_device *pDev);
+# endif /* RTLNX_VER_MAX(2,6,29) */
+    /** Pointer to the net filter instance. */
+    PVBOXNETFLTINS                  pVBoxNetFlt;
+    /** The number of filtered packages. */
+    uint64_t                        cFiltered;
+    /** The total number of packets */
+    uint64_t                        cTotal;
+} VBOXNETDEVICEOPSOVERRIDE, *PVBOXNETDEVICEOPSOVERRIDE;
+/** VBOXNETDEVICEOPSOVERRIDE::u32Magic value. */
+#define VBOXNETDEVICEOPSOVERRIDE_MAGIC  UINT32_C(0x00c0ffee)
+
+/**
+ * ndo_start_xmit wrapper that drops packets that shouldn't go to the wire
+ * because they belong on the internal network.
+ *
+ * @returns NETDEV_TX_XXX.
+ * @param   pSkb                The socket buffer to transmit.
+ * @param   pDev                The net device.
+ */
+static int vboxNetFltLinuxStartXmitFilter(struct sk_buff *pSkb, struct net_device *pDev)
+{
+    PVBOXNETDEVICEOPSOVERRIDE   pOverride = (PVBOXNETDEVICEOPSOVERRIDE)pDev->OVR_OPS;
+    uint8_t                     abHdrBuf[sizeof(RTNETETHERHDR) + sizeof(uint32_t) + RTNETIPV4_MIN_LEN];
+    PCRTNETETHERHDR             pEtherHdr;
+    PINTNETTRUNKSWPORT          pSwitchPort;
+    uint32_t                    cbHdrs;
+
+
+    /*
+     * Validate the override structure.
+     *
+     * Note! We're racing vboxNetFltLinuxUnhookDev here.  If this was supposed
+     *       to be production quality code, we would have to be much more
+     *       careful here and avoid the race.
+     */
+    if (   !RT_VALID_PTR(pOverride)
+        || pOverride->u32Magic != VBOXNETDEVICEOPSOVERRIDE_MAGIC
+# if RTLNX_VER_MIN(2,6,29)
+        || !RT_VALID_PTR(pOverride->pOrgOps)
+# endif
+        )
+    {
+        printk("vboxNetFltLinuxStartXmitFilter: bad override %p\n", pOverride);
+        dev_kfree_skb(pSkb);
+        return NETDEV_TX_OK;
+    }
+    pOverride->cTotal++;
+
+    /*
+     * Do the filtering base on the default OUI of our virtual NICs
+     *
+     * Note! In a real solution, we would ask the switch whether the
+     *       destination MAC is 100% to be on the internal network and then
+     *       drop it.
+     */
+    cbHdrs = skb_headlen(pSkb);
+    cbHdrs = RT_MIN(cbHdrs, sizeof(abHdrBuf));
+    pEtherHdr = (PCRTNETETHERHDR)skb_header_pointer(pSkb, 0, cbHdrs, &abHdrBuf[0]);
+    if (   pEtherHdr
+        && RT_VALID_PTR(pOverride->pVBoxNetFlt)
+        && (pSwitchPort = pOverride->pVBoxNetFlt->pSwitchPort) != NULL
+        && RT_VALID_PTR(pSwitchPort)
+        && cbHdrs >= 6)
+    {
+        INTNETSWDECISION enmDecision;
+
+        /** @todo consider reference counting, etc. */
+        enmDecision = pSwitchPort->pfnPreRecv(pSwitchPort, pEtherHdr, cbHdrs, INTNETTRUNKDIR_HOST);
+        if (enmDecision == INTNETSWDECISION_INTNET)
+        {
+            dev_kfree_skb(pSkb);
+            pOverride->cFiltered++;
+            return NETDEV_TX_OK;
+        }
+    }
+
+    return pOverride->OVR_XMIT(pSkb, pDev);
+}
+
+/**
+ * Hooks the device ndo_start_xmit operation of the device.
+ *
+ * @param   pThis               The net filter instance.
+ * @param   pDev                The net device.
+ */
+static void vboxNetFltLinuxHookDev(PVBOXNETFLTINS pThis, struct net_device *pDev)
+{
+    PVBOXNETDEVICEOPSOVERRIDE   pOverride;
+
+    /* Cancel override if ethtool_ops is missing (host-only case, @bugref{5712}) */
+    if (!RT_VALID_PTR(pDev->OVR_OPS))
+        return;
+    pOverride = RTMemAlloc(sizeof(*pOverride));
+    if (!pOverride)
+        return;
+    pOverride->pOrgOps              = pDev->OVR_OPS;
+    pOverride->Ops                  = *pDev->OVR_OPS;
+# if RTLNX_VER_MAX(2,6,29)
+    pOverride->pfnStartXmit         = pDev->hard_start_xmit;
+# else /* RTLNX_VER_MIN(2,6,29) */
+    pOverride->Ops.ndo_start_xmit   = vboxNetFltLinuxStartXmitFilter;
+# endif /* RTLNX_VER_MIN(2,6,29) */
+    pOverride->u32Magic             = VBOXNETDEVICEOPSOVERRIDE_MAGIC;
+    pOverride->cTotal               = 0;
+    pOverride->cFiltered            = 0;
+    pOverride->pVBoxNetFlt          = pThis;
+
+    RTSpinlockAcquire(pThis->hSpinlock); /* (this isn't necessary, but so what) */
+    ASMAtomicWritePtr((void * volatile *)&pDev->OVR_OPS, pOverride);
+# if RTLNX_VER_MAX(2,6,29)
+    ASMAtomicXchgPtr((void * volatile *)&pDev->hard_start_xmit, vboxNetFltLinuxStartXmitFilter);
+# endif /* RTLNX_VER_MAX(2,6,29) */
+    RTSpinlockRelease(pThis->hSpinlock);
+}
+
+/**
+ * Undos what vboxNetFltLinuxHookDev did.
+ *
+ * @param   pThis               The net filter instance.
+ * @param   pDev                The net device.  Can be NULL, in which case
+ *                              we'll try retrieve it from @a pThis.
+ */
+static void vboxNetFltLinuxUnhookDev(PVBOXNETFLTINS pThis, struct net_device *pDev)
+{
+    PVBOXNETDEVICEOPSOVERRIDE   pOverride;
+
+    RTSpinlockAcquire(pThis->hSpinlock);
+    if (!pDev)
+        pDev = ASMAtomicUoReadPtrT(&pThis->u.s.pDev, struct net_device *);
+    if (RT_VALID_PTR(pDev))
+    {
+        pOverride = (PVBOXNETDEVICEOPSOVERRIDE)pDev->OVR_OPS;
+        if (   RT_VALID_PTR(pOverride)
+            && pOverride->u32Magic == VBOXNETDEVICEOPSOVERRIDE_MAGIC
+            && RT_VALID_PTR(pOverride->pOrgOps)
+           )
+        {
+# if RTLNX_VER_MAX(2,6,29)
+            ASMAtomicWritePtr((void * volatile *)&pDev->hard_start_xmit, pOverride->pfnStartXmit);
+# endif /* RTLNX_VER_MAX(2,6,29) */
+            ASMAtomicWritePtr((void const * volatile *)&pDev->OVR_OPS, pOverride->pOrgOps);
+            ASMAtomicWriteU32(&pOverride->u32Magic, 0);
+        }
+        else
+            pOverride = NULL;
+    }
+    else
+        pOverride = NULL;
+    RTSpinlockRelease(pThis->hSpinlock);
+
+    if (pOverride)
+    {
+        printk("vboxnetflt: %llu out of %llu packets were not sent (directed to host)\n", pOverride->cFiltered, pOverride->cTotal);
+        RTMemFree(pOverride);
+    }
+}
+
+#endif /* VBOXNETFLT_WITH_HOST2WIRE_FILTER */
+
+
+/**
+ * Reads and retains the host interface handle.
+ *
+ * @returns The handle, NULL if detached.
+ * @param   pThis
+ */
+DECLINLINE(struct net_device *) vboxNetFltLinuxRetainNetDev(PVBOXNETFLTINS pThis)
+{
+#if 0
+    struct net_device *pDev = NULL;
+
+    Log(("vboxNetFltLinuxRetainNetDev\n"));
+    /*
+     * Be careful here to avoid problems racing the detached callback.
+     */
+    RTSpinlockAcquire(pThis->hSpinlock);
+    if (!ASMAtomicUoReadBool(&pThis->fDisconnectedFromHost))
+    {
+        pDev = (struct net_device *)ASMAtomicUoReadPtr((void * volatile *)&pThis->u.s.pDev);
+        if (pDev)
+        {
+            dev_hold(pDev);
+            Log(("vboxNetFltLinuxRetainNetDev: Device %p(%s) retained. ref=%d\n",
+                 pDev, pDev->name,
+#if RTLNX_VER_MIN(2,6,37)
+                 netdev_refcnt_read(pDev)
+#else
+                 atomic_read(&pDev->refcnt)
+#endif
+                 ));
+        }
+    }
+    RTSpinlockRelease(pThis->hSpinlock);
+
+    Log(("vboxNetFltLinuxRetainNetDev - done\n"));
+    return pDev;
+#else
+    return ASMAtomicUoReadPtrT(&pThis->u.s.pDev, struct net_device *);
+#endif
+}
+
+
+/**
+ * Release the host interface handle previously retained
+ * by vboxNetFltLinuxRetainNetDev.
+ *
+ * @param   pThis           The instance.
+ * @param   pDev            The vboxNetFltLinuxRetainNetDev
+ *                          return value, NULL is fine.
+ */
+DECLINLINE(void) vboxNetFltLinuxReleaseNetDev(PVBOXNETFLTINS pThis, struct net_device *pDev)
+{
+#if 0
+    Log(("vboxNetFltLinuxReleaseNetDev\n"));
+    NOREF(pThis);
+    if (pDev)
+    {
+        dev_put(pDev);
+        Log(("vboxNetFltLinuxReleaseNetDev: Device %p(%s) released. ref=%d\n",
+             pDev, pDev->name,
+#if RTLNX_VER_MIN(2,6,37)
+             netdev_refcnt_read(pDev)
+#else
+             atomic_read(&pDev->refcnt)
+#endif
+             ));
+    }
+    Log(("vboxNetFltLinuxReleaseNetDev - done\n"));
+#endif
+}
+
+#define VBOXNETFLT_CB_TAG(skb) (0xA1C90000 | (skb->dev->ifindex & 0xFFFF))
+#define VBOXNETFLT_SKB_TAG(skb) (*(uint32_t*)&((skb)->cb[sizeof((skb)->cb)-sizeof(uint32_t)]))
+
+/**
+ * Checks whether this is an mbuf created by vboxNetFltLinuxMBufFromSG,
+ * i.e. a buffer which we're pushing and should be ignored by the filter callbacks.
+ *
+ * @returns true / false accordingly.
+ * @param   pBuf            The sk_buff.
+ */
+DECLINLINE(bool) vboxNetFltLinuxSkBufIsOur(struct sk_buff *pBuf)
+{
+    return VBOXNETFLT_SKB_TAG(pBuf) == VBOXNETFLT_CB_TAG(pBuf);
+}
+
+
+/**
+ * Checks whether this SG list contains a GSO packet.
+ *
+ * @returns true / false accordingly.
+ * @param   pSG             The (scatter/)gather list.
+ */
+DECLINLINE(bool) vboxNetFltLinuxIsGso(PINTNETSG pSG)
+{
+#if defined(VBOXNETFLT_WITH_GSO_XMIT_WIRE) || defined(VBOXNETFLT_WITH_GSO_XMIT_HOST)
+    return !((PDMNETWORKGSOTYPE)pSG->GsoCtx.u8Type == PDMNETWORKGSOTYPE_INVALID);
+#else /* !VBOXNETFLT_WITH_GSO_XMIT_WIRE && !VBOXNETFLT_WITH_GSO_XMIT_HOST */
+    return false;
+#endif /* !VBOXNETFLT_WITH_GSO_XMIT_WIRE && !VBOXNETFLT_WITH_GSO_XMIT_HOST */
+}
+
+
+/**
+ * Find out the frame size (of a single segment in case of GSO frames).
+ *
+ * @returns the frame size.
+ * @param   pSG             The (scatter/)gather list.
+ */
+DECLINLINE(uint32_t) vboxNetFltLinuxFrameSize(PINTNETSG pSG)
+{
+    uint16_t u16Type = 0;
+    uint32_t cbVlanTag = 0;
+    if (pSG->aSegs[0].cb >= sizeof(RTNETETHERHDR))
+        u16Type = RT_BE2H_U16(((PCRTNETETHERHDR)pSG->aSegs[0].pv)->EtherType);
+    else if (pSG->cbTotal >= sizeof(RTNETETHERHDR))
+    {
+        uint32_t off = RT_UOFFSETOF(RTNETETHERHDR, EtherType);
+        uint32_t i;
+        for (i = 0; i < pSG->cSegsUsed; ++i)
+        {
+            if (off <= pSG->aSegs[i].cb)
+            {
+                if (off + sizeof(uint16_t) <= pSG->aSegs[i].cb)
+                    u16Type = RT_BE2H_U16(*(uint16_t *)((uintptr_t)pSG->aSegs[i].pv + off));
+                else if (i + 1 < pSG->cSegsUsed)
+                    u16Type = RT_BE2H_U16(  ((uint16_t)( ((uint8_t *)pSG->aSegs[i].pv)[off] ) << 8)
+                                          + *(uint8_t *)pSG->aSegs[i + 1].pv); /* ASSUMES no empty segments! */
+                /* else: frame is too short. */
+                break;
+            }
+            off -= pSG->aSegs[i].cb;
+        }
+    }
+    if (u16Type == RTNET_ETHERTYPE_VLAN)
+        cbVlanTag = 4;
+    return (vboxNetFltLinuxIsGso(pSG) ? (uint32_t)pSG->GsoCtx.cbMaxSeg + pSG->GsoCtx.cbHdrsTotal : pSG->cbTotal) - cbVlanTag;
+}
+
+
+/**
+ * Internal worker that create a linux sk_buff for a
+ * (scatter/)gather list.
+ *
+ * @returns Pointer to the sk_buff.
+ * @param   pThis           The instance.
+ * @param   pSG             The (scatter/)gather list.
+ * @param   fDstWire        Set if the destination is the wire.
