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* Description: EBTables 802.1Q match extension kernelspace module.
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* Authors: Nick Fedchik <nick@fedchik.org.ua>
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* Bart De Schuymer <bdschuym@pandora.be>
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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#include <linux/if_ether.h>
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#include <linux/if_vlan.h>
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#include <linux/module.h>
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#include <linux/moduleparam.h>
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#include <linux/netfilter/x_tables.h>
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#include <linux/netfilter_bridge/ebtables.h>
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#include <linux/netfilter_bridge/ebt_vlan.h>
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#define MODULE_VERS "0.6"
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MODULE_AUTHOR("Nick Fedchik <nick@fedchik.org.ua>");
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MODULE_DESCRIPTION("Ebtables: 802.1Q VLAN tag match");
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MODULE_LICENSE("GPL");
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#define GET_BITMASK(_BIT_MASK_) info->bitmask & _BIT_MASK_
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#define EXIT_ON_MISMATCH(_MATCH_,_MASK_) {if (!((info->_MATCH_ == _MATCH_)^!!(info->invflags & _MASK_))) return false; }
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ebt_vlan_mt(const struct sk_buff *skb, struct xt_action_param *par)
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const struct ebt_vlan_info *info = par->matchinfo;
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unsigned short TCI; /* Whole TCI, given from parsed frame */
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unsigned short id; /* VLAN ID, given from frame TCI */
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unsigned char prio; /* user_priority, given from frame TCI */
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/* VLAN encapsulated Type/Length field, given from orig frame */
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if (vlan_tx_tag_present(skb)) {
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TCI = vlan_tx_tag_get(skb);
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encap = skb->protocol;
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const struct vlan_hdr *fp;
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struct vlan_hdr _frame;
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fp = skb_header_pointer(skb, 0, sizeof(_frame), &_frame);
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TCI = ntohs(fp->h_vlan_TCI);
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encap = fp->h_vlan_encapsulated_proto;
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/* Tag Control Information (TCI) consists of the following elements:
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* - User_priority. The user_priority field is three bits in length,
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* interpreted as a binary number.
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* - Canonical Format Indicator (CFI). The Canonical Format Indicator
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* (CFI) is a single bit flag value. Currently ignored.
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* - VLAN Identifier (VID). The VID is encoded as
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* an unsigned binary number. */
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id = TCI & VLAN_VID_MASK;
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prio = (TCI >> 13) & 0x7;
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/* Checking VLAN Identifier (VID) */
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if (GET_BITMASK(EBT_VLAN_ID))
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EXIT_ON_MISMATCH(id, EBT_VLAN_ID);
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/* Checking user_priority */
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if (GET_BITMASK(EBT_VLAN_PRIO))
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EXIT_ON_MISMATCH(prio, EBT_VLAN_PRIO);
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/* Checking Encapsulated Proto (Length/Type) field */
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if (GET_BITMASK(EBT_VLAN_ENCAP))
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EXIT_ON_MISMATCH(encap, EBT_VLAN_ENCAP);
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static int ebt_vlan_mt_check(const struct xt_mtchk_param *par)
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struct ebt_vlan_info *info = par->matchinfo;
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const struct ebt_entry *e = par->entryinfo;
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/* Is it 802.1Q frame checked? */
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if (e->ethproto != htons(ETH_P_8021Q)) {
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pr_debug("passed entry proto %2.4X is not 802.1Q (8100)\n",
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/* Check for bitmask range
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* True if even one bit is out of mask */
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if (info->bitmask & ~EBT_VLAN_MASK) {
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pr_debug("bitmask %2X is out of mask (%2X)\n",
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info->bitmask, EBT_VLAN_MASK);
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/* Check for inversion flags range */
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if (info->invflags & ~EBT_VLAN_MASK) {
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pr_debug("inversion flags %2X is out of mask (%2X)\n",
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info->invflags, EBT_VLAN_MASK);
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/* Reserved VLAN ID (VID) values
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* -----------------------------
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* 0 - The null VLAN ID.
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* 1 - The default Port VID (PVID)
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* 0x0FFF - Reserved for implementation use.
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* if_vlan.h: VLAN_N_VID 4096. */
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if (GET_BITMASK(EBT_VLAN_ID)) {
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if (!!info->id) { /* if id!=0 => check vid range */
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if (info->id > VLAN_N_VID) {
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pr_debug("id %d is out of range (1-4096)\n",
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/* Note: This is valid VLAN-tagged frame point.
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* Any value of user_priority are acceptable,
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* but should be ignored according to 802.1Q Std.
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* So we just drop the prio flag. */
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info->bitmask &= ~EBT_VLAN_PRIO;
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/* Else, id=0 (null VLAN ID) => user_priority range (any?) */
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if (GET_BITMASK(EBT_VLAN_PRIO)) {
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if ((unsigned char) info->prio > 7) {
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pr_debug("prio %d is out of range (0-7)\n",
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/* Check for encapsulated proto range - it is possible to be
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* any value for u_short range.
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* if_ether.h: ETH_ZLEN 60 - Min. octets in frame sans FCS */
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if (GET_BITMASK(EBT_VLAN_ENCAP)) {
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if ((unsigned short) ntohs(info->encap) < ETH_ZLEN) {
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pr_debug("encap frame length %d is less than "
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"minimal\n", ntohs(info->encap));
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static struct xt_match ebt_vlan_mt_reg __read_mostly = {
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.family = NFPROTO_BRIDGE,
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.match = ebt_vlan_mt,
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.checkentry = ebt_vlan_mt_check,
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.matchsize = sizeof(struct ebt_vlan_info),
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static int __init ebt_vlan_init(void)
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pr_debug("ebtables 802.1Q extension module v" MODULE_VERS "\n");
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return xt_register_match(&ebt_vlan_mt_reg);
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static void __exit ebt_vlan_fini(void)
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xt_unregister_match(&ebt_vlan_mt_reg);
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module_init(ebt_vlan_init);
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module_exit(ebt_vlan_fini);