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