linux/net/llc/llc_station.c
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   1/*
   2 * llc_station.c - station component of 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/init.h>
  15#include <linux/module.h>
  16#include <linux/slab.h>
  17#include <net/llc.h>
  18#include <net/llc_sap.h>
  19#include <net/llc_conn.h>
  20#include <net/llc_c_ac.h>
  21#include <net/llc_s_ac.h>
  22#include <net/llc_c_ev.h>
  23#include <net/llc_c_st.h>
  24#include <net/llc_s_ev.h>
  25#include <net/llc_s_st.h>
  26#include <net/llc_pdu.h>
  27
  28/**
  29 * struct llc_station - LLC station component
  30 *
  31 * SAP and connection resource manager, one per adapter.
  32 *
  33 * @state: state of station
  34 * @xid_r_count: XID response PDU counter
  35 * @mac_sa: MAC source address
  36 * @sap_list: list of related SAPs
  37 * @ev_q: events entering state mach.
  38 * @mac_pdu_q: PDUs ready to send to MAC
  39 */
  40struct llc_station {
  41        u8                          state;
  42        u8                          xid_r_count;
  43        struct timer_list           ack_timer;
  44        u8                          retry_count;
  45        u8                          maximum_retry;
  46        struct {
  47                struct sk_buff_head list;
  48                spinlock_t          lock;
  49        } ev_q;
  50        struct sk_buff_head         mac_pdu_q;
  51};
  52
  53#define LLC_STATION_ACK_TIME (3 * HZ)
  54
  55int sysctl_llc_station_ack_timeout = LLC_STATION_ACK_TIME;
  56
  57/* Types of events (possible values in 'ev->type') */
  58#define LLC_STATION_EV_TYPE_SIMPLE      1
  59#define LLC_STATION_EV_TYPE_CONDITION   2
  60#define LLC_STATION_EV_TYPE_PRIM        3
  61#define LLC_STATION_EV_TYPE_PDU         4       /* command/response PDU */
  62#define LLC_STATION_EV_TYPE_ACK_TMR     5
  63#define LLC_STATION_EV_TYPE_RPT_STATUS  6
  64
  65/* Events */
  66#define LLC_STATION_EV_ENABLE_WITH_DUP_ADDR_CHECK               1
  67#define LLC_STATION_EV_ENABLE_WITHOUT_DUP_ADDR_CHECK            2
  68#define LLC_STATION_EV_ACK_TMR_EXP_LT_RETRY_CNT_MAX_RETRY       3
  69#define LLC_STATION_EV_ACK_TMR_EXP_EQ_RETRY_CNT_MAX_RETRY       4
  70#define LLC_STATION_EV_RX_NULL_DSAP_XID_C                       5
  71#define LLC_STATION_EV_RX_NULL_DSAP_0_XID_R_XID_R_CNT_EQ        6
  72#define LLC_STATION_EV_RX_NULL_DSAP_1_XID_R_XID_R_CNT_EQ        7
  73#define LLC_STATION_EV_RX_NULL_DSAP_TEST_C                      8
  74#define LLC_STATION_EV_DISABLE_REQ                              9
  75
  76struct llc_station_state_ev {
  77        u8               type;
  78        u8               prim;
  79        u8               prim_type;
  80        u8               reason;
  81        struct list_head node; /* node in station->ev_q.list */
  82};
  83
  84static __inline__ struct llc_station_state_ev *
  85                                        llc_station_ev(struct sk_buff *skb)
  86{
  87        return (struct llc_station_state_ev *)skb->cb;
  88}
  89
  90typedef int (*llc_station_ev_t)(struct sk_buff *skb);
  91
  92#define LLC_STATION_STATE_DOWN          1       /* initial state */
  93#define LLC_STATION_STATE_DUP_ADDR_CHK  2
  94#define LLC_STATION_STATE_UP            3
  95
  96#define LLC_NBR_STATION_STATES          3       /* size of state table */
  97
  98typedef int (*llc_station_action_t)(struct sk_buff *skb);
  99
 100/* Station component state table structure */
 101struct llc_station_state_trans {
 102        llc_station_ev_t ev;
 103        u8 next_state;
 104        llc_station_action_t *ev_actions;
 105};
 106
 107struct llc_station_state {
 108        u8 curr_state;
 109        struct llc_station_state_trans **transitions;
 110};
 111
 112static struct llc_station llc_main_station;
 113
 114static int llc_stat_ev_enable_with_dup_addr_check(struct sk_buff *skb)
 115{
 116        struct llc_station_state_ev *ev = llc_station_ev(skb);
 117
 118        return ev->type == LLC_STATION_EV_TYPE_SIMPLE &&
 119               ev->prim_type ==