+ */
+static struct sk_buff *vboxNetFltLinuxSkBufFromSG(PVBOXNETFLTINS pThis, PINTNETSG pSG, bool fDstWire)
+{
+    struct sk_buff *pPkt;
+    struct net_device *pDev;
+#if defined(VBOXNETFLT_WITH_GSO_XMIT_WIRE) || defined(VBOXNETFLT_WITH_GSO_XMIT_HOST)
+    unsigned fGsoType = 0;
+#endif
+
+    if (pSG->cbTotal == 0)
+    {
+        LogRel(("VBoxNetFlt: Dropped empty packet coming from internal network.\n"));
+        return NULL;
+    }
+    Log5(("VBoxNetFlt: Packet to %s of %d bytes (frame=%d).\n", fDstWire?"wire":"host", pSG->cbTotal, vboxNetFltLinuxFrameSize(pSG)));
+    if (fDstWire && (vboxNetFltLinuxFrameSize(pSG) > ASMAtomicReadU32(&pThis->u.s.cbMtu) + 14))
+    {
+        static bool s_fOnce = true;
+        if (s_fOnce)
+        {
+            s_fOnce = false;
+            printk("VBoxNetFlt: Dropped over-sized packet (%d bytes) coming from internal network.\n", vboxNetFltLinuxFrameSize(pSG));
+        }
+        return NULL;
+    }
+
+    /** @todo We should use fragments mapping the SG buffers with large packets.
+     *        256 bytes seems to be the a threshold used a lot for this.  It
+     *        requires some nasty work on the intnet side though...  */
+    /*
+     * Allocate a packet and copy over the data.
+     */
+    pDev = ASMAtomicUoReadPtrT(&pThis->u.s.pDev, struct net_device *);
+    pPkt = dev_alloc_skb(pSG->cbTotal + NET_IP_ALIGN);
+    if (RT_UNLIKELY(!pPkt))
+    {
+        Log(("vboxNetFltLinuxSkBufFromSG: Failed to allocate sk_buff(%u).\n", pSG->cbTotal));
+        pSG->pvUserData = NULL;
+        return NULL;
+    }
+    pPkt->dev       = pDev;
+    pPkt->ip_summed = CHECKSUM_NONE;
+
+    /* Align IP header on 16-byte boundary: 2 + 14 (ethernet hdr size). */
+    skb_reserve(pPkt, NET_IP_ALIGN);
+
+    /* Copy the segments. */
+    skb_put(pPkt, pSG->cbTotal);
+    IntNetSgRead(pSG, pPkt->data);
+
+#if defined(VBOXNETFLT_WITH_GSO_XMIT_WIRE) || defined(VBOXNETFLT_WITH_GSO_XMIT_HOST)
+    /*
+     * Setup GSO if used by this packet.
+     */
+    switch ((PDMNETWORKGSOTYPE)pSG->GsoCtx.u8Type)
+    {
+        default:
+            AssertMsgFailed(("%u (%s)\n", pSG->GsoCtx.u8Type, PDMNetGsoTypeName((PDMNETWORKGSOTYPE)pSG->GsoCtx.u8Type) ));
+            RT_FALL_THRU();
+        case PDMNETWORKGSOTYPE_INVALID:
+            fGsoType = 0;
+            break;
+        case PDMNETWORKGSOTYPE_IPV4_TCP:
+            fGsoType = SKB_GSO_TCPV4;
+            break;
+        case PDMNETWORKGSOTYPE_IPV6_TCP:
+            fGsoType = SKB_GSO_TCPV6;
+            break;
+    }
+    if (fGsoType)
+    {
+        struct skb_shared_info *pShInfo = skb_shinfo(pPkt);
+
+        pShInfo->gso_type = fGsoType | SKB_GSO_DODGY;
+        pShInfo->gso_size = pSG->GsoCtx.cbMaxSeg;
+        pShInfo->gso_segs = PDMNetGsoCalcSegmentCount(&pSG->GsoCtx, pSG->cbTotal);
+
+        /*
+         * We need to set checksum fields even if the packet goes to the host
+         * directly as it may be immediately forwarded by IP layer @bugref{5020}.
+         */
+        Assert(skb_headlen(pPkt) >= pSG->GsoCtx.cbHdrsTotal);
+        pPkt->ip_summed  = CHECKSUM_PARTIAL;
+# if RTLNX_VER_MIN(2,6,22)
+        pPkt->csum_start = skb_headroom(pPkt) + pSG->GsoCtx.offHdr2;
+        if (fGsoType & (SKB_GSO_TCPV4 | SKB_GSO_TCPV6))
+            pPkt->csum_offset = RT_UOFFSETOF(RTNETTCP, th_sum);
+        else
+            pPkt->csum_offset = RT_UOFFSETOF(RTNETUDP, uh_sum);
+# else
+        pPkt->h.raw = pPkt->data + pSG->GsoCtx.offHdr2;
+        if (fGsoType & (SKB_GSO_TCPV4 | SKB_GSO_TCPV6))
+            pPkt->csum = RT_UOFFSETOF(RTNETTCP, th_sum);
+        else
+            pPkt->csum = RT_UOFFSETOF(RTNETUDP, uh_sum);
+# endif
+        if (!fDstWire)
+            PDMNetGsoPrepForDirectUse(&pSG->GsoCtx, pPkt->data, pSG->cbTotal, PDMNETCSUMTYPE_PSEUDO);
+    }
+#endif /* VBOXNETFLT_WITH_GSO_XMIT_WIRE || VBOXNETFLT_WITH_GSO_XMIT_HOST */
+
+    /*
+     * Finish up the socket buffer.
+     */
+    pPkt->protocol = eth_type_trans(pPkt, pDev);
+    if (fDstWire)
+    {
+        VBOX_SKB_RESET_NETWORK_HDR(pPkt);
+
+        /* Restore ethernet header back. */
+        skb_push(pPkt, ETH_HLEN); /** @todo VLAN: +4 if VLAN? */
+        VBOX_SKB_RESET_MAC_HDR(pPkt);
+    }
+    VBOXNETFLT_SKB_TAG(pPkt) = VBOXNETFLT_CB_TAG(pPkt);
+
+    return pPkt;
+}
+
+
+/**
+ * Return the offset where to start checksum computation from.
+ *
+ * @returns the offset relative to pBuf->data.
+ * @param   pBuf                The socket buffer.
+ */
+DECLINLINE(unsigned) vboxNetFltLinuxGetChecksumStartOffset(struct sk_buff *pBuf)
+{
+#if RTLNX_VER_MIN(2,6,38)
+    return skb_checksum_start_offset(pBuf);
+#elif RTLNX_VER_MIN(2,6,22)
+    return pBuf->csum_start - skb_headroom(pBuf);
+#else
+    unsigned char *pTransportHdr = pBuf->h.raw;
+# if RTLNX_VER_MAX(2,6,19)
+    /*
+     * Try to work around the problem with CentOS 4.7 and 5.2 (2.6.9
+     * and 2.6.18 kernels), they pass wrong 'h' pointer down. We take IP
+     * header length from the header itself and reconstruct 'h' pointer
+     * to TCP (or whatever) header.
+     */
+    if (pBuf->h.raw == pBuf->nh.raw && pBuf->protocol == htons(ETH_P_IP))
+        pTransportHdr = pBuf->nh.raw + pBuf->nh.iph->ihl * 4;
+# endif
+    return pTransportHdr - pBuf->data;
+#endif
+}
+
+
+/**
+ * Initializes a SG list from an sk_buff.
+ *
+ * @param   pThis               The instance.
+ * @param   pBuf                The sk_buff.
+ * @param   pSG                 The SG.
+ * @param   cbExtra             The number of bytes of extra space allocated immediately after the SG.
+ * @param   cSegs               The number of segments allocated for the SG.
+ *                              This should match the number in the mbuf exactly!
+ * @param   fSrc                The source of the frame.
+ * @param   pGsoCtx             Pointer to the GSO context if it's a GSO
+ *                              internal network frame.  NULL if regular frame.
+ */
+static void vboxNetFltLinuxSkBufToSG(PVBOXNETFLTINS pThis, struct sk_buff *pBuf, PINTNETSG pSG,
+                                     unsigned cbExtra, unsigned cSegs, uint32_t fSrc, PCPDMNETWORKGSO pGsoCtx)
+{
+    int i;
+    NOREF(pThis);
+
+#ifndef VBOXNETFLT_SG_SUPPORT
+    Assert(!skb_shinfo(pBuf)->frag_list);
+#else /* VBOXNETFLT_SG_SUPPORT */
+    uint8_t *pExtra = (uint8_t *)&pSG->aSegs[cSegs];
+    unsigned cbConsumed = 0;
+    unsigned cbProduced = 0;
+
+# if RTLNX_VER_MIN(2,6,27)
+    /* Restore VLAN tag stripped by host hardware */
+    if (vlan_tx_tag_present(pBuf))
+    {
+        uint8_t *pMac = pBuf->data;
+        struct vlan_ethhdr *pVHdr = (struct vlan_ethhdr *)pExtra;
+        Assert(ETH_ALEN * 2 + VLAN_HLEN <= cbExtra);
+        memmove(pVHdr, pMac, ETH_ALEN * 2);
+        /* Consume whole Ethernet header: 2 addresses + EtherType (see @bugref{8599}) */
+        cbConsumed += ETH_ALEN * 2 + sizeof(uint16_t);
+        pVHdr->h_vlan_proto = RT_H2N_U16(ETH_P_8021Q);
+        pVHdr->h_vlan_TCI   = RT_H2N_U16(vlan_tx_tag_get(pBuf));
+        pVHdr->h_vlan_encapsulated_proto = *(uint16_t*)(pMac + ETH_ALEN * 2);
+        cbProduced += VLAN_ETH_HLEN;
+    }
+# endif /* RTLNX_VER_MIN(2,6,27) */
+
+    if (pBuf->ip_summed == CHECKSUM_PARTIAL && pBuf->pkt_type == PACKET_OUTGOING)
+    {
+        unsigned uCsumStartOffset = vboxNetFltLinuxGetChecksumStartOffset(pBuf);
+        unsigned uCsumStoreOffset = uCsumStartOffset + VBOX_SKB_CSUM_OFFSET(pBuf) - cbConsumed;
+        Log3(("cbConsumed=%u cbProduced=%u uCsumStartOffset=%u uCsumStoreOffset=%u\n",
+              cbConsumed, cbProduced, uCsumStartOffset, uCsumStoreOffset));
+        Assert(cbProduced + uCsumStoreOffset + sizeof(uint16_t) <= cbExtra);
+        /*
+         * We assume that the checksum is stored at the very end of the transport header
+         * so we will have all headers in a single fragment. If our assumption is wrong
+         * we may see suboptimal performance.
+         */
+        memmove(pExtra + cbProduced,
+                pBuf->data + cbConsumed,
+                uCsumStoreOffset);
+        unsigned uChecksum = skb_checksum(pBuf, uCsumStartOffset, pBuf->len - uCsumStartOffset, 0);
+        *(uint16_t*)(pExtra + cbProduced + uCsumStoreOffset) = csum_fold(uChecksum);
+        cbProduced += uCsumStoreOffset + sizeof(uint16_t);
+        cbConsumed += uCsumStoreOffset + sizeof(uint16_t);
+    }
+#endif /* VBOXNETFLT_SG_SUPPORT */
+
+    if (!pGsoCtx)
+        IntNetSgInitTempSegs(pSG, pBuf->len + cbProduced - cbConsumed, cSegs, 0 /*cSegsUsed*/);
+    else
+        IntNetSgInitTempSegsGso(pSG, pBuf->len + cbProduced - cbConsumed, cSegs, 0 /*cSegsUsed*/, pGsoCtx);
+
+    int iSeg = 0;
+#ifdef VBOXNETFLT_SG_SUPPORT
+    if (cbProduced)
+    {
+        pSG->aSegs[iSeg].cb = cbProduced;
+        pSG->aSegs[iSeg].pv = pExtra;
+        pSG->aSegs[iSeg++].Phys = NIL_RTHCPHYS;
+    }
+    pSG->aSegs[iSeg].cb = skb_headlen(pBuf) - cbConsumed;
+    pSG->aSegs[iSeg].pv = pBuf->data + cbConsumed;
+    pSG->aSegs[iSeg++].Phys = NIL_RTHCPHYS;
+    Assert(iSeg <= pSG->cSegsAlloc);
+
+# ifdef LOG_ENABLED
+    if (pBuf->data_len)
+        Log6(("  kmap_atomic:"));
+# endif /* LOG_ENABLED */
+    for (i = 0; i < skb_shinfo(pBuf)->nr_frags; i++)
+    {
+        skb_frag_t *pFrag = &skb_shinfo(pBuf)->frags[i];
+# if RTLNX_VER_MIN(5,4,0) || RTLNX_SUSE_MAJ_PREREQ(15, 2)
+        pSG->aSegs[iSeg].cb = pFrag->bv_len;
+        pSG->aSegs[iSeg].pv = VBOX_SKB_KMAP_FRAG(pFrag) + pFrag->bv_offset;
+# else /* < KERNEL_VERSION(5, 4, 0) */
+        pSG->aSegs[iSeg].cb = pFrag->size;
+        pSG->aSegs[iSeg].pv = VBOX_SKB_KMAP_FRAG(pFrag) + pFrag->page_offset;
+# endif /* >= KERNEL_VERSION(5, 4, 0) */
+        Log6((" %p", pSG->aSegs[iSeg].pv));
+        pSG->aSegs[iSeg++].Phys = NIL_RTHCPHYS;
+        Assert(iSeg <= pSG->cSegsAlloc);
+    }
+    struct sk_buff *pFragBuf;
+    for (pFragBuf = skb_shinfo(pBuf)->frag_list; pFragBuf; pFragBuf = pFragBuf->next)
+    {
+        pSG->aSegs[iSeg].cb = skb_headlen(pFragBuf);
+        pSG->aSegs[iSeg].pv = pFragBuf->data;
+        pSG->aSegs[iSeg++].Phys = NIL_RTHCPHYS;
+        Assert(iSeg <= pSG->cSegsAlloc);
+        for (i = 0; i < skb_shinfo(pFragBuf)->nr_frags; i++)
+        {
+            skb_frag_t *pFrag = &skb_shinfo(pFragBuf)->frags[i];
+# if RTLNX_VER_MIN(5,4,0) || RTLNX_SUSE_MAJ_PREREQ(15, 2)
+            pSG->aSegs[iSeg].cb = pFrag->bv_len;
+            pSG->aSegs[iSeg].pv = VBOX_SKB_KMAP_FRAG(pFrag) + pFrag->bv_offset;
+# else /* < KERNEL_VERSION(5, 4, 0) */
+            pSG->aSegs[iSeg].cb = pFrag->size;
+            pSG->aSegs[iSeg].pv = VBOX_SKB_KMAP_FRAG(pFrag) + pFrag->page_offset;
+# endif /* >= KERNEL_VERSION(5, 4, 0) */
+            Log6((" %p", pSG->aSegs[iSeg].pv));
+            pSG->aSegs[iSeg++].Phys = NIL_RTHCPHYS;
+            Assert(iSeg <= pSG->cSegsAlloc);
+        }
+    }
+# ifdef LOG_ENABLED
+    if (pBuf->data_len)
+        Log6(("\n"));
+# endif /* LOG_ENABLED */
+#else
+    pSG->aSegs[iSeg].cb = pBuf->len;
+    pSG->aSegs[iSeg].pv = pBuf->data;
+    pSG->aSegs[iSeg++].Phys = NIL_RTHCPHYS;
+#endif
+
+    pSG->cSegsUsed = iSeg;
+
+#if 0
+    if (cbProduced)
+    {
+        LogRel(("vboxNetFltLinuxSkBufToSG: original packet dump:\n%.*Rhxd\n", pBuf->len-pBuf->data_len, skb_mac_header(pBuf)));
+        LogRel(("vboxNetFltLinuxSkBufToSG: cbConsumed=%u cbProduced=%u cbExtra=%u\n", cbConsumed, cbProduced, cbExtra));
+        uint32_t offset = 0;
+        for (i = 0; i < pSG->cSegsUsed; ++i)
+        {
+            LogRel(("vboxNetFltLinuxSkBufToSG: seg#%d (%d bytes, starting at 0x%x):\n%.*Rhxd\n",
+                    i, pSG->aSegs[i].cb, offset, pSG->aSegs[i].cb, pSG->aSegs[i].pv));
+            offset += pSG->aSegs[i].cb;
+        }
+    }
+#endif
+
+#ifdef PADD_RUNT_FRAMES_FROM_HOST
+    /*
+     * Add a trailer if the frame is too small.
