xref: /openbmc/linux/net/bridge/br_stp_bpdu.c (revision b593bce5)
1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  *	Spanning tree protocol; BPDU handling
4  *	Linux ethernet bridge
5  *
6  *	Authors:
7  *	Lennert Buytenhek		<buytenh@gnu.org>
8  */
9 
10 #include <linux/kernel.h>
11 #include <linux/netfilter_bridge.h>
12 #include <linux/etherdevice.h>
13 #include <linux/llc.h>
14 #include <linux/slab.h>
15 #include <linux/pkt_sched.h>
16 #include <net/net_namespace.h>
17 #include <net/llc.h>
18 #include <net/llc_pdu.h>
19 #include <net/stp.h>
20 #include <asm/unaligned.h>
21 
22 #include "br_private.h"
23 #include "br_private_stp.h"
24 
25 #define STP_HZ		256
26 
27 #define LLC_RESERVE sizeof(struct llc_pdu_un)
28 
29 static int br_send_bpdu_finish(struct net *net, struct sock *sk,
30 			       struct sk_buff *skb)
31 {
32 	return dev_queue_xmit(skb);
33 }
34 
35 static void br_send_bpdu(struct net_bridge_port *p,
36 			 const unsigned char *data, int length)
37 {
38 	struct sk_buff *skb;
39 
40 	skb = dev_alloc_skb(length+LLC_RESERVE);
41 	if (!skb)
42 		return;
43 
44 	skb->dev = p->dev;
45 	skb->protocol = htons(ETH_P_802_2);
46 	skb->priority = TC_PRIO_CONTROL;
47 
48 	skb_reserve(skb, LLC_RESERVE);
49 	__skb_put_data(skb, data, length);
50 
51 	llc_pdu_header_init(skb, LLC_PDU_TYPE_U, LLC_SAP_BSPAN,
52 			    LLC_SAP_BSPAN, LLC_PDU_CMD);
53 	llc_pdu_init_as_ui_cmd(skb);
54 
55 	llc_mac_hdr_init(skb, p->dev->dev_addr, p->br->group_addr);
56 
57 	skb_reset_mac_header(skb);
58 
59 	NF_HOOK(NFPROTO_BRIDGE, NF_BR_LOCAL_OUT,
60 		dev_net(p->dev), NULL, skb, NULL, skb->dev,
61 		br_send_bpdu_finish);
62 }
63 
64 static inline void br_set_ticks(unsigned char *dest, int j)
65 {
66 	unsigned long ticks = (STP_HZ * j)/ HZ;
67 
68 	put_unaligned_be16(ticks, dest);
69 }
70 
71 static inline int br_get_ticks(const unsigned char *src)
72 {
73 	unsigned long ticks = get_unaligned_be16(src);
74 
75 	return DIV_ROUND_UP(ticks * HZ, STP_HZ);
76 }
77 
78 /* called under bridge lock */
79 void br_send_config_bpdu(struct net_bridge_port *p, struct br_config_bpdu *bpdu)
80 {
81 	unsigned char buf[35];
82 
83 	if (p->br->stp_enabled != BR_KERNEL_STP)
84 		return;
85 
86 	buf[0] = 0;
87 	buf[1] = 0;
88 	buf[2] = 0;
89 	buf[3] = BPDU_TYPE_CONFIG;
90 	buf[4] = (bpdu->topology_change ? 0x01 : 0) |
91 		(bpdu->topology_change_ack ? 0x80 : 0);
92 	buf[5] = bpdu->root.prio[0];
93 	buf[6] = bpdu->root.prio[1];
94 	buf[7] = bpdu->root.addr[0];
95 	buf[8] = bpdu->root.addr[1];
96 	buf[9] = bpdu->root.addr[2];
97 	buf[10] = bpdu->root.addr[3];
98 	buf[11] = bpdu->root.addr[4];
99 	buf[12] = bpdu->root.addr[5];
100 	buf[13] = (bpdu->root_path_cost >> 24) & 0xFF;
101 	buf[14] = (bpdu->root_path_cost >> 16) & 0xFF;
102 	buf[15] = (bpdu->root_path_cost >> 8) & 0xFF;
103 	buf[16] = bpdu->root_path_cost & 0xFF;
104 	buf[17] = bpdu->bridge_id.prio[0];
105 	buf[18] = bpdu->bridge_id.prio[1];
106 	buf[19] = bpdu->bridge_id.addr[0];
107 	buf[20] = bpdu->bridge_id.addr[1];
108 	buf[21] = bpdu->bridge_id.addr[2];
109 	buf[22] = bpdu->bridge_id.addr[3];
110 	buf[23] = bpdu->bridge_id.addr[4];
111 	buf[24] = bpdu->bridge_id.addr[5];
112 	buf[25] = (bpdu->port_id >> 8) & 0xFF;
113 	buf[26] = bpdu->port_id & 0xFF;
114 
115 	br_set_ticks(buf+27, bpdu->message_age);
116 	br_set_ticks(buf+29, bpdu->max_age);
117 	br_set_ticks(buf+31, bpdu->hello_time);
118 	br_set_ticks(buf+33, bpdu->forward_delay);
119 
120 	br_send_bpdu(p, buf, 35);
121 }
122 
123 /* called under bridge lock */
124 void br_send_tcn_bpdu(struct net_bridge_port *p)
125 {
126 	unsigned char buf[4];
127 
128 	if (p->br->stp_enabled != BR_KERNEL_STP)
129 		return;
130 
131 	buf[0] = 0;
132 	buf[1] = 0;
133 	buf[2] = 0;
134 	buf[3] = BPDU_TYPE_TCN;
135 	br_send_bpdu(p, buf, 4);
136 }
137 
138 /*
139  * Called from llc.
