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 static int debug;
  30 #define MODULE_VERS "0.6"
  31
  32 module_param(debug, int, 0);
  33 MODULE_PARM_DESC(debug, "debug=1 is turn on debug messages");
  34 MODULE_AUTHOR("Nick Fedchik <nick@fedchik.org.ua>");
  35 MODULE_DESCRIPTION("Ebtables: 802.1Q VLAN tag match");
  36 MODULE_LICENSE("GPL");
  37
  38
  39 #define DEBUG_MSG(args...) if (debug) printk (KERN_DEBUG "ebt_vlan: " args)
  40 #define GET_BITMASK(_BIT_MASK_) info->bitmask & _BIT_MASK_
  41 #define EXIT_ON_MISMATCH(_MATCH_,_MASK_) {if (!((info->_MATCH_ == _MATCH_)^!!(info->invflags & _MASK_))) return false; }
  42
  43 static bool
  44 ebt_vlan_mt(const struct sk_buff *skb, const struct xt_match_param *par)
  45 {
  46         const struct ebt_vlan_info *info = par->matchinfo;
  47         const struct vlan_hdr *fp;
  48         struct vlan_hdr _frame;
  49
  50         unsigned short TCI;     /* Whole TCI, given from parsed frame */
  51         unsigned short id;      /* VLAN ID, given from frame TCI */
  52         unsigned char prio;     /* user_priority, given from frame TCI */
  53         /* VLAN encapsulated Type/Length field, given from orig frame */
  54         __be16 encap;
  55
  56         fp = skb_header_pointer(skb, 0, sizeof(_frame), &_frame);
  57         if (fp == NULL)
  58                 return false;
  59
  60         /* Tag Control Information (TCI) consists of the following elements:
  61          * - User_priority. The user_priority field is three bits in length,
  62          * interpreted as a binary number.
  63          * - Canonical Format Indicator (CFI). The Canonical Format Indicator
  64          * (CFI) is a single bit flag value. Currently ignored.
  65          * - VLAN Identifier (VID). The VID is encoded as
  66          * an unsigned binary number. */
  67         TCI = ntohs(fp->h_vlan_TCI);
  68         id = TCI & VLAN_VID_MASK;
  69         prio = (TCI >> 13) & 0x7;
  70         encap = fp->h_vlan_encapsulated_proto;
  71
  72         /* Checking VLAN Identifier (VID) */
  73         if (GET_BITMASK(EBT_VLAN_ID))
  74                 EXIT_ON_MISMATCH(id, EBT_VLAN_ID);
  75
  76         /* Checking user_priority */
  77         if (GET_BITMASK(EBT_VLAN_PRIO))
  78                 EXIT_ON_MISMATCH(prio, EBT_VLAN_PRIO);
  79
  80         /* Checking Encapsulated Proto (Length/Type) field */
  81         if (GET_BITMASK(EBT_VLAN_ENCAP))
  82                 EXIT_ON_MISMATCH(encap, EBT_VLAN_ENCAP);
  83
  84         return true;
  85 }
  86
  87 static bool
  88 ebt_vlan_mt_check(const char *table, const void *entry,
  89                   const struct xt_match *match, void *data,
  90                   unsigned int hook_mask)
  91 {
  92         struct ebt_vlan_info *info = data;
  93         const struct ebt_entry *e = entry;
  94
  95         /* Is it 802.1Q frame checked? */
  96         if (e->ethproto != htons(ETH_P_8021Q)) {
  97                 DEBUG_MSG
  98                     ("passed entry proto %2.4X is not 802.1Q (8100)\n",
  99                      (unsigned short) ntohs(e->ethproto));
 100                 return false;
 101         }
 102
 103         /* Check for bitmask range
 104          * True if even one bit is out of mask */
 105         if (info->bitmask & ~EBT_VLAN_MASK) {
 106                 DEBUG_MSG("bitmask %2X is out of mask (%2X)\n",
 107                           info->bitmask, EBT_VLAN_MASK);
 108                 return false;
 109         }
 110
 111         /* Check for inversion flags range */
 112         if (info->invflags & ~EBT_VLAN_MASK) {
 113                 DEBUG_MSG("inversion flags %2X is out of mask (%2X)\n",
 114                           info->invflags, EBT_VLAN_MASK);
 115                 return false;
 116         }
 117
 118         /* Reserved VLAN ID (VID) values
 119          * -----------------------------
 120          * 0 - The null VLAN ID.
 121          * 1 - The default Port VID (PVID)
 122          * 0x0FFF - Reserved for implementation use.
 123          * if_vlan.h: VLAN_GROUP_ARRAY_LEN 4096. */
 124         if (GET_BITMASK(EBT_VLAN_ID)) {
 125                 if (!!info->id) { /* if id!=0 => check vid range */
 126                         if (info->id > VLAN_GROUP_ARRAY_LEN) {
 127                                 DEBUG_MSG
 128                                     ("id %d is out of range (1-4096)\n",
 129                                      info->id);
 130                                 return false;
 131                         }
 132                         /* Note: This is valid VLAN-tagged frame point.
 133                          * Any value of user_priority are acceptable,
 134                          * but should be ignored according to 802.1Q Std.
 135                          * So we just drop the prio flag. */
 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                         DEBUG_MSG("prio %d is out of range (0-7)\n",
 144                              info->prio);
 145                         return false;
 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         if (GET_BITMASK(EBT_VLAN_ENCAP)) {
 152                 if ((unsigned short) ntohs(info->encap) < ETH_ZLEN) {
 153                         DEBUG_MSG
 154                             ("encap frame length %d is less than minimal\n",
 155                              ntohs(info->encap));
 156                         return false;
 157                 }
 158         }
 159
 160         return true;
 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      = XT_ALIGN(sizeof(struct ebt_vlan_info)),
 170         .me             = THIS_MODULE,
 171 };
 172
 173 static int __init ebt_vlan_init(void)
 174 {
 175         DEBUG_MSG("ebtables 802.1Q extension module v"
 176                   MODULE_VERS "\n");
 177         DEBUG_MSG("module debug=%d\n", !!debug);
 178         return xt_register_match(&ebt_vlan_mt_reg);
 179 }
 180
 181 static void __exit ebt_vlan_fini(void)
 182 {
 183         xt_unregister_match(&ebt_vlan_mt_reg);
 184 }
 185
 186 module_init(ebt_vlan_init);
 187 module_exit(ebt_vlan_fini);