+     *
+     * Since we're getting to the packet before it is framed, it has not
+     * yet been padded. The current solution is to add a segment pointing
+     * to a buffer containing all zeros and pray that works for all frames...
+     */
+    if (pSG->cbTotal < 60 && (fSrc & INTNETTRUNKDIR_HOST))
+    {
+        Assert(pBuf->data_len == 0); /* Packets with fragments are never small! */
+        static uint8_t const s_abZero[128] = {0};
+
+        AssertReturnVoid(iSeg < cSegs);
+
+        pSG->aSegs[iSeg].Phys = NIL_RTHCPHYS;
+        pSG->aSegs[iSeg].pv = (void *)&s_abZero[0];
+        pSG->aSegs[iSeg++].cb = 60 - pSG->cbTotal;
+        pSG->cbTotal = 60;
+        pSG->cSegsUsed++;
+        Assert(iSeg <= pSG->cSegsAlloc)
+    }
+#endif
+
+    Log6(("vboxNetFltLinuxSkBufToSG: allocated=%d, segments=%d frags=%d next=%p frag_list=%p pkt_type=%x fSrc=%x\n",
+          pSG->cSegsAlloc, pSG->cSegsUsed, skb_shinfo(pBuf)->nr_frags, pBuf->next, skb_shinfo(pBuf)->frag_list, pBuf->pkt_type, fSrc));
+    for (i = 0; i < pSG->cSegsUsed; i++)
+        Log6(("vboxNetFltLinuxSkBufToSG:   #%d: cb=%d pv=%p\n",
+              i, pSG->aSegs[i].cb, pSG->aSegs[i].pv));
+}
+
+/**
+ * Packet handler; not really documented - figure it out yourself.
+ *
+ * @returns 0 or EJUSTRETURN - this is probably copy & pastry and thus wrong.
+ */
+#if RTLNX_VER_MIN(2,6,14)
+static int vboxNetFltLinuxPacketHandler(struct sk_buff *pBuf,
+                                        struct net_device *pSkbDev,
+                                        struct packet_type *pPacketType,
+                                        struct net_device *pOrigDev)
+#else
+static int vboxNetFltLinuxPacketHandler(struct sk_buff *pBuf,
+                                        struct net_device *pSkbDev,
+                                        struct packet_type *pPacketType)
+#endif
+{
+    PVBOXNETFLTINS pThis;
+    struct net_device *pDev;
+    LogFlow(("vboxNetFltLinuxPacketHandler: pBuf=%p pSkbDev=%p pPacketType=%p\n",
+             pBuf, pSkbDev, pPacketType));
+#if RTLNX_VER_MIN(2,6,18)
+    Log3(("vboxNetFltLinuxPacketHandler: skb len=%u data_len=%u truesize=%u next=%p nr_frags=%u gso_size=%u gso_seqs=%u gso_type=%x frag_list=%p pkt_type=%x\n",
+          pBuf->len, pBuf->data_len, pBuf->truesize, pBuf->next, skb_shinfo(pBuf)->nr_frags, skb_shinfo(pBuf)->gso_size, skb_shinfo(pBuf)->gso_segs, skb_shinfo(pBuf)->gso_type, skb_shinfo(pBuf)->frag_list, pBuf->pkt_type));
+# if RTLNX_VER_MIN(2,6,22)
+    Log6(("vboxNetFltLinuxPacketHandler: packet dump follows:\n%.*Rhxd\n", pBuf->len-pBuf->data_len, skb_mac_header(pBuf)));
+# endif
+#else
+    Log3(("vboxNetFltLinuxPacketHandler: skb len=%u data_len=%u truesize=%u next=%p nr_frags=%u tso_size=%u tso_seqs=%u frag_list=%p pkt_type=%x\n",
+          pBuf->len, pBuf->data_len, pBuf->truesize, pBuf->next, skb_shinfo(pBuf)->nr_frags, skb_shinfo(pBuf)->tso_size, skb_shinfo(pBuf)->tso_segs, skb_shinfo(pBuf)->frag_list, pBuf->pkt_type));
+#endif
+    /*
+     * Drop it immediately?
+     */
+    if (!pBuf)
+        return 0;
+
+    if (pBuf->pkt_type == PACKET_LOOPBACK)
+    {
+        /*
+         * We are not interested in loopbacked packets as they will always have
+         * another copy going to the wire.
+         */
+        Log2(("vboxNetFltLinuxPacketHandler: dropped loopback packet (cb=%u)\n", pBuf->len));
+        dev_kfree_skb(pBuf); /* We must 'consume' all packets we get (@bugref{6539})! */
+        return 0;
+    }
+
+    pThis = VBOX_FLT_PT_TO_INST(pPacketType);
+    pDev = ASMAtomicUoReadPtrT(&pThis->u.s.pDev, struct net_device *);
+    if (pDev != pSkbDev)
+    {
+        Log(("vboxNetFltLinuxPacketHandler: Devices do not match, pThis may be wrong! pThis=%p\n", pThis));
+        kfree_skb(pBuf); /* This is a failure, so we use kfree_skb instead of dev_kfree_skb. */
+        return 0;
+    }
+
+    Log6(("vboxNetFltLinuxPacketHandler: pBuf->cb dump:\n%.*Rhxd\n", sizeof(pBuf->cb), pBuf->cb));
+    if (vboxNetFltLinuxSkBufIsOur(pBuf))
+    {
+        Log2(("vboxNetFltLinuxPacketHandler: got our own sk_buff, drop it.\n"));
+        dev_kfree_skb(pBuf);
+        return 0;
+    }
+
+#ifndef VBOXNETFLT_SG_SUPPORT
+    {
+        /*
+         * Get rid of fragmented packets, they cause too much trouble.
+         */
+        unsigned int uMacLen = pBuf->mac_len;
+        struct sk_buff *pCopy = skb_copy(pBuf, GFP_ATOMIC);
+        dev_kfree_skb(pBuf);
+        if (!pCopy)
+        {
+            LogRel(("VBoxNetFlt: Failed to allocate packet buffer, dropping the packet.\n"));
+            return 0;
+        }
+        pBuf = pCopy;
+        /* Somehow skb_copy ignores mac_len */
+        pBuf->mac_len = uMacLen;
+# if RTLNX_VER_MIN(2,6,27)
+        /* Restore VLAN tag stripped by host hardware */
+        if (vlan_tx_tag_present(pBuf) && skb_headroom(pBuf) >= VLAN_ETH_HLEN)
+        {
+            uint8_t *pMac = (uint8_t*)skb_mac_header(pBuf);
+            struct vlan_ethhdr *pVHdr = (struct vlan_ethhdr *)(pMac - VLAN_HLEN);
+            memmove(pVHdr, pMac, ETH_ALEN * 2);
+            pVHdr->h_vlan_proto = RT_H2N_U16(ETH_P_8021Q);
+            pVHdr->h_vlan_TCI   = RT_H2N_U16(vlan_tx_tag_get(pBuf));
+            pBuf->mac_header   -= VLAN_HLEN;
+            pBuf->mac_len      += VLAN_HLEN;
+        }
+# endif /* RTLNX_VER_MIN(2,6,27) */
+
+# if RTLNX_VER_MIN(2,6,18)
+        Log3(("vboxNetFltLinuxPacketHandler: skb copy len=%u data_len=%u truesize=%u next=%p nr_frags=%u gso_size=%u gso_seqs=%u gso_type=%x frag_list=%p pkt_type=%x\n",
+              pBuf->len, pBuf->data_len, pBuf->truesize, pBuf->next, skb_shinfo(pBuf)->nr_frags, skb_shinfo(pBuf)->gso_size, skb_shinfo(pBuf)->gso_segs, skb_shinfo(pBuf)->gso_type, skb_shinfo(pBuf)->frag_list, pBuf->pkt_type));
+#  if RTLNX_VER_MIN(2,6,22)
+        Log6(("vboxNetFltLinuxPacketHandler: packet dump follows:\n%.*Rhxd\n", pBuf->len-pBuf->data_len, skb_mac_header(pBuf)));
+#  endif /* RTLNX_VER_MIN(2,6,22) */
+# else /* RTLNX_VER_MAX(2,6,18) */
+        Log3(("vboxNetFltLinuxPacketHandler: skb copy len=%u data_len=%u truesize=%u next=%p nr_frags=%u tso_size=%u tso_seqs=%u frag_list=%p pkt_type=%x\n",
+              pBuf->len, pBuf->data_len, pBuf->truesize, pBuf->next, skb_shinfo(pBuf)->nr_frags, skb_shinfo(pBuf)->tso_size, skb_shinfo(pBuf)->tso_segs, skb_shinfo(pBuf)->frag_list, pBuf->pkt_type));
+# endif /* RTLNX_VER_MAX(2,6,18) */
+    }
+#endif /* !VBOXNETFLT_SG_SUPPORT */
+
+#ifdef VBOXNETFLT_LINUX_NO_XMIT_QUEUE
+    /* Forward it to the internal network. */
+    vboxNetFltLinuxForwardToIntNet(pThis, pBuf);
+#else /* !VBOXNETFLT_LINUX_NO_XMIT_QUEUE */
+    /* Add the packet to transmit queue and schedule the bottom half. */
+    skb_queue_tail(&pThis->u.s.XmitQueue, pBuf);
+    schedule_work(&pThis->u.s.XmitTask);
+    Log6(("vboxNetFltLinuxPacketHandler: scheduled work %p for sk_buff %p\n",
+          &pThis->u.s.XmitTask, pBuf));
+#endif /* !VBOXNETFLT_LINUX_NO_XMIT_QUEUE */
+
+    /* It does not really matter what we return, it is ignored by the kernel. */
+    return 0;
+}
+
+/**
+ * Calculate the number of INTNETSEG segments the socket buffer will need.
+ *
+ * @returns Segment count.
+ * @param   pBuf                The socket buffer.
+ * @param   pcbTemp             Where to store the number of bytes of the part
+ *                              of the socket buffer that will be copied to
+ *                              a temporary storage.
+ */
+DECLINLINE(unsigned) vboxNetFltLinuxCalcSGSegments(struct sk_buff *pBuf, unsigned *pcbTemp)
+{
+    *pcbTemp = 0;
+#ifdef VBOXNETFLT_SG_SUPPORT
+    unsigned cSegs = 1 + skb_shinfo(pBuf)->nr_frags;
+    if (pBuf->ip_summed == CHECKSUM_PARTIAL && pBuf->pkt_type == PACKET_OUTGOING)
+    {
+        *pcbTemp = vboxNetFltLinuxGetChecksumStartOffset(pBuf) + VBOX_SKB_CSUM_OFFSET(pBuf) + sizeof(uint16_t);
+    }
+# if RTLNX_VER_MIN(2,6,27)
+    if (vlan_tx_tag_present(pBuf))
+    {
+        if (*pcbTemp)
+            *pcbTemp += VLAN_HLEN;
+        else
+            *pcbTemp = VLAN_ETH_HLEN;
+    }
+# endif /* RTLNX_VER_MIN(2,6,27) */
+    if (*pcbTemp)
+        ++cSegs;
+    struct sk_buff *pFrag;
+    for (pFrag = skb_shinfo(pBuf)->frag_list; pFrag; pFrag = pFrag->next)
+    {
+        Log6(("vboxNetFltLinuxCalcSGSegments: frag=%p len=%d data_len=%d frags=%d frag_list=%p next=%p\n",
+              pFrag, pFrag->len, pFrag->data_len, skb_shinfo(pFrag)->nr_frags, skb_shinfo(pFrag)->frag_list, pFrag->next));
+        cSegs += 1 + skb_shinfo(pFrag)->nr_frags;
+    }
+#else
+    unsigned cSegs = 1;
+#endif
+#ifdef PADD_RUNT_FRAMES_FROM_HOST
+    /* vboxNetFltLinuxSkBufToSG adds a padding segment if it's a runt. */
+    if (pBuf->len < 60)
+        cSegs++;
+#endif
+    return cSegs;
+}
+
+
+/**
+ * Destroy the intnet scatter / gather buffer created by
+ * vboxNetFltLinuxSkBufToSG.
+ *
+ * @param   pSG             The (scatter/)gather list.
+ * @param   pBuf            The original socket buffer that was used to create
+ *                          the scatter/gather list.
+ */
+static void vboxNetFltLinuxDestroySG(PINTNETSG pSG, struct sk_buff *pBuf)
+{
+#ifdef VBOXNETFLT_SG_SUPPORT
+    int i, iSeg = 1; /* Skip non-paged part of SKB */
+    /* Check if the extra buffer behind SG structure was used for modified packet header */
+    if (pBuf->data != pSG->aSegs[0].pv)
+        ++iSeg; /* Skip it as well */
+# ifdef LOG_ENABLED
+    if (pBuf->data_len)
+        Log6(("kunmap_atomic:"));
+# endif /* LOG_ENABLED */
+    /* iSeg now points to the first mapped fragment if there are any */
+    for (i = 0; i < skb_shinfo(pBuf)->nr_frags; i++)
+    {
+        Log6((" %p", pSG->aSegs[iSeg].pv));
+        VBOX_SKB_KUNMAP_FRAG(pSG->aSegs[iSeg++].pv);
+    }
+    struct sk_buff *pFragBuf;
+    for (pFragBuf = skb_shinfo(pBuf)->frag_list; pFragBuf; pFragBuf = pFragBuf->next)
+    {
+        ++iSeg; /* Non-fragment (unmapped) portion of chained SKB */
+        for (i = 0; i < skb_shinfo(pFragBuf)->nr_frags; i++)
+        {
+            Log6((" %p", pSG->aSegs[iSeg].pv));
+            VBOX_SKB_KUNMAP_FRAG(pSG->aSegs[iSeg++].pv);
+        }
+    }
+# ifdef LOG_ENABLED
+    if (pBuf->data_len)
+        Log6(("\n"));
+# endif /* LOG_ENABLED */
+#endif
+    NOREF(pSG);
+}
+
+#ifdef LOG_ENABLED
+/**
+ * Logging helper.
