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"); 168