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  *      This program is free software; you can redistribute it and/or
   9  *      modify it under the terms of the GNU General Public License
  10  *      as published by the Free Software Foundation; either version
  11  *      2 of the License, or (at your option) any later version.
  12  */
  13
  14 #include <linux/kernel.h>
  15 #include <linux/netfilter_bridge.h>
  16 #include <linux/etherdevice.h>
  17 #include <linux/llc.h>
  18 #include <net/net_namespace.h>
  19 #include <net/llc.h>
  20 #include <net/llc_pdu.h>
  21 #include <net/stp.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         skb = dev_alloc_skb(length+LLC_RESERVE);
  37         if (!skb)
  38                 return;
  39
  40         skb->dev = p->dev;
  41         skb->protocol = htons(ETH_P_802_2);
  42
  43         skb_reserve(skb, LLC_RESERVE);
  44         memcpy(__skb_put(skb, length), data, length);
  45
  46         llc_pdu_header_init(skb, LLC_PDU_TYPE_U, LLC_SAP_BSPAN,
  47                             LLC_SAP_BSPAN, LLC_PDU_CMD);
  48         llc_pdu_init_as_ui_cmd(skb);
  49
  50         llc_mac_hdr_init(skb, p->dev->dev_addr, p->br->group_addr);
  51
  52         NF_HOOK(PF_BRIDGE, NF_BR_LOCAL_OUT, skb, NULL, skb->dev,
  53                 dev_queue_xmit);
  54 }
  55
  56 static inline void br_set_ticks(unsigned char *dest, int j)
  57 {
  58         unsigned long ticks = (STP_HZ * j)/ HZ;
  59
  60         put_unaligned_be16(ticks, dest);
  61 }
  62
  63 static inline int br_get_ticks(const unsigned char *src)
  64 {
  65         unsigned long ticks = get_unaligned_be16(src);
  66
  67         return DIV_ROUND_UP(ticks * HZ, STP_HZ);
  68 }
  69
  70 /* called under bridge lock */
  71 void br_send_config_bpdu(struct net_bridge_port *p, struct br_config_bpdu *bpdu)
  72 {
  73         unsigned char buf[35];
  74
  75         if (p->br->stp_enabled != BR_KERNEL_STP)
  76                 return;
  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         if (p->br->stp_enabled != BR_KERNEL_STP)
 121                 return;
 122
 123         buf[0] = 0;
 124         buf[1] = 0;
 125         buf[2] = 0;
 126         buf[3] = BPDU_TYPE_TCN;
 127         br_send_bpdu(p, buf, 4);
 128 }
 129
 130 /*
 131  * Called from llc.
 132  *
 133  * NO locks, but rcu_read_lock (preempt_disabled)
 134  */
 135 void br_stp_rcv(const struct stp_proto *proto, struct sk_buff *skb,
 136                 struct net_device *dev)
 137 {
 138         const unsigned char *dest = eth_hdr(skb)->h_dest;
 139         struct net_bridge_port *p = rcu_dereference(dev->br_port);
 140         struct net_bridge *br;
 141         const unsigned char *buf;
 142
 143         if (!p)
 144                 goto err;
 145
 146         if (!pskb_may_pull(skb, 4))
 147                 goto err;
 148
 149         /* compare of protocol id and version */
 150         buf = skb->data;
 151         if (buf[0] != 0 || buf[1] != 0 || buf[2] != 0)
 152                 goto err;
 153
 154         br = p->br;
 155         spin_lock(&br->lock);
 156
 157         if (br->stp_enabled != BR_KERNEL_STP)
 158                 goto out;
 159
 160         if (!(br->dev->flags & IFF_UP))
 161                 goto out;
 162
 163         if (p->state == BR_STATE_DISABLED)
 164                 goto out;
 165
 166         if (compare_ether_addr(dest, br->group_addr) != 0)
 167                 goto out;
 168
 169         buf = skb_pull(skb, 3);
 170
 171         if (buf[0] == BPDU_TYPE_CONFIG) {
 172                 struct br_config_bpdu bpdu;
 173
 174                 if (!pskb_may_pull(skb, 32))
 175                         goto out;
 176
 177                 buf = skb->data;
 178                 bpdu.topology_change = (buf[1] & 0x01) ? 1 : 0;
 179                 bpdu.topology_change_ack = (buf[1] & 0x80) ? 1 : 0;
 180
 181                 bpdu.root.prio[0] = buf[2];
 182                 bpdu.root.prio[1] = buf[3];
 183                 bpdu.root.addr[0] = buf[4];
 184                 bpdu.root.addr[1] = buf[5];
 185                 bpdu.root.addr[2] = buf[6];
 186                 bpdu.root.addr[3] = buf[7];
 187                 bpdu.root.addr[4] = buf[8];
 188                 bpdu.root.addr[5] = buf[9];
 189                 bpdu.root_path_cost =
 190                         (buf[10] << 24) |
 191                         (buf[11] << 16) |
 192                         (buf[12] << 8) |
 193                         buf[13];
 194                 bpdu.bridge_id.prio[0] = buf[14];
 195                 bpdu.bridge_id.prio[1] = buf[15];
 196                 bpdu.bridge_id.addr[0] = buf[16];
 197                 bpdu.bridge_id.addr[1] = buf[17];
 198                 bpdu.bridge_id.addr[2] = buf[18];
 199                 bpdu.bridge_id.addr[3] = buf[19];
 200                 bpdu.bridge_id.addr[4] = buf[20];
 201                 bpdu.bridge_id.addr[5] = buf[21];
 202                 bpdu.port_id = (buf[22] << 8) | buf[23];
 203
 204                 bpdu.message_age = br_get_ticks(buf+24);
 205                 bpdu.max_age = br_get_ticks(buf+26);
 206                 bpdu.hello_time = br_get_ticks(buf+28);
 207                 bpdu.forward_delay = br_get_ticks(buf+30);
 208
 209                 br_received_config_bpdu(p, &bpdu);
 210         }
 211
 212         else if (buf[0] == BPDU_TYPE_TCN) {
 213                 br_received_tcn_bpdu(p);
 214         }
 215  out:
 216         spin_unlock(&br->lock);
 217  err:
 218         kfree_skb(skb);
 219 }