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Linux/net/802/stp.c

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

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