ebt_stp.c

  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
 19struct stp_header {
 20	u8 dsap;
 21	u8 ssap;
 22	u8 ctrl;
 23	u8 pid;
 24	u8 vers;
 25	u8 type;
 26};
 27
 28struct 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
 43static 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
119static bool
120ebt_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
153static 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
171static 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
181static int __init ebt_stp_init(void)
182{
183	return xt_register_match(&ebt_stp_mt_reg);
184}
185
186static void __exit ebt_stp_fini(void)
187{
188	xt_unregister_match(&ebt_stp_mt_reg);
189}
190
191module_init(ebt_stp_init);
192module_exit(ebt_stp_fini);
193MODULE_DESCRIPTION("Ebtables: Spanning Tree Protocol packet match");
194MODULE_LICENSE("GPL");