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