+ */
+static void vboxNetFltDumpPacket(PINTNETSG pSG, bool fEgress, const char *pszWhere, int iIncrement)
+{
+    int i, offSeg;
+    uint8_t *pInt, *pExt;
+    static int iPacketNo = 1;
+    iPacketNo += iIncrement;
+    if (fEgress)
+    {
+        pExt = pSG->aSegs[0].pv;
+        pInt = pExt + 6;
+    }
+    else
+    {
+        pInt = pSG->aSegs[0].pv;
+        pExt = pInt + 6;
+    }
+    Log(("VBoxNetFlt: (int)%02x:%02x:%02x:%02x:%02x:%02x"
+         " %s (%s)%02x:%02x:%02x:%02x:%02x:%02x (%u bytes) packet #%u\n",
+         pInt[0], pInt[1], pInt[2], pInt[3], pInt[4], pInt[5],
+         fEgress ? "-->" : "<--", pszWhere,
+         pExt[0], pExt[1], pExt[2], pExt[3], pExt[4], pExt[5],
+         pSG->cbTotal, iPacketNo));
+    if (pSG->cSegsUsed == 1)
+    {
+        Log4(("%.*Rhxd\n", pSG->aSegs[0].cb, pSG->aSegs[0].pv));
+    }
+    else
+    {
+        for (i = 0, offSeg = 0; i < pSG->cSegsUsed; i++)
+        {
+            Log4(("-- segment %d at 0x%x (%d bytes)\n --\n%.*Rhxd\n",
+                  i, offSeg, pSG->aSegs[i].cb, pSG->aSegs[i].cb, pSG->aSegs[i].pv));
+            offSeg += pSG->aSegs[i].cb;
+        }
+    }
+}
+#else
+# define vboxNetFltDumpPacket(a, b, c, d) do {} while (0)
+#endif
+
+#ifdef VBOXNETFLT_WITH_GSO_RECV
+
+/**
+ * Worker for vboxNetFltLinuxForwardToIntNet that checks if we can forwards a
+ * GSO socket buffer without having to segment it.
+ *
+ * @returns true on success, false if needs segmenting.
+ * @param   pThis               The net filter instance.
+ * @param   pSkb                The GSO socket buffer.
+ * @param   fSrc                The source.
+ * @param   pGsoCtx             Where to return the GSO context on success.
+ */
+static bool vboxNetFltLinuxCanForwardAsGso(PVBOXNETFLTINS pThis, struct sk_buff *pSkb, uint32_t fSrc,
+                                           PPDMNETWORKGSO pGsoCtx)
+{
+    PDMNETWORKGSOTYPE   enmGsoType;
+    uint16_t            uEtherType;
+    unsigned int        cbTransport;
+    unsigned int        offTransport;
+    unsigned int        cbTransportHdr;
+    unsigned            uProtocol;
+    union
+    {
+        RTNETIPV4           IPv4;
+        RTNETIPV6           IPv6;
+        RTNETTCP            Tcp;
+        uint8_t             ab[40];
+        uint16_t            au16[40/2];
+        uint32_t            au32[40/4];
+    }                   Buf;
+
+    /*
+     * Check the GSO properties of the socket buffer and make sure it fits.
+     */
+    /** @todo Figure out how to handle SKB_GSO_TCP_ECN! */
+    if (RT_UNLIKELY( skb_shinfo(pSkb)->gso_type & ~(SKB_GSO_DODGY | SKB_GSO_TCPV6 | SKB_GSO_TCPV4) ))
+    {
+        Log5(("vboxNetFltLinuxCanForwardAsGso: gso_type=%#x\n", skb_shinfo(pSkb)->gso_type));
+        return false;
+    }
+    if (RT_UNLIKELY(   skb_shinfo(pSkb)->gso_size < 1
+                    || pSkb->len > VBOX_MAX_GSO_SIZE ))
+    {
+        Log5(("vboxNetFltLinuxCanForwardAsGso: gso_size=%#x skb_len=%#x (max=%#x)\n", skb_shinfo(pSkb)->gso_size, pSkb->len, VBOX_MAX_GSO_SIZE));
+        return false;
+    }
+
+    /*
+     * Switch on the ethertype.
+     */
+    uEtherType = pSkb->protocol;
+    if (   uEtherType    == RT_H2N_U16_C(RTNET_ETHERTYPE_VLAN)
+        && pSkb->mac_len == sizeof(RTNETETHERHDR) + sizeof(uint32_t))
+    {
+        uint16_t const *puEtherType = skb_header_pointer(pSkb, sizeof(RTNETETHERHDR) + sizeof(uint16_t), sizeof(uint16_t), &Buf);
+        if (puEtherType)
+            uEtherType = *puEtherType;
+    }
+    switch (uEtherType)
+    {
+        case RT_H2N_U16_C(RTNET_ETHERTYPE_IPV4):
+        {
+            unsigned int cbHdr;
+            PCRTNETIPV4  pIPv4 = (PCRTNETIPV4)skb_header_pointer(pSkb, pSkb->mac_len, sizeof(Buf.IPv4), &Buf);
+            if (RT_UNLIKELY(!pIPv4))
+            {
+                Log5(("vboxNetFltLinuxCanForwardAsGso: failed to access IPv4 hdr\n"));
+                return false;
+            }
+
+            cbHdr       = pIPv4->ip_hl * 4;
+            cbTransport = RT_N2H_U16(pIPv4->ip_len);
+            if (RT_UNLIKELY(   cbHdr < RTNETIPV4_MIN_LEN
+                            || cbHdr > cbTransport ))
+            {
+                Log5(("vboxNetFltLinuxCanForwardAsGso: invalid IPv4 lengths: ip_hl=%u ip_len=%u\n", pIPv4->ip_hl, RT_N2H_U16(pIPv4->ip_len)));
+                return false;
+            }
+            cbTransport -= cbHdr;
+            offTransport = pSkb->mac_len + cbHdr;
+            uProtocol    = pIPv4->ip_p;
+            if (uProtocol == RTNETIPV4_PROT_TCP)
+                enmGsoType = PDMNETWORKGSOTYPE_IPV4_TCP;
+            else if (uProtocol == RTNETIPV4_PROT_UDP)
+                enmGsoType = PDMNETWORKGSOTYPE_IPV4_UDP;
+            else /** @todo IPv6: 4to6 tunneling */
+                enmGsoType = PDMNETWORKGSOTYPE_INVALID;
+            break;
+        }
+
+        case RT_H2N_U16_C(RTNET_ETHERTYPE_IPV6):
+        {
+            PCRTNETIPV6 pIPv6 = (PCRTNETIPV6)skb_header_pointer(pSkb, pSkb->mac_len, sizeof(Buf.IPv6), &Buf);
+            if (RT_UNLIKELY(!pIPv6))
+            {
+                Log5(("vboxNetFltLinuxCanForwardAsGso: failed to access IPv6 hdr\n"));
+                return false;
+            }
+
+            cbTransport  = RT_N2H_U16(pIPv6->ip6_plen);
+            offTransport = pSkb->mac_len + sizeof(RTNETIPV6);
+            uProtocol    = pIPv6->ip6_nxt;
+            /** @todo IPv6: Dig our way out of the other headers. */
+            if (uProtocol == RTNETIPV4_PROT_TCP)
+                enmGsoType = PDMNETWORKGSOTYPE_IPV6_TCP;
+            else if (uProtocol == RTNETIPV4_PROT_UDP)
+                enmGsoType = PDMNETWORKGSOTYPE_IPV6_UDP;
+            else
+                enmGsoType = PDMNETWORKGSOTYPE_INVALID;
+            break;
+        }
+
+        default:
+            Log5(("vboxNetFltLinuxCanForwardAsGso: uEtherType=%#x\n", RT_H2N_U16(uEtherType)));
+            return false;
+    }
+
+    if (enmGsoType == PDMNETWORKGSOTYPE_INVALID)
+    {
+        Log5(("vboxNetFltLinuxCanForwardAsGso: Unsupported protocol %d\n", uProtocol));
+        return false;
+    }
+
+    if (RT_UNLIKELY(   offTransport + cbTransport <= offTransport
+                    || offTransport + cbTransport > pSkb->len
+                    || cbTransport < (uProtocol == RTNETIPV4_PROT_TCP ? RTNETTCP_MIN_LEN : RTNETUDP_MIN_LEN)) )
+    {
+        Log5(("vboxNetFltLinuxCanForwardAsGso: Bad transport length; off=%#x + cb=%#x => %#x; skb_len=%#x (%s)\n",
+              offTransport, cbTransport, offTransport + cbTransport, pSkb->len, PDMNetGsoTypeName(enmGsoType) ));
+        return false;
+    }
+
+    /*
+     * Check the TCP/UDP bits.
+     */
+    if (uProtocol == RTNETIPV4_PROT_TCP)
+    {
+        PCRTNETTCP pTcp = (PCRTNETTCP)skb_header_pointer(pSkb, offTransport, sizeof(Buf.Tcp), &Buf);
+        if (RT_UNLIKELY(!pTcp))
+        {
+            Log5(("vboxNetFltLinuxCanForwardAsGso: failed to access TCP hdr\n"));
+            return false;
+        }
+
+        cbTransportHdr = pTcp->th_off * 4;
+        pGsoCtx->cbHdrsSeg = offTransport + cbTransportHdr;
+        if (RT_UNLIKELY(   cbTransportHdr < RTNETTCP_MIN_LEN
+                        || cbTransportHdr > cbTransport
+                        || offTransport + cbTransportHdr >= UINT8_MAX
+                        || offTransport + cbTransportHdr >= pSkb->len ))
+        {
+            Log5(("vboxNetFltLinuxCanForwardAsGso: No space for TCP header; off=%#x cb=%#x skb_len=%#x\n", offTransport, cbTransportHdr, pSkb->len));
+            return false;
+        }
+
+    }
+    else
+    {
+        Assert(uProtocol == RTNETIPV4_PROT_UDP);
+        cbTransportHdr = sizeof(RTNETUDP);
+        pGsoCtx->cbHdrsSeg = offTransport; /* Exclude UDP header */
+        if (RT_UNLIKELY(   offTransport + cbTransportHdr >= UINT8_MAX
+                        || offTransport + cbTransportHdr >= pSkb->len ))
+        {
+            Log5(("vboxNetFltLinuxCanForwardAsGso: No space for UDP header; off=%#x skb_len=%#x\n", offTransport, pSkb->len));
+            return false;
+        }
+    }
+
+    /*
+     * We're good, init the GSO context.
+     */
+    pGsoCtx->u8Type       = enmGsoType;
+    pGsoCtx->cbHdrsTotal  = offTransport + cbTransportHdr;
+    pGsoCtx->cbMaxSeg     = skb_shinfo(pSkb)->gso_size;
+    pGsoCtx->offHdr1      = pSkb->mac_len;
+    pGsoCtx->offHdr2      = offTransport;
+    pGsoCtx->u8Unused     = 0;
+
+    return true;
+}
+
+/**
+ * Forward the socket buffer as a GSO internal network frame.
+ *
+ * @returns IPRT status code.
+ * @param   pThis               The net filter instance.
+ * @param   pSkb                The GSO socket buffer.
+ * @param   fSrc                The source.
+ * @param   pGsoCtx             Where to return the GSO context on success.
+ */
+static int vboxNetFltLinuxForwardAsGso(PVBOXNETFLTINS pThis, struct sk_buff *pSkb, uint32_t fSrc, PCPDMNETWORKGSO pGsoCtx)
+{
+    int         rc;
+    unsigned    cbExtra;
+    unsigned    cSegs = vboxNetFltLinuxCalcSGSegments(pSkb, &cbExtra);
+    PINTNETSG pSG = (PINTNETSG)alloca(RT_UOFFSETOF_DYN(INTNETSG, aSegs[cSegs]) + cbExtra);
+    if (RT_LIKELY(pSG))
+    {
+        vboxNetFltLinuxSkBufToSG(pThis, pSkb, pSG, cbExtra, cSegs, fSrc, pGsoCtx);
+
+        vboxNetFltDumpPacket(pSG, false, (fSrc & INTNETTRUNKDIR_HOST) ? "host" : "wire", 1);
+        pThis->pSwitchPort->pfnRecv(pThis->pSwitchPort, NULL /* pvIf */, pSG, fSrc);
+
+        vboxNetFltLinuxDestroySG(pSG, pSkb);
+        rc = VINF_SUCCESS;
+    }
+    else
+    {
+        Log(("VBoxNetFlt: Dropping the sk_buff (failure case).\n"));
+        rc = VERR_NO_MEMORY;
+    }
+    return rc;
+}
+
+#endif /* VBOXNETFLT_WITH_GSO_RECV */
+
+/**
+ * Worker for vboxNetFltLinuxForwardToIntNet.
+ *
+ * @returns VINF_SUCCESS or VERR_NO_MEMORY.
+ * @param   pThis               The net filter instance.
+ * @param   pBuf                The socket buffer.
+ * @param   fSrc                The source.
+ */
+static int vboxNetFltLinuxForwardSegment(PVBOXNETFLTINS pThis, struct sk_buff *pBuf, uint32_t fSrc)
+{
+    int         rc;
+    unsigned    cbExtra;
+    unsigned    cSegs = vboxNetFltLinuxCalcSGSegments(pBuf, &cbExtra);
+    PINTNETSG pSG = (PINTNETSG)alloca(RT_UOFFSETOF_DYN(INTNETSG, aSegs[cSegs]) + cbExtra);
+    if (RT_LIKELY(pSG))
+    {
+        vboxNetFltLinuxSkBufToSG(pThis, pBuf, pSG, cbExtra, cSegs, fSrc, NULL /*pGsoCtx*/);
+
+        vboxNetFltDumpPacket(pSG, false, (fSrc & INTNETTRUNKDIR_HOST) ? "host" : "wire", 1);
+        pThis->pSwitchPort->pfnRecv(pThis->pSwitchPort, NULL /* pvIf */, pSG, fSrc);
+
+        vboxNetFltLinuxDestroySG(pSG, pBuf);
+        rc = VINF_SUCCESS;
+    }
+    else
+    {
+        Log(("VBoxNetFlt: Failed to allocate SG buffer.\n"));
+        rc = VERR_NO_MEMORY;
+    }
+    return rc;
+}
+
+
+/**
+ * I won't disclose what I do, figure it out yourself, including pThis referencing.
