1/*
2 *  ebt_stp
3 *
4 *	Authors:
5 *	Bart De Schuymer <bdschuym@pandora.be>
6 *	Stephen Hemminger <shemminger@osdl.org>
7 *
8 *  July, 2003
9 */
10
11#include <linux/netfilter_bridge/ebtables.h>
12#include <linux/netfilter_bridge/ebt_stp.h>
13#include <linux/etherdevice.h>
14#include <linux/module.h>
15
16#define BPDU_TYPE_CONFIG 0
17#define BPDU_TYPE_TCN 0x80
18
19struct stp_header {
20	uint8_t dsap;
21	uint8_t ssap;
22	uint8_t ctrl;
23	uint8_t pid;
24	uint8_t vers;
25	uint8_t type;
26};
27
28struct stp_config_pdu {
29	uint8_t flags;
30	uint8_t root[8];
31	uint8_t root_cost[4];
32	uint8_t sender[8];
33	uint8_t port[2];
34	uint8_t msg_age[2];
35	uint8_t max_age[2];
36	uint8_t hello_time[2];
37	uint8_t 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
43static int ebt_filter_config(struct ebt_stp_info *info,
44   struct stp_config_pdu *stpc)
45{
46	struct ebt_stp_config_info *c;
47	uint16_t v16;
48	uint32_t v32;
49	int verdict, i;
50
51	c = &info->config;
52	if ((info->bitmask & EBT_STP_FLAGS) &&
53	    FWINV(c->flags != stpc->flags, EBT_STP_FLAGS))
54		return EBT_NOMATCH;
55	if (info->bitmask & EBT_STP_ROOTPRIO) {
56		v16 = NR16(stpc->root);
57		if (FWINV(v16 < c->root_priol ||
58		    v16 > c->root_priou, EBT_STP_ROOTPRIO))
59			return EBT_NOMATCH;
60	}
61	if (info->bitmask & EBT_STP_ROOTADDR) {
62		verdict = 0;
63		for (i = 0; i < 6; i++)
64			verdict |= (stpc->root[2+i] ^ c->root_addr[i]) &
65				   c->root_addrmsk[i];
66		if (FWINV(verdict != 0, EBT_STP_ROOTADDR))
67			return EBT_NOMATCH;
68	}
69	if (info->bitmask & EBT_STP_ROOTCOST) {
70		v32 = NR32(stpc->root_cost);
71		if (FWINV(v32 < c->root_costl ||
72		    v32 > c->root_costu, EBT_STP_ROOTCOST))
73			return EBT_NOMATCH;
74	}
75	if (info->bitmask & EBT_STP_SENDERPRIO) {
76		v16 = NR16(stpc->sender);
77		if (FWINV(v16 < c->sender_priol ||
78		    v16 > c->sender_priou, EBT_STP_SENDERPRIO))
79			return EBT_NOMATCH;
80	}
81	if (info->bitmask & EBT_STP_SENDERADDR) {
82		verdict = 0;
83		for (i = 0; i < 6; i++)
84			verdict |= (stpc->sender[2+i] ^ c->sender_addr[i]) &
85				   c->sender_addrmsk[i];
86		if (FWINV(verdict != 0, EBT_STP_SENDERADDR))
87			return EBT_NOMATCH;
88	}
89	if (info->bitmask & EBT_STP_PORT) {
90		v16 = NR16(stpc->port);
91		if (FWINV(v16 < c->portl ||
92		    v16 > c->portu, EBT_STP_PORT))
93			return EBT_NOMATCH;
94	}
95	if (info->bitmask & EBT_STP_MSGAGE) {
96		v16 = NR16(stpc->msg_age);
97		if (FWINV(v16 < c->msg_agel ||
98		    v16 > c->msg_ageu, EBT_STP_MSGAGE))
99			return EBT_NOMATCH;
100	}
101	if (info->bitmask & EBT_STP_MAXAGE) {
102		v16 = NR16(stpc->max_age);
103		if (FWINV(v16 < c->max_agel ||
104		    v16 > c->max_ageu, EBT_STP_MAXAGE))
105			return EBT_NOMATCH;
