1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * ebt_stp
4 *
5 * Authors:
6 * Bart De Schuymer <bdschuym@pandora.be>
7 * Stephen Hemminger <shemminger@osdl.org>
8 *
9 * July, 2003
10 */
11 #include <linux/etherdevice.h>
12 #include <linux/module.h>
13 #include <linux/netfilter/x_tables.h>
14 #include <linux/netfilter_bridge/ebtables.h>
15 #include <linux/netfilter_bridge/ebt_stp.h>
16
17 #define BPDU_TYPE_CONFIG 0
18
19 struct stp_header {
20 u8 dsap;
21 u8 ssap;
22 u8 ctrl;
23 u8 pid;
24 u8 vers;
25 u8 type;
26 };
27
28 struct stp_config_pdu {
29 u8 flags;
30 u8 root[8];
31 u8 root_cost[4];
32 u8 sender[8];
33 u8 port[2];
34 u8 msg_age[2];
35 u8 max_age[2];
36 u8 hello_time[2];
37 u8 forward_delay[2];
38 };
39
40 #define NR16(p) (p[0] << 8 | p[1])
41 #define NR32(p) ((p[0] << 24) | (p[1] << 16) | (p[2] << 8) | p[3])
42
ebt_filter_config(const struct ebt_stp_info * info,const struct stp_config_pdu * stpc)43 static bool ebt_filter_config(const struct ebt_stp_info *info,
44 const struct stp_config_pdu *stpc)
45 {
46 const struct ebt_stp_config_info *c;
47 u16 v16;
48 u32 v32;
49
50 c = &info->config;
51 if ((info->bitmask & EBT_STP_FLAGS) &&
52 NF_INVF(info, EBT_STP_FLAGS, c->flags != stpc->flags))
53 return false;
54 if (info->bitmask & EBT_STP_ROOTPRIO) {
55 v16 = NR16(stpc->root);
56 if (NF_INVF(info, EBT_STP_ROOTPRIO,
57 v16 < c->root_priol || v16 > c->root_priou))
58 return false;
59 }
60 if (info->bitmask & EBT_STP_ROOTADDR) {
61 if (NF_INVF(info, EBT_STP_ROOTADDR,
62 !ether_addr_equal_masked(&stpc->root[2],
63 c->root_addr,
64 c->root_addrmsk)))
65 return false;
66 }
67 if (info->bitmask & EBT_STP_ROOTCOST) {
68 v32 = NR32(stpc->root_cost);
69 if (NF_INVF(info, EBT_STP_ROOTCOST,
70 v32 < c->root_costl || v32 > c->root_costu))
71 return false;
72 }
73 if (info->bitmask & EBT_STP_SENDERPRIO) {
74 v16 = NR16(stpc->sender);
75 if (NF_INVF(info, EBT_STP_SENDERPRIO,
76 v16 < c->sender_priol || v16 > c->sender_priou))
77 return false;
78 }
79 if (info->bitmask & EBT_STP_SENDERADDR) {
80 if (NF_INVF(info, EBT_STP_SENDERADDR,
81 !ether_addr_equal_masked(&stpc->sender[2],
82 c->sender_addr,
83 c->sender_addrmsk)))
84 return false;
85 }
86 if (info->bitmask & EBT_STP_PORT) {
87 v16 = NR16(stpc->port);
88 if (NF_INVF(info, EBT_STP_PORT,
89 v16 < c->portl || v16 > c->portu))
90 return false;
91 }
92 if (info->bitmask & EBT_STP_MSGAGE) {
93 v16 = NR16(stpc->msg_age);
94 if (NF_INVF(info, EBT_STP_MSGAGE,
95 v16 < c->msg_agel || v16 > c->msg_ageu))
96 return false;
97 }
98 if (info->bitmask & EBT_STP_MAXAGE) {
99 v16 = NR16(stpc->max_age);
100 if (NF_INVF(info, EBT_STP_MAXAGE,
101 v16 < c->max_agel || v16 > c->max_ageu))
102 return false;
103 }
104 if (info->bitmask & EBT_STP_HELLOTIME) {
105 v16 = NR16(stpc->hello_time);
106 if (NF_INVF(info, EBT_STP_HELLOTIME,
107 v16 < c->hello_timel || v16 > c->hello_timeu))
108 return false;
109 }
110 if (info->bitmask & EBT_STP_FWDD) {
111 v16 = NR16(stpc->forward_delay);
112 if (NF_INVF(info, EBT_STP_FWDD,
113 v16 < c->forward_delayl || v16 > c->forward_delayu))
114 return false;
115 }
116 return true;
117 }
118
119 static bool
ebt_stp_mt(const struct sk_buff * skb,struct xt_action_param * par)120 ebt_stp_mt(const struct sk_buff *skb, struct xt_action_param *par)
121 {
122 const struct ebt_stp_info *info = par->matchinfo;
123 const struct stp_header *sp;
124 struct stp_header _stph;
125 const u8 header[6] = {0x42, 0x42, 0x03, 0x00, 0x00, 0x00};
126
127 sp = skb_header_pointer(skb, 0, sizeof(_stph), &_stph);
128 if (sp == NULL)
129 return false;
130
131 /* The stp code only considers these */
132 if (memcmp(sp, header, sizeof(header)))
133 return false;
134
135 if ((info->bitmask & EBT_STP_TYPE) &&
136 NF_INVF(info, EBT_STP_TYPE, info->type != sp->type))
137 return false;
138
139 if (sp->type == BPDU_TYPE_CONFIG &&
140 info->bitmask & EBT_STP_CONFIG_MASK) {
141 const struct stp_config_pdu *st;
142 struct stp_config_pdu _stpc;
143
144 st = skb_header_pointer(skb, sizeof(_stph),
145 sizeof(_stpc), &_stpc);
146 if (st == NULL)
147 return false;
148 return ebt_filter_config(info, st);
149 }
150 return true;
151 }
152
ebt_stp_mt_check(const struct xt_mtchk_param * par)153 static int ebt_stp_mt_check(const struct xt_mtchk_param *par)
154 {
155 const struct ebt_stp_info *info = par->matchinfo;
156 const struct ebt_entry *e = par->entryinfo;
157
158 if (info->bitmask & ~EBT_STP_MASK || info->invflags & ~EBT_STP_MASK ||
159 !(info->bitmask & EBT_STP_MASK))
160 return -EINVAL;
161 /* Make sure the match only receives stp frames */
162 if (!par->nft_compat &&
163 (!ether_addr_equal(e->destmac, eth_stp_addr) ||
164 !(e->bitmask & EBT_DESTMAC) ||
165 !is_broadcast_ether_addr(e->destmsk)))
166 return -EINVAL;
167
168 return 0;
169 }
170
171 static struct xt_match ebt_stp_mt_reg __read_mostly = {
172 .name = "stp",
173 .revision = 0,
174 .family = NFPROTO_BRIDGE,
175 .match = ebt_stp_mt,
176 .checkentry = ebt_stp_mt_check,
177 .matchsize = sizeof(struct ebt_stp_info),
178 .me = THIS_MODULE,
179 };
180
ebt_stp_init(void)181 static int __init ebt_stp_init(void)
182 {
183 return xt_register_match(&ebt_stp_mt_reg);
184 }
185
ebt_stp_fini(void)186 static void __exit ebt_stp_fini(void)
187 {
188 xt_unregister_match(&ebt_stp_mt_reg);
189 }
190
191 module_init(ebt_stp_init);
192 module_exit(ebt_stp_fini);
193 MODULE_DESCRIPTION("Ebtables: Spanning Tree Protocol packet match");
194 MODULE_LICENSE("GPL");
195