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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  *      $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/llc_pdu.h>
  21
  22 #include "br_private.h"
  23 #include "br_private_stp.h"
  24
  25 #define STP_HZ          256
  26
  27 static void br_send_bpdu(struct net_bridge_port *p, unsigned char *data, int length)
  28 {
  29         struct net_device *dev;
  30         struct sk_buff *skb;
  31         int size;
  32
  33         if (!p->br->stp_enabled)
  34                 return;
  35
  36         size = length + 2*ETH_ALEN + 2;
  37         if (size < 60)
  38                 size = 60;
  39
  40         dev = p->dev;
  41
  42         if ((skb = dev_alloc_skb(size)) == NULL) {
  43                 printk(KERN_INFO "br: memory squeeze!\n");
  44                 return;
  45         }
  46
  47         skb->dev = dev;
  48         skb->protocol = htons(ETH_P_802_2);
  49         skb->mac.raw = skb_put(skb, size);
  50         memcpy(skb->mac.raw, bridge_ula, ETH_ALEN);
  51         memcpy(skb->mac.raw+ETH_ALEN, dev->dev_addr, ETH_ALEN);
  52         skb->mac.raw[2*ETH_ALEN] = 0;
  53         skb->mac.raw[2*ETH_ALEN+1] = length;
  54         skb->nh.raw = skb->mac.raw + 2*ETH_ALEN + 2;
  55         memcpy(skb->nh.raw, data, length);
  56         memset(skb->nh.raw + length, 0xa5, size - length - 2*ETH_ALEN - 2);
  57
  58         NF_HOOK(PF_BRIDGE, NF_BR_LOCAL_OUT, skb, NULL, skb->dev,
  59                 dev_queue_xmit);
  60 }
  61
  62 static inline void br_set_ticks(unsigned char *dest, int j)
  63 {
  64         unsigned long ticks = (STP_HZ * j)/ HZ;
  65
  66         *((__be16 *) dest) = htons(ticks);
  67 }
  68
  69 static inline int br_get_ticks(const unsigned char *src)
  70 {
  71         unsigned long ticks = ntohs(*(__be16 *)src);
  72
  73         return (ticks * HZ + STP_HZ - 1) / STP_HZ;
  74 }
  75
  76 /* called under bridge lock */
  77 void br_send_config_bpdu(struct net_bridge_port *p, struct br_config_bpdu *bpdu)
  78 {
  79         unsigned char buf[38];
  80
  81         buf[0] = 0x42;
  82         buf[1] = 0x42;
  83         buf[2] = 0x03;
  84         buf[3] = 0;
  85         buf[4] = 0;
  86         buf[5] = 0;
  87         buf[6] = BPDU_TYPE_CONFIG;
  88         buf[7] = (bpdu->topology_change ? 0x01 : 0) |
  89                 (bpdu->topology_change_ack ? 0x80 : 0);
  90         buf[8] = bpdu->root.prio[0];
  91         buf[9] = bpdu->root.prio[1];
  92         buf[10] = bpdu->root.addr[0];
  93         buf[11] = bpdu->root.addr[1];
  94         buf[12] = bpdu->root.addr[2];
  95         buf[13] = bpdu->root.addr[3];
  96         buf[14] = bpdu->root.addr[4];
  97         buf[15] = bpdu->root.addr[5];
  98         buf[16] = (bpdu->root_path_cost >> 24) & 0xFF;
  99         buf[17] = (bpdu->root_path_cost >> 16) & 0xFF;
 100         buf[18] = (bpdu->root_path_cost >> 8) & 0xFF;
 101         buf[19] = bpdu->root_path_cost & 0xFF;
 102         buf[20] = bpdu->bridge_id.prio[0];
 103         buf[21] = bpdu->bridge_id.prio[1];
 104         buf[22] = bpdu->bridge_id.addr[0];
 105         buf[23] = bpdu->bridge_id.addr[1];
 106         buf[24] = bpdu->bridge_id.addr[2];
 107         buf[25] = bpdu->bridge_id.addr[3];
 108         buf[26] = bpdu->bridge_id.addr[4];
 109         buf[27] = bpdu->bridge_id.addr[5];
 110         buf[28] = (bpdu->port_id >> 8) & 0xFF;
 111         buf[29] = bpdu->port_id & 0xFF;
 112
 113         br_set_ticks(buf+30, bpdu->message_age);
 114         br_set_ticks(buf+32, bpdu->max_age);
 115         br_set_ticks(buf+34, bpdu->hello_time);
 116         br_set_ticks(buf+36, bpdu->forward_delay);
 117
 118         br_send_bpdu(p, buf, 38);
 119 }
 120
 121 /* called under bridge lock */
 122 void br_send_tcn_bpdu(struct net_bridge_port *p)
 123 {
 124         unsigned char buf[7];
 125
 126         buf[0] = 0x42;
 127         buf[1] = 0x42;
 128         buf[2] = 0x03;
 129         buf[3] = 0;
 130         buf[4] = 0;
 131         buf[5] = 0;
 132         buf[6] = BPDU_TYPE_TCN;
 133         br_send_bpdu(p, buf, 7);
 134 }
 135
 136 /*
 137  * Called from llc.
