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
  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
  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
  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 */
  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 */
 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  */
 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 (!ether_addr_equal(dest, br->group_addr))
 171                 goto out;
 172
 173         if (p->flags & BR_BPDU_GUARD) {
 174                 br_notice(br, "BPDU received on blocked port %u(%s)\n",
 175                           (unsigned int) p->port_no, p->dev->name);
 176                 br_stp_disable_port(p);
 177                 goto out;
 178         }
 179
 180         buf = skb_pull(skb, 3);
 181
 182         if (buf[0] == BPDU_TYPE_CONFIG) {
 183                 struct br_config_bpdu bpdu;
 184
 185                 if (!pskb_may_pull(skb, 32))
 186                         goto out;
 187
 188                 buf = skb->data;
 189                 bpdu.topology_change = (buf[1] & 0x01) ? 1 : 0;
 190                 bpdu.topology_change_ack = (buf[1] & 0x80) ? 1 : 0;
 191
 192                 bpdu.root.prio[0] = buf[2];
 193                 bpdu.root.prio[1] = buf[3];
 194                 bpdu.root.addr[0] = buf[4];
 195                 bpdu.root.addr[1] = buf[5];
 196                 bpdu.root.addr[2] = buf[6];
 197                 bpdu.root.addr[3] = buf[7];
 198                 bpdu.root.addr[4] = buf[8];
 199                 bpdu.root.addr[5] = buf[9];
 200                 bpdu.root_path_cost =
 201                         (buf[10] << 24) |
 202                         (buf[11] << 16) |
 203                         (buf[12] << 8) |
 204                         buf[13];
 205                 bpdu.bridge_id.prio[0] = buf[14];
 206                 bpdu.bridge_id.prio[1] = buf[15];
 207                 bpdu.bridge_id.addr[0] = buf[16];
 208                 bpdu.bridge_id.addr[1] = buf[17];
 209                 bpdu.bridge_id.addr[2] = buf[18];
 210                 bpdu.bridge_id.addr[3] = buf[19];
 211                 bpdu.bridge_id.addr[4] = buf[20];
 212                 bpdu.bridge_id.addr[5] = buf[21];
 213                 bpdu.port_id = (buf[22] << 8) | buf[23];
 214
 215                 bpdu.message_age = br_get_ticks(buf+24);
 216                 bpdu.max_age = br_get_ticks(buf+26);
 217                 bpdu.hello_time = br_get_ticks(buf+28);
 218                 bpdu.forward_delay = br_get_ticks(buf+30);
 219
 220                 if (bpdu.message_age > bpdu.max_age) {
 221                         if (net_ratelimit())
 222                                 br_notice(p->br,
 223                                           "port %u config from %pM"
 224                                           " (message_age %ul > max_age %ul)\n",
 225                                           p->port_no,
 226                                           eth_hdr(skb)->h_source,
 227                                           bpdu.message_age, bpdu.max_age);
 228                         goto out;
 229                 }
 230
 231                 br_received_config_bpdu(p, &bpdu);
 232         } else if (buf[0] == BPDU_TYPE_TCN) {
 233                 br_received_tcn_bpdu(p);
 234         }
 235  out:
 236         spin_unlock(&br->lock);
 237  err:
 238         kfree_skb(skb);
 239 }