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