1 /* 2 * llc_input.c - Minimal input path for LLC 3 * 4 * Copyright (c) 1997 by Procom Technology, Inc. 5 * 2001-2003 by Arnaldo Carvalho de Melo <acme@conectiva.com.br> 6 * 7 * This program can be redistributed or modified under the terms of the 8 * GNU General Public License as published by the Free Software Foundation. 9 * This program is distributed without any warranty or implied warranty 10 * of merchantability or fitness for a particular purpose. 11 * 12 * See the GNU General Public License for more details. 13 */ 14 #include <linux/netdevice.h> 15 #include <linux/slab.h> 16 #include <linux/export.h> 17 #include <net/net_namespace.h> 18 #include <net/llc.h> 19 #include <net/llc_pdu.h> 20 #include <net/llc_sap.h> 21 22 #if 0 23 #define dprintk(args...) printk(KERN_DEBUG args) 24 #else 25 #define dprintk(args...) 26 #endif 27 28 /* 29 * Packet handler for the station, registerable because in the minimal 30 * LLC core that is taking shape only the very minimal subset of LLC that 31 * is needed for things like IPX, Appletalk, etc will stay, with all the 32 * rest in the llc1 and llc2 modules. 33 */ 34 static void (*llc_station_handler)(struct sk_buff *skb); 35 36 /* 37 * Packet handlers for LLC_DEST_SAP and LLC_DEST_CONN. 38 */ 39 static void (*llc_type_handlers[2])(struct llc_sap *sap, 40 struct sk_buff *skb); 41 llc_add_pack(int type,void (* handler)(struct llc_sap * sap,struct sk_buff * skb))42 void llc_add_pack(int type, void (*handler)(struct llc_sap *sap, 43 struct sk_buff *skb)) 44 { 45 smp_wmb(); /* ensure initialisation is complete before it's called */ 46 if (type == LLC_DEST_SAP || type == LLC_DEST_CONN) 47 llc_type_handlers[type - 1] = handler; 48 } 49 llc_remove_pack(int type)50 void llc_remove_pack(int type) 51 { 52 if (type == LLC_DEST_SAP || type == LLC_DEST_CONN) 53 llc_type_handlers[type - 1] = NULL; 54 synchronize_net(); 55 } 56 llc_set_station_handler(void (* handler)(struct sk_buff * skb))57 void llc_set_station_handler(void (*handler)(struct sk_buff *skb)) 58 { 59 /* Ensure initialisation is complete before it's called */ 60 if (handler) 61 smp_wmb(); 62 63 llc_station_handler = handler; 64 65 if (!handler) 66 synchronize_net(); 67 } 68 69 /** 70 * llc_pdu_type - returns which LLC component must handle for PDU 71 * @skb: input skb 72 * 73 * This function returns which LLC component must handle this PDU. 74 */ llc_pdu_type(struct sk_buff * skb)75 static __inline__ int llc_pdu_type(struct sk_buff *skb) 76 { 77 int type = LLC_DEST_CONN; /* I-PDU or S-PDU type */ 78 struct llc_pdu_sn *pdu = llc_pdu_sn_hdr(skb); 79 80 if ((pdu->ctrl_1 & LLC_PDU_TYPE_MASK) != LLC_PDU_TYPE_U) 81 goto out; 82 switch (LLC_U_PDU_CMD(pdu)) { 83 case LLC_1_PDU_CMD_XID: 84 case LLC_1_PDU_CMD_UI: 85 case LLC_1_PDU_CMD_TEST: 86 type = LLC_DEST_SAP; 87 break; 88 case LLC_2_PDU_CMD_SABME: 89 case LLC_2_PDU_CMD_DISC: 90 case LLC_2_PDU_RSP_UA: 91 case LLC_2_PDU_RSP_DM: 92 case LLC_2_PDU_RSP_FRMR: 93 break; 94 default: 95 type = LLC_DEST_INVALID; 96 break; 97 } 98 out: 99 return type; 100 } 101 102 /** 103 * llc_fixup_skb - initializes skb pointers 104 * @skb: This argument points to incoming skb 105 * 106 * Initializes internal skb pointer to start of network layer by deriving 107 * length of LLC header; finds length of LLC control field in LLC header 108 * by looking at the two lowest-order bits of the first control field 109 * byte; field is either 3 or 4 bytes long. 110 */ llc_fixup_skb(struct sk_buff * skb)111 static inline