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
  25 static LIST_HEAD(snap_list);
  26 static DEFINE_SPINLOCK(snap_lock);
  27 static struct llc_sap *snap_sap;
  28
  29 /*
  30  *      Find a snap client by matching the 5 bytes.
  31  */
  32 static 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  */
  48 static 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
  73 out:
  74         return rc;
  75
  76 drop:
  77         kfree_skb(skb);
  78         goto out;
  79 }
  80
  81 /*
  82  *      Put a SNAP header on a frame and pass to 802.2
  83  */
  84 static 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  */
  95 EXPORT_SYMBOL(register_snap_client);
  96 EXPORT_SYMBOL(unregister_snap_client);
  97
  98 static const char snap_err_msg[] __initconst =
  99         KERN_CRIT "SNAP - unable to register with 802.2\n";
 100
 101 static 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
 112 module_init(snap_init);
 113
 114 static void __exit snap_exit(void)
 115 {
 116         llc_sap_put(snap_sap);
 117 }
 118
 119 module_exit(snap_exit);
 120
 121
 122 /*
 123  *      Register SNAP clients. We don't yet use this for IP.
 124  */
 125 struct 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         }
 146 out:
 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  */
 156 void 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
 167 MODULE_LICENSE("GPL");