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Linux/net/bridge/netfilter/ebt_vlan.c

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  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);
186 

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