LXR linux/net/802/psnap.c

   1/*
   2 *      SNAP data link layer. Derived from 802.2
   3 *
   4 *              Alan Cox <alan@lxorguk.ukuu.org.uk>,
   5 *              from the 802.2 layer by Greg Page.
   6 *              Merged in additions from Greg Page's psnap.c.
   7 *
   8 *              This program is free software; you can redistribute it and/or
   9 *              modify it under the terms of the GNU General Public License
  10 *              as published by the Free Software Foundation; either version
  11 *              2 of the License, or (at your option) any later version.
  12 */
  13
  14#include <linux/module.h>
  15#include <linux/netdevice.h>
  16#include <linux/skbuff.h>
  17#include <net/datalink.h>
  18#include <net/llc.h>
  19#include <net/psnap.h>
  20#include <linux/mm.h>
  21#include <linux/in.h>
  22#include <linux/init.h>
  23#include <linux/rculist.h>
  24
  25static LIST_HEAD(snap_list);
  26static DEFINE_SPINLOCK(snap_lock);
  27static struct llc_sap *snap_sap;
  28
  29/*
  30 *      Find a snap client by matching the 5 bytes.
  31 */
  32static struct datalink_proto *find_snap_client(const unsigned char *desc)
  33{
  34        struct datalink_proto *proto = NULL, *p;
  35
  36        list_for_each_entry_rcu(p, &snap_list, node) {
  37                if (!memcmp(p->type, desc, 5)) {
  38                        proto = p;
  39                        break;
  40                }
  41        }
  42        return proto;
  43}
  44
  45/*
  46 *      A SNAP packet has arrived
  47 */
  48static int snap_rcv(struct sk_buff *skb, struct net_device *dev,
  49                    struct packet_type *pt, struct net_device *orig_dev)
  50{
  51        int rc = 1;
  52        struct datalink_proto *proto;
  53        static struct packet_type snap_packet_type = {
  54                .type = cpu_to_be16(ETH_P_SNAP),
  55        };
  56
  57        if (unlikely(!pskb_may_pull(skb, 5)))
  58                goto drop;
  59
  60        rcu_read_lock();
  61        proto = find_snap_client(skb_transport_header(skb));
  62        if (proto) {
  63                /* Pass the frame on. */
  64                skb->transport_header += 5;
  65                skb_pull_rcsum(skb, 5);
  66                rc = proto->rcvfunc(skb, dev, &snap_packet_type, orig_dev);
  67        }
  68        rcu_read_unlock();
  69
  70        if (unlikely(!proto))
  71                goto drop;
  72
  73out:
  74        return rc;
  75
  76drop:
  77        kfree_skb(skb);
  78        goto out;
  79}
  80
  81/*
  82 *      Put a SNAP header on a frame and pass to 802.2
  83 */
  84static int snap_request(struct datalink_proto *dl,
  85                        struct sk_buff *skb, u8 *dest)
  86{
  87        memcpy(skb_push(skb, 5), dl->type, 5);
  88        llc_build_and_send_ui_pkt(snap_sap, skb, dest, snap_sap->laddr.lsap);
  89        return 0;
  90}
  91
  92/*
  93 *      Set up the SNAP layer
  94 */
  95EXPORT_SYMBOL(register_snap_client);
  96EXPORT_SYMBOL(unregister_snap_client);
  97
  98static const char snap_err_msg[] __initconst =
  99        KERN_CRIT "SNAP - unable to register with 802.2\n";
 100
 101static int __init snap_init(void)
 102{
 103        snap_sap = llc_sap_open(0xAA, snap_rcv);
 104        if (!snap_sap) {
 105                printk(snap_err_msg);
 106                return -EBUSY;
 107        }
 108
 109        return 0;
 110}
 111
 112module_init(snap_init);
 113
 114static void __exit snap_exit(void)
 115{
 116        llc_sap_put(snap_sap);
 117}
 118
 119module_exit(snap_exit);
 120
 121
 122/*
 123 *      Register SNAP clients. We don't yet use this for IP.
 124 */
 125struct datalink_proto *register_snap_client(const unsigned char *desc,
 126                                            int (*rcvfunc)(struct sk_buff *,
 127                                                           struct net_device *,
 128                                                           struct packet_type *,
 129                                                           struct net_device *))
 130{
 131        struct datalink_proto *proto = NULL;
 132
 133        spin_lock_bh(&snap_lock);
 134
 135        if (find_snap_client(desc))
 136                goto out;
 137
 138        proto = kmalloc(sizeof(*proto), GFP_ATOMIC);
 139        if (proto) {
 140                memcpy(proto->type, desc, 5);
 141                proto->rcvfunc          = rcvfunc;
 142                proto->header_length    = 5 + 3; /* snap + 802.2 */
 143                proto->request          = snap_request;
 144                list_add_rcu(&proto->node, &snap_list);
 145        }
 146out:
 147        spin_unlock_bh(&snap_lock);
 148
 149        synchronize_net();
 150        return proto;
 151}
 152
 153/*
 154 *      Unregister SNAP clients. Protocols no longer want to play with us ...
 155 */
 156void unregister_snap_client(struct datalink_proto *proto)
 157{
 158        spin_lock_bh(&snap_lock);
 159        list_del_rcu(&proto->node);
 160        spin_unlock_bh(&snap_lock);
 161
 162        synchronize_net();
 163
 164        kfree(proto);
 165}
 166
 167MODULE_LICENSE("GPL");
 168