+ *
+ * @param   pThis       The net filter instance.
+ * @param   pBuf        The socket buffer.
+ * @param   fSrc        Where the packet comes from.
+ */
+static void vboxNetFltLinuxForwardToIntNetInner(PVBOXNETFLTINS pThis, struct sk_buff *pBuf, uint32_t fSrc)
+{
+#ifdef VBOXNETFLT_WITH_GSO
+    if (skb_is_gso(pBuf))
+    {
+        PDMNETWORKGSO GsoCtx;
+        Log6(("vboxNetFltLinuxForwardToIntNetInner: skb len=%u data_len=%u truesize=%u next=%p"
+              " nr_frags=%u gso_size=%u gso_seqs=%u gso_type=%x frag_list=%p pkt_type=%x ip_summed=%d\n",
+              pBuf->len, pBuf->data_len, pBuf->truesize, pBuf->next,
+              skb_shinfo(pBuf)->nr_frags, skb_shinfo(pBuf)->gso_size,
+              skb_shinfo(pBuf)->gso_segs, skb_shinfo(pBuf)->gso_type,
+              skb_shinfo(pBuf)->frag_list, pBuf->pkt_type, pBuf->ip_summed));
+
+        if (RT_LIKELY(fSrc & INTNETTRUNKDIR_HOST))
+        {
+            /*
+             * skb_gso_segment does the following. Do we need to do it as well?
+             */
+# if RTLNX_VER_MIN(2,6,22)
+            skb_reset_mac_header(pBuf);
+            pBuf->mac_len = pBuf->network_header - pBuf->mac_header;
+# else
+            pBuf->mac.raw = pBuf->data;
+            pBuf->mac_len = pBuf->nh.raw - pBuf->data;
+# endif
+        }
+
+# ifdef VBOXNETFLT_WITH_GSO_RECV
+        if (   (skb_shinfo(pBuf)->gso_type & (SKB_GSO_TCPV6 | SKB_GSO_TCPV4))
+            && vboxNetFltLinuxCanForwardAsGso(pThis, pBuf, fSrc, &GsoCtx) )
+            vboxNetFltLinuxForwardAsGso(pThis, pBuf, fSrc, &GsoCtx);
+        else
+# endif /* VBOXNETFLT_WITH_GSO_RECV */
+        {
+            /* Need to segment the packet */
+            struct sk_buff *pNext;
+            struct sk_buff *pSegment = skb_gso_segment(pBuf, 0 /*supported features*/);
+            if (IS_ERR(pSegment))
+            {
+                LogRel(("VBoxNetFlt: Failed to segment a packet (%d).\n", PTR_ERR(pSegment)));
+                return;
+            }
+
+            for (; pSegment; pSegment = pNext)
+            {
+                Log6(("vboxNetFltLinuxForwardToIntNetInner: segment len=%u data_len=%u truesize=%u next=%p"
+                      " nr_frags=%u gso_size=%u gso_seqs=%u gso_type=%x frag_list=%p pkt_type=%x\n",
+                      pSegment->len, pSegment->data_len, pSegment->truesize, pSegment->next,
+                      skb_shinfo(pSegment)->nr_frags, skb_shinfo(pSegment)->gso_size,
+                      skb_shinfo(pSegment)->gso_segs, skb_shinfo(pSegment)->gso_type,
+                      skb_shinfo(pSegment)->frag_list, pSegment->pkt_type));
+                pNext = pSegment->next;
+                pSegment->next = 0;
+                vboxNetFltLinuxForwardSegment(pThis, pSegment, fSrc);
+                dev_kfree_skb(pSegment);
+            }
+        }
+    }
+    else
+#endif /* VBOXNETFLT_WITH_GSO */
+    {
+        Log6(("vboxNetFltLinuxForwardToIntNetInner: ptk_type=%d ip_summed=%d len=%d"
+              " data_len=%d headroom=%d hdr_len=%d csum_offset=%d\n",
+              pBuf->pkt_type, pBuf->ip_summed, pBuf->len, pBuf->data_len, skb_headroom(pBuf),
+              skb_headlen(pBuf), vboxNetFltLinuxGetChecksumStartOffset(pBuf)));
+#ifndef VBOXNETFLT_SG_SUPPORT
+        if (pBuf->ip_summed == CHECKSUM_PARTIAL && pBuf->pkt_type == PACKET_OUTGOING)
+        {
+# if RTLNX_VER_MIN(2,6,19)
+            int rc = VBOX_SKB_CHECKSUM_HELP(pBuf);
+# else
+            /*
+             * Try to work around the problem with CentOS 4.7 and 5.2 (2.6.9
+             * and 2.6.18 kernels), they pass wrong 'h' pointer down. We take IP
+             * header length from the header itself and reconstruct 'h' pointer
+             * to TCP (or whatever) header.
+             */
+            unsigned char *tmp = pBuf->h.raw;
+            if (pBuf->h.raw == pBuf->nh.raw && pBuf->protocol == htons(ETH_P_IP))
+                pBuf->h.raw = pBuf->nh.raw + pBuf->nh.iph->ihl * 4;
+            int rc = VBOX_SKB_CHECKSUM_HELP(pBuf);
+            /* Restore the original (wrong) pointer. */
+            pBuf->h.raw = tmp;
+# endif
+            if (rc)
+            {
+                LogRel(("VBoxNetFlt: Failed to compute checksum, dropping the packet.\n"));
+                return;
+            }
+        }
+#endif /* !VBOXNETFLT_SG_SUPPORT */
+        vboxNetFltLinuxForwardSegment(pThis, pBuf, fSrc);
+    }
+}
+
+
+/**
+ * Temporarily adjust pBuf->data so it always points to the Ethernet header,
+ * then forward it to the internal network.
+ *
+ * @param   pThis       The net filter instance.
+ * @param   pBuf        The socket buffer.  This is consumed by this function.
+ */
+static void vboxNetFltLinuxForwardToIntNet(PVBOXNETFLTINS pThis, struct sk_buff *pBuf)
+{
+    uint32_t fSrc = pBuf->pkt_type == PACKET_OUTGOING ? INTNETTRUNKDIR_HOST : INTNETTRUNKDIR_WIRE;
+
+    if (RT_UNLIKELY(fSrc & INTNETTRUNKDIR_WIRE))
+    {
+        /*
+         * The packet came from the wire and the driver has already consumed
+         * mac header. We need to restore it back. Moreover, after we are
+         * through with this skb we need to restore its original state!
+         */
+        skb_push(pBuf, pBuf->mac_len);
+        Log5(("vboxNetFltLinuxForwardToIntNet: mac_len=%d data=%p mac_header=%p network_header=%p\n",
+              pBuf->mac_len, pBuf->data, skb_mac_header(pBuf), skb_network_header(pBuf)));
+    }
+
+    vboxNetFltLinuxForwardToIntNetInner(pThis, pBuf, fSrc);
+
+    /*
+     * Restore the original state of skb as there are other handlers this skb
+     * will be provided to.
+     */
+    if (RT_UNLIKELY(fSrc & INTNETTRUNKDIR_WIRE))
+        skb_pull(pBuf, pBuf->mac_len);
+
+    dev_kfree_skb(pBuf);
+}
+
+
+#ifndef VBOXNETFLT_LINUX_NO_XMIT_QUEUE
+/**
+ * Work queue handler that forwards the socket buffers queued by
+ * vboxNetFltLinuxPacketHandler to the internal network.
+ *
+ * @param   pWork               The work queue.
+ */
+# if RTLNX_VER_MIN(2,6,20)
+static void vboxNetFltLinuxXmitTask(struct work_struct *pWork)
+# else
+static void vboxNetFltLinuxXmitTask(void *pWork)
+# endif
+{
+    PVBOXNETFLTINS  pThis   = VBOX_FLT_XT_TO_INST(pWork);
+    struct sk_buff *pBuf;
+
+    Log6(("vboxNetFltLinuxXmitTask: Got work %p.\n", pWork));
+
+    /*
+     * Active? Retain the instance and increment the busy counter.
+     */
+    if (vboxNetFltTryRetainBusyActive(pThis))
+    {
+        while ((pBuf = skb_dequeue(&pThis->u.s.XmitQueue)) != NULL)
+            vboxNetFltLinuxForwardToIntNet(pThis, pBuf);
+
+        vboxNetFltRelease(pThis, true /* fBusy */);
+    }
+    else
+    {
+        /** @todo Shouldn't we just drop the packets here? There is little point in
+         *        making them accumulate when the VM is paused and it'll only waste
+         *        kernel memory anyway... Hmm. maybe wait a short while (2-5 secs)
+         *        before start draining the packets (goes for the intnet ring buf
+         *        too)? */
+    }
+}
+#endif /* !VBOXNETFLT_LINUX_NO_XMIT_QUEUE */
+
+/**
+ * Reports the GSO capabilities of the hardware NIC.
+ *
+ * @param   pThis               The net filter instance.  The caller hold a
+ *                              reference to this.
+ */
+static void vboxNetFltLinuxReportNicGsoCapabilities(PVBOXNETFLTINS pThis)
+{
+#if defined(VBOXNETFLT_WITH_GSO_XMIT_WIRE) || defined(VBOXNETFLT_WITH_GSO_XMIT_HOST)
+    if (vboxNetFltTryRetainBusyNotDisconnected(pThis))
+    {
+        struct net_device  *pDev;
+        unsigned int        fFeatures;
+
+        RTSpinlockAcquire(pThis->hSpinlock);
+
+        pDev = ASMAtomicUoReadPtrT(&pThis->u.s.pDev, struct net_device *);
+        if (pDev)
+            fFeatures = pDev->features;
+        else
+            fFeatures = 0;
+
+        RTSpinlockRelease(pThis->hSpinlock);
+
+        if (pThis->pSwitchPort)
+        {
+            /* Set/update the GSO capabilities of the NIC. */
+            uint32_t fGsoCapabilites = 0;
+            if (fFeatures & NETIF_F_TSO)
+                fGsoCapabilites |= RT_BIT_32(PDMNETWORKGSOTYPE_IPV4_TCP);
+            if (fFeatures & NETIF_F_TSO6)
+                fGsoCapabilites |= RT_BIT_32(PDMNETWORKGSOTYPE_IPV6_TCP);
+            Log3(("vboxNetFltLinuxReportNicGsoCapabilities: reporting wire %s%s\n",
+                  (fGsoCapabilites & RT_BIT_32(PDMNETWORKGSOTYPE_IPV4_TCP)) ? "tso " : "",
+                  (fGsoCapabilites & RT_BIT_32(PDMNETWORKGSOTYPE_IPV6_TCP)) ? "tso6 " : ""));
+            pThis->pSwitchPort->pfnReportGsoCapabilities(pThis->pSwitchPort, fGsoCapabilites, INTNETTRUNKDIR_WIRE);
+        }
+
+        vboxNetFltRelease(pThis, true /*fBusy*/);
+    }
+#endif /* VBOXNETFLT_WITH_GSO_XMIT_WIRE || VBOXNETFLT_WITH_GSO_XMIT_HOST */
+}
+
+/**
+ * Helper that determines whether the host (ignoreing us) is operating the
+ * interface in promiscuous mode or not.
+ */
+static bool vboxNetFltLinuxPromiscuous(PVBOXNETFLTINS pThis)
+{
+    bool                fRc  = false;
+    struct net_device * pDev = vboxNetFltLinuxRetainNetDev(pThis);
+    if (pDev)
+    {
+        fRc = !!(pDev->promiscuity - (ASMAtomicUoReadBool(&pThis->u.s.fPromiscuousSet) & 1));
+        LogFlow(("vboxNetFltPortOsIsPromiscuous: returns %d, pDev->promiscuity=%d, fPromiscuousSet=%d\n",
+                 fRc, pDev->promiscuity, pThis->u.s.fPromiscuousSet));
+        vboxNetFltLinuxReleaseNetDev(pThis, pDev);
+    }
+    return fRc;
+}
+
+/**
+ * Does this device needs link state change signaled?
+ * Currently we need it for our own VBoxNetAdp and TAP.
+ */
+static bool vboxNetFltNeedsLinkState(PVBOXNETFLTINS pThis, struct net_device *pDev)
+{
+    if (pDev->ethtool_ops && pDev->ethtool_ops->get_drvinfo)
+    {
+        struct ethtool_drvinfo Info;
+
+        memset(&Info, 0, sizeof(Info));
+        Info.cmd = ETHTOOL_GDRVINFO;
+        pDev->ethtool_ops->get_drvinfo(pDev, &Info);
+        Log3(("%s: driver=%.*s version=%.*s bus_info=%.*s\n",
+              __FUNCTION__,
+              sizeof(Info.driver),   Info.driver,
+              sizeof(Info.version),  Info.version,
+              sizeof(Info.bus_info), Info.bus_info));
+
+        if (!strncmp(Info.driver, "vboxnet", sizeof(Info.driver)))
+            return true;
+
+#if RTLNX_VER_MIN(2,6,36) /* TAP started doing carrier */
+        return !strncmp(Info.driver,   "tun", 4)
+            && !strncmp(Info.bus_info, "tap", 4);
+#endif
+    }
+
+    return false;
+}
+
+#if RTLNX_VER_MAX(2,6,18)
+DECLINLINE(void) netif_tx_lock_bh(struct net_device *pDev)
+{
+    spin_lock_bh(&pDev->xmit_lock);
+}
+
+DECLINLINE(void) netif_tx_unlock_bh(struct net_device *pDev)
+{
+    spin_unlock_bh(&pDev->xmit_lock);
+}
+#endif
+
+/**
+ * Some devices need link state change when filter attaches/detaches
+ * since the filter is their link in a sense.
+ */
+static void vboxNetFltSetLinkState(PVBOXNETFLTINS pThis, struct net_device *pDev, bool fLinkUp)
+{
+    if (vboxNetFltNeedsLinkState(pThis, pDev))
+    {
+        Log3(("%s: bringing device link %s\n",
+              __FUNCTION__, fLinkUp ? "up" : "down"));
+        netif_tx_lock_bh(pDev);
+        if (fLinkUp)
+            netif_carrier_on(pDev);
+        else
+            netif_carrier_off(pDev);
+        netif_tx_unlock_bh(pDev);
+    }
+}
+
+/**
+ * Internal worker for vboxNetFltLinuxNotifierCallback.
+ *
+ * @returns VBox status code.
+ * @param   pThis           The instance.
+ * @param   pDev            The device to attach to.
+ */
+static int vboxNetFltLinuxAttachToInterface(PVBOXNETFLTINS pThis, struct net_device *pDev)
+{
+    LogFlow(("vboxNetFltLinuxAttachToInterface: pThis=%p (%s)\n", pThis, pThis->szName));
+
+    /*
+     * Retain and store the device.
