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 <net/llc.h> 16 #include <net/llc_pdu.h> 17 #include <net/llc_sap.h> 18 19 #if 0 20 #define dprintk(args...) printk(KERN_DEBUG args) 21 #else 22 #define dprintk(args...) 23 #endif 24 25 /* 26 * Packet handler for the station, registerable because in the minimal 27 * LLC core that is taking shape only the very minimal subset of LLC that 28 * is needed for things like IPX, Appletalk, etc will stay, with all the 29 * rest in the llc1 and llc2 modules. 30 */ 31 static void (*llc_station_handler)(struct sk_buff *skb); 32 33 /* 34 * Packet handlers for LLC_DEST_SAP and LLC_DEST_CONN. 35 */ 36 static void (*llc_type_handlers[2])(struct llc_sap *sap, 37 struct sk_buff *skb); 38 39 void llc_add_pack(int type, void (*handler)(struct llc_sap *sap, 40 struct sk_buff *skb)) 41 { 42 if (type == LLC_DEST_SAP || type == LLC_DEST_CONN) 43 llc_type_handlers[type - 1] = handler; 44 } 45 46 void llc_remove_pack(int type) 47 { 48 if (type == LLC_DEST_SAP || type == LLC_DEST_CONN) 49 llc_type_handlers[type - 1] = NULL; 50 } 51 52 void llc_set_station_handler(void (*handler)(struct sk_buff *skb)) 53 { 54 llc_station_handler = handler; 55 } 56 57 /** 58 * llc_pdu_type - returns which LLC component must handle for PDU 59 * @skb: input skb 60 * 61 * This function returns which LLC component must handle this PDU. 62 */ 63 static __inline__ int llc_pdu_type(struct sk_buff *skb) 64 { 65 int type = LLC_DEST_CONN; /* I-PDU or S-PDU type */ 66 struct llc_pdu_sn *pdu = llc_pdu_sn_hdr(skb); 67 68 if ((pdu->ctrl_1 & LLC_PDU_TYPE_MASK) != LLC_PDU_TYPE_U) 69 goto out; 70 switch (LLC_U_PDU_CMD(pdu)) { 71 case LLC_1_PDU_CMD_XID: 72 case LLC_1_PDU_CMD_UI: 73 case LLC_1_PDU_CMD_TEST: 74 type = LLC_DEST_SAP; 75 break; 76 case LLC_2_PDU_CMD_SABME: 77 case LLC_2_PDU_CMD_DISC: 78 case LLC_2_PDU_RSP_UA: 79 case LLC_2_PDU_RSP_DM: 80 case LLC_2_PDU_RSP_FRMR: 81 break; 82 default: 83 type = LLC_DEST_INVALID; 84 break; 85 } 86 out: 87 return type; 88 } 89 90 /** 91 * llc_fixup_skb - initializes skb pointers 92 * @skb: This argument points to incoming skb 93 * 94 * Initializes internal skb pointer to start of network layer by deriving 95 * length of LLC header; finds length of LLC control field in LLC header 96 * by looking at the two lowest-order bits of the first control field 97 * byte; field is either 3 or 4 bytes long. 98 */ 99 static inline int llc_fixup_skb(struct sk_buff *skb) 100 { 101 u8 llc_len = 2; 102 struct llc_pdu_un *pdu; 103 104 if (unlikely(!pskb_may_pull(skb, sizeof(*pdu)))) 105 return 0; 106 107 pdu = (struct llc_pdu_un *)skb->data; 108 if ((pdu->ctrl_1 & LLC_PDU_TYPE_MASK) == LLC_PDU_TYPE_U) 109 llc_len = 1; 110 llc_len += 2; 111 112 if (unlikely(!pskb_may_pull(skb, llc_len))) 113 return 0; 114 115 skb->h.raw += llc_len; 116 skb_pull(skb, llc_len); 117 if (skb->protocol == htons(ETH_P_802_2)) { 118 u16 pdulen = eth_hdr(skb)->h_proto, 119 data_size = ntohs(pdulen) - llc_len; 120 121 skb_trim(skb, data_size); 122 } 123 return 1; 124 } 125 126 /** 127 * llc_rcv - 802.2 entry point from net lower layers 128 * @skb: received pdu 129 * @dev: device that receive pdu 130 * @pt: packet type 131 * 132 * When the system receives a 802.2 frame this function is called. It 133 * checks SAP and connection of received pdu and passes frame to 134 * llc_{station,sap,conn}_rcv for sending to proper state machine. If 135 * the frame is related to a busy connection (a connection is sending 136 * data now), it queues this frame in the connection's backlog. 137 */ 138 int llc_rcv(struct sk_buff *skb, struct net_device *dev, 139 struct packet_type *pt, struct net_device *orig_dev) 140 { 141 struct llc_sap *sap; 142 struct llc_pdu_sn *pdu; 143 int dest; 144 145 /* 146 * When the interface is in promisc. mode, drop all the crap that it 147 * receives, do not try to analyse it. 148 */ 149 if (unlikely(skb->pkt_type == PACKET_OTHERHOST)) { 150 dprintk("%s: PACKET_OTHERHOST\n", __FUNCTION__); 151 goto drop; 152 } 153 skb = skb_share_check(skb, GFP_ATOMIC); 154 if (unlikely(!skb)) 155 goto out; 156 if (unlikely(!llc_fixup_skb(skb))) 157 goto drop; 158 pdu = llc_pdu_sn_hdr(skb); 159 if (unlikely(!pdu->dsap)) /* NULL DSAP, refer to station */ 160 goto handle_station; 161 sap = llc_sap_find(pdu->dsap); 162 if (unlikely(!sap)) {/* unknown SAP */ 163 dprintk("%s: llc_sap_find(%02X) failed!\n", __FUNCTION__, 164 pdu->dsap); 165 goto drop; 166 } 167 /* 168 * First the upper layer protocols that don't need the full 169 * LLC functionality 170 */ 171 if (sap->rcv_func) { 172 sap->rcv_func(skb, dev, pt, orig_dev); 173 goto out_put; 174 } 175 dest = llc_pdu_type(skb); 176 if (unlikely(!dest || !llc_type_handlers[dest - 1])) 177 goto drop_put; 178 llc_type_handlers[dest - 1](sap, skb); 179 out_put: 180 llc_sap_put(sap); 181 out: 182 return 0; 183 drop: 184 kfree_skb(skb); 185 goto out; 186 drop_put: 187 kfree_skb(skb); 188 goto out_put; 189 handle_station: 190 if (!llc_station_handler) 191 goto drop; 192 llc_station_handler(skb); 193 goto out; 194 } 195 196 EXPORT_SYMBOL(llc_add_pack); 197 EXPORT_SYMBOL(llc_remove_pack); 198 EXPORT_SYMBOL(llc_set_station_handler); 199