net/802/psnap.c

   1 /*
   2  *      SNAP data link layer. Derived from 802.2
   3  *
   4  *              Alan Cox <Alan.Cox@linux.org>,
   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
  24 static LIST_HEAD(snap_list);
  25 static DEFINE_SPINLOCK(snap_lock);
  26 static struct llc_sap *snap_sap;
  27
  28 /*
  29  *      Find a snap client by matching the 5 bytes.
  30  */
  31 static struct datalink_proto *find_snap_client(unsigned char *desc)
  32 {
  33         struct list_head *entry;
  34         struct datalink_proto *proto = NULL, *p;
  35
  36         list_for_each_rcu(entry, &snap_list) {
  37                 p = list_entry(entry, struct datalink_proto, 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 = __constant_htons(ETH_P_SNAP),
  56         };
  57
  58         rcu_read_lock();
  59         proto = find_snap_client(skb->h.raw);
  60         if (proto) {
  61                 /* Pass the frame on. */
  62                 u8 *hdr = skb->data;
  63                 skb->h.raw  += 5;
  64                 skb_pull(skb, 5);
  65                 skb_postpull_rcsum(skb, hdr, 5);
  66                 rc = proto->rcvfunc(skb, dev, &snap_packet_type, orig_dev);
  67         } else {
  68                 skb->sk = NULL;
  69                 kfree_skb(skb);
  70                 rc = 1;
  71         }
  72
  73         rcu_read_unlock();
  74         return rc;
  75 }
  76
  77 /*
  78  *      Put a SNAP header on a frame and pass to 802.2
  79  */
  80 static int snap_request(struct datalink_proto *dl,
  81                         struct sk_buff *skb, u8 *dest)
  82 {
  83         memcpy(skb_push(skb, 5), dl->type, 5);
  84         llc_build_and_send_ui_pkt(snap_sap, skb, dest, snap_sap->laddr.lsap);
  85         return 0;
  86 }
  87
  88 /*
  89  *      Set up the SNAP layer
  90  */
  91 EXPORT_SYMBOL(register_snap_client);
  92 EXPORT_SYMBOL(unregister_snap_client);
  93
  94 static char snap_err_msg[] __initdata =
  95         KERN_CRIT "SNAP - unable to register with 802.2\n";
  96
  97 static int __init snap_init(void)
  98 {
  99         snap_sap = llc_sap_open(0xAA, snap_rcv);
 100
 101         if (!snap_sap)
 102                 printk(snap_err_msg);
 103
 104         return 0;
 105 }
 106
 107 module_init(snap_init);
 108
 109 static void __exit snap_exit(void)
 110 {
 111         llc_sap_put(snap_sap);
 112 }
 113
 114 module_exit(snap_exit);
 115
 116
 117 /*
 118  *      Register SNAP clients. We don't yet use this for IP.
 119  */
 120 struct datalink_proto *register_snap_client(unsigned char *desc,
 121                                             int (*rcvfunc)(struct sk_buff *,
 122                                                            struct net_device *,
 123                                                            struct packet_type *,
 124                                                            struct net_device *))
 125 {
 126         struct datalink_proto *proto = NULL;
 127
 128         spin_lock_bh(&snap_lock);
 129
 130         if (find_snap_client(desc))
 131                 goto out;
 132
 133         proto = kmalloc(sizeof(*proto), GFP_ATOMIC);
 134         if (proto) {
 135                 memcpy(proto->type, desc,5);
 136                 proto->rcvfunc          = rcvfunc;
 137                 proto->header_length    = 5 + 3; /* snap + 802.2 */
 138                 proto->request          = snap_request;
 139                 list_add_rcu(&proto->node, &snap_list);
 140         }
 141 out:
 142         spin_unlock_bh(&snap_lock);
 143
 144         synchronize_net();
 145         return proto;
 146 }
 147
 148 /*
 149  *      Unregister SNAP clients. Protocols no longer want to play with us ...
 150  */
 151 void unregister_snap_client(struct datalink_proto *proto)
 152 {
 153         spin_lock_bh(&snap_lock);
 154         list_del_rcu(&proto->node);
 155         spin_unlock_bh(&snap_lock);
 156
 157         synchronize_net();
 158
 159         kfree(proto);
 160 }
 161
 162 MODULE_LICENSE("GPL");