net/bridge/netfilter/ebt_vlan.c

   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, see <http://www.gnu.org/licenses/>.
  18  */
  19
  20 #include <linux/if_ether.h>
  21 #include <linux/if_vlan.h>
  22 #include <linux/module.h>
  23 #include <linux/moduleparam.h>
  24 #include <linux/netfilter/x_tables.h>
  25 #include <linux/netfilter_bridge/ebtables.h>
  26 #include <linux/netfilter_bridge/ebt_vlan.h>
  27
  28 #define MODULE_VERS "0.6"
  29
  30 MODULE_AUTHOR("Nick Fedchik <nick@fedchik.org.ua>");
  31 MODULE_DESCRIPTION("Ebtables: 802.1Q VLAN tag match");
  32 MODULE_LICENSE("GPL");
  33
  34 #define GET_BITMASK(_BIT_MASK_) info->bitmask & _BIT_MASK_
  35 #define EXIT_ON_MISMATCH(_MATCH_,_MASK_) {if (!((info->_MATCH_ == _MATCH_)^!!(info->invflags & _MASK_))) return false; }
  36
  37 static bool
  38 ebt_vlan_mt(const struct sk_buff *skb, struct xt_action_param *par)
  39 {
  40         const struct ebt_vlan_info *info = par->matchinfo;
  41
  42         unsigned short TCI;     /* Whole TCI, given from parsed frame */
  43         unsigned short id;      /* VLAN ID, given from frame TCI */
  44         unsigned char prio;     /* user_priority, given from frame TCI */
  45         /* VLAN encapsulated Type/Length field, given from orig frame */
  46         __be16 encap;
  47
  48         if (vlan_tx_tag_present(skb)) {
  49                 TCI = vlan_tx_tag_get(skb);
  50                 encap = skb->protocol;
  51         } else {
  52                 const struct vlan_hdr *fp;
  53                 struct vlan_hdr _frame;
  54
  55                 fp = skb_header_pointer(skb, 0, sizeof(_frame), &_frame);
  56                 if (fp == NULL)
  57                         return false;
  58
  59                 TCI = ntohs(fp->h_vlan_TCI);
  60                 encap = fp->h_vlan_encapsulated_proto;
  61         }
  62
  63         /* Tag Control Information (TCI) consists of the following elements:
  64          * - User_priority. The user_priority field is three bits in length,
  65          * interpreted as a binary number.
  66          * - Canonical Format Indicator (CFI). The Canonical Format Indicator
  67          * (CFI) is a single bit flag value. Currently ignored.
  68          * - VLAN Identifier (VID). The VID is encoded as
  69          * an unsigned binary number. */
  70         id = TCI & VLAN_VID_MASK;
  71         prio = (TCI >> 13) & 0x7;
  72
  73         /* Checking VLAN Identifier (VID) */
  74         if (GET_BITMASK(EBT_VLAN_ID))
  75                 EXIT_ON_MISMATCH(id, EBT_VLAN_ID);
  76
  77         /* Checking user_priority */
  78         if (GET_BITMASK(EBT_VLAN_PRIO))
  79                 EXIT_ON_MISMATCH(prio, EBT_VLAN_PRIO);
  80
  81         /* Checking Encapsulated Proto (Length/Type) field */
  82         if (GET_BITMASK(EBT_VLAN_ENCAP))
  83                 EXIT_ON_MISMATCH(encap, EBT_VLAN_ENCAP);
  84
  85         return true;
  86 }
  87
  88 static int ebt_vlan_mt_check(const struct xt_mtchk_param *par)
  89 {
  90         struct ebt_vlan_info *info = par->matchinfo;
  91         const struct ebt_entry *e = par->entryinfo;
  92
  93         /* Is it 802.1Q frame checked? */
  94         if (e->ethproto != htons(ETH_P_8021Q)) {
  95                 pr_debug("passed entry proto %2.4X is not 802.1Q (8100)\n",
  96                          ntohs(e->ethproto));
  97                 return -EINVAL;
  98         }
  99
 100         /* Check for bitmask range
 101          * True if even one bit is out of mask */
 102         if (info->bitmask & ~EBT_VLAN_MASK) {
 103                 pr_debug("bitmask %2X is out of mask (%2X)\n",
 104                          info->bitmask, EBT_VLAN_MASK);
 105                 return -EINVAL;
 106         }
 107
 108         /* Check for inversion flags range */
 109         if (info->invflags & ~EBT_VLAN_MASK) {
 110                 pr_debug("inversion flags %2X is out of mask (%2X)\n",
 111                          info->invflags, EBT_VLAN_MASK);
 112                 return -EINVAL;
 113         }
 114
 115         /* Reserved VLAN ID (VID) values
 116          * -----------------------------
 117          * 0 - The null VLAN ID.
 118          * 1 - The default Port VID (PVID)
 119          * 0x0FFF - Reserved for implementation use.
 120          * if_vlan.h: VLAN_N_VID 4096. */
 121         if (GET_BITMASK(EBT_VLAN_ID)) {
 122                 if (!!info->id) { /* if id!=0 => check vid range */
 123                         if (info->id > VLAN_N_VID) {
 124                                 pr_debug("id %d is out of range (1-4096)\n",
 125                                          info->id);
 126                                 return -EINVAL;
 127                         }
 128                         /* Note: This is valid VLAN-tagged frame point.
 129                          * Any value of user_priority are acceptable,
 130                          * but should be ignored according to 802.1Q Std.
 131                          * So we just drop the prio flag. */
 132                         info->bitmask &= ~EBT_VLAN_PRIO;
 133                 }
 134                 /* Else, id=0 (null VLAN ID)  => user_priority range (any?) */
 135         }
 136
 137         if (GET_BITMASK(EBT_VLAN_PRIO)) {
 138                 if ((unsigned char) info->prio > 7) {
 139                         pr_debug("prio %d is out of range (0-7)\n",
 140                                  info->prio);
 141                         return -EINVAL;
 142                 }
 143         }
 144         /* Check for encapsulated proto range - it is possible to be
 145          * any value for u_short range.
 146          * if_ether.h:  ETH_ZLEN        60   -  Min. octets in frame sans FCS */
 147         if (GET_BITMASK(EBT_VLAN_ENCAP)) {
 148                 if ((unsigned short) ntohs(info->encap) < ETH_ZLEN) {
 149                         pr_debug("encap frame length %d is less than "
 150                                  "minimal\n", ntohs(info->encap));
 151                         return -EINVAL;
 152                 }
 153         }
 154
 155         return 0;
 156 }
 157
 158 static struct xt_match ebt_vlan_mt_reg __read_mostly = {
 159         .name           = "vlan",
 160         .revision       = 0,
 161         .family         = NFPROTO_BRIDGE,
 162         .match          = ebt_vlan_mt,
 163         .checkentry     = ebt_vlan_mt_check,
 164         .matchsize      = sizeof(struct ebt_vlan_info),
 165         .me             = THIS_MODULE,
 166 };
 167
 168 static int __init ebt_vlan_init(void)
 169 {
 170         pr_debug("ebtables 802.1Q extension module v" MODULE_VERS "\n");
 171         return xt_register_match(&ebt_vlan_mt_reg);
 172 }
 173
 174 static void __exit ebt_vlan_fini(void)
 175 {
 176         xt_unregister_match(&ebt_vlan_mt_reg);
 177 }
 178
 179 module_init(ebt_vlan_init);
 180 module_exit(ebt_vlan_fini);