 138  *
 139  * NO locks, but rcu_read_lock (preempt_disabled)
 140  */
 141 int br_stp_rcv(struct sk_buff *skb, struct net_device *dev,
 142                struct packet_type *pt, struct net_device *orig_dev)
 143 {
 144         const struct llc_pdu_un *pdu = llc_pdu_un_hdr(skb);
 145         const unsigned char *dest = eth_hdr(skb)->h_dest;
 146         struct net_bridge_port *p = rcu_dereference(dev->br_port);
 147         struct net_bridge *br;
 148         const unsigned char *buf;
 149
 150         if (!p)
 151                 goto err;
 152
 153         if (pdu->ssap != LLC_SAP_BSPAN
 154             || pdu->dsap != LLC_SAP_BSPAN
 155             || pdu->ctrl_1 != LLC_PDU_TYPE_U)
 156                 goto err;
 157
 158         if (!pskb_may_pull(skb, 4))
 159                 goto err;
 160
 161         /* compare of protocol id and version */
 162         buf = skb->data;
 163         if (buf[0] != 0 || buf[1] != 0 || buf[2] != 0)
 164                 goto err;
 165
 166         br = p->br;
 167         spin_lock(&br->lock);
 168
 169         if (p->state == BR_STATE_DISABLED
 170             || !br->stp_enabled
 171             || !(br->dev->flags & IFF_UP))
 172                 goto out;
 173
 174         if (compare_ether_addr(dest, bridge_ula) != 0)
 175                 goto out;
 176
 177         buf = skb_pull(skb, 3);
 178
 179         if (buf[0] == BPDU_TYPE_CONFIG) {
 180                 struct br_config_bpdu bpdu;
 181
 182                 if (!pskb_may_pull(skb, 32))
 183                         goto out;
 184
 185                 buf = skb->data;
 186                 bpdu.topology_change = (buf[1] & 0x01) ? 1 : 0;
 187                 bpdu.topology_change_ack = (buf[1] & 0x80) ? 1 : 0;
 188
 189                 bpdu.root.prio[0] = buf[2];
 190                 bpdu.root.prio[1] = buf[3];
 191                 bpdu.root.addr[0] = buf[4];
 192                 bpdu.root.addr[1] = buf[5];
 193                 bpdu.root.addr[2] = buf[6];
 194                 bpdu.root.addr[3] = buf[7];
 195                 bpdu.root.addr[4] = buf[8];
 196                 bpdu.root.addr[5] = buf[9];
 197                 bpdu.root_path_cost =
 198                         (buf[10] << 24) |
 199                         (buf[11] << 16) |
 200                         (buf[12] << 8) |
 201                         buf[13];
 202                 bpdu.bridge_id.prio[0] = buf[14];
 203                 bpdu.bridge_id.prio[1] = buf[15];
 204                 bpdu.bridge_id.addr[0] = buf[16];
 205                 bpdu.bridge_id.addr[1] = buf[17];
 206                 bpdu.bridge_id.addr[2] = buf[18];
 207                 bpdu.bridge_id.addr[3] = buf[19];
 208                 bpdu.bridge_id.addr[4] = buf[20];
 209                 bpdu.bridge_id.addr[5] = buf[21];
 210                 bpdu.port_id = (buf[22] << 8) | buf[23];
 211
 212                 bpdu.message_age = br_get_ticks(buf+24);
 213                 bpdu.max_age = br_get_ticks(buf+26);
 214                 bpdu.hello_time = br_get_ticks(buf+28);
 215                 bpdu.forward_delay = br_get_ticks(buf+30);
 216
 217                 br_received_config_bpdu(p, &bpdu);
 218         }
 219
 220         else if (buf[0] == BPDU_TYPE_TCN) {
 221                 br_received_tcn_bpdu(p);
 222         }
 223  out:
 224         spin_unlock(&br->lock);
 225  err:
 226         kfree_skb(skb);
 227         return 0;
 228 }