 120                              LLC_STATION_EV_ENABLE_WITH_DUP_ADDR_CHECK ? 0 : 1;
 121}
 122
 123static int llc_stat_ev_enable_without_dup_addr_check(struct sk_buff *skb)
 124{
 125        struct llc_station_state_ev *ev = llc_station_ev(skb);
 126
 127        return ev->type == LLC_STATION_EV_TYPE_SIMPLE &&
 128               ev->prim_type ==
 129                        LLC_STATION_EV_ENABLE_WITHOUT_DUP_ADDR_CHECK ? 0 : 1;
 130}
 131
 132static int llc_stat_ev_ack_tmr_exp_lt_retry_cnt_max_retry(struct sk_buff *skb)
 133{
 134        struct llc_station_state_ev *ev = llc_station_ev(skb);
 135
 136        return ev->type == LLC_STATION_EV_TYPE_ACK_TMR &&
 137                llc_main_station.retry_count <
 138                llc_main_station.maximum_retry ? 0 : 1;
 139}
 140
 141static int llc_stat_ev_ack_tmr_exp_eq_retry_cnt_max_retry(struct sk_buff *skb)
 142{
 143        struct llc_station_state_ev *ev = llc_station_ev(skb);
 144
 145        return ev->type == LLC_STATION_EV_TYPE_ACK_TMR &&
 146                llc_main_station.retry_count ==
 147                llc_main_station.maximum_retry ? 0 : 1;
 148}
 149
 150static int llc_stat_ev_rx_null_dsap_xid_c(struct sk_buff *skb)
 151{
 152        struct llc_station_state_ev *ev = llc_station_ev(skb);
 153        struct llc_pdu_un *pdu = llc_pdu_un_hdr(skb);
 154
 155        return ev->type == LLC_STATION_EV_TYPE_PDU &&
 156               LLC_PDU_IS_CMD(pdu) &&                   /* command PDU */
 157               LLC_PDU_TYPE_IS_U(pdu) &&                /* U type PDU */
 158               LLC_U_PDU_CMD(pdu) == LLC_1_PDU_CMD_XID &&
 159               !pdu->dsap ? 0 : 1;                      /* NULL DSAP value */
 160}
 161
 162static int llc_stat_ev_rx_null_dsap_0_xid_r_xid_r_cnt_eq(struct sk_buff *skb)
 163{
 164        struct llc_station_state_ev *ev = llc_station_ev(skb);
 165        struct llc_pdu_un *pdu = llc_pdu_un_hdr(skb);
 166
 167        return ev->type == LLC_STATION_EV_TYPE_PDU &&
 168               LLC_PDU_IS_RSP(pdu) &&                   /* response PDU */
 169               LLC_PDU_TYPE_IS_U(pdu) &&                /* U type PDU */
 170               LLC_U_PDU_RSP(pdu) == LLC_1_PDU_CMD_XID &&
 171               !pdu->dsap &&                            /* NULL DSAP value */
 172               !llc_main_station.xid_r_count ? 0 : 1;
 173}
 174
 175static int llc_stat_ev_rx_null_dsap_1_xid_r_xid_r_cnt_eq(struct sk_buff *skb)
 176{
 177        struct llc_station_state_ev *ev = llc_station_ev(skb);
 178        struct llc_pdu_un *pdu = llc_pdu_un_hdr(skb);
 179
 180        return ev->type == LLC_STATION_EV_TYPE_PDU &&
 181               LLC_PDU_IS_RSP(pdu) &&                   /* response PDU */
 182               LLC_PDU_TYPE_IS_U(pdu) &&                /* U type PDU */
 183               LLC_U_PDU_RSP(pdu) == LLC_1_PDU_CMD_XID &&
 184               !pdu->dsap &&                            /* NULL DSAP value */
 185               llc_main_station.xid_r_count == 1 ? 0 : 1;
 186}
 187
 188static int llc_stat_ev_rx_null_dsap_test_c(struct sk_buff *skb)
 189{
 190        struct llc_station_state_ev *ev = llc_station_ev(skb);
 191        struct llc_pdu_un *pdu = llc_pdu_un_hdr(skb);
 192
 193        return ev->type == LLC_STATION_EV_TYPE_PDU &&
 194               LLC_PDU_IS_CMD(pdu) &&                   /* command PDU */
 195               LLC_PDU_TYPE_IS_U(pdu) &&                /* U type PDU */
 196               LLC_U_PDU_CMD(pdu) == LLC_1_PDU_CMD_TEST &&
 197               !pdu->dsap ? 0 : 1;                      /* NULL DSAP */
 198}
 199
 200static int llc_stat_ev_disable_req(struct sk_buff *skb)
 201{
 202        struct llc_station_state_ev *ev = llc_station_ev(skb);
 203
 204        return ev->type == LLC_STATION_EV_TYPE_PRIM &&
 205               ev->prim == LLC_DISABLE_PRIM &&
 206               ev->prim_type == LLC_PRIM_TYPE_REQ ? 0 : 1;
 207}
 208
 209/**
 210 *      llc_station_send_pdu - queues PDU to send
 211 *      @skb: Address of the PDU
 212 *
 213 *      Queues a PDU to send to the MAC layer.
