LXR linux/net/bridge/netfilter/ebt

   1/*
   2 * Description: EBTables 802.1Q match extension kernelspace module.
   3 * Authors: Nick Fedchik <nick@fedchik.org.ua>
   4 *          Bart De Schuymer <bdschuym@pandora.be>
   5 *
   6 * This program is free software; you can redistribute it and/or modify
   7 * it under the terms of the GNU General Public License as published by
   8 * the Free Software Foundation; either version 2 of the License, or
   9 * (at your option) any later version.
  10 *
  11 * This program is distributed in the hope that it will be useful,
  12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 * GNU General Public License for more details.
  15 *
  16 * You should have received a copy of the GNU General Public License
  17 * along with this program; if not, write to the Free Software
  18 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  19 */
  20
  21#include <linux/if_ether.h>
  22#include <linux/if_vlan.h>
  23#include <linux/module.h>
  24#include <linux/moduleparam.h>
  25#include <linux/netfilter/x_tables.h>
  26#include <linux/netfilter_bridge/ebtables.h>
  27#include <linux/netfilter_bridge/ebt_vlan.h>
  28
  29#define MODULE_VERS "0.6"
  30
  31MODULE_AUTHOR("Nick Fedchik <nick@fedchik.org.ua>");
  32MODULE_DESCRIPTION("Ebtables: 802.1Q VLAN tag match");
  33MODULE_LICENSE("GPL");
  34
  35#define GET_BITMASK(_BIT_MASK_) info->bitmask & _BIT_MASK_
  36#define EXIT_ON_MISMATCH(_MATCH_,_MASK_) {if (!((info->_MATCH_ == _MATCH_)^!!(info->invflags & _MASK_))) return false; }
  37
  38static bool
  39ebt_vlan_mt(const struct sk_buff *skb, struct xt_action_param *par)
  40{
  41        const struct ebt_vlan_info *info = par->matchinfo;
  42
  43        unsigned short TCI;     /* Whole TCI, given from parsed frame */
  44        unsigned short id;      /* VLAN ID, given from frame TCI */
  45        unsigned char prio;     /* user_priority, given from frame TCI */
  46        /* VLAN encapsulated Type/Length field, given from orig frame */
  47        __be16 encap;
  48
  49        if (vlan_tx_tag_present(skb)) {
  50                TCI = vlan_tx_tag_get(skb);
  51                encap = skb->protocol;
  52        } else {
  53                const struct vlan_hdr *fp;
  54                struct vlan_hdr _frame;
  55
  56                fp = skb_header_pointer(skb, 0, sizeof(_frame), &_frame);
  57                if (fp == NULL)
  58                        return false;
  59
  60                TCI = ntohs(fp->h_vlan_TCI);
  61                encap = fp->h_vlan_encapsulated_proto;
  62        }
  63
  64        /* Tag Control Information (TCI) consists of the following elements:
  65         * - User_priority. The user_priority field is three bits in length,
  66         * interpreted as a binary number.
  67         * - Canonical Format Indicator (CFI). The Canonical Format Indicator
  68         * (CFI) is a single bit flag value. Currently ignored.
