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 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"); 168