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 int br_send_bpdu_finish(struct net *net, struct sock *sk,
  34                                struct sk_buff *skb)
  35 {
  36         return dev_queue_xmit(skb);
  37 }
  38
  39 static void br_send_bpdu(struct net_bridge_port *p,
  40                          const unsigned char *data, int length)
  41 {
  42         struct sk_buff *skb;
  43
  44         skb = dev_alloc_skb(length+LLC_RESERVE);
  45         if (!skb)
  46                 return;
  47
  48         skb->dev = p->dev;
  49         skb->protocol = htons(ETH_P_802_2);
  50         skb->priority = TC_PRIO_CONTROL;
  51
  52         skb_reserve(skb, LLC_RESERVE);
  53         __skb_put_data(skb, data, length);
  54
  55         llc_pdu_header_init(skb, LLC_PDU_TYPE_U, LLC_SAP_BSPAN,
  56                             LLC_SAP_BSPAN, LLC_PDU_CMD);
  57         llc_pdu_init_as_ui_cmd(skb);
  58
  59         llc_mac_hdr_init(skb, p->dev->dev_addr, p->br->group_addr);
  60
  61         skb_reset_mac_header(skb);
  62
  63         NF_HOOK(NFPROTO_BRIDGE, NF_BR_LOCAL_OUT,
  64                 dev_net(p->dev), NULL, skb, NULL, skb->dev,
  65                 br_send_bpdu_finish);
  66 }
  67
  68 static inline void br_set_ticks(unsigned char *dest, int j)
  69 {
  70         unsigned long ticks = (STP_HZ * j)/ HZ;
  71
  72         put_unaligned_be16(ticks, dest);
  73 }
  74
  75 static inline int br_get_ticks(const unsigned char *src)
  76 {
  77         unsigned long ticks = get_unaligned_be16(src);
  78
  79         return DIV_ROUND_UP(ticks * HZ, STP_HZ);
  80 }
  81
  82 /* called under bridge lock */
  83 void br_send_config_bpdu(struct net_bridge_port *p, struct br_config_bpdu *bpdu)
  84 {
  85         unsigned char buf[35];
  86
  87         if (p->br->stp_enabled != BR_KERNEL_STP)
  88                 return;
  89
  90         buf[0] = 0;
  91         buf[1] = 0;
  92         buf[2] = 0;
  93         buf[3] = BPDU_TYPE_CONFIG;
  94         buf[4] = (bpdu->topology_change ? 0x01 : 0) |
  95                 (bpdu->topology_change_ack ? 0x80 : 0);
  96         buf[5] = bpdu->root.prio[0];
  97         buf[6] = bpdu->root.prio[1];
  98         buf[7] = bpdu->root.addr[0];
  99         buf[8] = bpdu->root.addr[1];
 100         buf[9] = bpdu->root.addr[2];
 101         buf[10] = bpdu->root.addr[3];
 102         buf[11] = bpdu->root.addr[4];
 103         buf[12] = bpdu->root.addr[5];
 104         buf[13] = (bpdu->root_path_cost >> 24) & 0xFF;
 105         buf[14] = (bpdu->root_path_cost >> 16) & 0xFF;
 106         buf[15] = (bpdu->root_path_cost >> 8) & 0xFF;
 107         buf[16] = bpdu->root_path_cost & 0xFF;
 108         buf[17] = bpdu->bridge_id.prio[0];
 109         buf[18] = bpdu->bridge_id.prio[1];
 110         buf[19] = bpdu->bridge_id.addr[0];
 111         buf[20] = bpdu->bridge_id.addr[1];
 112         buf[21] = bpdu->bridge_id.addr[2];
 113         buf[22] = bpdu->bridge_id.addr[3];
 114         buf[23] = bpdu->bridge_id.addr[4];
 115         buf[24] = bpdu->bridge_id.addr[5];
 116         buf[25] = (bpdu->port_id >> 8) & 0xFF;
 117         buf[26] = bpdu->port_id & 0xFF;
 118
 119         br_set_ticks(buf+27, bpdu->message_age);
 120         br_set_ticks(buf+29, bpdu->max_age);
 121         br_set_ticks(buf+31, bpdu->hello_time);
 122         br_set_ticks(buf+33, bpdu->forward_delay);
 123
 124         br_send_bpdu(p, buf, 35);
 125 }
 126
 127 /* called under bridge lock */
 128 void br_send_tcn_bpdu(struct net_bridge_port *p)
 129 {
 130         unsigned char buf[4];
 131
 132         if (p->br->stp_enabled != BR_KERNEL_STP)
 133                 return;
 134
 135         buf[0] = 0;
 136         buf[1] = 0;
 137         buf[2] = 0;
 138         buf[3] = BPDU_TYPE_TCN;
 139         br_send_bpdu(p, buf, 4);
 140 }
 141
 142 /*
 143  * Called from llc.
