net/802/stp.c

   1 /*
   2  *      STP SAP demux
   3  *
   4  *      Copyright (c) 2008 Patrick McHardy <kaber@trash.net>
   5  *
   6  *      This program is free software; you can redistribute it and/or
   7  *      modify it under the terms of the GNU General Public License
   8  *      version 2 as published by the Free Software Foundation.
   9  */
  10 #include <linux/mutex.h>
  11 #include <linux/skbuff.h>
  12 #include <linux/etherdevice.h>
  13 #include <linux/llc.h>
  14 #include <net/llc.h>
  15 #include <net/llc_pdu.h>
  16 #include <net/stp.h>
  17
  18 /* 01:80:c2:00:00:20 - 01:80:c2:00:00:2F */
  19 #define GARP_ADDR_MIN   0x20
  20 #define GARP_ADDR_MAX   0x2F
  21 #define GARP_ADDR_RANGE (GARP_ADDR_MAX - GARP_ADDR_MIN)
  22
  23 static const struct stp_proto *garp_protos[GARP_ADDR_RANGE + 1] __read_mostly;
  24 static const struct stp_proto *stp_proto __read_mostly;
  25
  26 static struct llc_sap *sap __read_mostly;
  27 static unsigned int sap_registered;
  28 static DEFINE_MUTEX(stp_proto_mutex);
  29
  30 /* Called under rcu_read_lock from LLC */
  31 static int stp_pdu_rcv(struct sk_buff *skb, struct net_device *dev,
  32                        struct packet_type *pt, struct net_device *orig_dev)
  33 {
  34         const struct ethhdr *eh = eth_hdr(skb);
  35         const struct llc_pdu_un *pdu = llc_pdu_un_hdr(skb);
  36         const struct stp_proto *proto;
  37
  38         if (pdu->ssap != LLC_SAP_BSPAN ||
  39             pdu->dsap != LLC_SAP_BSPAN ||
  40             pdu->ctrl_1 != LLC_PDU_TYPE_U)
  41                 goto err;
  42
  43         if (eh->h_dest[5] >= GARP_ADDR_MIN && eh->h_dest[5] <= GARP_ADDR_MAX) {
  44                 proto = rcu_dereference(garp_protos[eh->h_dest[5] -
  45                                                     GARP_ADDR_MIN]);
  46                 if (proto &&
  47                     compare_ether_addr(eh->h_dest, proto->group_address))
  48                         goto err;
  49         } else
  50                 proto = rcu_dereference(stp_proto);
  51
  52         if (!proto)
  53                 goto err;
  54
  55         proto->rcv(proto, skb, dev);
  56         return 0;
  57
  58 err:
  59         kfree_skb(skb);
  60         return 0;
  61 }
  62
  63 int stp_proto_register(const struct stp_proto *proto)
  64 {
  65         int err = 0;
  66
  67         mutex_lock(&stp_proto_mutex);
  68         if (sap_registered++ == 0) {
  69                 sap = llc_sap_open(LLC_SAP_BSPAN, stp_pdu_rcv);
  70                 if (!sap) {
  71                         err = -ENOMEM;
  72                         goto out;
  73                 }
  74         }
  75         if (is_zero_ether_addr(proto->group_address))
  76                 rcu_assign_pointer(stp_proto, proto);
  77         else
  78                 rcu_assign_pointer(garp_protos[proto->group_address[5] -
  79                                                GARP_ADDR_MIN], proto);
  80 out:
  81         mutex_unlock(&stp_proto_mutex);
  82         return err;
  83 }
  84 EXPORT_SYMBOL_GPL(stp_proto_register);
  85
  86 void stp_proto_unregister(const struct stp_proto *proto)
  87 {
  88         mutex_lock(&stp_proto_mutex);
  89         if (is_zero_ether_addr(proto->group_address))
  90                 rcu_assign_pointer(stp_proto, NULL);
  91         else
  92                 rcu_assign_pointer(garp_protos[proto->group_address[5] -
  93                                                GARP_ADDR_MIN], NULL);
  94         synchronize_rcu();
  95
  96         if (--sap_registered == 0)
  97                 llc_sap_put(sap);
  98         mutex_unlock(&stp_proto_mutex);
  99 }
 100 EXPORT_SYMBOL_GPL(stp_proto_unregister);
 101
 102 MODULE_LICENSE("GPL");