1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* 3 * SNAP data link layer. Derived from 802.2 4 * 5 * Alan Cox <alan@lxorguk.ukuu.org.uk>, 6 * from the 802.2 layer by Greg Page. 7 * Merged in additions from Greg Page's psnap.c. 8 */ 9 10 #include <linux/module.h> 11 #include <linux/netdevice.h> 12 #include <linux/skbuff.h> 13 #include <linux/slab.h> 14 #include <net/datalink.h> 15 #include <net/llc.h> 16 #include <net/psnap.h> 17 #include <linux/mm.h> 18 #include <linux/in.h> 19 #include <linux/init.h> 20 #include <linux/rculist.h> 21 22 static LIST_HEAD(snap_list); 23 static DEFINE_SPINLOCK(snap_lock); 24 static struct llc_sap *snap_sap; 25 26 /* 27 * Find a snap client by matching the 5 bytes. 28 */ 29 static struct datalink_proto *find_snap_client(const unsigned char *desc) 30 { 31 struct datalink_proto *proto = NULL, *p; 32 33 list_for_each_entry_rcu(p, &snap_list, node, lockdep_is_held(&snap_lock)) { 34 if (!memcmp(p->type, desc, 5)) { 35 proto = p; 36 break; 37 } 38 } 39 return proto; 40 } 41 42 /* 43 * A SNAP packet has arrived 44 */ 45 static int snap_rcv(struct sk_buff *skb, struct net_device *dev, 46 struct packet_type *pt, struct net_device *orig_dev) 47 { 48 int rc = 1; 49 struct datalink_proto *proto; 50 static struct packet_type snap_packet_type = { 51 .type = cpu_to_be16(ETH_P_SNAP), 52 }; 53 54 if (unlikely(!pskb_may_pull(skb, 5))) 55 goto drop; 56 57 rcu_read_lock(); 58 proto = find_snap_client(skb_transport_header(skb)); 59 if (proto) { 60 /* Pass the frame on. */ 61 skb->transport_header += 5; 62 skb_pull_rcsum(skb, 5); 63 rc = proto->rcvfunc(skb, dev, &snap_packet_type, orig_dev); 64 } 65 rcu_read_unlock(); 66 67 if (unlikely(!proto)) 68 goto drop; 69 70 out: 71 return rc; 72 73 drop: 74 kfree_skb(skb); 75 goto out; 76 } 77 78 /* 79 * Put a SNAP header on a frame and pass to 802.2 80 */ 81 static int snap_request(struct datalink_proto *dl, 82 struct sk_buff *skb, const u8 *dest) 83 { 84 memcpy(skb_push(skb, 5), dl->type, 5); 85 llc_build_and_send_ui_pkt(snap_sap, skb, dest, snap_sap->laddr.lsap); 86 return 0; 87 } 88 89 /* 90 * Set up the SNAP layer 91 */ 92 EXPORT_SYMBOL(register_snap_client); 93 EXPORT_SYMBOL(unregister_snap_client); 94 95 static const char snap_err_msg[] __initconst = 96 KERN_CRIT "SNAP - unable to register with 802.2\n"; 97 98 static int __init snap_init(void) 99 { 100 snap_sap = llc_sap_open(0xAA, snap_rcv); 101 if (!snap_sap) { 102 printk(snap_err_msg); 103 return -EBUSY; 104 } 105 106 return 0; 107 } 108 109 module_init(snap_init); 110 111 static void __exit snap_exit(void) 112 { 113 llc_sap_put(snap_sap); 114 } 115 116 module_exit(snap_exit); 117 118 119 /* 120 * Register SNAP clients. We don't yet use this for IP. 121 */ 122 struct datalink_proto *register_snap_client(const unsigned char *desc, 123 int (*rcvfunc)(struct sk_buff *, 124 struct net_device *, 125 struct packet_type *, 126 struct net_device *)) 127 { 128 struct datalink_proto *proto = NULL; 129 130 spin_lock_bh(&snap_lock); 131 132 if (find_snap_client(desc)) 133 goto out; 134 135 proto = kmalloc(sizeof(*proto), GFP_ATOMIC); 136 if (proto) { 137 memcpy(proto->type, desc, 5); 138 proto->rcvfunc = rcvfunc; 139 proto->header_length = 5 + 3; /* snap + 802.2 */ 140 proto->request = snap_request; 141 list_add_rcu(&proto->node, &snap_list); 142 } 143 out: 144 spin_unlock_bh(&snap_lock); 145 146 return proto; 147 } 148 149 /* 150 * Unregister SNAP clients. Protocols no longer want to play with us ... 151 */ 152 void unregister_snap_client(struct datalink_proto *proto) 153 { 154 spin_lock_bh(&snap_lock); 155 list_del_rcu(&proto->node); 156 spin_unlock_bh(&snap_lock); 157 158 synchronize_net(); 159 160 kfree(proto); 161 } 162 163 MODULE_LICENSE("GPL"); 164