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root/net/bridge/netfilter/ebt_vlan.c

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DEFINITIONS

This source file includes following definitions.
  1. ebt_vlan_mt
  2. ebt_vlan_mt_check
  3. ebt_vlan_init
  4. ebt_vlan_fini

/*
 * Description: EBTables 802.1Q match extension kernelspace module.
 * Authors: Nick Fedchik <nick@fedchik.org.ua>
 *          Bart De Schuymer <bdschuym@pandora.be>
 *
 * 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; either version 2 of the License, or
 * (at your option) any later version.
 *
 * 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, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#include <linux/if_ether.h>
#include <linux/if_vlan.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/netfilter/x_tables.h>
#include <linux/netfilter_bridge/ebtables.h>
#include <linux/netfilter_bridge/ebt_vlan.h>

static int debug;
#define MODULE_VERS "0.6"

module_param(debug, int, 0);
MODULE_PARM_DESC(debug, "debug=1 is turn on debug messages");
MODULE_AUTHOR("Nick Fedchik <nick@fedchik.org.ua>");
MODULE_DESCRIPTION("Ebtables: 802.1Q VLAN tag match");
MODULE_LICENSE("GPL");


#define DEBUG_MSG(args...) if (debug) printk (KERN_DEBUG "ebt_vlan: " args)
#define GET_BITMASK(_BIT_MASK_) info->bitmask & _BIT_MASK_
#define EXIT_ON_MISMATCH(_MATCH_,_MASK_) {if (!((info->_MATCH_ == _MATCH_)^!!(info->invflags & _MASK_))) return false; }

static bool
ebt_vlan_mt(const struct sk_buff *skb, const struct xt_match_param *par)
{
        const struct ebt_vlan_info *info = par->matchinfo;
        const struct vlan_hdr *fp;
        struct vlan_hdr _frame;

        unsigned short TCI;     /* Whole TCI, given from parsed frame */
        unsigned short id;      /* VLAN ID, given from frame TCI */
        unsigned char prio;     /* user_priority, given from frame TCI */
        /* VLAN encapsulated Type/Length field, given from orig frame */
        __be16 encap;

        fp = skb_header_pointer(skb, 0, sizeof(_frame), &_frame);
        if (fp == NULL)
                return false;

        /* Tag Control Information (TCI) consists of the following elements:
         * - User_priority. The user_priority field is three bits in length,
         * interpreted as a binary number.
         * - Canonical Format Indicator (CFI). The Canonical Format Indicator
         * (CFI) is a single bit flag value. Currently ignored.
         * - VLAN Identifier (VID). The VID is encoded as
         * an unsigned binary number. */
        TCI = ntohs(fp->h_vlan_TCI);
        id = TCI & VLAN_VID_MASK;
        prio = (TCI >> 13) & 0x7;
        encap = fp->h_vlan_encapsulated_proto;

        /* Checking VLAN Identifier (VID) */
        if (GET_BITMASK(EBT_VLAN_ID))
                EXIT_ON_MISMATCH(id, EBT_VLAN_ID);

        /* Checking user_priority */
        if (GET_BITMASK(EBT_VLAN_PRIO))
                EXIT_ON_MISMATCH(prio, EBT_VLAN_PRIO);

        /* Checking Encapsulated Proto (Length/Type) field */
        if (GET_BITMASK(EBT_VLAN_ENCAP))
                EXIT_ON_MISMATCH(encap, EBT_VLAN_ENCAP);

        return true;
}

static bool ebt_vlan_mt_check(const struct xt_mtchk_param *par)
{
        struct ebt_vlan_info *info = par->matchinfo;
        const struct ebt_entry *e = par->entryinfo;

        /* Is it 802.1Q frame checked? */
        if (e->ethproto != htons(ETH_P_8021Q)) {
                DEBUG_MSG
                    ("passed entry proto %2.4X is not 802.1Q (8100)\n",
                     (unsigned short) ntohs(e->ethproto));
                return false;
        }

        /* Check for bitmask range
         * True if even one bit is out of mask */
        if (info->bitmask & ~EBT_VLAN_MASK) {
                DEBUG_MSG("bitmask %2X is out of mask (%2X)\n",
                          info->bitmask, EBT_VLAN_MASK);
                return false;
        }

        /* Check for inversion flags range */
        if (info->invflags & ~EBT_VLAN_MASK) {
                DEBUG_MSG("inversion flags %2X is out of mask (%2X)\n",
                          info->invflags, EBT_VLAN_MASK);
                return false;
        }

        /* Reserved VLAN ID (VID) values
         * -----------------------------
         * 0 - The null VLAN ID.
         * 1 - The default Port VID (PVID)
         * 0x0FFF - Reserved for implementation use.
         * if_vlan.h: VLAN_GROUP_ARRAY_LEN 4096. */
        if (GET_BITMASK(EBT_VLAN_ID)) {
                if (!!info->id) { /* if id!=0 => check vid range */
                        if (info->id > VLAN_GROUP_ARRAY_LEN) {
                                DEBUG_MSG
                                    ("id %d is out of range (1-4096)\n",
                                     info->id);
                                return false;
                        }
                        /* Note: This is valid VLAN-tagged frame point.
                         * Any value of user_priority are acceptable,
                         * but should be ignored according to 802.1Q Std.
                         * So we just drop the prio flag. */
                        info->bitmask &= ~EBT_VLAN_PRIO;
                }
                /* Else, id=0 (null VLAN ID)  => user_priority range (any?) */
        }

        if (GET_BITMASK(EBT_VLAN_PRIO)) {
                if ((unsigned char) info->prio > 7) {
                        DEBUG_MSG("prio %d is out of range (0-7)\n",
                             info->prio);
                        return false;
                }
        }
        /* Check for encapsulated proto range - it is possible to be
         * any value for u_short range.
         * if_ether.h:  ETH_ZLEN        60   -  Min. octets in frame sans FCS */
        if (GET_BITMASK(EBT_VLAN_ENCAP)) {
                if ((unsigned short) ntohs(info->encap) < ETH_ZLEN) {
                        DEBUG_MSG
                            ("encap frame length %d is less than minimal\n",
                             ntohs(info->encap));
                        return false;
                }
        }

        return true;
}

static struct xt_match ebt_vlan_mt_reg __read_mostly = {
        .name           = "vlan",
        .revision       = 0,
        .family         = NFPROTO_BRIDGE,
        .match          = ebt_vlan_mt,
        .checkentry     = ebt_vlan_mt_check,
        .matchsize      = XT_ALIGN(sizeof(struct ebt_vlan_info)),
        .me             = THIS_MODULE,
};

static int __init ebt_vlan_init(void)
{
        DEBUG_MSG("ebtables 802.1Q extension module v"
                  MODULE_VERS "\n");
        DEBUG_MSG("module debug=%d\n", !!debug);
        return xt_register_match(&ebt_vlan_mt_reg);
}

static void __exit ebt_vlan_fini(void)
{
        xt_unregister_match(&ebt_vlan_mt_reg);
}

module_init(ebt_vlan_init);
module_exit(ebt_vlan_fini);

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