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
ebt_vlan_mt(const struct sk_buff * skb,struct xt_action_param * par)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
ebt_vlan_mt_check(const struct xt_mtchk_param * par)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
ebt_vlan_init(void)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
ebt_vlan_fini(void)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);
181