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#define dprintk(args...) 20 21/* 22 * Packet handler for the station, registerable because in the minimal 23 * LLC core that is taking shape only the very minimal subset of LLC that 24 * is needed for things like IPX, Appletalk, etc will stay, with all the 25 * rest in the llc1 and llc2 modules. 26 */ 27static void (*llc_station_handler)(struct sk_buff *skb); 28 29/* 30 * Packet handlers for LLC_DEST_SAP and LLC_DEST_CONN. 31 */ 32static void (*llc_type_handlers[2])(struct llc_sap *sap, 33 struct sk_buff *skb); 34 35void llc_add_pack(int type, void (*handler)(struct llc_sap *sap, 36 struct sk_buff *skb)) 37{ 38 if (type == LLC_DEST_SAP || type == LLC_DEST_CONN) 39 llc_type_handlers[type - 1] = handler; 40} 41 42void llc_remove_pack(int type) 43{ 44 if (type == LLC_DEST_SAP || type == LLC_DEST_CONN) 45 llc_type_handlers[type - 1] = NULL; 46} 47 48void llc_set_station_handler(void (*handler)(struct sk_buff *skb)) 49{ 50 llc_station_handler = handler; 51} 52 53/** 54 * llc_pdu_type - returns which LLC component must handle for PDU 55 * @skb: input skb 56 * 57 * This function returns which LLC component must handle this PDU. 58 */ 59static __inline__ int llc_pdu_type(struct sk_buff *skb) 60{ 61 int type = LLC_DEST_CONN; /* I-PDU or S-PDU type */ 62 struct llc_pdu_sn *pdu = llc_pdu_sn_hdr(skb); 63 64 if ((pdu->ctrl_1 & LLC_PDU_TYPE_MASK) != LLC_PDU_TYPE_U) 65 goto out; 66 switch (LLC_U_PDU_CMD(pdu)) { 67 case LLC_1_PDU_CMD_XID: 68 case LLC_1_PDU_CMD_UI: 69 case LLC_1_PDU_CMD_TEST: 70 type = LLC_DEST_SAP; 71 break; 72 case LLC_2_PDU_CMD_SABME: 73 case LLC_2_PDU_CMD_DISC: 74 case LLC_2_PDU_RSP_UA: 75 case LLC_2_PDU_RSP_DM: 76 case LLC_2_PDU_RSP_FRMR: 77 break; 78 default: 79 type = LLC_DEST_INVALID; 80 break; 81 } 82out: 83 return type; 84} 85 86/** 87 * llc_fixup_skb - initializes skb pointers 88 * @skb: This argument points to incoming skb 89 * 90 * Initializes internal skb pointer to start of network layer by deriving 91 * length of LLC header; finds length of LLC control field in LLC header 92 * by looking at the two lowest-order bits of the first control field 93 * byte; field is either 3 or 4 bytes long. 94 */ 95static inline int llc_fixup_skb(struct sk_buff *skb) 96{ 97 u8 llc_len = 2; 98 struct llc_pdu_un *pdu; 99 100 if (unlikely(!pskb_may_pull(skb, sizeof(*pdu)))) 101 return 0; 102 103 pdu = (struct llc_pdu_un *)skb->data; 104 if ((pdu->ctrl_1 & LLC_PDU_TYPE_MASK) == LLC_PDU_TYPE_U) 105 llc_len = 1; 106 llc_len += 2; 107 108 if (unlikely(!pskb_may_pull(skb, llc_len))) 109 return 0; 110 111 skb->transport_header += llc_len; 112 skb_pull(skb, llc_len); 113 if (skb->protocol == htons(ETH_P_802_2)) { 114 __be16 pdulen = eth_hdr(skb)->h_proto; 115 u16 data_size = ntohs(pdulen) - llc_len; 116 117 if (unlikely(pskb_trim_rcsum(skb, data_size))) 118 return 0; 119 } 120 return 1; 121} 122 123/** 124 * llc_rcv - 802.2 entry point from net lower layers 125 * @skb: received pdu 126 * @dev: device that receive pdu 127 * @pt: packet type 128 * 129 * When the system receives a 802.2 frame this function is called. It 130 * checks SAP and connection of received pdu and passes frame to 131 * llc_{station,sap,conn}_rcv for sending to proper state machine. If 132 * the frame is related to a busy connection (a connection is sending 133 * data now), it queues this frame in the connection's backlog. 134 */ 135int llc_rcv(struct sk_buff *skb, struct net_device *dev, 136 struct packet_type *pt, struct net_device *orig_dev) 137{ 138 struct llc_sap *sap; 139 struct llc_pdu_sn *pdu; 140 int dest; 141 int (*rcv)(struct sk_buff *, struct net_device *, 142 struct packet_type *, struct net_device *); 143 144 /* 145 * When the interface is in promisc. mode, drop all the crap that it 146 * receives, do not try to analyse it. 147 */ 148 if (unlikely(skb->pkt_type == PACKET_OTHERHOST)) { 149 dprintk("%s: PACKET_OTHERHOST\n", __FUNCTION__); 150 goto drop; 151 } 152 skb = skb_share_check(skb, GFP_ATOMIC); 153 if (unlikely(!skb)) 154 goto out; 155 if (unlikely(!llc_fixup_skb(skb))) 156 goto drop; 157 pdu = llc_pdu_sn_hdr(skb); 158 if (unlikely(!pdu->dsap)) /* NULL DSAP, refer to station */ 159 goto handle_station; 160 sap = llc_sap_find(pdu->dsap); 161 if (unlikely(!sap)) {/* unknown SAP */ 162 dprintk("%s: llc_sap_find(%02X) failed!\n", __FUNCTION__, 163 pdu->dsap); 164 goto drop; 165 } 166 /* 167 * First the upper layer protocols that don't need the full 168 * LLC functionality 169 */ 170 rcv = rcu_dereference(sap->rcv_func); 171 if (rcv) { 172 struct sk_buff *cskb = skb_clone(skb, GFP_ATOMIC); 173 if (cskb) 174 rcv(cskb, dev, pt, orig_dev); 175 } 176 dest = llc_pdu_type(skb); 177 if (unlikely(!dest || !llc_type_handlers[dest - 1])) 178 goto drop_put; 179 llc_type_handlers[dest - 1](sap, skb); 180out_put: 181 llc_sap_put(sap); 182out: 183 return 0; 184drop: 185 kfree_skb(skb); 186 goto out; 187drop_put: 188 kfree_skb(skb); 189 goto out_put; 190handle_station: 191 if (!llc_station_handler) 192 goto drop; 193 llc_station_handler(skb); 194 goto out; 195} 196 197EXPORT_SYMBOL(llc_add_pack); 198EXPORT_SYMBOL(llc_remove_pack); 199EXPORT_SYMBOL(llc_set_station_handler); 200