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// SPDX-License-Identifier: GPL-2.0-or-later
/*
* SNAP data link layer. Derived from 802.2
*
* Alan Cox <alan@lxorguk.ukuu.org.uk>,
* from the 802.2 layer by Greg Page.
* Merged in additions from Greg Page's psnap.c.
*/
#include <linux/module.h>
#include <linux/netdevice.h>
#include <linux/skbuff.h>
#include <linux/slab.h>
#include <net/datalink.h>
#include <net/llc.h>
#include <net/psnap.h>
#include <linux/mm.h>
#include <linux/in.h>
#include <linux/init.h>
#include <linux/rculist.h>
static LIST_HEAD(snap_list);
static DEFINE_SPINLOCK(snap_lock);
static struct llc_sap *snap_sap;
/*
* Find a snap client by matching the 5 bytes.
*/
static struct datalink_proto *find_snap_client(const unsigned char *desc)
{
struct datalink_proto *proto = NULL, *p;
list_for_each_entry_rcu(p, &snap_list, node, lockdep_is_held(&snap_lock)) {
if (!memcmp(p->type, desc, 5)) {
proto = p;
break;
}
}
return proto;
}
/*
* A SNAP packet has arrived
*/
static int snap_rcv(struct sk_buff *skb, struct net_device *dev,
struct packet_type *pt, struct net_device *orig_dev)
{
int rc = 1;
struct datalink_proto *proto;
static struct packet_type snap_packet_type = {
.type = cpu_to_be16(ETH_P_SNAP),
};
if (unlikely(!pskb_may_pull(skb, 5)))
goto drop;
rcu_read_lock();
proto = find_snap_client(skb_transport_header(skb));
if (proto) {
/* Pass the frame on. */
skb->transport_header += 5;
skb_pull_rcsum(skb, 5);
rc = proto->rcvfunc(skb, dev, &snap_packet_type, orig_dev);
}
rcu_read_unlock();
if (unlikely(!proto))
goto drop;
out:
return rc;
drop:
kfree_skb(skb);
goto out;
}
/*
* Put a SNAP header on a frame and pass to 802.2
*/
static int snap_request(struct datalink_proto *dl,
struct sk_buff *skb, const u8 *dest)
{
memcpy(skb_push(skb, 5), dl->type, 5);
llc_build_and_send_ui_pkt(snap_sap, skb, dest, snap_sap->laddr.lsap);
return 0;
}
/*
* Set up the SNAP layer
*/
EXPORT_SYMBOL(register_snap_client);
EXPORT_SYMBOL(unregister_snap_client);
static const char snap_err_msg[] __initconst =
KERN_CRIT "SNAP - unable to register with 802.2\n";
static int __init snap_init(void)
{
snap_sap = llc_sap_open(0xAA, snap_rcv);
if (!snap_sap) {
printk(snap_err_msg);
return -EBUSY;
}
return 0;
}
module_init(snap_init);
static void __exit snap_exit(void)
{
llc_sap_put(snap_sap);
}
module_exit(snap_exit);
/*
* Register SNAP clients. We don't yet use this for IP.
*/
struct datalink_proto *register_snap_client(const unsigned char *desc,
int (*rcvfunc)(struct sk_buff *,
struct net_device *,
struct packet_type *,
struct net_device *))
{
struct datalink_proto *proto = NULL;
spin_lock_bh(&snap_lock);
if (find_snap_client(desc))
goto out;
proto = kmalloc(sizeof(*proto), GFP_ATOMIC);
if (proto) {
memcpy(proto->type, desc, 5);
proto->rcvfunc = rcvfunc;
proto->header_length = 5 + 3; /* snap + 802.2 */
proto->request = snap_request;
list_add_rcu(&proto->node, &snap_list);
}
out:
spin_unlock_bh(&snap_lock);
return proto;
}
/*
* Unregister SNAP clients. Protocols no longer want to play with us ...
*/
void unregister_snap_client(struct datalink_proto *proto)
{
spin_lock_bh(&snap_lock);
list_del_rcu(&proto->node);
spin_unlock_bh(&snap_lock);
synchronize_net();
kfree(proto);
}
MODULE_LICENSE("GPL");
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