 144  *
 145  * NO locks, but rcu_read_lock
 146  */
 147 void br_stp_rcv(const struct stp_proto *proto, struct sk_buff *skb,
 148                 struct net_device *dev)
 149 {
 150         const unsigned char *dest = eth_hdr(skb)->h_dest;
 151         struct net_bridge_port *p;
 152         struct net_bridge *br;
 153         const unsigned char *buf;
 154
 155         if (!pskb_may_pull(skb, 4))
 156                 goto err;
 157
 158         /* compare of protocol id and version */
 159         buf = skb->data;
 160         if (buf[0] != 0 || buf[1] != 0 || buf[2] != 0)
 161                 goto err;
 162
 163         p = br_port_get_check_rcu(dev);
 164         if (!p)
 165                 goto err;
 166
 167         br = p->br;
 168         spin_lock(&br->lock);
 169
 170         if (br->stp_enabled != BR_KERNEL_STP)
 171                 goto out;
 172
 173         if (!(br->dev->flags & IFF_UP))
 174                 goto out;
 175
 176         if (p->state == BR_STATE_DISABLED)
 177                 goto out;
 178
 179         if (!ether_addr_equal(dest, br->group_addr))
 180                 goto out;
 181
 182         if (p->flags & BR_BPDU_GUARD) {
 183                 br_notice(br, "BPDU received on blocked port %u(%s)\n",
 184                           (unsigned int) p->port_no, p->dev->name);
 185                 br_stp_disable_port(p);
 186                 goto out;
 187         }
 188
 189         buf = skb_pull(skb, 3);
 190
 191         if (buf[0] == BPDU_TYPE_CONFIG) {
 192                 struct br_config_bpdu bpdu;
 193
 194                 if (!pskb_may_pull(skb, 32))
 195                         goto out;
 196
 197                 buf = skb->data;
 198                 bpdu.topology_change = (buf[1] & 0x01) ? 1 : 0;
 199                 bpdu.topology_change_ack = (buf[1] & 0x80) ? 1 : 0;
 200
 201                 bpdu.root.prio[0] = buf[2];
 202                 bpdu.root.prio[1] = buf[3];
 203                 bpdu.root.addr[0] = buf[4];
 204                 bpdu.root.addr[1] = buf[5];
 205                 bpdu.root.addr[2] = buf[6];
 206                 bpdu.root.addr[3] = buf[7];
 207                 bpdu.root.addr[4] = buf[8];
 208                 bpdu.root.addr[5] = buf[9];
 209                 bpdu.root_path_cost =
 210                         (buf[10] << 24) |
 211                         (buf[11] << 16) |
 212                         (buf[12] << 8) |
 213                         buf[13];
 214                 bpdu.bridge_id.prio[0] = buf[14];
 215                 bpdu.bridge_id.prio[1] = buf[15];
 216                 bpdu.bridge_id.addr[0] = buf[16];
 217                 bpdu.bridge_id.addr[1] = buf[17];
 218                 bpdu.bridge_id.addr[2] = buf[18];
 219                 bpdu.bridge_id.addr[3] = buf[19];
 220                 bpdu.bridge_id.addr[4] = buf[20];
 221                 bpdu.bridge_id.addr[5] = buf[21];
 222                 bpdu.port_id = (buf[22] << 8) | buf[23];
 223
 224                 bpdu.message_age = br_get_ticks(buf+24);
 225                 bpdu.max_age = br_get_ticks(buf+26);
 226                 bpdu.hello_time = br_get_ticks(buf+28);
 227                 bpdu.forward_delay = br_get_ticks(buf+30);
 228
 229                 if (bpdu.message_age > bpdu.max_age) {
 230                         if (net_ratelimit())
 231                                 br_notice(p->br,
 232                                           "port %u config from %pM"
 233                                           " (message_age %ul > max_age %ul)\n",
 234                                           p->port_no,
 235                                           eth_hdr(skb)->h_source,
 236                                           bpdu.message_age, bpdu.max_age);
 237                         goto out;
 238                 }
 239
 240                 br_received_config_bpdu(p, &bpdu);
 241         } else if (buf[0] == BPDU_TYPE_TCN) {
 242                 br_received_tcn_bpdu(p);
 243         }
 244  out:
 245         spin_unlock(&br->lock);
 246  err:
 247         kfree_skb(skb);
 248 }