106	}
107	if (info->bitmask & EBT_STP_HELLOTIME) {
108		v16 = NR16(stpc->hello_time);
109		if (FWINV(v16 < c->hello_timel ||
110		    v16 > c->hello_timeu, EBT_STP_HELLOTIME))
111			return EBT_NOMATCH;
112	}
113	if (info->bitmask & EBT_STP_FWDD) {
114		v16 = NR16(stpc->forward_delay);
115		if (FWINV(v16 < c->forward_delayl ||
116		    v16 > c->forward_delayu, EBT_STP_FWDD))
117			return EBT_NOMATCH;
118	}
119	return EBT_MATCH;
120}
121
122static int ebt_filter_stp(const struct sk_buff *skb, const struct net_device *in,
123   const struct net_device *out, const void *data, unsigned int datalen)
124{
125	struct ebt_stp_info *info = (struct ebt_stp_info *)data;
126	struct stp_header _stph, *sp;
127	uint8_t header[6] = {0x42, 0x42, 0x03, 0x00, 0x00, 0x00};
128
129	sp = skb_header_pointer(skb, 0, sizeof(_stph), &_stph);
130	if (sp == NULL)
131		return EBT_NOMATCH;
132
133	/* The stp code only considers these */
134	if (memcmp(sp, header, sizeof(header)))
135		return EBT_NOMATCH;
136
137	if (info->bitmask & EBT_STP_TYPE
138	    && FWINV(info->type != sp->type, EBT_STP_TYPE))
139		return EBT_NOMATCH;
140
141	if (sp->type == BPDU_TYPE_CONFIG &&
142	    info->bitmask & EBT_STP_CONFIG_MASK) {
143		struct stp_config_pdu _stpc, *st;
144
145		st = skb_header_pointer(skb, sizeof(_stph),
146					sizeof(_stpc), &_stpc);
147		if (st == NULL)
148			return EBT_NOMATCH;
149		return ebt_filter_config(info, st);
150	}
151	return EBT_MATCH;
152}
153
154static int ebt_stp_check(const char *tablename, unsigned int hookmask,
155   const struct ebt_entry *e, void *data, unsigned int datalen)
156{
157	struct ebt_stp_info *info = (struct ebt_stp_info *)data;
158	int len = EBT_ALIGN(sizeof(struct ebt_stp_info));
159	uint8_t bridge_ula[6] = { 0x01, 0x80, 0xc2, 0x00, 0x00, 0x00 };
160	uint8_t msk[6] = { 0xff, 0xff, 0xff, 0xff, 0xff, 0xff };
161
162	if (info->bitmask & ~EBT_STP_MASK || info->invflags & ~EBT_STP_MASK ||
163	    !(info->bitmask & EBT_STP_MASK))
164		return -EINVAL;
165	if (datalen != len)
166		return -EINVAL;
167	/* Make sure the match only receives stp frames */
168	if (compare_ether_addr(e->destmac, bridge_ula) ||
169	    compare_ether_addr(e->destmsk, msk) || !(e->bitmask & EBT_DESTMAC))
170		return -EINVAL;
171
172	return 0;
173}
174
175static struct ebt_match filter_stp =
176{
177	.name		= EBT_STP_MATCH,
178	.match		= ebt_filter_stp,
179	.check		= ebt_stp_check,
180	.me		= THIS_MODULE,
181};
182
183static int __init ebt_stp_init(void)
184{
185	return ebt_register_match(&filter_stp);
186}
187
188static void __exit ebt_stp_fini(void)
189{
190	ebt_unregister_match(&filter_stp);
191}
192
193module_init(ebt_stp_init);
194module_exit(ebt_stp_fini);
195MODULE_LICENSE("GPL");
196