linux/net/802/stp.c
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   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
  25static const struct stp_proto __rcu *garp_protos[GARP_ADDR_RANGE + 1] __read_mostly;
  26static const struct stp_proto __rcu *stp_proto __read_mostly;
  27
  28static struct llc_sap *sap __read_mostly;
  29static unsigned int sap_registered;
  30static DEFINE_MUTEX(stp_proto_mutex);
  31
  32/* Called under rcu_read_lock from LLC */
  33static 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
  60err:
  61        kfree_skb(skb);
  62        return 0;
  63}
  64
  65int 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);
  82out:
  83        mutex_unlock(&stp_proto_mutex);
  84        return err;
  85}
  86EXPORT_SYMBOL_GPL(stp_proto_register);
  87
  88void 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}
 102EXPORT_SYMBOL_GPL(stp_proto_unregister);
 103
 104MODULE_LICENSE("GPL");
 105
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