LXR linux/net/802/stp.c

   1// SPDX-License-Identifier: GPL-2.0-only
   2/*
   3 *      STP SAP demux
   4 *
   5 *      Copyright (c) 2008 Patrick McHardy <kaber@trash.net>
   6 */
   7#include <linux/mutex.h>
   8#include <linux/skbuff.h>
   9#include <linux/etherdevice.h>
  10#include <linux/llc.h>
  11#include <linux/slab.h>
  12#include <linux/module.h>
  13#include <net/llc.h>
  14#include <net/llc_pdu.h>
  15#include <net/stp.h>
  16
  17/* 01:80:c2:00:00:20 - 01:80:c2:00:00:2F */
  18#define GARP_ADDR_MIN   0x20
  19#define GARP_ADDR_MAX   0x2F
  20#define GARP_ADDR_RANGE (GARP_ADDR_MAX - GARP_ADDR_MIN)
  21
  22static const struct stp_proto __rcu *garp_protos[GARP_ADDR_RANGE + 1] __read_mostly;
  23static const struct stp_proto __rcu *stp_proto __read_mostly;
  24
  25static struct llc_sap *sap __read_mostly;
  26static unsigned int sap_registered;
  27static DEFINE_MUTEX(stp_proto_mutex);
  28
  29/* Called under rcu_read_lock from LLC */
  30static int stp_pdu_rcv(struct sk_buff *skb, struct net_device *dev,
  31                       struct packet_type *pt, struct net_device *orig_dev)
  32{
  33        const struct ethhdr *eh = eth_hdr(skb);
  34        const struct llc_pdu_un *pdu = llc_pdu_un_hdr(skb);
  35        const struct stp_proto *proto;
  36
  37        if (pdu->ssap != LLC_SAP_BSPAN ||
  38            pdu->dsap != LLC_SAP_BSPAN ||
  39            pdu->ctrl_1 != LLC_PDU_TYPE_U)
  40                goto err;
  41
  42        if (eh->h_dest[5] >= GARP_ADDR_MIN && eh->h_dest[5] <= GARP_ADDR_MAX) {
  43                proto = rcu_dereference(garp_protos[eh->h_dest[5] -
  44                                                    GARP_ADDR_MIN]);
  45                if (proto &&
  46                    !ether_addr_equal(eh->h_dest, proto->group_address))
  47                        goto err;
  48        } else
  49                proto = rcu_dereference(stp_proto);
  50
  51        if (!proto)
  52                goto err;
  53
  54        proto->rcv(proto, skb, dev);
  55        return 0;
  56
  57err:
  58        kfree_skb(skb);
  59        return 0;
  60}
  61
  62int stp_proto_register(const struct stp_proto *proto)
  63{
  64        int err = 0;
  65
  66        mutex_lock(&stp_proto_mutex);
  67        if (sap_registered++ == 0) {
  68                sap = llc_sap_open(LLC_SAP_BSPAN, stp_pdu_rcv);
  69                if (!sap) {
  70                        err = -ENOMEM;
  71                        goto out;
  72                }
  73        }
  74        if (is_zero_ether_addr(proto->group_address))
  75                rcu_assign_pointer(stp_proto, proto);
  76        else
  77                rcu_assign_pointer(garp_protos[proto->group_address[5] -
  78                                               GARP_ADDR_MIN], proto);
  79out:
  80        mutex_unlock(&stp_proto_mutex);
  81        return err;
  82}
  83EXPORT_SYMBOL_GPL(stp_proto_register);
  84
  85void stp_proto_unregister(const struct stp_proto *proto)
  86{
  87        mutex_lock(&stp_proto_mutex);
  88        if (is_zero_ether_addr(proto->group_address))
  89                RCU_INIT_POINTER(stp_proto, NULL);
  90        else
  91                RCU_INIT_POINTER(garp_protos[proto->group_address[5] -
  92                                               GARP_ADDR_MIN], NULL);
  93        synchronize_rcu();
  94
  95        if (--sap_registered == 0)
  96                llc_sap_put(sap);
  97        mutex_unlock(&stp_proto_mutex);
  98}
  99EXPORT_SYMBOL_GPL(stp_proto_unregister);
 100
 101MODULE_LICENSE("GPL");
 102