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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 <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 | #include <linux/rculist.h> |
24 | |
25 | static LIST_HEAD(snap_list); |
26 | static DEFINE_SPINLOCK(snap_lock); |
27 | static struct llc_sap *snap_sap; |
28 | |
29 | /* |
30 | * Find a snap client by matching the 5 bytes. |
31 | */ |
32 | static struct datalink_proto *find_snap_client(const unsigned char *desc) |
33 | { |
34 | struct datalink_proto *proto = NULL, *p; |
35 | |
36 | list_for_each_entry_rcu(p, &snap_list, node) { |
37 | if (!memcmp(p->type, desc, 5)) { |
38 | proto = p; |
39 | break; |
40 | } |
41 | } |
42 | return proto; |
43 | } |
44 | |
45 | /* |
46 | * A SNAP packet has arrived |
47 | */ |
48 | static int snap_rcv(struct sk_buff *skb, struct net_device *dev, |
49 | struct packet_type *pt, struct net_device *orig_dev) |
50 | { |
51 | int rc = 1; |
52 | struct datalink_proto *proto; |
53 | static struct packet_type snap_packet_type = { |
54 | .type = cpu_to_be16(ETH_P_SNAP), |
55 | }; |
56 | |
57 | if (unlikely(!pskb_may_pull(skb, 5))) |
58 | goto drop; |
59 | |
60 | rcu_read_lock(); |
61 | proto = find_snap_client(skb_transport_header(skb)); |
62 | if (proto) { |
63 | /* Pass the frame on. */ |
64 | skb->transport_header += 5; |
65 | skb_pull_rcsum(skb, 5); |
66 | rc = proto->rcvfunc(skb, dev, &snap_packet_type, orig_dev); |
67 | } |
68 | rcu_read_unlock(); |
69 | |
70 | if (unlikely(!proto)) |
71 | goto drop; |
72 | |
73 | out: |
74 | return rc; |
75 | |
76 | drop: |
77 | kfree_skb(skb); |
78 | goto out; |
79 | } |
80 | |
81 | /* |
82 | * Put a SNAP header on a frame and pass to 802.2 |
83 | */ |
84 | static int snap_request(struct datalink_proto *dl, |
85 | struct sk_buff *skb, u8 *dest) |
86 | { |
87 | memcpy(skb_push(skb, 5), dl->type, 5); |
88 | llc_build_and_send_ui_pkt(snap_sap, skb, dest, snap_sap->laddr.lsap); |
89 | return 0; |
90 | } |
91 | |
92 | /* |
93 | * Set up the SNAP layer |
94 | */ |
95 | EXPORT_SYMBOL(register_snap_client); |
96 | EXPORT_SYMBOL(unregister_snap_client); |
97 | |
98 | static const char snap_err_msg[] __initconst = |
99 | KERN_CRIT "SNAP - unable to register with 802.2\n"; |
100 | |
101 | static int __init snap_init(void) |
102 | { |
103 | snap_sap = llc_sap_open(0xAA, snap_rcv); |
104 | if (!snap_sap) { |
105 | printk(snap_err_msg); |
106 | return -EBUSY; |
107 | } |
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(const 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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