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
18MODULE_AUTHOR("Nick Fedchik <nick@fedchik.org.ua>");
19MODULE_DESCRIPTION("Ebtables: 802.1Q VLAN tag match");
20MODULE_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
25static bool
26ebt_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
77static 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
151static 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
161static 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
167static void __exit ebt_vlan_fini(void)
168{
169	xt_unregister_match(&ebt_vlan_mt_reg);
170}
171
172module_init(ebt_vlan_init);
173module_exit(ebt_vlan_fini);
174