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  *      $Id: br_stp_bpdu.c,v 1.3 2001/11/10 02:35:25 davem Exp $
   9  *
  10  *      This program is free software; you can redistribute it and/or
  11  *      modify it under the terms of the GNU General Public License
  12  *      as published by the Free Software Foundation; either version
  13  *      2 of the License, or (at your option) any later version.
  14  */
  15
  16 #include <linux/kernel.h>
  17 #include <linux/netfilter_bridge.h>
  18 #include <linux/etherdevice.h>
  19 #include <linux/llc.h>
  20 #include <net/net_namespace.h>
  21 #include <net/llc.h>
  22 #include <net/llc_pdu.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         NF_HOOK(PF_BRIDGE, NF_BR_LOCAL_OUT, skb, NULL, skb->dev,
  54                 dev_queue_xmit);
  55 }
  56
  57 static inline void br_set_ticks(unsigned char *dest, int j)
  58 {
  59         unsigned long ticks = (STP_HZ * j)/ HZ;
  60
  61         put_unaligned(htons(ticks), (__be16 *)dest);
  62 }
  63
  64 static inline int br_get_ticks(const unsigned char *src)
  65 {
  66         unsigned long ticks = ntohs(get_unaligned((__be16 *)src));
  67
  68         return DIV_ROUND_UP(ticks * HZ, STP_HZ);
  69 }
  70
  71 /* called under bridge lock */
  72 void br_send_config_bpdu(struct net_bridge_port *p, struct br_config_bpdu *bpdu)
  73 {
  74         unsigned char buf[35];
  75
  76         if (p->br->stp_enabled != BR_KERNEL_STP)
  77                 return;
  78
  79         buf[0] = 0;
  80         buf[1] = 0;
  81         buf[2] = 0;
  82         buf[3] = BPDU_TYPE_CONFIG;
  83         buf[4] = (bpdu->topology_change ? 0x01 : 0) |
  84                 (bpdu->topology_change_ack ? 0x80 : 0);
  85         buf[5] = bpdu->root.prio[0];
  86         buf[6] = bpdu->root.prio[1];
  87         buf[7] = bpdu->root.addr[0];
  88         buf[8] = bpdu->root.addr[1];
  89         buf[9] = bpdu->root.addr[2];
  90         buf[10] = bpdu->root.addr[3];
  91         buf[11] = bpdu->root.addr[4];
  92         buf[12] = bpdu->root.addr[5];
  93         buf[13] = (bpdu->root_path_cost >> 24) & 0xFF;
  94         buf[14] = (bpdu->root_path_cost >> 16) & 0xFF;
  95         buf[15] = (bpdu->root_path_cost >> 8) & 0xFF;
  96         buf[16] = bpdu->root_path_cost & 0xFF;
  97         buf[17] = bpdu->bridge_id.prio[0];
  98         buf[18] = bpdu->bridge_id.prio[1];
  99         buf[19] = bpdu->bridge_id.addr[0];
 100         buf[20] = bpdu->bridge_id.addr[1];
 101         buf[21] = bpdu->bridge_id.addr[2];
 102         buf[22] = bpdu->bridge_id.addr[3];
 103         buf[23] = bpdu->bridge_id.addr[4];
 104         buf[24] = bpdu->bridge_id.addr[5];
 105         buf[25] = (bpdu->port_id >> 8) & 0xFF;
 106         buf[26] = bpdu->port_id & 0xFF;
 107
 108         br_set_ticks(buf+27, bpdu->message_age);
 109         br_set_ticks(buf+29, bpdu->max_age);
 110         br_set_ticks(buf+31, bpdu->hello_time);
 111         br_set_ticks(buf+33, bpdu->forward_delay);
 112
 113         br_send_bpdu(p, buf, 35);
 114 }
 115
 116 /* called under bridge lock */
 117 void br_send_tcn_bpdu(struct net_bridge_port *p)
 118 {
 119         unsigned char buf[4];
 120
 121         if (p->br->stp_enabled != BR_KERNEL_STP)
 122                 return;
 123
 124         buf[0] = 0;
 125         buf[1] = 0;
 126         buf[2] = 0;
 127         buf[3] = BPDU_TYPE_TCN;
 128         br_send_bpdu(p, buf, 4);
 129 }
 130
 131 /*
 132  * Called from llc.
