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

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