1 /*
2 * SNAP data link layer. Derived from 802.2
3 *
4 * Alan Cox <Alan.Cox@linux.org>,
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 <net/datalink.h>
18 #include <net/llc.h>
19 #include <net/psnap.h>
20 #include <linux/mm.h>
21 #include <linux/in.h>
22 #include <linux/init.h>
23
24 static LIST_HEAD(snap_list);
25 static DEFINE_SPINLOCK(snap_lock);
26 static struct llc_sap *snap_sap;
27
28 /*
29 * Find a snap client by matching the 5 bytes.
30 */
31 static struct datalink_proto *find_snap_client(unsigned char *desc)
32 {
33 struct list_head *entry;
34 struct datalink_proto *proto = NULL, *p;
35
36 list_for_each_rcu(entry, &snap_list) {
37 p = list_entry(entry, struct datalink_proto, 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 = __constant_htons(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 char snap_err_msg[] __initdata =
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
106 if (!snap_sap)
107 printk(snap_err_msg);
108
109 return 0;
110 }
111
112 module_init(snap_init);
113
114 static void __exit snap_exit(void)
115 {
116 llc_sap_put(snap_sap);
117 }
118
119 module_exit(snap_exit);
120
121
122 /*
123 * Register SNAP clients. We don't yet use this for IP.
124 */
125 struct datalink_proto *register_snap_client(unsigned char *desc,
126 int (*rcvfunc)(struct sk_buff *,
127 struct net_device *,
128 struct packet_type *,
129 struct net_device *))
130 {
131 struct datalink_proto *proto = NULL;
132
133 spin_lock_bh(&snap_lock);
134
135 if (find_snap_client(desc))
136 goto out;
137
138 proto = kmalloc(sizeof(*proto), GFP_ATOMIC);
139 if (proto) {
140 memcpy(proto->type, desc,5);
141 proto->rcvfunc = rcvfunc;
142 proto->header_length = 5 + 3; /* snap + 802.2 */
143 proto->request = snap_request;
144 list_add_rcu(&proto->node, &snap_list);
145 }
146 out:
147 spin_unlock_bh(&snap_lock);
148
149 synchronize_net();
150 return proto;
151 }
152
153 /*
154 * Unregister SNAP clients. Protocols no longer want to play with us ...
155 */
156 void unregister_snap_client(struct datalink_proto *proto)
157 {
158 spin_lock_bh(&snap_lock);
159 list_del_rcu(&proto->node);
160 spin_unlock_bh(&snap_lock);
161
162 synchronize_net();
163
164 kfree(proto);
165 }
166
167 MODULE_LICENSE("GPL");
168
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