+     */
+    dev_hold(pDev);
+
+    RTSpinlockAcquire(pThis->hSpinlock);
+    ASMAtomicUoWritePtr(&pThis->u.s.pDev, pDev);
+    RTSpinlockRelease(pThis->hSpinlock);
+
+    Log(("vboxNetFltLinuxAttachToInterface: Device %p(%s) retained. ref=%d\n",
+          pDev, pDev->name,
+#if RTLNX_VER_MIN(2,6,37)
+          netdev_refcnt_read(pDev)
+#else
+          atomic_read(&pDev->refcnt)
+#endif
+          ));
+    Log(("vboxNetFltLinuxAttachToInterface: Got pDev=%p pThis=%p pThis->u.s.pDev=%p\n",
+          pDev, pThis, ASMAtomicUoReadPtrT(&pThis->u.s.pDev, struct net_device *)));
+
+    /* Get the mac address while we still have a valid net_device reference. */
+    memcpy(&pThis->u.s.MacAddr, pDev->dev_addr, sizeof(pThis->u.s.MacAddr));
+    /* Initialize MTU */
+    pThis->u.s.cbMtu = pDev->mtu;
+
+    /*
+     * Install a packet filter for this device with a protocol wildcard (ETH_P_ALL).
+     */
+    pThis->u.s.PacketType.type = __constant_htons(ETH_P_ALL);
+    pThis->u.s.PacketType.dev  = pDev;
+    pThis->u.s.PacketType.func = vboxNetFltLinuxPacketHandler;
+    dev_add_pack(&pThis->u.s.PacketType);
+    ASMAtomicUoWriteBool(&pThis->u.s.fPacketHandler, true);
+    Log(("vboxNetFltLinuxAttachToInterface: this=%p: Packet handler installed.\n", pThis));
+
+#ifdef VBOXNETFLT_WITH_HOST2WIRE_FILTER
+    vboxNetFltLinuxHookDev(pThis, pDev);
+#endif
+
+    /*
+     * Are we the "carrier" for this device (e.g. vboxnet or tap)?
+     */
+    vboxNetFltSetLinkState(pThis, pDev, true);
+
+    /*
+     * Set indicators that require the spinlock. Be abit paranoid about racing
+     * the device notification handle.
+     */
+    RTSpinlockAcquire(pThis->hSpinlock);
+    pDev = ASMAtomicUoReadPtrT(&pThis->u.s.pDev, struct net_device *);
+    if (pDev)
+    {
+        ASMAtomicUoWriteBool(&pThis->fDisconnectedFromHost, false);
+        ASMAtomicUoWriteBool(&pThis->u.s.fRegistered, true);
+        pDev = NULL; /* don't dereference it */
+    }
+    RTSpinlockRelease(pThis->hSpinlock);
+
+    /*
+     * Report GSO capabilities
+     */
+    Assert(pThis->pSwitchPort);
+    if (vboxNetFltTryRetainBusyNotDisconnected(pThis))
+    {
+        vboxNetFltLinuxReportNicGsoCapabilities(pThis);
+        pThis->pSwitchPort->pfnReportMacAddress(pThis->pSwitchPort, &pThis->u.s.MacAddr);
+        pThis->pSwitchPort->pfnReportPromiscuousMode(pThis->pSwitchPort, vboxNetFltLinuxPromiscuous(pThis));
+        pThis->pSwitchPort->pfnReportNoPreemptDsts(pThis->pSwitchPort, INTNETTRUNKDIR_WIRE | INTNETTRUNKDIR_HOST);
+        vboxNetFltRelease(pThis, true /*fBusy*/);
+    }
+
+    LogRel(("VBoxNetFlt: attached to '%s' / %RTmac\n", pThis->szName, &pThis->u.s.MacAddr));
+    return VINF_SUCCESS;
+}
+
+
+static int vboxNetFltLinuxUnregisterDevice(PVBOXNETFLTINS pThis, struct net_device *pDev)
+{
+    bool fRegistered;
+    Assert(!pThis->fDisconnectedFromHost);
+
+#ifdef VBOXNETFLT_WITH_HOST2WIRE_FILTER
+    vboxNetFltLinuxUnhookDev(pThis, pDev);
+#endif
+
+    if (ASMAtomicCmpXchgBool(&pThis->u.s.fPacketHandler, false, true))
+    {
+        dev_remove_pack(&pThis->u.s.PacketType);
+        Log(("vboxNetFltLinuxUnregisterDevice: this=%p: packet handler removed.\n", pThis));
+    }
+
+    RTSpinlockAcquire(pThis->hSpinlock);
+    fRegistered = ASMAtomicXchgBool(&pThis->u.s.fRegistered, false);
+    if (fRegistered)
+    {
+        ASMAtomicWriteBool(&pThis->fDisconnectedFromHost, true);
+        ASMAtomicUoWriteNullPtr(&pThis->u.s.pDev);
+    }
+    RTSpinlockRelease(pThis->hSpinlock);
+
+    if (fRegistered)
+    {
+#ifndef VBOXNETFLT_LINUX_NO_XMIT_QUEUE
+        skb_queue_purge(&pThis->u.s.XmitQueue);
+#endif
+        Log(("vboxNetFltLinuxUnregisterDevice: this=%p: xmit queue purged.\n", pThis));
+        Log(("vboxNetFltLinuxUnregisterDevice: Device %p(%s) released. ref=%d\n",
+             pDev, pDev->name,
+#if RTLNX_VER_MIN(2,6,37)
+             netdev_refcnt_read(pDev)
+#else
+             atomic_read(&pDev->refcnt)
+#endif
+           ));
+        dev_put(pDev);
+    }
+
+    return NOTIFY_OK;
+}
+
+static int vboxNetFltLinuxDeviceIsUp(PVBOXNETFLTINS pThis, struct net_device *pDev)
+{
+    /* Check if we are not suspended and promiscuous mode has not been set. */
+    if (   pThis->enmTrunkState == INTNETTRUNKIFSTATE_ACTIVE
+        && !ASMAtomicUoReadBool(&pThis->u.s.fPromiscuousSet))
+    {
+        /* Note that there is no need for locking as the kernel got hold of the lock already. */
+        dev_set_promiscuity(pDev, 1);
+        ASMAtomicWriteBool(&pThis->u.s.fPromiscuousSet, true);
+        Log(("vboxNetFltLinuxDeviceIsUp: enabled promiscuous mode on %s (%d)\n", pThis->szName, pDev->promiscuity));
+    }
+    else
+        Log(("vboxNetFltLinuxDeviceIsUp: no need to enable promiscuous mode on %s (%d)\n", pThis->szName, pDev->promiscuity));
+    return NOTIFY_OK;
+}
+
+static int vboxNetFltLinuxDeviceGoingDown(PVBOXNETFLTINS pThis, struct net_device *pDev)
+{
+    /* Undo promiscuous mode if we has set it. */
+    if (ASMAtomicUoReadBool(&pThis->u.s.fPromiscuousSet))
+    {
+        /* Note that there is no need for locking as the kernel got hold of the lock already. */
+        dev_set_promiscuity(pDev, -1);
+        ASMAtomicWriteBool(&pThis->u.s.fPromiscuousSet, false);
+        Log(("vboxNetFltLinuxDeviceGoingDown: disabled promiscuous mode on %s (%d)\n", pThis->szName, pDev->promiscuity));
+    }
+    else
+        Log(("vboxNetFltLinuxDeviceGoingDown: no need to disable promiscuous mode on %s (%d)\n", pThis->szName, pDev->promiscuity));
+    return NOTIFY_OK;
+}
+
+/**
+ * Callback for listening to MTU change event.
+ *
+ * We need to track changes of host's inteface MTU to discard over-sized frames
+ * coming from the internal network as they may hang the TX queue of host's
+ * adapter.
+ *
+ * @returns NOTIFY_OK
+ * @param   pThis               The netfilter instance.
+ * @param   pDev                Pointer to device structure of host's interface.
+ */
+static int vboxNetFltLinuxDeviceMtuChange(PVBOXNETFLTINS pThis, struct net_device *pDev)
+{
+    ASMAtomicWriteU32(&pThis->u.s.cbMtu, pDev->mtu);
+    Log(("vboxNetFltLinuxDeviceMtuChange: set MTU for %s to %d\n", pThis->szName, pDev->mtu));
+    return NOTIFY_OK;
+}
+
+#ifdef LOG_ENABLED
+/** Stringify the NETDEV_XXX constants. */
+static const char *vboxNetFltLinuxGetNetDevEventName(unsigned long ulEventType)
+{
+    const char *pszEvent = "NETDEV_<unknown>";
+    switch (ulEventType)
+    {
+        case NETDEV_REGISTER: pszEvent = "NETDEV_REGISTER"; break;
+        case NETDEV_UNREGISTER: pszEvent = "NETDEV_UNREGISTER"; break;
+        case NETDEV_UP: pszEvent = "NETDEV_UP"; break;
+        case NETDEV_DOWN: pszEvent = "NETDEV_DOWN"; break;
+        case NETDEV_REBOOT: pszEvent = "NETDEV_REBOOT"; break;
+        case NETDEV_CHANGENAME: pszEvent = "NETDEV_CHANGENAME"; break;
+        case NETDEV_CHANGE: pszEvent = "NETDEV_CHANGE"; break;
+        case NETDEV_CHANGEMTU: pszEvent = "NETDEV_CHANGEMTU"; break;
+        case NETDEV_CHANGEADDR: pszEvent = "NETDEV_CHANGEADDR"; break;
+        case NETDEV_GOING_DOWN: pszEvent = "NETDEV_GOING_DOWN"; break;
+# ifdef NETDEV_FEAT_CHANGE
+        case NETDEV_FEAT_CHANGE: pszEvent = "NETDEV_FEAT_CHANGE"; break;
+# endif
+    }
+    return pszEvent;
+}
+#endif /* LOG_ENABLED */
+
+/**
+ * Callback for listening to netdevice events.
+ *
+ * This works the rediscovery, clean up on unregistration, promiscuity on
+ * up/down, and GSO feature changes from ethtool.
+ *
+ * @returns NOTIFY_OK
+ * @param   self                Pointer to our notifier registration block.
+ * @param   ulEventType         The event.
+ * @param   ptr                 Event specific, but it is usually the device it
+ *                              relates to.
+ */
+static int vboxNetFltLinuxNotifierCallback(struct notifier_block *self, unsigned long ulEventType, void *ptr)
+
+{
+    PVBOXNETFLTINS      pThis = VBOX_FLT_NB_TO_INST(self);
+    struct net_device  *pMyDev = ASMAtomicUoReadPtrT(&pThis->u.s.pDev, struct net_device *);
+    struct net_device  *pDev  = VBOX_NETDEV_NOTIFIER_INFO_TO_DEV(ptr);
+    int                 rc    = NOTIFY_OK;
+
+    Log(("VBoxNetFlt: got event %s(0x%lx) on %s, pDev=%p pThis=%p pThis->u.s.pDev=%p\n",
+         vboxNetFltLinuxGetNetDevEventName(ulEventType), ulEventType, pDev->name, pDev, pThis, pMyDev));
+
+    if (ulEventType == NETDEV_REGISTER)
+    {
+#if RTLNX_VER_MIN(2,6,24) /* cgroups/namespaces introduced */
+# if RTLNX_VER_MIN(2,6,26)
+#  define VBOX_DEV_NET(dev)             dev_net(dev)
+#  define VBOX_NET_EQ(n1, n2)           net_eq((n1), (n2))
+# else
+#  define VBOX_DEV_NET(dev)             ((dev)->nd_net)
+#  define VBOX_NET_EQ(n1, n2)           ((n1) == (n2))
+# endif
+        struct net *pMyNet = current->nsproxy->net_ns;
+        struct net *pDevNet = VBOX_DEV_NET(pDev);
+
+        if (VBOX_NET_EQ(pDevNet, pMyNet))
+#endif  /* namespaces */
+        {
+            if (strcmp(pDev->name, pThis->szName) == 0)
+            {
+                vboxNetFltLinuxAttachToInterface(pThis, pDev);
+            }
+        }
+    }
+    else
+    {
+        if (pDev == pMyDev)
+        {
+            switch (ulEventType)
+            {
+                case NETDEV_UNREGISTER:
+                    rc = vboxNetFltLinuxUnregisterDevice(pThis, pDev);
+                    break;
+                case NETDEV_UP:
+                    rc = vboxNetFltLinuxDeviceIsUp(pThis, pDev);
+                    break;
+                case NETDEV_GOING_DOWN:
+                    rc = vboxNetFltLinuxDeviceGoingDown(pThis, pDev);
+                    break;
+                case NETDEV_CHANGEMTU:
+                    rc = vboxNetFltLinuxDeviceMtuChange(pThis, pDev);
+                    break;
+                case NETDEV_CHANGENAME:
+                    break;
+#ifdef NETDEV_FEAT_CHANGE
+                case NETDEV_FEAT_CHANGE:
+                    vboxNetFltLinuxReportNicGsoCapabilities(pThis);
+                    break;
+#endif
+            }
+        }
+    }
+
+    return rc;
+}
+
+/*
+ * Initial enumeration of netdevs.  Called with NETDEV_REGISTER by
+ * register_netdevice_notifier() under rtnl lock.