 214 */
 215static void llc_station_send_pdu(struct sk_buff *skb)
 216{
 217        skb_queue_tail(&llc_main_station.mac_pdu_q, skb);
 218        while ((skb = skb_dequeue(&llc_main_station.mac_pdu_q)) != NULL)
 219                if (dev_queue_xmit(skb))
 220                        break;
 221}
 222
 223static int llc_station_ac_start_ack_timer(struct sk_buff *skb)
 224{
 225        mod_timer(&llc_main_station.ack_timer,
 226                  jiffies + sysctl_llc_station_ack_timeout);
 227        return 0;
 228}
 229
 230static int llc_station_ac_set_retry_cnt_0(struct sk_buff *skb)
 231{
 232        llc_main_station.retry_count = 0;
 233        return 0;
 234}
 235
 236static int llc_station_ac_inc_retry_cnt_by_1(struct sk_buff *skb)
 237{
 238        llc_main_station.retry_count++;
 239        return 0;
 240}
 241
 242static int llc_station_ac_set_xid_r_cnt_0(struct sk_buff *skb)
 243{
 244        llc_main_station.xid_r_count = 0;
 245        return 0;
 246}
 247
 248static int llc_station_ac_inc_xid_r_cnt_by_1(struct sk_buff *skb)
 249{
 250        llc_main_station.xid_r_count++;
 251        return 0;
 252}
 253
 254static int llc_station_ac_send_null_dsap_xid_c(struct sk_buff *skb)
 255{
 256        int rc = 1;
 257        struct sk_buff *nskb = llc_alloc_frame(NULL, skb->dev, LLC_PDU_TYPE_U,
 258                                               sizeof(struct llc_xid_info));
 259
 260        if (!nskb)
 261                goto out;
 262        llc_pdu_header_init(nskb, LLC_PDU_TYPE_U, 0, 0, LLC_PDU_CMD);
 263        llc_pdu_init_as_xid_cmd(nskb, LLC_XID_NULL_CLASS_2, 127);
 264        rc = llc_mac_hdr_init(nskb, skb->dev->dev_addr, skb->dev->dev_addr);
 265        if (unlikely(rc))
 266                goto free;
 267        llc_station_send_pdu(nskb);
 268out:
 269        return rc;
 270free:
 271        kfree_skb(nskb);
 272        goto out;
 273}
 274
 275static int llc_station_ac_send_xid_r(struct sk_buff *skb)
 276{
 277        u8 mac_da[ETH_ALEN], dsap;
 278        int rc = 1;
 279        struct sk_buff *nskb = llc_alloc_frame(NULL, skb->dev, LLC_PDU_TYPE_U,
 280                                               sizeof(struct llc_xid_info));
 281
 282        if (!nskb)
 283                goto out;
 284        rc = 0;
 285        llc_pdu_decode_sa(skb, mac_da);
 286        llc_pdu_decode_ssap(skb, &dsap);
 287        llc_pdu_header_init(nskb, LLC_PDU_TYPE_U, 0, dsap, LLC_PDU_RSP);
 288        llc_pdu_init_as_xid_rsp(nskb, LLC_XID_NULL_CLASS_2, 127);
 289        rc = llc_mac_hdr_init(nskb, skb->dev->dev_addr, mac_da);
 290        if (unlikely(rc))
 291                goto free;
 292        llc_station_send_pdu(nskb);
 293out:
 294        return rc;
 295free:
 296        kfree_skb(nskb);
 297        goto out;
 298}
 299
 300static int llc_station_ac_send_test_r(struct sk_buff *skb)
 301{
 302        u8 mac_da[ETH_ALEN], dsap;
 303        int rc = 1;
 304        u32 data_size;
 305        struct sk_buff *nskb;
 306
 307        /* The test request command is type U (llc_len = 3) */
 308        data_size = ntohs(eth_hdr(skb)->h_proto) - 3;
