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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