snap: remove one synchronize_net()
[linux-2.6.git] / 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
24 static const struct stp_proto __rcu *garp_protos[GARP_ADDR_RANGE + 1] __read_mostly;
25 static const struct stp_proto __rcu *stp_proto __read_mostly;
26
27 static struct llc_sap *sap __read_mostly;
28 static unsigned int sap_registered;
29 static DEFINE_MUTEX(stp_proto_mutex);
30
31 /* Called under rcu_read_lock from LLC */
32 static 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
59 err:
60         kfree_skb(skb);
61         return 0;
62 }
63
64 int 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);
81 out:
82         mutex_unlock(&stp_proto_mutex);
83         return err;
84 }
85 EXPORT_SYMBOL_GPL(stp_proto_register);
86
87 void 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 }
101 EXPORT_SYMBOL_GPL(stp_proto_unregister);
102
103 MODULE_LICENSE("GPL");