+ */
+static int vboxNetFltLinuxEnumeratorCallback(struct notifier_block *self, unsigned long ulEventType, void *ptr)
+{
+    PVBOXNETFLTINS pThis = ((PVBOXNETFLTNOTIFIER)self)->pThis;
+    struct net_device *dev  = VBOX_NETDEV_NOTIFIER_INFO_TO_DEV(ptr);
+    struct in_device *in_dev;
+    struct inet6_dev *in6_dev;
+
+    if (ulEventType != NETDEV_REGISTER)
+        return NOTIFY_OK;
+
+    if (RT_UNLIKELY(pThis->pSwitchPort->pfnNotifyHostAddress == NULL))
+        return NOTIFY_OK;
+
+    /*
+     * IPv4
+     */
+#if RTLNX_VER_MIN(2,6,14)
+    in_dev = __in_dev_get_rtnl(dev);
+#else
+    in_dev = __in_dev_get(dev);
+#endif
+    if (in_dev != NULL)
+    {
+        struct in_ifaddr *ifa;
+
+        for (ifa = in_dev->ifa_list; ifa; ifa = ifa->ifa_next) {
+            if (VBOX_IPV4_IS_LOOPBACK(ifa->ifa_address))
+                return NOTIFY_OK;
+
+            if (   dev != pThis->u.s.pDev
+                && VBOX_IPV4_IS_LINKLOCAL_169(ifa->ifa_address))
+                continue;
+
+            Log(("%s: %s: IPv4 addr %RTnaipv4 mask %RTnaipv4\n",
+                 __FUNCTION__, VBOX_NETDEV_NAME(dev),
+                 ifa->ifa_address, ifa->ifa_mask));
+
+            pThis->pSwitchPort->pfnNotifyHostAddress(pThis->pSwitchPort,
+                /* :fAdded */ true, kIntNetAddrType_IPv4, &ifa->ifa_address);
+        }
+    }
+
+    /*
+     * IPv6
+     */
+    in6_dev = __in6_dev_get(dev);
+    if (in6_dev != NULL)
+    {
+        struct inet6_ifaddr *ifa;
+
+        read_lock_bh(&in6_dev->lock);
+#if RTLNX_VER_MIN(2,6,35)
+        list_for_each_entry(ifa, &in6_dev->addr_list, if_list)
+#else
+        for (ifa = in6_dev->addr_list; ifa != NULL; ifa = ifa->if_next)
+#endif
+        {
+            if (   dev != pThis->u.s.pDev
+                && ipv6_addr_type(&ifa->addr) & (IPV6_ADDR_LINKLOCAL | IPV6_ADDR_LOOPBACK))
+                continue;
+
+            Log(("%s: %s: IPv6 addr %RTnaipv6/%u\n",
+                 __FUNCTION__, VBOX_NETDEV_NAME(dev),
+                 &ifa->addr, (unsigned)ifa->prefix_len));
+
+            pThis->pSwitchPort->pfnNotifyHostAddress(pThis->pSwitchPort,
+                /* :fAdded */ true, kIntNetAddrType_IPv6, &ifa->addr);
+        }
+        read_unlock_bh(&in6_dev->lock);
+    }
+
+    return NOTIFY_OK;
+}
+
+
+static int vboxNetFltLinuxNotifierIPv4Callback(struct notifier_block *self, unsigned long ulEventType, void *ptr)
+{
+    PVBOXNETFLTINS     pThis = RT_FROM_MEMBER(self, VBOXNETFLTINS, u.s.NotifierIPv4);
+    struct net_device *pDev, *pEventDev;
+    struct in_ifaddr  *ifa   = (struct in_ifaddr *)ptr;
+    bool               fMyDev;
+    int                rc    = NOTIFY_OK;
+
+    pDev = vboxNetFltLinuxRetainNetDev(pThis);
+    pEventDev = ifa->ifa_dev->dev;
+    fMyDev = (pDev == pEventDev);
+    Log(("VBoxNetFlt: %s: IPv4 event %s(0x%lx) %s: addr %RTnaipv4 mask %RTnaipv4\n",
+         pDev ? VBOX_NETDEV_NAME(pDev) : "<unknown>",
+         vboxNetFltLinuxGetNetDevEventName(ulEventType), ulEventType,
+         pEventDev ? VBOX_NETDEV_NAME(pEventDev) : "<unknown>",
+         ifa->ifa_address, ifa->ifa_mask));
+
+    if (pDev != NULL)
+        vboxNetFltLinuxReleaseNetDev(pThis, pDev);
+
+    if (VBOX_IPV4_IS_LOOPBACK(ifa->ifa_address))
+        return NOTIFY_OK;
+
+    if (   !fMyDev
+        && VBOX_IPV4_IS_LINKLOCAL_169(ifa->ifa_address))
+        return NOTIFY_OK;
+
+    if (pThis->pSwitchPort->pfnNotifyHostAddress)
+    {
+        bool fAdded;
+        if (ulEventType == NETDEV_UP)
+            fAdded = true;
+        else if (ulEventType == NETDEV_DOWN)
+            fAdded = false;
+        else
+            return NOTIFY_OK;
+
+        pThis->pSwitchPort->pfnNotifyHostAddress(pThis->pSwitchPort, fAdded,
+                                                 kIntNetAddrType_IPv4, &ifa->ifa_local);
+    }
+
+    return rc;
+}
+
+
+static int vboxNetFltLinuxNotifierIPv6Callback(struct notifier_block *self, unsigned long ulEventType, void *ptr)
+{
+    PVBOXNETFLTINS       pThis = RT_FROM_MEMBER(self, VBOXNETFLTINS, u.s.NotifierIPv6);
+    struct net_device   *pDev, *pEventDev;
+    struct inet6_ifaddr *ifa   = (struct inet6_ifaddr *)ptr;
+    bool                 fMyDev;
+    int                  rc    = NOTIFY_OK;
+
+    pDev = vboxNetFltLinuxRetainNetDev(pThis);
+    pEventDev = ifa->idev->dev;
+    fMyDev = (pDev == pEventDev);
+    Log(("VBoxNetFlt: %s: IPv6 event %s(0x%lx) %s: %RTnaipv6\n",
+         pDev ? VBOX_NETDEV_NAME(pDev) : "<unknown>",
+         vboxNetFltLinuxGetNetDevEventName(ulEventType), ulEventType,
+         pEventDev ? VBOX_NETDEV_NAME(pEventDev) : "<unknown>",
+         &ifa->addr));
+
+    if (pDev != NULL)
+        vboxNetFltLinuxReleaseNetDev(pThis, pDev);
+
+    if (   !fMyDev
+        && ipv6_addr_type(&ifa->addr) & (IPV6_ADDR_LINKLOCAL | IPV6_ADDR_LOOPBACK))
+        return NOTIFY_OK;
+
+    if (pThis->pSwitchPort->pfnNotifyHostAddress)
+    {
+        bool fAdded;
+        if (ulEventType == NETDEV_UP)
+            fAdded = true;
+        else if (ulEventType == NETDEV_DOWN)
+            fAdded = false;
+        else
+            return NOTIFY_OK;
+
+        pThis->pSwitchPort->pfnNotifyHostAddress(pThis->pSwitchPort, fAdded,
+                                                 kIntNetAddrType_IPv6, &ifa->addr);
+    }
+
+    return rc;
+}
+
+
+bool vboxNetFltOsMaybeRediscovered(PVBOXNETFLTINS pThis)
+{
+    return !ASMAtomicUoReadBool(&pThis->fDisconnectedFromHost);
+}
+
+int  vboxNetFltPortOsXmit(PVBOXNETFLTINS pThis, void *pvIfData, PINTNETSG pSG, uint32_t fDst)
+{
+    struct net_device * pDev;
+    int err;
+    int rc = VINF_SUCCESS;
+    IPRT_LINUX_SAVE_EFL_AC();
+    NOREF(pvIfData);
+
+    LogFlow(("vboxNetFltPortOsXmit: pThis=%p (%s)\n", pThis, pThis->szName));
+
+    pDev = vboxNetFltLinuxRetainNetDev(pThis);
+    if (pDev)
+    {
+        /*
+         * Create a sk_buff for the gather list and push it onto the wire.
+         */
+        if (fDst & INTNETTRUNKDIR_WIRE)
+        {
+            struct sk_buff *pBuf = vboxNetFltLinuxSkBufFromSG(pThis, pSG, true);
+            if (pBuf)
+            {
+                vboxNetFltDumpPacket(pSG, true, "wire", 1);
+                Log6(("vboxNetFltPortOsXmit: pBuf->cb dump:\n%.*Rhxd\n", sizeof(pBuf->cb), pBuf->cb));
+                Log6(("vboxNetFltPortOsXmit: dev_queue_xmit(%p)\n", pBuf));
+                err = dev_queue_xmit(pBuf);
+                if (err)
+                    rc = RTErrConvertFromErrno(err);
+            }
+            else
+                rc = VERR_NO_MEMORY;
+        }
+
+        /*
+         * Create a sk_buff for the gather list and push it onto the host stack.
+         */
+        if (fDst & INTNETTRUNKDIR_HOST)
+        {
+            struct sk_buff *pBuf = vboxNetFltLinuxSkBufFromSG(pThis, pSG, false);
+            if (pBuf)
+            {
+                vboxNetFltDumpPacket(pSG, true, "host", (fDst & INTNETTRUNKDIR_WIRE) ? 0 : 1);
+                Log6(("vboxNetFltPortOsXmit: pBuf->cb dump:\n%.*Rhxd\n", sizeof(pBuf->cb), pBuf->cb));
+                Log6(("vboxNetFltPortOsXmit: netif_rx_ni(%p)\n", pBuf));
+#if RTLNX_VER_MIN(5,18,0) || RTLNX_RHEL_MIN(9,1)
+                local_bh_disable();
+                err = netif_rx(pBuf);
+                local_bh_enable();
+#else
+                err = netif_rx_ni(pBuf);
+#endif
+                if (err)
+                    rc = RTErrConvertFromErrno(err);
+            }
+            else
+                rc = VERR_NO_MEMORY;
+        }
+
+        vboxNetFltLinuxReleaseNetDev(pThis, pDev);
+    }
+
+    IPRT_LINUX_RESTORE_EFL_AC();
+    return rc;
+}
+
+
+void vboxNetFltPortOsSetActive(PVBOXNETFLTINS pThis, bool fActive)
+{
+    struct net_device *pDev;
+    IPRT_LINUX_SAVE_EFL_AC();
+
+    LogFlow(("vboxNetFltPortOsSetActive: pThis=%p (%s), fActive=%RTbool, fDisablePromiscuous=%RTbool\n",
+             pThis, pThis->szName, fActive, pThis->fDisablePromiscuous));
+
+    if (pThis->fDisablePromiscuous)
+        return;
+
+    pDev = vboxNetFltLinuxRetainNetDev(pThis);
+    if (pDev)
+    {
+        /*
+         * This api is a bit weird, the best reference is the code.
+         *
+         * Also, we have a bit or race conditions wrt the maintenance of
+         * host the interface promiscuity for vboxNetFltPortOsIsPromiscuous.
+         */
+#ifdef LOG_ENABLED
+        u_int16_t fIf;
+        unsigned const cPromiscBefore = pDev->promiscuity;
+#endif
+        if (fActive)
+        {
+            Assert(!pThis->u.s.fPromiscuousSet);
+
+            rtnl_lock();
+            dev_set_promiscuity(pDev, 1);
+            rtnl_unlock();
+            pThis->u.s.fPromiscuousSet = true;
+            Log(("vboxNetFltPortOsSetActive: enabled promiscuous mode on %s (%d)\n", pThis->szName, pDev->promiscuity));
+        }
+        else
+        {
+            if (pThis->u.s.fPromiscuousSet)
+            {
+                rtnl_lock();
+                dev_set_promiscuity(pDev, -1);
+                rtnl_unlock();
+                Log(("vboxNetFltPortOsSetActive: disabled promiscuous mode on %s (%d)\n", pThis->szName, pDev->promiscuity));
+            }
+            pThis->u.s.fPromiscuousSet = false;
+
+#ifdef LOG_ENABLED
+            fIf = dev_get_flags(pDev);
+            Log(("VBoxNetFlt: fIf=%#x; %d->%d\n", fIf, cPromiscBefore, pDev->promiscuity));
+#endif
+        }
+
+        vboxNetFltLinuxReleaseNetDev(pThis, pDev);
+    }
+    IPRT_LINUX_RESTORE_EFL_AC();
+}
+
+
+int vboxNetFltOsDisconnectIt(PVBOXNETFLTINS pThis)
+{
+    /*
+     * Remove packet handler when we get disconnected from internal switch as
+     * we don't want the handler to forward packets to disconnected switch.
+     */
+    if (ASMAtomicCmpXchgBool(&pThis->u.s.fPacketHandler, false, true))
+    {
+        IPRT_LINUX_SAVE_EFL_AC();
+        dev_remove_pack(&pThis->u.s.PacketType);
+        Log(("vboxNetFltOsDisconnectIt: this=%p: Packet handler removed.\n", pThis));
+        IPRT_LINUX_RESTORE_EFL_AC();
+    }
+    return VINF_SUCCESS;
+}
+
+
+int  vboxNetFltOsConnectIt(PVBOXNETFLTINS pThis)
+{
+    IPRT_LINUX_SAVE_EFL_AC();
+
+    /*
+     * Report the GSO capabilities of the host and device (if connected).
+     * Note! No need to mark ourselves busy here.
+     */
+    /** @todo duplicate work here now? Attach */
+#if defined(VBOXNETFLT_WITH_GSO_XMIT_HOST)
+    Log3(("vboxNetFltOsConnectIt: reporting host tso tso6\n"));
+    pThis->pSwitchPort->pfnReportGsoCapabilities(pThis->pSwitchPort,
+                                                 0
+                                                 | RT_BIT_32(PDMNETWORKGSOTYPE_IPV4_TCP)
+                                                 | RT_BIT_32(PDMNETWORKGSOTYPE_IPV6_TCP)
+                                                 , INTNETTRUNKDIR_HOST);
+
+#endif
+    vboxNetFltLinuxReportNicGsoCapabilities(pThis);
+
+    IPRT_LINUX_RESTORE_EFL_AC();
+    return VINF_SUCCESS;
+}
+
+
+void vboxNetFltOsDeleteInstance(PVBOXNETFLTINS pThis)
+{
+    struct net_device  *pDev;
+    bool                fRegistered;
+    IPRT_LINUX_SAVE_EFL_AC();
+
+#ifdef VBOXNETFLT_WITH_HOST2WIRE_FILTER
+    vboxNetFltLinuxUnhookDev(pThis, NULL);
+#endif
+
+    /** @todo This code may race vboxNetFltLinuxUnregisterDevice (very very
+     *        unlikely, but none the less).  Since it doesn't actually update the
+     *        state (just reads it), it is likely to panic in some interesting
+     *        ways. */
+
+    RTSpinlockAcquire(pThis->hSpinlock);
+    pDev = ASMAtomicUoReadPtrT(&pThis->u.s.pDev, struct net_device *);
+    fRegistered = ASMAtomicXchgBool(&pThis->u.s.fRegistered, false);
+    RTSpinlockRelease(pThis->hSpinlock);
+
+    if (fRegistered)
+    {
+        vboxNetFltSetLinkState(pThis, pDev, false);
+
+#ifndef VBOXNETFLT_LINUX_NO_XMIT_QUEUE
+        skb_queue_purge(&pThis->u.s.XmitQueue);
+#endif
+        Log(("vboxNetFltOsDeleteInstance: this=%p: xmit queue purged.\n", pThis));
+        Log(("vboxNetFltOsDeleteInstance: Device %p(%s) released. ref=%d\n",
+             pDev, pDev->name,
+#if RTLNX_VER_MIN(2,6,37)
+             netdev_refcnt_read(pDev)
+#else
+             atomic_read(&pDev->refcnt)
+#endif
+             ));
+        dev_put(pDev);
+    }
+
+    unregister_inet6addr_notifier(&pThis->u.s.NotifierIPv6);
+    unregister_inetaddr_notifier(&pThis->u.s.NotifierIPv4);
+
+    Log(("vboxNetFltOsDeleteInstance: this=%p: Notifier removed.\n", pThis));
+    unregister_netdevice_notifier(&pThis->u.s.Notifier);
+    module_put(THIS_MODULE);
+
+    IPRT_LINUX_RESTORE_EFL_AC();
+}
+
+
+int  vboxNetFltOsInitInstance(PVBOXNETFLTINS pThis, void *pvContext)
+{
+    int err;
+    IPRT_LINUX_SAVE_EFL_AC();
+    NOREF(pvContext);
+
+    pThis->u.s.Notifier.notifier_call = vboxNetFltLinuxNotifierCallback;
+    err = register_netdevice_notifier(&pThis->u.s.Notifier);
+    if (err)
+    {
+        IPRT_LINUX_RESTORE_EFL_AC();
+        return VERR_INTNET_FLT_IF_FAILED;
+    }
+    if (!pThis->u.s.fRegistered)
+    {
+        unregister_netdevice_notifier(&pThis->u.s.Notifier);
+        LogRel(("VBoxNetFlt: failed to find %s.\n", pThis->szName));
+        IPRT_LINUX_RESTORE_EFL_AC();
+        return VERR_INTNET_FLT_IF_NOT_FOUND;
+    }
+
+    Log(("vboxNetFltOsInitInstance: this=%p: Notifier installed.\n", pThis));
+    if (   pThis->fDisconnectedFromHost
+        || !try_module_get(THIS_MODULE))
+    {
+        IPRT_LINUX_RESTORE_EFL_AC();
+        return VERR_INTNET_FLT_IF_FAILED;
+    }
+
+    if (pThis->pSwitchPort->pfnNotifyHostAddress)
+    {
+        VBOXNETFLTNOTIFIER Enumerator;
+
+        /*
+         * register_inetaddr_notifier() and register_inet6addr_notifier()
+         * do not call the callback for existing devices.  Enumerating
+         * all network devices explicitly is a bit of an ifdef mess,
+         * so co-opt register_netdevice_notifier() to do that for us.
