1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * Description: EBTables 802.1Q match extension kernelspace module.
4 * Authors: Nick Fedchik <nick@fedchik.org.ua>
5 * Bart De Schuymer <bdschuym@pandora.be>
6 */
7
8 #include <linux/if_ether.h>
9 #include <linux/if_vlan.h>
10 #include <linux/module.h>
11 #include <linux/moduleparam.h>
12 #include <linux/netfilter/x_tables.h>
13 #include <linux/netfilter_bridge/ebtables.h>
14 #include <linux/netfilter_bridge/ebt_vlan.h>
15
16 #define MODULE_VERS "0.6"
17
18 MODULE_AUTHOR("Nick Fedchik <nick@fedchik.org.ua>");
19 MODULE_DESCRIPTION("Ebtables: 802.1Q VLAN tag match");
20 MODULE_LICENSE("GPL");
21
22 #define GET_BITMASK(_BIT_MASK_) info->bitmask & _BIT_MASK_
23 #define EXIT_ON_MISMATCH(_MATCH_,_MASK_) {if (!((info->_MATCH_ == _MATCH_)^!!(info->invflags & _MASK_))) return false; }
24
25 static bool
26 ebt_vlan_mt(const struct sk_buff *skb, struct xt_action_param *par)
27 {
28 const struct ebt_vlan_info *info = par->matchinfo;
29
30 unsigned short TCI; /* Whole TCI, given from parsed frame */
31 unsigned short id; /* VLAN ID, given from frame TCI */
32 unsigned char prio; /* user_priority, given from frame TCI */
33 /* VLAN encapsulated Type/Length field, given from orig frame */
34 __be16 encap;
35
36 if (skb_vlan_tag_present(skb)) {
37 TCI = skb_vlan_tag_get(skb);
38 encap = skb->protocol;
39 } else {
40 const struct vlan_hdr *fp;
41 struct vlan_hdr _frame;
42
43 fp = skb_header_pointer(skb, 0, sizeof(_frame), &_frame);
44 if (fp == NULL)
45 return false;
46
47 TCI = ntohs(fp->h_vlan_TCI);
48 encap = fp->h_vlan_encapsulated_proto;
49 }
50
51 /* Tag Control Information (TCI) consists of the following elements:
52 * - User_priority. The user_priority field is three bits in length,
53 * interpreted as a binary number.
54 * - Canonical Format Indicator (CFI). The Canonical Format Indicator
55 * (CFI) is a single bit flag value. Currently ignored.
56 * - VLAN Identifier (VID). The VID is encoded as
57 * an unsigned binary number.
58 */
59 id = TCI & VLAN_VID_MASK;
60 prio = (TCI >> 13) & 0x7;
61
62 /* Checking VLAN Identifier (VID) */
63 if (GET_BITMASK(EBT_VLAN_ID))
64 EXIT_ON_MISMATCH(id, EBT_VLAN_ID);
65
66 /* Checking user_priority */
67 if (GET_BITMASK(EBT_VLAN_PRIO))
68 EXIT_ON_MISMATCH(prio, EBT_VLAN_PRIO);
69
70 /* Checking Encapsulated Proto (Length/Type) field */
71 if (GET_BITMASK(EBT_VLAN_ENCAP))
72 EXIT_ON_MISMATCH(encap, EBT_VLAN_ENCAP);
73
74 return true;
75 }
76
77 static int ebt_vlan_mt_check(const struct xt_mtchk_param *par)
78 {
79 struct ebt_vlan_info *info = par->matchinfo;
80 const struct ebt_entry *e = par->entryinfo;
81
82 /* Is it 802.1Q frame checked? */
83 if (e->ethproto != htons(ETH_P_8021Q)) {
84 pr_debug("passed entry proto %2.4X is not 802.1Q (8100)\n",
85 ntohs(e->ethproto));
86 return -EINVAL;
87 }
88
89 /* Check for bitmask range
90 * True if even one bit is out of mask
91 */
92 if (info->bitmask & ~EBT_VLAN_MASK) {
93 pr_debug("bitmask %2X is out of mask (%2X)\n",
94 info->bitmask, EBT_VLAN_MASK);
95 return -EINVAL;
96 }
97
98 /* Check for inversion flags range */
99 if (info->invflags & ~EBT_VLAN_MASK) {
100 pr_debug("inversion flags %2X is out of mask (%2X)\n",
101 info->invflags, EBT_VLAN_MASK);
102 return -EINVAL;
103 }
104
105 /* Reserved VLAN ID (VID) values
106 * -----------------------------
107 * 0 - The null VLAN ID.
108 * 1 - The default Port VID (PVID)
109 * 0x0FFF - Reserved for implementation use.
110 * if_vlan.h: VLAN_N_VID 4096.
111 */
112 if (GET_BITMASK(EBT_VLAN_ID)) {
113 if (!!info->id) { /* if id!=0 => check vid range */
114 if (info->id > VLAN_N_VID) {
115 pr_debug("id %d is out of range (1-4096)\n",
116 info->id);
117 return -EINVAL;
118 }
119 /* Note: This is valid VLAN-tagged frame point.
120 * Any value of user_priority are acceptable,
121 * but should be ignored according to 802.1Q Std.
122 * So we just drop the prio flag.
123 */
124 info->bitmask &= ~EBT_VLAN_PRIO;
125 }
126 /* Else, id=0 (null VLAN ID) => user_priority range (any?) */
127 }
128
129 if (GET_BITMASK(EBT_VLAN_PRIO)) {
130 if ((unsigned char) info->prio > 7) {
131 pr_debug("prio %d is out of range (0-7)\n",
132 info->prio);
133 return -EINVAL;
134 }
135 }
136 /* Check for encapsulated proto range - it is possible to be
137 * any value for u_short range.
138 * if_ether.h: ETH_ZLEN 60 - Min. octets in frame sans FCS
139 */
140 if (GET_BITMASK(EBT_VLAN_ENCAP)) {
141 if ((unsigned short) ntohs(info->encap) < ETH_ZLEN) {
142 pr_debug("encap frame length %d is less than "
143 "minimal\n", ntohs(info->encap));
144 return -EINVAL;
145 }
146 }
147
148 return 0;
149 }
150
151 static struct xt_match ebt_vlan_mt_reg __read_mostly = {
152 .name = "vlan",
153 .revision = 0,
154 .family = NFPROTO_BRIDGE,
155 .match = ebt_vlan_mt,
156 .checkentry = ebt_vlan_mt_check,
157 .matchsize = sizeof(struct ebt_vlan_info),
158 .me = THIS_MODULE,
159 };
160
161 static int __init ebt_vlan_init(void)
162 {
163 pr_debug("ebtables 802.1Q extension module v" MODULE_VERS "\n");
164 return xt_register_match(&ebt_vlan_mt_reg);
165 }
166
167 static void __exit ebt_vlan_fini(void)
168 {
169 xt_unregister_match(&ebt_vlan_mt_reg);
170 }
171
172 module_init(ebt_vlan_init);
173 module_exit(ebt_vlan_fini);
174
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