int llc_fixup_skb(struct sk_buff *skb) 112 { 113 u8 llc_len = 2; 114 struct llc_pdu_un *pdu; 115 116 if (unlikely(!pskb_may_pull(skb, sizeof(*pdu)))) 117 return 0; 118 119 pdu = (struct llc_pdu_un *)skb->data; 120 if ((pdu->ctrl_1 & LLC_PDU_TYPE_MASK) == LLC_PDU_TYPE_U) 121 llc_len = 1; 122 llc_len += 2; 123 124 if (unlikely(!pskb_may_pull(skb, llc_len))) 125 return 0; 126 127 skb_pull(skb, llc_len); 128 skb_reset_transport_header(skb); 129 if (skb->protocol == htons(ETH_P_802_2)) { 130 __be16 pdulen; 131 s32 data_size; 132 133 if (skb->mac_len < ETH_HLEN) 134 return 0; 135 136 pdulen = eth_hdr(skb)->h_proto; 137 data_size = ntohs(pdulen) - llc_len; 138 139 if (data_size < 0 || 140 !pskb_may_pull(skb, data_size)) 141 return 0; 142 if (unlikely(pskb_trim_rcsum(skb, data_size))) 143 return 0; 144 } 145 return 1; 146 } 147 148 /** 149 * llc_rcv - 802.2 entry point from net lower layers 150 * @skb: received pdu 151 * @dev: device that receive pdu 152 * @pt: packet type 153 * @orig_dev: the original receive net device 154 * 155 * When the system receives a 802.2 frame this function is called. It 156 * checks SAP and connection of received pdu and passes frame to 157 * llc_{station,sap,conn}_rcv for sending to proper state machine. If 158 * the frame is related to a busy connection (a connection is sending 159 * data now), it queues this frame in the connection's backlog. 160 */ llc_rcv(struct sk_buff * skb,struct net_device * dev,struct packet_type * pt,struct net_device * orig_dev)161 int llc_rcv(struct sk_buff *skb, struct net_device *dev, 162 struct packet_type *pt, struct net_device *orig_dev) 163 { 164 struct llc_sap *sap; 165 struct llc_pdu_sn *pdu; 166 int dest; 167 int (*rcv)(struct sk_buff *, struct net_device *, 168 struct packet_type *, struct net_device *); 169 void (*sta_handler)(struct sk_buff *skb); 170 void (*sap_handler)(struct llc_sap *sap, struct sk_buff *skb); 171 172 /* 173 * When the interface is in promisc. mode, drop all the crap that it 174 * receives, do not try to analyse it. 175 */ 176 if (unlikely(skb->pkt_type == PACKET_OTHERHOST)) { 177 dprintk("%s: PACKET_OTHERHOST\n", __func__); 178 goto drop; 179 } 180 skb = skb_share_check(skb, GFP_ATOMIC); 181 if (unlikely(!skb)) 182 goto out; 183 if (unlikely(!llc_fixup_skb(skb))) 184 goto drop; 185 pdu = llc_pdu_sn_hdr(skb); 186 if (unlikely(!pdu->dsap)) /* NULL DSAP, refer to station */ 187 goto handle_station; 188 sap = llc_sap_find(pdu->dsap); 189 if (unlikely(!sap)) {/* unknown SAP */ 190 dprintk("%s: llc_sap_find(%02X) failed!\n", __func__, 191 pdu->dsap); 192 goto drop; 193 } 194 /* 195 * First the upper layer protocols that don't need the full 196 * LLC functionality 197 */ 198 rcv = rcu_dereference(sap->rcv_func); 199 dest = llc_pdu_type(skb); 200 sap_handler = dest ? READ_ONCE(llc_type_handlers[dest - 1]) : NULL; 201 if (unlikely(!sap_handler)) { 202 if (rcv) 203 rcv(skb, dev, pt, orig_dev); 204 else 205 kfree_skb(skb); 206 } else { 207 if (rcv) { 208 struct sk_buff *cskb = skb_clone(skb, GFP_ATOMIC); 209 if (cskb) 210 rcv(cskb, dev, pt, orig_dev); 211 } 212 sap_handler(sap, skb); 213 } 214 llc_sap_put(sap); 215 out: 216 return 0; 217 drop: 218 kfree_skb(skb); 219 goto out; 220 handle_station: 221 sta_handler = READ_ONCE(llc_station_handler); 222 if (!sta_handler) 223 goto drop; 224 sta_handler(skb); 225 goto out; 226 } 227 228 EXPORT_SYMBOL(llc_add_pack); 229 EXPORT_SYMBOL(llc_remove_pack); 230 EXPORT_SYMBOL(llc_set_station_handler); 231