xref: /openbmc/linux/net/802/psnap.c (revision 2ef6db76)
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  */
find_snap_client(const unsigned char * desc)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->type, desc, 5)) {
35 			proto = p;
36 			break;
37 		}
38 	}
39 	return proto;
40 }
41 
42 /*
43  *	A SNAP packet has arrived
44  */
snap_rcv(struct sk_buff * skb,struct net_device * dev,struct packet_type * pt,struct net_device * orig_dev)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(skb_transport_header(skb));
59 	if (proto) {
60 		/* Pass the frame on. */
61 		skb->transport_header += 5;
62 		skb_pull_rcsum(skb, 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  */
snap_request(struct datalink_proto * dl,struct sk_buff * skb,const u8 * dest)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(snap_sap, skb, dest, 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 
snap_init(void)98 static int __init snap_init(void)
99 {
100 	snap_sap = llc_sap_open(0xAA, 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 
snap_exit(void)111 static void __exit snap_exit(void)
112 {
113 	llc_sap_put(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  */
register_snap_client(const unsigned char * desc,int (* rcvfunc)(struct sk_buff *,struct net_device *,struct packet_type *,struct net_device *))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(&snap_lock);
131 
132 	if (find_snap_client(desc))
133 		goto out;
134 
135 	proto = kmalloc(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(&proto->node, &snap_list);
142 	}
143 out:
144 	spin_unlock_bh(&snap_lock);
145 
146 	return proto;
147 }
148 
149 /*
150  *	Unregister SNAP clients. Protocols no longer want to play with us ...
151  */
unregister_snap_client(struct datalink_proto * proto)152 void unregister_snap_client(struct datalink_proto *proto)
153 {
154 	spin_lock_bh(&snap_lock);
155 	list_del_rcu(&proto->node);
156 	spin_unlock_bh(&snap_lock);
157 
158 	synchronize_net();
159 
160 	kfree(proto);
161 }
162 
163 MODULE_LICENSE("GPL");
164