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 <linux/slab.h>
  15 #include <linux/module.h>
  16 #include <net/llc.h>
  17 #include <net/llc_pdu.h>
  18 #include <net/stp.h>
  19
  20 /* 01:80:c2:00:00:20 - 01:80:c2:00:00:2F */
  21 #define GARP_ADDR_MIN   0x20
  22 #define GARP_ADDR_MAX   0x2F
  23 #define GARP_ADDR_RANGE (GARP_ADDR_MAX - GARP_ADDR_MIN)
  24
  25 static const struct stp_proto __rcu *garp_protos[GARP_ADDR_RANGE + 1] __read_mostly;
  26 static const struct stp_proto __rcu *stp_proto __read_mostly;
  27
  28 static struct llc_sap *sap __read_mostly;
  29 static unsigned int sap_registered;
  30 static DEFINE_MUTEX(stp_proto_mutex);
  31
  32 /* Called under rcu_read_lock from LLC */
  33 static int stp_pdu_rcv(struct sk_buff *skb, struct net_device *dev,
  34                        struct packet_type *pt, struct net_device *orig_dev)
  35 {
  36         const struct ethhdr *eh = eth_hdr(skb);
  37         const struct llc_pdu_un *pdu = llc_pdu_un_hdr(skb);
  38         const struct stp_proto *proto;
  39
  40         if (pdu->ssap != LLC_SAP_BSPAN ||
  41             pdu->dsap != LLC_SAP_BSPAN ||
  42             pdu->ctrl_1 != LLC_PDU_TYPE_U)
  43                 goto err;
  44
  45         if (eh->h_dest[5] >= GARP_ADDR_MIN && eh->h_dest[5] <= GARP_ADDR_MAX) {
  46                 proto = rcu_dereference(garp_protos[eh->h_dest[5] -
  47                                                     GARP_ADDR_MIN]);
  48                 if (proto &&
  49                     !ether_addr_equal(eh->h_dest, proto->group_address))
  50                         goto err;
  51         } else
  52                 proto = rcu_dereference(stp_proto);
  53
  54         if (!proto)
  55                 goto err;
  56
  57         proto->rcv(proto, skb, dev);
  58         return 0;
  59
  60 err:
  61         kfree_skb(skb);
  62         return 0;
  63 }
  64
  65 int stp_proto_register(const struct stp_proto *proto)
  66 {
  67         int err = 0;
  68
  69         mutex_lock(&stp_proto_mutex);
  70         if (sap_registered++ == 0) {
  71                 sap = llc_sap_open(LLC_SAP_BSPAN, stp_pdu_rcv);
  72                 if (!sap) {
  73                         err = -ENOMEM;
  74                         goto out;
  75                 }
  76         }
  77         if (is_zero_ether_addr(proto->group_address))
  78                 rcu_assign_pointer(stp_proto, proto);
  79         else
  80                 rcu_assign_pointer(garp_protos[proto->group_address[5] -
  81                                                GARP_ADDR_MIN], proto);
  82 out:
  83         mutex_unlock(&stp_proto_mutex);
  84         return err;
  85 }
  86 EXPORT_SYMBOL_GPL(stp_proto_register);
  87
  88 void stp_proto_unregister(const struct stp_proto *proto)
  89 {
  90         mutex_lock(&stp_proto_mutex);
  91         if (is_zero_ether_addr(proto->group_address))
  92                 RCU_INIT_POINTER(stp_proto, NULL);
  93         else
  94                 RCU_INIT_POINTER(garp_protos[proto->group_address[5] -
  95                                                GARP_ADDR_MIN], NULL);
  96         synchronize_rcu();
  97
  98         if (--sap_registered == 0)
  99                 llc_sap_put(sap);
 100         mutex_unlock(&stp_proto_mutex);
 101 }
 102 EXPORT_SYMBOL_GPL(stp_proto_unregister);
 103
 104 MODULE_LICENSE("GPL");