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, 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
  31 MODULE_AUTHOR("Nick Fedchik <nick@fedchik.org.ua>");
  32 MODULE_DESCRIPTION("Ebtables: 802.1Q VLAN tag match");
  33 MODULE_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
  38 static bool
  39 ebt_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
  89 static 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
 159 static 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
 169 static 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
 175 static void __exit ebt_vlan_fini(void)
 176 {
 177         xt_unregister_match(&ebt_vlan_mt_reg);
 178 }
 179
 180 module_init(ebt_vlan_init);
 181 module_exit(ebt_vlan_fini);