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, offset: 0, len: sizeof(_frame), buffer: &_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(target: &ebt_vlan_mt_reg); |
165 | } |
166 | |
167 | static void __exit ebt_vlan_fini(void) |
168 | { |
169 | xt_unregister_match(target: &ebt_vlan_mt_reg); |
170 | } |
171 | |
172 | module_init(ebt_vlan_init); |
173 | module_exit(ebt_vlan_fini); |
174 | |