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
30MODULE_AUTHOR("Nick Fedchik <nick@fedchik.org.ua>");
31MODULE_DESCRIPTION("Ebtables: 802.1Q VLAN tag match");
32MODULE_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
37static bool
38ebt_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	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
88static 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
158static 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
168static 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
174static void __exit ebt_vlan_fini(void)
175{
176	xt_unregister_match(&ebt_vlan_mt_reg);
177}
178
179module_init(ebt_vlan_init);
180module_exit(ebt_vlan_fini);
181