1 /*
2 * SNAP data link layer. Derived from 802.2
3 *
4 * Alan Cox <Alan.Cox@linux.org>, from the 802.2 layer by Greg Page.
5 * Merged in additions from Greg Page's psnap.c.
6 *
7 * This program is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU General Public License
9 * as published by the Free Software Foundation; either version
10 * 2 of the License, or (at your option) any later version.
11 */
12
13 #include <linux/module.h>
14 #include <linux/netdevice.h>
15 #include <linux/skbuff.h>
16 #include <net/datalink.h>
17 #include <net/p8022.h>
18 #include <net/psnap.h>
19 #include <linux/mm.h>
20 #include <linux/in.h>
21 #include <linux/init.h>
22
23 static struct datalink_proto *snap_list = NULL;
24 static struct datalink_proto *snap_dl = NULL; /* 802.2 DL for SNAP */
25
26 /*
27 * Find a snap client by matching the 5 bytes.
28 */
29
30 static struct datalink_proto *find_snap_client(unsigned char *desc)
31 {
32 struct datalink_proto *proto;
33
34 for (proto = snap_list; proto != NULL && memcmp(proto->type, desc, 5) ; proto = proto->next);
35 return proto;
36 }
37
38 /*
39 * A SNAP packet has arrived
40 */
41
42 int snap_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt)
43 {
44 static struct packet_type psnap_packet_type =
45 {
46 0,
47 NULL, /* All Devices */
48 snap_rcv,
49 NULL,
50 NULL,
51 };
52
53 struct datalink_proto *proto;
54
55 proto = find_snap_client(skb->h.raw);
56 if (proto != NULL)
57 {
58 /*
59 * Pass the frame on.
60 */
61
62 skb->h.raw += 5;
63 skb->nh.raw += 5;
64 skb_pull(skb,5);
65 if (psnap_packet_type.type == 0)
66 psnap_packet_type.type=htons(ETH_P_SNAP);
67
68 return proto->rcvfunc(skb, dev, &psnap_packet_type);
69 }
70 skb->sk = NULL;
71 kfree_skb(skb);
72 return 0;
73 }
74
75 /*
76 * Put a SNAP header on a frame and pass to 802.2
77 */
78
79 static void snap_datalink_header(struct datalink_proto *dl, struct sk_buff *skb, unsigned char *dest_node)
80 {
81 memcpy(skb_push(skb,5),dl->type,5);
82 snap_dl->datalink_header(snap_dl, skb, dest_node);
83 }
84
85 /*
86 * Set up the SNAP layer
87 */
88
89 EXPORT_SYMBOL(register_snap_client);
90 EXPORT_SYMBOL(unregister_snap_client);
91
92 static int __init snap_init(void)
93 {
94 snap_dl=register_8022_client(0xAA, snap_rcv);
95 if(snap_dl==NULL)
96 printk("SNAP - unable to register with 802.2\n");
97 return 0;
98 }
99 module_init(snap_init);
100
101 /*
102 * Register SNAP clients. We don't yet use this for IP.
103 */
104
105 struct datalink_proto *register_snap_client(unsigned char *desc, int (*rcvfunc)(struct sk_buff *, struct net_device *, struct packet_type *))
106 {
107 struct datalink_proto *proto;
108
109 if (find_snap_client(desc) != NULL)
110 return NULL;
111
112 proto = (struct datalink_proto *) kmalloc(sizeof(*proto), GFP_ATOMIC);
113 if (proto != NULL)
114 {
115 memcpy(proto->type, desc,5);
116 proto->type_len = 5;
117 proto->rcvfunc = rcvfunc;
118 proto->header_length = 5+snap_dl->header_length;
119 proto->datalink_header = snap_datalink_header;
120 proto->string_name = "SNAP";
121 proto->next = snap_list;
122 snap_list = proto;
123 }
124
125 return proto;
126 }
127
128 /*
129 * Unregister SNAP clients. Protocols no longer want to play with us ...
130 */
131
132 void unregister_snap_client(unsigned char *desc)
133 {
134 struct datalink_proto **clients = &snap_list;
135 struct datalink_proto *tmp;
136 unsigned long flags;
137
138 save_flags(flags);
139 cli();
140
141 while ((tmp = *clients) != NULL)
142 {
143 if (memcmp(tmp->type,desc,5) == 0)
144 {
145 *clients = tmp->next;
146 kfree(tmp);
147 break;
148 }
149 else
150 clients = &tmp->next;
151 }
152
153 restore_flags(flags);
154 }
155
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