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
  19 #include "br_private.h"
  20 #include "br_private_stp.h"
  21
  22 #define JIFFIES_TO_TICKS(j) (((j) << 8) / HZ)
  23 #define TICKS_TO_JIFFIES(j) (((j) * HZ) >> 8)
  24
  25 static void br_send_bpdu(struct net_bridge_port *p, unsigned char *data, int length)
  26 {
  27         struct net_device *dev;
  28         struct sk_buff *skb;
  29         int size;
  30
  31         if (!p->br->stp_enabled)
  32                 return;
  33
  34         size = length + 2*ETH_ALEN + 2;
  35         if (size < 60)
  36                 size = 60;
  37
  38         dev = p->dev;
  39
  40         if ((skb = dev_alloc_skb(size)) == NULL) {
  41                 printk(KERN_INFO "br: memory squeeze!\n");
  42                 return;
  43         }
  44
  45         skb->dev = dev;
  46         skb->protocol = htons(ETH_P_802_2);
  47         skb->mac.raw = skb_put(skb, size);
  48         memcpy(skb->mac.raw, bridge_ula, ETH_ALEN);
  49         memcpy(skb->mac.raw+ETH_ALEN, dev->dev_addr, ETH_ALEN);
  50         skb->mac.raw[2*ETH_ALEN] = 0;
  51         skb->mac.raw[2*ETH_ALEN+1] = length;
  52         skb->nh.raw = skb->mac.raw + 2*ETH_ALEN + 2;
  53         memcpy(skb->nh.raw, data, length);
  54         memset(skb->nh.raw + length, 0xa5, size - length - 2*ETH_ALEN - 2);
  55
  56         NF_HOOK(PF_BRIDGE, NF_BR_LOCAL_OUT, skb, NULL, skb->dev,
  57                 dev_queue_xmit);
  58 }
  59
  60 static __inline__ void br_set_ticks(unsigned char *dest, int jiff)
  61 {
  62         __u16 ticks;
  63
  64         ticks = JIFFIES_TO_TICKS(jiff);
  65         dest[0] = (ticks >> 8) & 0xFF;
  66         dest[1] = ticks & 0xFF;
  67 }
  68
  69 static __inline__ int br_get_ticks(unsigned char *dest)
  70 {
  71         return TICKS_TO_JIFFIES((dest[0] << 8) | dest[1]);
  72 }
  73
  74 /* called under bridge lock */
  75 void br_send_config_bpdu(struct net_bridge_port *p, struct br_config_bpdu *bpdu)
  76 {
  77         unsigned char buf[38];
  78
  79         buf[0] = 0x42;
  80         buf[1] = 0x42;
  81         buf[2] = 0x03;
  82         buf[3] = 0;
  83         buf[4] = 0;
  84         buf[5] = 0;
  85         buf[6] = BPDU_TYPE_CONFIG;
  86         buf[7] = (bpdu->topology_change ? 0x01 : 0) |
  87                 (bpdu->topology_change_ack ? 0x80 : 0);
  88         buf[8] = bpdu->root.prio[0];
  89         buf[9] = bpdu->root.prio[1];
  90         buf[10] = bpdu->root.addr[0];
  91         buf[11] = bpdu->root.addr[1];
  92         buf[12] = bpdu->root.addr[2];
  93         buf[13] = bpdu->root.addr[3];
  94         buf[14] = bpdu->root.addr[4];
  95         buf[15] = bpdu->root.addr[5];
  96         buf[16] = (bpdu->root_path_cost >> 24) & 0xFF;
  97         buf[17] = (bpdu->root_path_cost >> 16) & 0xFF;
  98         buf[18] = (bpdu->root_path_cost >> 8) & 0xFF;
  99         buf[19] = bpdu->root_path_cost & 0xFF;
 100         buf[20] = bpdu->bridge_id.prio[0];
 101         buf[21] = bpdu->bridge_id.prio[1];
 102         buf[22] = bpdu->bridge_id.addr[0];
 103         buf[23] = bpdu->bridge_id.addr[1];
 104         buf[24] = bpdu->bridge_id.addr[2];
 105         buf[25] = bpdu->bridge_id.addr[3];
 106         buf[26] = bpdu->bridge_id.addr[4];
 107         buf[27] = bpdu->bridge_id.addr[5];
 108         buf[28] = (bpdu->port_id >> 8) & 0xFF;
 109         buf[29] = bpdu->port_id & 0xFF;
 110
 111         br_set_ticks(buf+30, bpdu->message_age);
 112         br_set_ticks(buf+32, bpdu->max_age);