140  *
141  * NO locks, but rcu_read_lock
142  */
143 void br_stp_rcv(const struct stp_proto *proto, struct sk_buff *skb,
144 		struct net_device *dev)
145 {
146 	struct net_bridge_port *p;
147 	struct net_bridge *br;
148 	const unsigned char *buf;
149 
150 	if (!pskb_may_pull(skb, 4))
151 		goto err;
152 
153 	/* compare of protocol id and version */
154 	buf = skb->data;
155 	if (buf[0] != 0 || buf[1] != 0 || buf[2] != 0)
156 		goto err;
157 
158 	p = br_port_get_check_rcu(dev);
159 	if (!p)
160 		goto err;
161 
162 	br = p->br;
163 	spin_lock(&br->lock);
164 
165 	if (br->stp_enabled != BR_KERNEL_STP)
166 		goto out;
167 
168 	if (!(br->dev->flags & IFF_UP))
169 		goto out;
170 
171 	if (p->state == BR_STATE_DISABLED)
172 		goto out;
173 
174 	if (!ether_addr_equal(eth_hdr(skb)->h_dest, br->group_addr))
175 		goto out;
176 
177 	if (p->flags & BR_BPDU_GUARD) {
178 		br_notice(br, "BPDU received on blocked port %u(%s)\n",
179 			  (unsigned int) p->port_no, p->dev->name);
180 		br_stp_disable_port(p);
181 		goto out;
182 	}
183 
184 	buf = skb_pull(skb, 3);
185 
186 	if (buf[0] == BPDU_TYPE_CONFIG) {
187 		struct br_config_bpdu bpdu;
188 
189 		if (!pskb_may_pull(skb, 32))
190 			goto out;
191 
192 		buf = skb->data;
193 		bpdu.topology_change = (buf[1] & 0x01) ? 1 : 0;
194 		bpdu.topology_change_ack = (buf[1] & 0x80) ? 1 : 0;
195 
196 		bpdu.root.prio[0] = buf[2];
197 		bpdu.root.prio[1] = buf[3];
198 		bpdu.root.addr[0] = buf[4];
199 		bpdu.root.addr[1] = buf[5];
200 		bpdu.root.addr[2] = buf[6];
201 		bpdu.root.addr[3] = buf[7];
202 		bpdu.root.addr[4] = buf[8];
203 		bpdu.root.addr[5] = buf[9];
204 		bpdu.root_path_cost =
205 			(buf[10] << 24) |
206 			(buf[11] << 16) |
207 			(buf[12] << 8) |
208 			buf[13];
209 		bpdu.bridge_id.prio[0] = buf[14];
210 		bpdu.bridge_id.prio[1] = buf[15];
211 		bpdu.bridge_id.addr[0] = buf[16];
212 		bpdu.bridge_id.addr[1] = buf[17];
213 		bpdu.bridge_id.addr[2] = buf[18];
214 		bpdu.bridge_id.addr[3] = buf[19];
215 		bpdu.bridge_id.addr[4] = buf[20];
216 		bpdu.bridge_id.addr[5] = buf[21];
217 		bpdu.port_id = (buf[22] << 8) | buf[23];
218 
219 		bpdu.message_age = br_get_ticks(buf+24);
220 		bpdu.max_age = br_get_ticks(buf+26);
221 		bpdu.hello_time = br_get_ticks(buf+28);
222 		bpdu.forward_delay = br_get_ticks(buf+30);
223 
224 		if (bpdu.message_age > bpdu.max_age) {
225 			if (net_ratelimit())
226 				br_notice(p->br,
227 					  "port %u config from %pM"
228 					  " (message_age %ul > max_age %ul)\n",
229 					  p->port_no,
230 					  eth_hdr(skb)->h_source,
231 					  bpdu.message_age, bpdu.max_age);
232 			goto out;
233 		}
234 
235 		br_received_config_bpdu(p, &bpdu);
236 	} else if (buf[0] == BPDU_TYPE_TCN) {
237 		br_received_tcn_bpdu(p);
238 	}
239  out:
240 	spin_unlock(&br->lock);
241  err:
242 	kfree_skb(skb);
243 }
244