 133  *
 134  * NO locks, but rcu_read_lock (preempt_disabled)
 135  */
 136 int br_stp_rcv(struct sk_buff *skb, struct net_device *dev,
 137                struct packet_type *pt, struct net_device *orig_dev)
 138 {
 139         const struct llc_pdu_un *pdu = llc_pdu_un_hdr(skb);
 140         const unsigned char *dest = eth_hdr(skb)->h_dest;
 141         struct net_bridge_port *p = rcu_dereference(dev->br_port);
 142         struct net_bridge *br;
 143         const unsigned char *buf;
 144
 145         if (dev_net(dev) != &init_net)
 146                 goto err;
 147
 148         if (!p)
 149                 goto err;
 150
 151         if (pdu->ssap != LLC_SAP_BSPAN
 152             || pdu->dsap != LLC_SAP_BSPAN
 153             || pdu->ctrl_1 != LLC_PDU_TYPE_U)
 154                 goto err;
 155
 156         if (!pskb_may_pull(skb, 4))
 157                 goto err;
 158
 159         /* compare of protocol id and version */
 160         buf = skb->data;
 161         if (buf[0] != 0 || buf[1] != 0 || buf[2] != 0)
 162                 goto err;
 163
 164         br = p->br;
 165         spin_lock(&br->lock);
 166
 167         if (br->stp_enabled != BR_KERNEL_STP)
 168                 goto out;
 169
 170         if (!(br->dev->flags & IFF_UP))
 171                 goto out;
 172
 173         if (p->state == BR_STATE_DISABLED)
 174                 goto out;
 175
 176         if (compare_ether_addr(dest, br->group_addr) != 0)
 177                 goto out;
 178
 179         buf = skb_pull(skb, 3);
 180
 181         if (buf[0] == BPDU_TYPE_CONFIG) {
 182                 struct br_config_bpdu bpdu;
 183
 184                 if (!pskb_may_pull(skb, 32))
 185                         goto out;
 186
 187                 buf = skb->data;
 188                 bpdu.topology_change = (buf[1] & 0x01) ? 1 : 0;
 189                 bpdu.topology_change_ack = (buf[1] & 0x80) ? 1 : 0;
 190
 191                 bpdu.root.prio[0] = buf[2];
 192                 bpdu.root.prio[1] = buf[3];
 193                 bpdu.root.addr[0] = buf[4];
 194                 bpdu.root.addr[1] = buf[5];
 195                 bpdu.root.addr[2] = buf[6];
 196                 bpdu.root.addr[3] = buf[7];
 197                 bpdu.root.addr[4] = buf[8];
 198                 bpdu.root.addr[5] = buf[9];
 199                 bpdu.root_path_cost =
 200                         (buf[10] << 24) |
 201                         (buf[11] << 16) |
 202                         (buf[12] << 8) |
 203                         buf[13];
 204                 bpdu.bridge_id.prio[0] = buf[14];
 205                 bpdu.bridge_id.prio[1] = buf[15];
 206                 bpdu.bridge_id.addr[0] = buf[16];
 207                 bpdu.bridge_id.addr[1] = buf[17];
 208                 bpdu.bridge_id.addr[2] = buf[18];
 209                 bpdu.bridge_id.addr[3] = buf[19];
 210                 bpdu.bridge_id.addr[4] = buf[20];
 211                 bpdu.bridge_id.addr[5] = buf[21];
 212                 bpdu.port_id = (buf[22] << 8) | buf[23];
 213
 214                 bpdu.message_age = br_get_ticks(buf+24);
 215                 bpdu.max_age = br_get_ticks(buf+26);
 216                 bpdu.hello_time = br_get_ticks(buf+28);
 217                 bpdu.forward_delay = br_get_ticks(buf+30);
 218
 219                 br_received_config_bpdu(p, &bpdu);
 220         }
 221
 222         else if (buf[0] == BPDU_TYPE_TCN) {
 223                 br_received_tcn_bpdu(p);
 224         }
 225  out:
 226         spin_unlock(&br->lock);
 227  err:
 228         kfree_skb(skb);
 229         return 0;
 230 }