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