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 42 void llc_add_pack(int type, void (*handler)(struct llc_sap *sap, 43 struct sk_buff *skb)) 44 { 45 if (type == LLC_DEST_SAP || type == LLC_DEST_CONN) 46 llc_type_handlers[type - 1] = handler; 47 } 48 49 void llc_remove_pack(int type) 50 { 51 if (type == LLC_DEST_SAP || type == LLC_DEST_CONN) 52 llc_type_handlers[type - 1] = NULL; 53 } 54 55 void llc_set_station_handler(void (*handler)(struct sk_buff *skb)) 56 { 57 llc_station_handler = handler; 58 } 59 60 /** 61 * llc_pdu_type - returns which LLC component must handle for PDU 62 * @skb: input skb 63 * 64 * This function returns which LLC component must handle this PDU. 65 */ 66 static __inline__ int llc_pdu_type(struct sk_buff *skb) 67 { 68 int type = LLC_DEST_CONN; /* I-PDU or S-PDU type */ 69 struct llc_pdu_sn *pdu = llc_pdu_sn_hdr(skb); 70 71 if ((pdu->ctrl_1 & LLC_PDU_TYPE_MASK) != LLC_PDU_TYPE_U) 72 goto out; 73 switch (LLC_U_PDU_CMD(pdu)) { 74 case LLC_1_PDU_CMD_XID: 75 case LLC_1_PDU_CMD_UI: 76 case LLC_1_PDU_CMD_TEST: 77 type = LLC_DEST_SAP; 78 break; 79 case LLC_2_PDU_CMD_SABME: 80 case LLC_2_PDU_CMD_DISC: 81 case LLC_2_PDU_RSP_UA: 82 case LLC_2_PDU_RSP_DM: 83 case LLC_2_PDU_RSP_FRMR: 84 break; 85 default: 86 type = LLC_DEST_INVALID; 87 break; 88 } 89 out: 90 return type; 91 } 92 93 /** 94 * llc_fixup_skb - initializes skb pointers 95 * @skb: This argument points to incoming skb 96 * 97 * Initializes internal skb pointer to start of network layer by deriving 98 * length of LLC header; finds length of LLC control field in LLC header 99 * by looking at the two lowest-order bits of the first control field 100 * byte; field is either 3 or 4 bytes long. 101 */ 102 static inline int llc_fixup_skb(struct sk_buff *skb) 103 { 104 u8 llc_len = 2; 105 struct llc_pdu_un *pdu; 106 107 if (unlikely(!pskb_may_pull(skb, sizeof(*pdu)))) 108 return 0; 109 110 pdu = (struct llc_pdu_un *)skb->data; 111 if ((pdu->ctrl_1 & LLC_PDU_TYPE_MASK) == LLC_PDU_TYPE_U) 112 llc_len = 1; 113 llc_len += 2; 114 115 if (unlikely(!pskb_may_pull(skb, llc_len))) 116 return 0; 117 118 skb->transport_header += llc_len; 119 skb_pull(skb, llc_len); 120 if (skb->protocol == htons(ETH_P_802_2)) { 121 __be16 pdulen = eth_hdr(skb)->h_proto; 122 s32 data_size = ntohs(pdulen) - llc_len; 123 124 if (data_size < 0 || 125 !pskb_may_pull(skb, data_size)) 126 return 0; 127 if (unlikely(pskb_trim_rcsum(skb, data_size))) 128 return 0; 129 } 130 return 1; 131 } 132 133 /** 134 * llc_rcv - 802.2 entry point from net lower layers 135 * @skb: received pdu 136 * @dev: device that receive pdu 137 * @pt: packet type 138 * 139 * When the system receives a 802.2 frame this function is called. It 140 * checks SAP and connection of received pdu and passes frame to 141 * llc_{station,sap,conn}_rcv for sending to proper state machine. If 142 * the frame is related to a busy connection (a connection is sending 143 * data now), it queues this frame in the connection's backlog. 144 */ 145 int llc_rcv(struct sk_buff *skb, struct net_device *dev, 146 struct packet_type *pt, struct net_device *orig_dev) 147 { 148 struct llc_sap *sap; 149 struct llc_pdu_sn *pdu; 150 int dest; 151 int (*rcv)(struct sk_buff *, struct net_device *, 152 struct packet_type *, struct net_device *); 153 154 if (!net_eq(dev_net(dev), &init_net)) 155 goto drop; 156 157 /* 158 * When the interface is in promisc. mode, drop all the crap that it 159 * receives, do not try to analyse it. 160 */ 161 if (unlikely(skb->pkt_type == PACKET_OTHERHOST)) { 162 dprintk("%s: PACKET_OTHERHOST\n", __func__); 163 goto drop; 164 } 165 skb = skb_share_check(skb, GFP_ATOMIC); 166 if (unlikely(!skb)) 167 goto out; 168 if (unlikely(!llc_fixup_skb(skb))) 169 goto drop; 170 pdu = llc_pdu_sn_hdr(skb); 171 if (unlikely(!pdu->dsap)) /* NULL DSAP, refer to station */ 172 goto handle_station; 173 sap = llc_sap_find(pdu->dsap); 174 if (unlikely(!sap)) {/* unknown SAP */ 175 dprintk("%s: llc_sap_find(%02X) failed!\n", __func__, 176 pdu->dsap); 177 goto drop; 178 } 179 /* 180 * First the upper layer protocols that don't need the full 181 * LLC functionality 182 */ 183 rcv = rcu_dereference(sap->rcv_func); 184 dest = llc_pdu_type(skb); 185 if (unlikely(!dest || !llc_type_handlers[dest - 1])) { 186 if (rcv) 187 rcv(skb, dev, pt, orig_dev); 188 else 189 kfree_skb(skb); 190 } else { 191 if (rcv) { 192 struct sk_buff *cskb = skb_clone(skb, GFP_ATOMIC); 193 if (cskb) 194 rcv(cskb, dev, pt, orig_dev); 195 } 196 llc_type_handlers[dest - 1](sap, skb); 197 } 198 llc_sap_put(sap); 199 out: 200 return 0; 201 drop: 202 kfree_skb(skb); 203 goto out; 204 handle_station: 205 if (!llc_station_handler) 206 goto drop; 207 llc_station_handler(skb); 208 goto out; 209 } 210 211 EXPORT_SYMBOL(llc_add_pack); 212 EXPORT_SYMBOL(llc_remove_pack); 213 EXPORT_SYMBOL(llc_set_station_handler); 214