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