llc_input.c revision 5a0e3ad6af8660be21ca98a971cd00f331318c05
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#if 0 22#define dprintk(args...) printk(KERN_DEBUG args) 23#else 24#define dprintk(args...) 25#endif 26 27/* 28 * Packet handler for the station, registerable because in the minimal 29 * LLC core that is taking shape only the very minimal subset of LLC that 30 * is needed for things like IPX, Appletalk, etc will stay, with all the 31 * rest in the llc1 and llc2 modules. 32 */ 33static void (*llc_station_handler)(struct sk_buff *skb); 34 35/* 36 * Packet handlers for LLC_DEST_SAP and LLC_DEST_CONN. 37 */ 38static void (*llc_type_handlers[2])(struct llc_sap *sap, 39 struct sk_buff *skb); 40 41void llc_add_pack(int type, void (*handler)(struct llc_sap *sap, 42 struct sk_buff *skb)) 43{ 44 if (type == LLC_DEST_SAP || type == LLC_DEST_CONN) 45 llc_type_handlers[type - 1] = handler; 46} 47 48void llc_remove_pack(int type) 49{ 50 if (type == LLC_DEST_SAP || type == LLC_DEST_CONN) 51 llc_type_handlers[type - 1] = NULL; 52} 53 54void llc_set_station_handler(void (*handler)(struct sk_buff *skb)) 55{ 56 llc_station_handler = handler; 57} 58 59/** 60 * llc_pdu_type - returns which LLC component must handle for PDU 61 * @skb: input skb 62 * 63 * This function returns which LLC component must handle this PDU. 64 */ 65static __inline__ int llc_pdu_type(struct sk_buff *skb) 66{ 67 int type = LLC_DEST_CONN; /* I-PDU or S-PDU type */ 68 struct llc_pdu_sn *pdu = llc_pdu_sn_hdr(skb); 69 70 if ((pdu->ctrl_1 & LLC_PDU_TYPE_MASK) != LLC_PDU_TYPE_U) 71 goto out; 72 switch (LLC_U_PDU_CMD(pdu)) { 73 case LLC_1_PDU_CMD_XID: 74 case LLC_1_PDU_CMD_UI: 75 case LLC_1_PDU_CMD_TEST: 76 type = LLC_DEST_SAP; 77 break; 78 case LLC_2_PDU_CMD_SABME: 79 case LLC_2_PDU_CMD_DISC: 80 case LLC_2_PDU_RSP_UA: 81 case LLC_2_PDU_RSP_DM: 82 case LLC_2_PDU_RSP_FRMR: 83 break; 84 default: 85 type = LLC_DEST_INVALID; 86 break; 87 } 88out: 89 return type; 90} 91 92/** 93 * llc_fixup_skb - initializes skb pointers 94 * @skb: This argument points to incoming skb 95 * 96 * Initializes internal skb pointer to start of network layer by deriving 97 * length of LLC header; finds length of LLC control field in LLC header 98 * by looking at the two lowest-order bits of the first control field 99 * byte; field is either 3 or 4 bytes long. 100 */ 101static inline int llc_fixup_skb(struct sk_buff *skb) 102{ 103 u8 llc_len = 2; 104 struct llc_pdu_un *pdu; 105 106 if (unlikely(!pskb_may_pull(skb, sizeof(*pdu)))) 107 return 0; 108 109 pdu = (struct llc_pdu_un *)skb->data; 110 if ((pdu->ctrl_1 & LLC_PDU_TYPE_MASK) == LLC_PDU_TYPE_U) 111 llc_len = 1; 112 llc_len += 2; 113 114 if (unlikely(!pskb_may_pull(skb, llc_len))) 115 return 0; 116 117 skb->transport_header += llc_len; 118 skb_pull(skb, llc_len); 119 if (skb->protocol == htons(ETH_P_802_2)) { 120 __be16 pdulen = eth_hdr(skb)->h_proto; 121 s32 data_size = ntohs(pdulen) - llc_len; 122 123 if (data_size < 0 || 124 ((skb_tail_pointer(skb) - 125 (u8 *)pdu) - llc_len) < 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 */ 145int 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 if (rcv) { 185 struct sk_buff *cskb = skb_clone(skb, GFP_ATOMIC); 186 if (cskb) 187 rcv(cskb, dev, pt, orig_dev); 188 } 189 dest = llc_pdu_type(skb); 190 if (unlikely(!dest || !llc_type_handlers[dest - 1])) 191 goto drop_put; 192 llc_type_handlers[dest - 1](sap, skb); 193out_put: 194 llc_sap_put(sap); 195out: 196 return 0; 197drop: 198 kfree_skb(skb); 199 goto out; 200drop_put: 201 kfree_skb(skb); 202 goto out_put; 203handle_station: 204 if (!llc_station_handler) 205 goto drop; 206 llc_station_handler(skb); 207 goto out; 208} 209 210EXPORT_SYMBOL(llc_add_pack); 211EXPORT_SYMBOL(llc_remove_pack); 212EXPORT_SYMBOL(llc_set_station_handler); 213