 113         br_set_ticks(buf+34, bpdu->hello_time);
 114         br_set_ticks(buf+36, bpdu->forward_delay);
 115
 116         br_send_bpdu(p, buf, 38);
 117 }
 118
 119 /* called under bridge lock */
 120 void br_send_tcn_bpdu(struct net_bridge_port *p)
 121 {
 122         unsigned char buf[7];
 123
 124         buf[0] = 0x42;
 125         buf[1] = 0x42;
 126         buf[2] = 0x03;
 127         buf[3] = 0;
 128         buf[4] = 0;
 129         buf[5] = 0;
 130         buf[6] = BPDU_TYPE_TCN;
 131         br_send_bpdu(p, buf, 7);
 132 }
 133
 134 static const unsigned char header[6] = {0x42, 0x42, 0x03, 0x00, 0x00, 0x00};
 135
 136 /* NO locks */
 137 int br_stp_handle_bpdu(struct sk_buff *skb)
 138 {
 139         struct net_bridge_port *p = skb->dev->br_port;
 140         struct net_bridge *br = p->br;
 141         unsigned char *buf;
 142
 143         /* insert into forwarding database after filtering to avoid spoofing */
 144         br_fdb_update(p->br, p, eth_hdr(skb)->h_source);
 145
 146         /* need at least the 802 and STP headers */
 147         if (!pskb_may_pull(skb, sizeof(header)+1) ||
 148             memcmp(skb->data, header, sizeof(header)))
 149                 goto err;
 150
 151         buf = skb_pull(skb, sizeof(header));
 152
 153         spin_lock_bh(&br->lock);
 154         if (p->state == BR_STATE_DISABLED
 155             || !(br->dev->flags & IFF_UP)
 156             || !br->stp_enabled)
 157                 goto out;
 158
 159         if (buf[0] == BPDU_TYPE_CONFIG) {
 160                 struct br_config_bpdu bpdu;
 161
 162                 if (!pskb_may_pull(skb, 32))
 163                     goto out;
 164
 165                 buf = skb->data;
 166                 bpdu.topology_change = (buf[1] & 0x01) ? 1 : 0;
 167                 bpdu.topology_change_ack = (buf[1] & 0x80) ? 1 : 0;
 168
 169                 bpdu.root.prio[0] = buf[2];
 170                 bpdu.root.prio[1] = buf[3];
 171                 bpdu.root.addr[0] = buf[4];
 172                 bpdu.root.addr[1] = buf[5];
 173                 bpdu.root.addr[2] = buf[6];
 174                 bpdu.root.addr[3] = buf[7];
 175                 bpdu.root.addr[4] = buf[8];
 176                 bpdu.root.addr[5] = buf[9];
 177                 bpdu.root_path_cost =
 178                         (buf[10] << 24) |
 179                         (buf[11] << 16) |
 180                         (buf[12] << 8) |
 181                         buf[13];
 182                 bpdu.bridge_id.prio[0] = buf[14];
 183                 bpdu.bridge_id.prio[1] = buf[15];
 184                 bpdu.bridge_id.addr[0] = buf[16];
 185                 bpdu.bridge_id.addr[1] = buf[17];
 186                 bpdu.bridge_id.addr[2] = buf[18];
 187                 bpdu.bridge_id.addr[3] = buf[19];
 188                 bpdu.bridge_id.addr[4] = buf[20];
 189                 bpdu.bridge_id.addr[5] = buf[21];
 190                 bpdu.port_id = (buf[22] << 8) | buf[23];
 191
 192                 bpdu.message_age = br_get_ticks(buf+24);
 193                 bpdu.max_age = br_get_ticks(buf+26);
 194                 bpdu.hello_time = br_get_ticks(buf+28);
 195                 bpdu.forward_delay = br_get_ticks(buf+30);
 196
 197                 br_received_config_bpdu(p, &bpdu);
 198         }
 199
 200         else if (buf[0] == BPDU_TYPE_TCN) {
 201                 br_received_tcn_bpdu(p);
 202         }
 203  out:
 204         spin_unlock_bh(&br->lock);
 205  err:
 206         kfree_skb(skb);
 207         return 0;
 208 }