  69         * - VLAN Identifier (VID). The VID is encoded as
  70         * an unsigned binary number. */
  71        id = TCI & VLAN_VID_MASK;
  72        prio = (TCI >> 13) & 0x7;
  73
  74        /* Checking VLAN Identifier (VID) */
  75        if (GET_BITMASK(EBT_VLAN_ID))
  76                EXIT_ON_MISMATCH(id, EBT_VLAN_ID);
  77
  78        /* Checking user_priority */
  79        if (GET_BITMASK(EBT_VLAN_PRIO))
  80                EXIT_ON_MISMATCH(prio, EBT_VLAN_PRIO);
  81
  82        /* Checking Encapsulated Proto (Length/Type) field */
  83        if (GET_BITMASK(EBT_VLAN_ENCAP))
  84                EXIT_ON_MISMATCH(encap, EBT_VLAN_ENCAP);
  85
  86        return true;
  87}
  88
  89static int ebt_vlan_mt_check(const struct xt_mtchk_param *par)
  90{
  91        struct ebt_vlan_info *info = par->matchinfo;
  92        const struct ebt_entry *e = par->entryinfo;
  93
  94        /* Is it 802.1Q frame checked? */
  95        if (e->ethproto != htons(ETH_P_8021Q)) {
  96                pr_debug("passed entry proto %2.4X is not 802.1Q (8100)\n",
  97                         ntohs(e->ethproto));
  98                return -EINVAL;
  99        }
 100
 101        /* Check for bitmask range
 102         * True if even one bit is out of mask */
 103        if (info->bitmask & ~EBT_VLAN_MASK) {
 104                pr_debug("bitmask %2X is out of mask (%2X)\n",
 105                         info->bitmask, EBT_VLAN_MASK);
 106                return -EINVAL;
 107        }
 108
 109        /* Check for inversion flags range */
 110        if (info->invflags & ~EBT_VLAN_MASK) {
 111                pr_debug("inversion flags %2X is out of mask (%2X)\n",
 112                         info->invflags, EBT_VLAN_MASK);
 113                return -EINVAL;
 114        }
 115
 116        /* Reserved VLAN ID (VID) values
 117         * -----------------------------
 118         * 0 - The null VLAN ID.
 119         * 1 - The default Port VID (PVID)
 120         * 0x0FFF - Reserved for implementation use.
 121         * if_vlan.h: VLAN_N_VID 4096. */
 122        if (GET_BITMASK(EBT_VLAN_ID)) {
 123                if (!!info->id) { /* if id!=0 => check vid range */
 124                        if (info->id > VLAN_N_VID) {
 125                                pr_debug("id %d is out of range (1-4096)\n",
 126                                         info->id);
 127                                return -EINVAL;
 128                        }
 129                        /* Note: This is valid VLAN-tagged frame point.
 130                         * Any value of user_priority are acceptable,
 131                         * but should be ignored according to 802.1Q Std.
 132                         * So we just drop the prio flag. */
 133                        info->bitmask &= ~EBT_VLAN_PRIO;
 134                }
 135                /* Else, id=0 (null VLAN ID)  => user_priority range (any?) */
 136        }
 137
 138        if (GET_BITMASK(EBT_VLAN_PRIO)) {
 139                if ((unsigned char) info->prio > 7) {
 140                        pr_debug("prio %d is out of range (0-7)\n",
 141                                 info->prio);
 142                        return -EINVAL;
 143                }
 144        }
 145        /* Check for encapsulated proto range - it is possible to be
 146         * any value for u_short range.
 147         * if_ether.h:  ETH_ZLEN        60   -  Min. octets in frame sans FCS */
 148        if (GET_BITMASK(EBT_VLAN_ENCAP)) {
 149                if ((unsigned short) ntohs(info->encap) < ETH_ZLEN) {
 150                        pr_debug("encap frame length %d is less than "
 151                                 "minimal\n", ntohs(info->encap));
 152                        return -EINVAL;
 153                }
 154        }
 155
 156        return 0;
 157}
 158
 159static struct xt_match ebt_vlan_mt_reg __read_mostly = {
 160        .name           = "vlan",
 161        .revision       = 0,
 162        .family         = NFPROTO_BRIDGE,
 163        .match          = ebt_vlan_mt,
 164        .checkentry     = ebt_vlan_mt_check,
 165        .matchsize      = sizeof(struct ebt_vlan_info),
 166        .me             = THIS_MODULE,
 167};
 168
 169static int __init ebt_vlan_init(void)
 170{
 171        pr_debug("ebtables 802.1Q extension module v" MODULE_VERS "\n");
 172        return xt_register_match(&ebt_vlan_mt_reg);
 173}
 174
 175static void __exit ebt_vlan_fini(void)
 176{
 177        xt_unregister_match(&ebt_vlan_mt_reg);
 178}
 179
 180module_init(ebt_vlan_init);
 181module_exit(ebt_vlan_fini);
 182