linux/net/bridge/br_stp_bpdu.c
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   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 (!ether_addr_equal(dest, br->group_addr))
 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                if (bpdu.message_age > bpdu.max_age) {
 214                        if (net_ratelimit())
 215                                br_notice(p->br,
 216                                          "port %u config from %pM"
 217                                          " (message_age %ul > max_age %ul)\n",
 218                                          p->port_no,
 219                                          eth_hdr(skb)->h_source,
 220                                          bpdu.message_age, bpdu.max_age);
 221                        goto out;
 222                }
 223
 224                br_received_config_bpdu(p, &bpdu);
 225        } else if (buf[0] == BPDU_TYPE_TCN) {
 226                br_received_tcn_bpdu(p);
 227        }
 228 out:
 229        spin_unlock(&br->lock);
 230 err:
 231        kfree_skb(skb);
 232}
 233
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