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 (skb_vlan_tag_present(skb)) {
  49                 TCI = skb_vlan_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          */
  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          */
 104         if (info->bitmask & ~EBT_VLAN_MASK) {
 105                 pr_debug("bitmask %2X is out of mask (%2X)\n",
 106                          info->bitmask, EBT_VLAN_MASK);
 107                 return -EINVAL;
 108         }
 109
 110         /* Check for inversion flags range */
 111         if (info->invflags & ~EBT_VLAN_MASK) {
 112                 pr_debug("inversion flags %2X is out of mask (%2X)\n",
 113                          info->invflags, EBT_VLAN_MASK);
 114                 return -EINVAL;
 115         }
 116
 117         /* Reserved VLAN ID (VID) values
 118          * -----------------------------
 119          * 0 - The null VLAN ID.
 120          * 1 - The default Port VID (PVID)
 121          * 0x0FFF - Reserved for implementation use.
 122          * if_vlan.h: VLAN_N_VID 4096.
 123          */
 124         if (GET_BITMASK(EBT_VLAN_ID)) {
 125                 if (!!info->id) { /* if id!=0 => check vid range */
 126                         if (info->id > VLAN_N_VID) {
 127                                 pr_debug("id %d is out of range (1-4096)\n",
 128                                          info->id);
 129                                 return -EINVAL;
 130                         }
 131                         /* Note: This is valid VLAN-tagged frame point.
 132                          * Any value of user_priority are acceptable,
 133                          * but should be ignored according to 802.1Q Std.
 134                          * So we just drop the prio flag.
 135                          */
 136                         info->bitmask &= ~EBT_VLAN_PRIO;
 137                 }
 138                 /* Else, id=0 (null VLAN ID)  => user_priority range (any?) */
 139         }
 140
 141         if (GET_BITMASK(EBT_VLAN_PRIO)) {
 142                 if ((unsigned char) info->prio > 7) {
 143                         pr_debug("prio %d is out of range (0-7)\n",
 144                                  info->prio);
 145                         return -EINVAL;
 146                 }
 147         }
 148         /* Check for encapsulated proto range - it is possible to be
 149          * any value for u_short range.
 150          * if_ether.h:  ETH_ZLEN        60   -  Min. octets in frame sans FCS
 151          */
 152         if (GET_BITMASK(EBT_VLAN_ENCAP)) {
 153                 if ((unsigned short) ntohs(info->encap) < ETH_ZLEN) {
 154                         pr_debug("encap frame length %d is less than "
 155                                  "minimal\n", ntohs(info->encap));
 156                         return -EINVAL;
 157                 }
 158         }
 159
 160         return 0;
 161 }
 162
 163 static struct xt_match ebt_vlan_mt_reg __read_mostly = {
 164         .name           = "vlan",
 165         .revision       = 0,
 166         .family         = NFPROTO_BRIDGE,
 167         .match          = ebt_vlan_mt,
 168         .checkentry     = ebt_vlan_mt_check,
 169         .matchsize      = sizeof(struct ebt_vlan_info),
 170         .me             = THIS_MODULE,
 171 };
 172
 173 static int __init ebt_vlan_init(void)
 174 {
 175         pr_debug("ebtables 802.1Q extension module v" MODULE_VERS "\n");
 176         return xt_register_match(&ebt_vlan_mt_reg);
 177 }
 178
 179 static void __exit ebt_vlan_fini(void)
 180 {
 181         xt_unregister_match(&ebt_vlan_mt_reg);
 182 }
 183
 184 module_init(ebt_vlan_init);
 185 module_exit(ebt_vlan_fini);