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 <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
  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
  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
  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 */
  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 */
 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  */
 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 (!ether_addr_equal(dest, br->group_addr))
 173                 goto out;
 174
 175         if (p->flags & BR_BPDU_GUARD) {
 176                 br_notice(br, "BPDU received on blocked port %u(%s)\n",
 177                           (unsigned int) p->port_no, p->dev->name);
 178                 br_stp_disable_port(p);
 179                 goto out;
 180         }
 181
 182         buf = skb_pull(skb, 3);
 183
 184         if (buf[0] == BPDU_TYPE_CONFIG) {
 185                 struct br_config_bpdu bpdu;
 186
 187                 if (!pskb_may_pull(skb, 32))
 188                         goto out;
 189
 190                 buf = skb->data;
 191                 bpdu.topology_change = (buf[1] & 0x01) ? 1 : 0;
 192                 bpdu.topology_change_ack = (buf[1] & 0x80) ? 1 : 0;
 193
 194                 bpdu.root.prio[0] = buf[2];
 195                 bpdu.root.prio[1] = buf[3];
 196                 bpdu.root.addr[0] = buf[4];
 197                 bpdu.root.addr[1] = buf[5];
 198                 bpdu.root.addr[2] = buf[6];
 199                 bpdu.root.addr[3] = buf[7];
 200                 bpdu.root.addr[4] = buf[8];
 201                 bpdu.root.addr[5] = buf[9];
 202                 bpdu.root_path_cost =
 203                         (buf[10] << 24) |
 204                         (buf[11] << 16) |
 205                         (buf[12] << 8) |
 206                         buf[13];
 207                 bpdu.bridge_id.prio[0] = buf[14];
 208                 bpdu.bridge_id.prio[1] = buf[15];
 209                 bpdu.bridge_id.addr[0] = buf[16];
 210                 bpdu.bridge_id.addr[1] = buf[17];
 211                 bpdu.bridge_id.addr[2] = buf[18];
 212                 bpdu.bridge_id.addr[3] = buf[19];
 213                 bpdu.bridge_id.addr[4] = buf[20];
 214                 bpdu.bridge_id.addr[5] = buf[21];
 215                 bpdu.port_id = (buf[22] << 8) | buf[23];
 216
 217                 bpdu.message_age = br_get_ticks(buf+24);
 218                 bpdu.max_age = br_get_ticks(buf+26);
 219                 bpdu.hello_time = br_get_ticks(buf+28);
 220                 bpdu.forward_delay = br_get_ticks(buf+30);
 221
 222                 if (bpdu.message_age > bpdu.max_age) {
 223                         if (net_ratelimit())
 224                                 br_notice(p->br,
 225                                           "port %u config from %pM"
 226                                           " (message_age %ul > max_age %ul)\n",
 227                                           p->port_no,
 228                                           eth_hdr(skb)->h_source,
 229                                           bpdu.message_age, bpdu.max_age);
 230                         goto out;
 231                 }
 232
 233                 br_received_config_bpdu(p, &bpdu);
 234         } else if (buf[0] == BPDU_TYPE_TCN) {
 235                 br_received_tcn_bpdu(p);
 236         }
 237  out:
 238         spin_unlock(&br->lock);
 239  err:
 240         kfree_skb(skb);
 241 }