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/net/802/psnap.c

http://github.com/mirrors/linux
C | 163 lines | 108 code | 28 blank | 27 comment | 7 complexity | bc5d9b1644a9a4b1ea9fabf58eb12c23 MD5 | raw file
  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
 22static LIST_HEAD(snap_list);
 23static DEFINE_SPINLOCK(snap_lock);
 24static struct llc_sap *snap_sap;
 25
 26/*
 27 *	Find a snap client by matching the 5 bytes.
 28 */
 29static 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 */
 45static 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
 70out:
 71	return rc;
 72
 73drop:
 74	kfree_skb(skb);
 75	goto out;
 76}
 77
 78/*
 79 *	Put a SNAP header on a frame and pass to 802.2
 80 */
 81static int snap_request(struct datalink_proto *dl,
 82			struct sk_buff *skb, 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 */
 92EXPORT_SYMBOL(register_snap_client);
 93EXPORT_SYMBOL(unregister_snap_client);
 94
 95static const char snap_err_msg[] __initconst =
 96	KERN_CRIT "SNAP - unable to register with 802.2\n";
 97
 98static 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
109module_init(snap_init);
110
111static void __exit snap_exit(void)
112{
113	llc_sap_put(snap_sap);
114}
115
116module_exit(snap_exit);
117
118
119/*
120 *	Register SNAP clients. We don't yet use this for IP.
121 */
122struct 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	}
143out:
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 */
152void 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
163MODULE_LICENSE("GPL");