 309        nskb = llc_alloc_frame(NULL, skb->dev, LLC_PDU_TYPE_U, data_size);
 310
 311        if (!nskb)
 312                goto out;
 313        rc = 0;
 314        llc_pdu_decode_sa(skb, mac_da);
 315        llc_pdu_decode_ssap(skb, &dsap);
 316        llc_pdu_header_init(nskb, LLC_PDU_TYPE_U, 0, dsap, LLC_PDU_RSP);
 317        llc_pdu_init_as_test_rsp(nskb, skb);
 318        rc = llc_mac_hdr_init(nskb, skb->dev->dev_addr, mac_da);
 319        if (unlikely(rc))
 320                goto free;
 321        llc_station_send_pdu(nskb);
 322out:
 323        return rc;
 324free:
 325        kfree_skb(nskb);
 326        goto out;
 327}
 328
 329static int llc_station_ac_report_status(struct sk_buff *skb)
 330{
 331        return 0;
 332}
 333
 334/* COMMON STATION STATE transitions */
 335
 336/* dummy last-transition indicator; common to all state transition groups
 337 * last entry for this state
 338 * all members are zeros, .bss zeroes it
 339 */
 340static struct llc_station_state_trans llc_stat_state_trans_end;
 341
 342/* DOWN STATE transitions */
 343
 344/* state transition for LLC_STATION_EV_ENABLE_WITH_DUP_ADDR_CHECK event */
 345static llc_station_action_t llc_stat_down_state_actions_1[] = {
 346        [0] = llc_station_ac_start_ack_timer,
 347        [1] = llc_station_ac_set_retry_cnt_0,
 348        [2] = llc_station_ac_set_xid_r_cnt_0,
 349        [3] = llc_station_ac_send_null_dsap_xid_c,
 350        [4] = NULL,
 351};
 352
 353static struct llc_station_state_trans llc_stat_down_state_trans_1 = {
 354        .ev         = llc_stat_ev_enable_with_dup_addr_check,
 355        .next_state = LLC_STATION_STATE_DUP_ADDR_CHK,
 356        .ev_actions = llc_stat_down_state_actions_1,
 357};
 358
 359/* state transition for LLC_STATION_EV_ENABLE_WITHOUT_DUP_ADDR_CHECK event */
 360static llc_station_action_t llc_stat_down_state_actions_2[] = {
 361        [0] = llc_station_ac_report_status,     /* STATION UP */
 362        [1] = NULL,
 363};
 364
 365static struct llc_station_state_trans llc_stat_down_state_trans_2 = {
 366        .ev         = llc_stat_ev_enable_without_dup_addr_check,
 367        .next_state = LLC_STATION_STATE_UP,
 368        .ev_actions = llc_stat_down_state_actions_2,
 369};
 370
 371/* array of pointers; one to each transition */
 372static struct llc_station_state_trans *llc_stat_dwn_state_trans[] = {
 373        [0] = &llc_stat_down_state_trans_1,
 374        [1] = &llc_stat_down_state_trans_2,
 375        [2] = &llc_stat_state_trans_end,
 376};
 377
 378/* UP STATE transitions */
 379/* state transition for LLC_STATION_EV_DISABLE_REQ event */
 380static llc_station_action_t llc_stat_up_state_actions_1[] = {
 381        [0] = llc_station_ac_report_status,     /* STATION DOWN */
 382        [1] = NULL,
 383};
 384
 385static struct llc_station_state_trans llc_stat_up_state_trans_1 = {
 386        .ev         = llc_stat_ev_disable_req,
 387        .next_state = LLC_STATION_STATE_DOWN,
 388        .ev_actions = llc_stat_up_state_actions_1,
 389};
 390
 391/* state transition for LLC_STATION_EV_RX_NULL_DSAP_XID_C event */
