diff options
Diffstat (limited to 'net/802/psnap.c')
| -rw-r--r-- | net/802/psnap.c | 163 |
1 files changed, 163 insertions, 0 deletions
diff --git a/net/802/psnap.c b/net/802/psnap.c new file mode 100644 index 000000000..4492e8d7a --- /dev/null +++ b/net/802/psnap.c @@ -0,0 +1,163 @@ +// 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, 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"); |