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1 | /* | |
2 | * SNAP data link layer. Derived from 802.2 | |
3 | * | |
4 | * Alan Cox <alan@lxorguk.ukuu.org.uk>, | |
5 | * from the 802.2 layer by Greg Page. | |
6 | * Merged in additions from Greg Page's psnap.c. | |
7 | * | |
8 | * This program is free software; you can redistribute it and/or | |
9 | * modify it under the terms of the GNU General Public License | |
10 | * as published by the Free Software Foundation; either version | |
11 | * 2 of the License, or (at your option) any later version. | |
12 | */ | |
13 | ||
14 | #include <linux/module.h> | |
15 | #include <linux/netdevice.h> | |
16 | #include <linux/skbuff.h> | |
17 | #include <linux/slab.h> | |
18 | #include <net/datalink.h> | |
19 | #include <net/llc.h> | |
20 | #include <net/psnap.h> | |
21 | #include <linux/mm.h> | |
22 | #include <linux/in.h> | |
23 | #include <linux/init.h> | |
24 | #include <linux/rculist.h> | |
25 | ||
26 | static LIST_HEAD(snap_list); | |
27 | static DEFINE_SPINLOCK(snap_lock); | |
28 | static struct llc_sap *snap_sap; | |
29 | ||
30 | /* | |
31 | * Find a snap client by matching the 5 bytes. | |
32 | */ | |
33 | static struct datalink_proto *find_snap_client(const unsigned char *desc) | |
34 | { | |
35 | struct datalink_proto *proto = NULL, *p; | |
36 | ||
37 | list_for_each_entry_rcu(p, &snap_list, node) { | |
38 | if (!memcmp(p->type, desc, 5)) { | |
39 | proto = p; | |
40 | break; | |
41 | } | |
42 | } | |
43 | return proto; | |
44 | } | |
45 | ||
46 | /* | |
47 | * A SNAP packet has arrived | |
48 | */ | |
49 | static int snap_rcv(struct sk_buff *skb, struct net_device *dev, | |
50 | struct packet_type *pt, struct net_device *orig_dev) | |
51 | { | |
52 | int rc = 1; | |
53 | struct datalink_proto *proto; | |
54 | static struct packet_type snap_packet_type = { | |
55 | .type = cpu_to_be16(ETH_P_SNAP), | |
56 | }; | |
57 | ||
58 | if (unlikely(!pskb_may_pull(skb, 5))) | |
59 | goto drop; | |
60 | ||
61 | rcu_read_lock(); | |
62 | proto = find_snap_client(skb_transport_header(skb)); | |
63 | if (proto) { | |
64 | /* Pass the frame on. */ | |
65 | skb->transport_header += 5; | |
66 | skb_pull_rcsum(skb, 5); | |
67 | rc = proto->rcvfunc(skb, dev, &snap_packet_type, orig_dev); | |
68 | } | |
69 | rcu_read_unlock(); | |
70 | ||
71 | if (unlikely(!proto)) | |
72 | goto drop; | |
73 | ||
74 | out: | |
75 | return rc; | |
76 | ||
77 | drop: | |
78 | kfree_skb(skb); | |
79 | goto out; | |
80 | } | |
81 | ||
82 | /* | |
83 | * Put a SNAP header on a frame and pass to 802.2 | |
84 | */ | |
85 | static int snap_request(struct datalink_proto *dl, | |
86 | struct sk_buff *skb, u8 *dest) | |
87 | { | |
88 | memcpy(skb_push(skb, 5), dl->type, 5); | |
89 | llc_build_and_send_ui_pkt(snap_sap, skb, dest, snap_sap->laddr.lsap); | |
90 | return 0; | |
91 | } | |
92 | ||
93 | /* | |
94 | * Set up the SNAP layer | |
95 | */ | |
96 | EXPORT_SYMBOL(register_snap_client); | |
97 | EXPORT_SYMBOL(unregister_snap_client); | |
98 | ||
99 | static const char snap_err_msg[] __initconst = | |
100 | KERN_CRIT "SNAP - unable to register with 802.2\n"; | |
101 | ||
102 | static int __init snap_init(void) | |
103 | { | |
104 | snap_sap = llc_sap_open(0xAA, snap_rcv); | |
105 | if (!snap_sap) { | |
106 | printk(snap_err_msg); | |
107 | return -EBUSY; | |
108 | } | |
109 | ||
110 | return 0; | |
111 | } | |
112 | ||
113 | module_init(snap_init); | |
114 | ||
115 | static void __exit snap_exit(void) | |
116 | { | |
117 | llc_sap_put(snap_sap); | |
118 | } | |
119 | ||
120 | module_exit(snap_exit); | |
121 | ||
122 | ||
123 | /* | |
124 | * Register SNAP clients. We don't yet use this for IP. | |
125 | */ | |
126 | struct datalink_proto *register_snap_client(const unsigned char *desc, | |
127 | int (*rcvfunc)(struct sk_buff *, | |
128 | struct net_device *, | |
129 | struct packet_type *, | |
130 | struct net_device *)) | |
131 | { | |
132 | struct datalink_proto *proto = NULL; | |
133 | ||
134 | spin_lock_bh(&snap_lock); | |
135 | ||
136 | if (find_snap_client(desc)) | |
137 | goto out; | |
138 | ||
139 | proto = kmalloc(sizeof(*proto), GFP_ATOMIC); | |
140 | if (proto) { | |
141 | memcpy(proto->type, desc, 5); | |
142 | proto->rcvfunc = rcvfunc; | |
143 | proto->header_length = 5 + 3; /* snap + 802.2 */ | |
144 | proto->request = snap_request; | |
145 | list_add_rcu(&proto->node, &snap_list); | |
146 | } | |
147 | out: | |
148 | spin_unlock_bh(&snap_lock); | |
149 | ||
150 | synchronize_net(); | |
151 | return proto; | |
152 | } | |
153 | ||
154 | /* | |
155 | * Unregister SNAP clients. Protocols no longer want to play with us ... | |
156 | */ | |
157 | void unregister_snap_client(struct datalink_proto *proto) | |
158 | { | |
159 | spin_lock_bh(&snap_lock); | |
160 | list_del_rcu(&proto->node); | |
161 | spin_unlock_bh(&snap_lock); | |
162 | ||
163 | synchronize_net(); | |
164 | ||
165 | kfree(proto); | |
166 | } | |
167 | ||
168 | MODULE_LICENSE("GPL"); |