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