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

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