+         */
+        RT_ZERO(Enumerator);
+        Enumerator.Notifier.notifier_call = vboxNetFltLinuxEnumeratorCallback;
+        Enumerator.pThis = pThis;
+
+        err = register_netdevice_notifier(&Enumerator.Notifier);
+        if (err)
+        {
+            LogRel(("%s: failed to enumerate network devices: error %d\n", __FUNCTION__, err));
+            IPRT_LINUX_RESTORE_EFL_AC();
+            return VINF_SUCCESS;
+        }
+
+        unregister_netdevice_notifier(&Enumerator.Notifier);
+
+        pThis->u.s.NotifierIPv4.notifier_call = vboxNetFltLinuxNotifierIPv4Callback;
+        err = register_inetaddr_notifier(&pThis->u.s.NotifierIPv4);
+        if (err)
+            LogRel(("%s: failed to register IPv4 notifier: error %d\n", __FUNCTION__, err));
+
+        pThis->u.s.NotifierIPv6.notifier_call = vboxNetFltLinuxNotifierIPv6Callback;
+        err = register_inet6addr_notifier(&pThis->u.s.NotifierIPv6);
+        if (err)
+            LogRel(("%s: failed to register IPv6 notifier: error %d\n", __FUNCTION__, err));
+    }
+
+    IPRT_LINUX_RESTORE_EFL_AC();
+    return VINF_SUCCESS;
+}
+
+int  vboxNetFltOsPreInitInstance(PVBOXNETFLTINS pThis)
+{
+    IPRT_LINUX_SAVE_EFL_AC();
+
+    /*
+     * Init the linux specific members.
+     */
+    ASMAtomicUoWriteNullPtr(&pThis->u.s.pDev);
+    pThis->u.s.fRegistered     = false;
+    pThis->u.s.fPromiscuousSet = false;
+    pThis->u.s.fPacketHandler  = false;
+    memset(&pThis->u.s.PacketType, 0, sizeof(pThis->u.s.PacketType));
+#ifndef VBOXNETFLT_LINUX_NO_XMIT_QUEUE
+    skb_queue_head_init(&pThis->u.s.XmitQueue);
+# if RTLNX_VER_MIN(2,6,20)
+    INIT_WORK(&pThis->u.s.XmitTask, vboxNetFltLinuxXmitTask);
+# else
+    INIT_WORK(&pThis->u.s.XmitTask, vboxNetFltLinuxXmitTask, &pThis->u.s.XmitTask);
+# endif
+#endif
+
+    IPRT_LINUX_RESTORE_EFL_AC();
+    return VINF_SUCCESS;
+}
+
+
+void vboxNetFltPortOsNotifyMacAddress(PVBOXNETFLTINS pThis, void *pvIfData, PCRTMAC pMac)
+{
+    NOREF(pThis); NOREF(pvIfData); NOREF(pMac);
+}
+
+
+int vboxNetFltPortOsConnectInterface(PVBOXNETFLTINS pThis, void *pvIf, void **pvIfData)
+{
+    /* Nothing to do */
+    NOREF(pThis); NOREF(pvIf); NOREF(pvIfData);
+    return VINF_SUCCESS;
+}
+
+
+int vboxNetFltPortOsDisconnectInterface(PVBOXNETFLTINS pThis, void *pvIfData)
+{
+    /* Nothing to do */
+    NOREF(pThis); NOREF(pvIfData);
+    return VINF_SUCCESS;
+}
+
diff --git a/src/VBox/HostDrivers/VBoxNetFlt/linux/files_vboxnetflt b/src/VBox/HostDrivers/VBoxNetFlt/linux/files_vboxnetflt
new file mode 100755
index 00000000..f2f8f1f4
--- /dev/null
+++ b/src/VBox/HostDrivers/VBoxNetFlt/linux/files_vboxnetflt
@@ -0,0 +1,113 @@
+#!/bin/sh
+# $Id: files_vboxnetflt $
+## @file
+# Shared file between Makefile.kmk and export_modules.sh.
+#
+
+#
+# Copyright (C) 2007-2023 Oracle and/or its affiliates.
+#
+# This file is part of VirtualBox base platform packages, as
+# available from https://www.virtualbox.org.
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License
+# as published by the Free Software Foundation, in version 3 of the
+# License.
+#
+# This program is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, see <https://www.gnu.org/licenses>.
+#
+# The contents of this file may alternatively be used under the terms
+# of the Common Development and Distribution License Version 1.0
+# (CDDL), a copy of it is provided in the "COPYING.CDDL" file included
+# in the VirtualBox distribution, in which case the provisions of the
+# CDDL are applicable instead of those of the GPL.
+#
+# You may elect to license modified versions of this file under the
+# terms and conditions of either the GPL or the CDDL or both.
+#
+# SPDX-License-Identifier: GPL-3.0-only OR CDDL-1.0
+#
+
+VBOX_VBOXNETFLT_SOURCES=" \
+    ${PATH_ROOT}/include/iprt/alloc.h=>include/iprt/alloc.h \
+    ${PATH_ROOT}/include/iprt/alloca.h=>include/iprt/alloca.h \
+    ${PATH_ROOT}/include/iprt/asm.h=>include/iprt/asm.h \
+    ${PATH_ROOT}/include/iprt/asm-amd64-x86.h=>include/iprt/asm-amd64-x86.h \
+    ${PATH_ROOT}/include/iprt/asm-math.h=>include/iprt/asm-math.h \
+    ${PATH_ROOT}/include/iprt/assert.h=>include/iprt/assert.h \
+    ${PATH_ROOT}/include/iprt/assertcompile.h=>include/iprt/assertcompile.h \
+    ${PATH_ROOT}/include/iprt/avl.h=>include/iprt/avl.h \
+    ${PATH_ROOT}/include/iprt/cdefs.h=>include/iprt/cdefs.h \
+    ${PATH_ROOT}/include/iprt/cpuset.h=>include/iprt/cpuset.h \
+    ${PATH_ROOT}/include/iprt/ctype.h=>include/iprt/ctype.h \
+    ${PATH_ROOT}/include/iprt/err.h=>include/iprt/err.h \
+    ${PATH_ROOT}/include/iprt/errcore.h=>include/iprt/errcore.h \
+    ${PATH_ROOT}/include/iprt/heap.h=>include/iprt/heap.h \
+    ${PATH_ROOT}/include/iprt/initterm.h=>include/iprt/initterm.h \
+    ${PATH_ROOT}/include/iprt/latin1.h=>include/iprt/latin1.h \
+    ${PATH_ROOT}/include/iprt/log.h=>include/iprt/log.h \
+    ${PATH_ROOT}/include/iprt/mangling.h=>include/iprt/mangling.h \
+    ${PATH_ROOT}/include/iprt/mem.h=>include/iprt/mem.h \
+    ${PATH_ROOT}/include/iprt/memobj.h=>include/iprt/memobj.h \
+    ${PATH_ROOT}/include/iprt/mp.h=>include/iprt/mp.h \
+    ${PATH_ROOT}/include/iprt/net.h=>include/iprt/net.h \
+    ${PATH_ROOT}/include/iprt/param.h=>include/iprt/param.h \
+    ${PATH_ROOT}/include/iprt/power.h=>include/iprt/power.h \
+    ${PATH_ROOT}/include/iprt/process.h=>include/iprt/process.h \
+    ${PATH_ROOT}/include/iprt/semaphore.h=>include/iprt/semaphore.h \
+    ${PATH_ROOT}/include/iprt/spinlock.h=>include/iprt/spinlock.h \
+    ${PATH_ROOT}/include/iprt/stdarg.h=>include/iprt/stdarg.h \
+    ${PATH_ROOT}/include/iprt/stdint.h=>include/iprt/stdint.h \
+    ${PATH_ROOT}/include/iprt/string.h=>include/iprt/string.h \
+    ${PATH_ROOT}/include/iprt/thread.h=>include/iprt/thread.h \
+    ${PATH_ROOT}/include/iprt/time.h=>include/iprt/time.h \
+    ${PATH_ROOT}/include/iprt/timer.h=>include/iprt/timer.h \
+    ${PATH_ROOT}/include/iprt/types.h=>include/iprt/types.h \
+    ${PATH_ROOT}/include/iprt/uint64.h=>include/iprt/uint64.h \
+    ${PATH_ROOT}/include/iprt/uni.h=>include/iprt/uni.h \
+    ${PATH_ROOT}/include/iprt/utf16.h=>include/iprt/utf16.h \
+    ${PATH_ROOT}/include/iprt/uuid.h=>include/iprt/uuid.h \
+    ${PATH_ROOT}/include/iprt/x86-helpers.h=>include/iprt/x86-helpers.h \
+    ${PATH_ROOT}/include/iprt/linux/version.h=>include/iprt/linux/version.h \
+    ${PATH_ROOT}/include/iprt/nocrt/limits.h=>include/iprt/nocrt/limits.h \
+    ${PATH_ROOT}/include/VBox/cdefs.h=>include/VBox/cdefs.h \
+    ${PATH_ROOT}/include/VBox/err.h=>include/VBox/err.h \
+    ${PATH_ROOT}/include/VBox/log.h=>include/VBox/log.h \
+    ${PATH_ROOT}/include/VBox/intnet.h=>include/VBox/intnet.h \
+    ${PATH_ROOT}/include/VBox/intnetinline.h=>include/VBox/intnetinline.h \
+    ${PATH_ROOT}/include/VBox/vmm/pdmnetinline.h=>include/VBox/vmm/pdmnetinline.h \
+    ${PATH_ROOT}/include/VBox/param.h=>include/VBox/param.h \
+    ${PATH_ROOT}/include/VBox/vmm/stam.h=>include/VBox/vmm/stam.h \
+    ${PATH_ROOT}/include/VBox/sup.h=>include/VBox/sup.h \
+    ${PATH_ROOT}/include/VBox/types.h=>include/VBox/types.h \
+    ${PATH_ROOT}/include/VBox/SUPDrvMangling.h=>include/VBox/SUPDrvMangling.h \
+    ${PATH_ROOT}/src/VBox/HostDrivers/VBoxNetFlt/linux/VBoxNetFlt-linux.c=>linux/VBoxNetFlt-linux.c \
+    ${PATH_ROOT}/src/VBox/HostDrivers/VBoxNetFlt/VBoxNetFlt.c=>VBoxNetFlt.c \
+    ${PATH_ROOT}/src/VBox/HostDrivers/VBoxNetFlt/VBoxNetFltInternal.h=>VBoxNetFltInternal.h \
+    ${PATH_ROOT}/src/VBox/HostDrivers/Support/SUPDrvIDC.h=>SUPDrvIDC.h \
+    ${PATH_ROOT}/src/VBox/HostDrivers/Support/SUPR0IdcClient.c=>SUPR0IdcClient.c \
+    ${PATH_ROOT}/src/VBox/HostDrivers/Support/SUPR0IdcClientComponent.c=>SUPR0IdcClientComponent.c \
+    ${PATH_ROOT}/src/VBox/HostDrivers/Support/SUPR0IdcClientInternal.h=>SUPR0IdcClientInternal.h \
+    ${PATH_ROOT}/src/VBox/HostDrivers/Support/linux/SUPR0IdcClient-linux.c=>linux/SUPR0IdcClient-linux.c \
+    ${PATH_ROOT}/src/VBox/Installer/linux/Makefile-footer.gmk=>Makefile-footer.gmk \
+    ${PATH_ROOT}/src/VBox/Installer/linux/Makefile-header.gmk=>Makefile-header.gmk \
+    ${PATH_ROOT}/src/VBox/Runtime/common/math/gcc/divdi3.c=>math/gcc/divdi3.c \
+    ${PATH_ROOT}/src/VBox/Runtime/common/math/gcc/moddi3.c=>math/gcc/moddi3.c \
+    ${PATH_ROOT}/src/VBox/Runtime/common/math/gcc/qdivrem.c=>math/gcc/qdivrem.c \
+    ${PATH_ROOT}/src/VBox/Runtime/common/math/gcc/quad.h=>math/gcc/quad.h \
+    ${PATH_ROOT}/src/VBox/Runtime/common/math/gcc/udivdi3.c=>math/gcc/udivdi3.c \
+    ${PATH_ROOT}/src/VBox/Runtime/common/math/gcc/udivmoddi4.c=>math/gcc/udivmoddi4.c \
+    ${PATH_ROOT}/src/VBox/Runtime/common/math/gcc/umoddi3.c=>math/gcc/umoddi3.c \
+    ${PATH_ROOT}/src/VBox/Runtime/r0drv/linux/the-linux-kernel.h=>r0drv/linux/the-linux-kernel.h \
+    ${PATH_OUT}/version-generated.h=>version-generated.h \
+    ${PATH_OUT}/revision-generated.h=>revision-generated.h \
+    ${PATH_OUT}/product-generated.h=>product-generated.h \
+"
+