1 | // SPDX-License-Identifier: GPL-2.0-or-later |
2 | /* |
3 | * SNAP data link layer. Derived from 802.2 |
4 | * |
5 | * Alan Cox <alan@lxorguk.ukuu.org.uk>, |
6 | * from the 802.2 layer by Greg Page. |
7 | * Merged in additions from Greg Page's psnap.c. |
8 | */ |
9 | |
10 | #include <linux/module.h> |
11 | #include <linux/netdevice.h> |
12 | #include <linux/skbuff.h> |
13 | #include <linux/slab.h> |
14 | #include <net/datalink.h> |
15 | #include <net/llc.h> |
16 | #include <net/psnap.h> |
17 | #include <linux/mm.h> |
18 | #include <linux/in.h> |
19 | #include <linux/init.h> |
20 | #include <linux/rculist.h> |
21 | |
22 | static LIST_HEAD(snap_list); |
23 | static DEFINE_SPINLOCK(snap_lock); |
24 | static struct llc_sap *snap_sap; |
25 | |
26 | /* |
27 | * Find a snap client by matching the 5 bytes. |
28 | */ |
29 | static struct datalink_proto *find_snap_client(const unsigned char *desc) |
30 | { |
31 | struct datalink_proto *proto = NULL, *p; |
32 | |
33 | list_for_each_entry_rcu(p, &snap_list, node, lockdep_is_held(&snap_lock)) { |
34 | if (!memcmp(p: p->type, q: desc, size: 5)) { |
35 | proto = p; |
36 | break; |
37 | } |
38 | } |
39 | return proto; |
40 | } |
41 | |
42 | /* |
43 | * A SNAP packet has arrived |
44 | */ |
45 | static int snap_rcv(struct sk_buff *skb, struct net_device *dev, |
46 | struct packet_type *pt, struct net_device *orig_dev) |
47 | { |
48 | int rc = 1; |
49 | struct datalink_proto *proto; |
50 | static struct packet_type snap_packet_type = { |
51 | .type = cpu_to_be16(ETH_P_SNAP), |
52 | }; |
53 | |
54 | if (unlikely(!pskb_may_pull(skb, 5))) |
55 | goto drop; |
56 | |
57 | rcu_read_lock(); |
58 | proto = find_snap_client(desc: skb_transport_header(skb)); |
59 | if (proto) { |
60 | /* Pass the frame on. */ |
61 | skb->transport_header += 5; |
62 | skb_pull_rcsum(skb, len: 5); |
63 | rc = proto->rcvfunc(skb, dev, &snap_packet_type, orig_dev); |
64 | } |
65 | rcu_read_unlock(); |
66 | |
67 | if (unlikely(!proto)) |
68 | goto drop; |
69 | |
70 | out: |
71 | return rc; |
72 | |
73 | drop: |
74 | kfree_skb(skb); |
75 | goto out; |
76 | } |
77 | |
78 | /* |
79 | * Put a SNAP header on a frame and pass to 802.2 |
80 | */ |
81 | static int snap_request(struct datalink_proto *dl, |
82 | struct sk_buff *skb, const u8 *dest) |
83 | { |
84 | memcpy(skb_push(skb, 5), dl->type, 5); |
85 | llc_build_and_send_ui_pkt(sap: snap_sap, skb, dmac: dest, dsap: snap_sap->laddr.lsap); |
86 | return 0; |
87 | } |
88 | |
89 | /* |
90 | * Set up the SNAP layer |
91 | */ |
92 | EXPORT_SYMBOL(register_snap_client); |
93 | EXPORT_SYMBOL(unregister_snap_client); |
94 | |
95 | static const char snap_err_msg[] __initconst = |
96 | KERN_CRIT "SNAP - unable to register with 802.2\n" ; |
97 | |
98 | static int __init snap_init(void) |
99 | { |
100 | snap_sap = llc_sap_open(lsap: 0xAA, rcv: snap_rcv); |
101 | if (!snap_sap) { |
102 | printk(snap_err_msg); |
103 | return -EBUSY; |
104 | } |
105 | |
106 | return 0; |
107 | } |
108 | |
109 | module_init(snap_init); |
110 | |
111 | static void __exit snap_exit(void) |
112 | { |
113 | llc_sap_put(sap: snap_sap); |
114 | } |
115 | |
116 | module_exit(snap_exit); |
117 | |
118 | |
119 | /* |
120 | * Register SNAP clients. We don't yet use this for IP. |
121 | */ |
122 | struct datalink_proto *register_snap_client(const unsigned char *desc, |
123 | int (*rcvfunc)(struct sk_buff *, |
124 | struct net_device *, |
125 | struct packet_type *, |
126 | struct net_device *)) |
127 | { |
128 | struct datalink_proto *proto = NULL; |
129 | |
130 | spin_lock_bh(lock: &snap_lock); |
131 | |
132 | if (find_snap_client(desc)) |
133 | goto out; |
134 | |
135 | proto = kmalloc(size: sizeof(*proto), GFP_ATOMIC); |
136 | if (proto) { |
137 | memcpy(proto->type, desc, 5); |
138 | proto->rcvfunc = rcvfunc; |
139 | proto->header_length = 5 + 3; /* snap + 802.2 */ |
140 | proto->request = snap_request; |
141 | list_add_rcu(new: &proto->node, head: &snap_list); |
142 | } |
143 | out: |
144 | spin_unlock_bh(lock: &snap_lock); |
145 | |
146 | return proto; |
147 | } |
148 | |
149 | /* |
150 | * Unregister SNAP clients. Protocols no longer want to play with us ... |
151 | */ |
152 | void unregister_snap_client(struct datalink_proto *proto) |
153 | { |
154 | spin_lock_bh(lock: &snap_lock); |
155 | list_del_rcu(entry: &proto->node); |
156 | spin_unlock_bh(lock: &snap_lock); |
157 | |
158 | synchronize_net(); |
159 | |
160 | kfree(objp: proto); |
161 | } |
162 | |
163 | MODULE_DESCRIPTION("SNAP data link layer. Derived from 802.2" ); |
164 | MODULE_LICENSE("GPL" ); |
165 | |