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/net_namespace.h> 16 #include <net/llc.h> 17 #include <net/llc_pdu.h> 18 #include <net/llc_sap.h> 19 20 #if 0 21 #define dprintk(args...) printk(KERN_DEBUG args) 22 #else 23 #define dprintk(args...) 24 #endif 25 26 /* 27 * Packet handler for the station, registerable because in the minimal 28 * LLC core that is taking shape only the very minimal subset of LLC that 29 * is needed for things like IPX, Appletalk, etc will stay, with all the 30 * rest in the llc1 and llc2 modules. 31 */ 32 static void (*llc_station_handler)(struct sk_buff *skb); 33 34 /* 35 * Packet handlers for LLC_DEST_SAP and LLC_DEST_CONN. 36 */ 37 static void (*llc_type_handlers[2])(struct llc_sap *sap, 38 struct sk_buff *skb); 39 40 void llc_add_pack(int type, void (*handler)(struct llc_sap *sap, 41 struct sk_buff *skb)) 42 { 43 if (type == LLC_DEST_SAP || type == LLC_DEST_CONN) 44 llc_type_handlers[type - 1] = handler; 45 } 46 47 void llc_remove_pack(int type) 48 { 49 if (type == LLC_DEST_SAP || type == LLC_DEST_CONN) 50 llc_type_handlers[type - 1] = NULL; 51 } 52 53 void llc_set_station_handler(void (*handler)(struct sk_buff *skb)) 54 { 55 llc_station_handler = handler; 56 } 57 58 /** 59 * llc_pdu_type - returns which LLC component must handle for PDU 60 * @skb: input skb 61 * 62 * This function returns which LLC component must handle this PDU. 63 */ 64 static __inline__ int llc_pdu_type(struct sk_buff *skb) 65 { 66 int type = LLC_DEST_CONN; /* I-PDU or S-PDU type */ 67 struct llc_pdu_sn *pdu = llc_pdu_sn_hdr(skb); 68 69 if ((pdu->ctrl_1 & LLC_PDU_TYPE_MASK) != LLC_PDU_TYPE_U) 70 goto out; 71 switch (LLC_U_PDU_CMD(pdu)) { 72 case LLC_1_PDU_CMD_XID: 73 case LLC_1_PDU_CMD_UI: 74 case LLC_1_PDU_CMD_TEST: 75 type = LLC_DEST_SAP; 76 break; 77 case LLC_2_PDU_CMD_SABME: 78 case LLC_2_PDU_CMD_DISC: 79 case LLC_2_PDU_RSP_UA: 80 case LLC_2_PDU_RSP_DM: 81 case LLC_2_PDU_RSP_FRMR: 82 break; 83 default: 84 type = LLC_DEST_INVALID; 85 break; 86 } 87 out: 88 return type; 89 } 90 91 /** 92 * llc_fixup_skb - initializes skb pointers 93 * @skb: This argument points to incoming skb 94 * 95 * Initializes internal skb pointer to start of network layer by deriving 96 * length of LLC header; finds length of LLC control field in LLC header 97 * by looking at the two lowest-order bits of the first control field 98 * byte; field is either 3 or 4 bytes long. 99 */ 100 static inline int llc_fixup_skb(struct sk_buff *skb) 101 { 102 u8 llc_len = 2; 103 struct llc_pdu_un *pdu; 104 105 if (unlikely(!pskb_may_pull(skb, sizeof(*pdu)))) 106 return 0; 107 108 pdu = (struct llc_pdu_un *)skb->data; 109 if ((pdu->ctrl_1 & LLC_PDU_TYPE_MASK) == LLC_PDU_TYPE_U) 110 llc_len = 1; 111 llc_len += 2; 112 113 if (unlikely(!pskb_may_pull(skb, llc_len))) 114 return 0; 115 116 skb->transport_header += llc_len; 117 skb_pull(skb, llc_len); 118 if (skb->protocol == htons(ETH_P_802_2)) { 119 __be16 pdulen = eth_hdr(skb)->h_proto; 120 s32 data_size = ntohs(pdulen) - llc_len; 121 122 if (data_size < 0 || 123 ((skb_tail_pointer(skb) - 124 (u8 *)pdu) - llc_len) < data_size) 125 return 0; 126 if (unlikely(pskb_trim_rcsum(skb, data_size))) 127 return 0; 128 } 129 return 1; 130 } 131 132 /** 133 * llc_rcv - 802.2 entry point from net lower layers 134 * @skb: received pdu 135 * @dev: device that receive pdu 136 * @pt: packet type 137 * 138 * When the system receives a 802.2 frame this function is called. It 139 * checks SAP and connection of received pdu and passes frame to 140 * llc_{station,sap,conn}_rcv for sending to proper state machine. If 141 * the frame is related to a busy connection (a connection is sending 142 * data now), it queues this frame in the connection's backlog. 143 */ 144 int llc_rcv(struct sk_buff *skb, struct net_device *dev, 145 struct packet_type *pt, struct net_device *orig_dev) 146 { 147 struct llc_sap *sap; 148 struct llc_pdu_sn *pdu; 149 int dest; 150 int (*rcv)(struct sk_buff *, struct net_device *, 151 struct packet_type *, struct net_device *); 152 153 if (!net_eq(dev_net(dev), &init_net)) 154 goto drop; 155 156 /* 157 * When the interface is in promisc. mode, drop all the crap that it 158 * receives, do not try to analyse it. 159 */ 160 if (unlikely(skb->pkt_type == PACKET_OTHERHOST)) { 161 dprintk("%s: PACKET_OTHERHOST\n", __func__); 162 goto drop; 163 } 164 skb = skb_share_check(skb, GFP_ATOMIC); 165 if (unlikely(!skb)) 166 goto out; 167 if (unlikely(!llc_fixup_skb(skb))) 168 goto drop; 169 pdu = llc_pdu_sn_hdr(skb); 170 if (unlikely(!pdu->dsap)) /* NULL DSAP, refer to station */ 171 goto handle_station; 172 sap = llc_sap_find(pdu->dsap); 173 if (unlikely(!sap)) {/* unknown SAP */ 174 dprintk("%s: llc_sap_find(%02X) failed!\n", __func__, 175 pdu->dsap); 176 goto drop; 177 } 178 /* 179 * First the upper layer protocols that don't need the full 180 * LLC functionality 181 */ 182 rcv = rcu_dereference(sap->rcv_func); 183 if (rcv) { 184 struct sk_buff *cskb = skb_clone(skb, GFP_ATOMIC); 185 if (cskb) 186 rcv(cskb, dev, pt, orig_dev); 187 } 188 dest = llc_pdu_type(skb); 189 if (unlikely(!dest || !llc_type_handlers[dest - 1])) 190 goto drop_put; 191 llc_type_handlers[dest - 1](sap, skb); 192 out_put: 193 llc_sap_put(sap); 194 out: 195 return 0; 196 drop: 197 kfree_skb(skb); 198 goto out; 199 drop_put: 200 kfree_skb(skb); 201 goto out_put; 202 handle_station: 203 if (!llc_station_handler) 204 goto drop; 205 llc_station_handler(skb); 206 goto out; 207 } 208 209 EXPORT_SYMBOL(llc_add_pack); 210 EXPORT_SYMBOL(llc_remove_pack); 211 EXPORT_SYMBOL(llc_set_station_handler); 212