LXR linux/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
  23static const struct stp_proto *garp_protos[GARP_ADDR_RANGE + 1] __read_mostly;
  24static const struct stp_proto *stp_proto __read_mostly;
  25
  26static struct llc_sap *sap __read_mostly;
  27static unsigned int sap_registered;
  28static DEFINE_MUTEX(stp_proto_mutex);
  29
  30/* Called under rcu_read_lock from LLC */
  31static 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
  58err:
  59        kfree_skb(skb);
  60        return 0;
  61}
  62
  63int 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);
  80out:
  81        mutex_unlock(&stp_proto_mutex);
  82        return err;
  83}
  84EXPORT_SYMBOL_GPL(stp_proto_register);
  85
  86void 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}
 100EXPORT_SYMBOL_GPL(stp_proto_unregister);
 101
 102MODULE_LICENSE("GPL");
 103