Root/net/bridge/br_stp_bpdu.c

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
32static 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
59static 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
66static 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 */
74void 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 */
119void 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 */
138void 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

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