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