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