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163 lines
3.3 KiB
163 lines
3.3 KiB
// 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 <[email protected]>, |
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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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