 392static llc_station_action_t llc_stat_up_state_actions_2[] = {
 393        [0] = llc_station_ac_send_xid_r,
 394        [1] = NULL,
 395};
 396
 397static struct llc_station_state_trans llc_stat_up_state_trans_2 = {
 398        .ev         = llc_stat_ev_rx_null_dsap_xid_c,
 399        .next_state = LLC_STATION_STATE_UP,
 400        .ev_actions = llc_stat_up_state_actions_2,
 401};
 402
 403/* state transition for LLC_STATION_EV_RX_NULL_DSAP_TEST_C event */
 404static llc_station_action_t llc_stat_up_state_actions_3[] = {
 405        [0] = llc_station_ac_send_test_r,
 406        [1] = NULL,
 407};
 408
 409static struct llc_station_state_trans llc_stat_up_state_trans_3 = {
 410        .ev         = llc_stat_ev_rx_null_dsap_test_c,
 411        .next_state = LLC_STATION_STATE_UP,
 412        .ev_actions = llc_stat_up_state_actions_3,
 413};
 414
 415/* array of pointers; one to each transition */
 416static struct llc_station_state_trans *llc_stat_up_state_trans [] = {
 417        [0] = &llc_stat_up_state_trans_1,
 418        [1] = &llc_stat_up_state_trans_2,
 419        [2] = &llc_stat_up_state_trans_3,
 420        [3] = &llc_stat_state_trans_end,
 421};
 422
 423/* DUP ADDR CHK STATE transitions */
 424/* state transition for LLC_STATION_EV_RX_NULL_DSAP_0_XID_R_XID_R_CNT_EQ
 425 * event
 426 */
 427static llc_station_action_t llc_stat_dupaddr_state_actions_1[] = {
 428        [0] = llc_station_ac_inc_xid_r_cnt_by_1,
 429        [1] = NULL,
 430};
 431
 432static struct llc_station_state_trans llc_stat_dupaddr_state_trans_1 = {
 433        .ev         = llc_stat_ev_rx_null_dsap_0_xid_r_xid_r_cnt_eq,
 434        .next_state = LLC_STATION_STATE_DUP_ADDR_CHK,
 435        .ev_actions = llc_stat_dupaddr_state_actions_1,
 436};
 437
 438/* state transition for LLC_STATION_EV_RX_NULL_DSAP_1_XID_R_XID_R_CNT_EQ
 439 * event
 440 */
 441static llc_station_action_t llc_stat_dupaddr_state_actions_2[] = {
 442        [0] = llc_station_ac_report_status,     /* DUPLICATE ADDRESS FOUND */
 443        [1] = NULL,
 444};
 445
 446static struct llc_station_state_trans llc_stat_dupaddr_state_trans_2 = {
 447        .ev         = llc_stat_ev_rx_null_dsap_1_xid_r_xid_r_cnt_eq,
 448        .next_state = LLC_STATION_STATE_DOWN,
 449        .ev_actions = llc_stat_dupaddr_state_actions_2,
 450};
 451
 452/* state transition for LLC_STATION_EV_RX_NULL_DSAP_XID_C event */
 453static llc_station_action_t llc_stat_dupaddr_state_actions_3[] = {
 454        [0] = llc_station_ac_send_xid_r,
 455        [1] = NULL,
 456};
 457
 458static struct llc_station_state_trans llc_stat_dupaddr_state_trans_3 = {
 459        .ev         = llc_stat_ev_rx_null_dsap_xid_c,
 460        .next_state = LLC_STATION_STATE_DUP_ADDR_CHK,
 461        .ev_actions = llc_stat_dupaddr_state_actions_3,
 462};
 463
 464/* state transition for LLC_STATION_EV_ACK_TMR_EXP_LT_RETRY_CNT_MAX_RETRY
 465 * event
 466 */
 467static llc_station_action_t llc_stat_dupaddr_state_actions_4[] = {
 468        [0] = llc_station_ac_start_ack_timer,
 469        [1] = llc_station_ac_inc_retry_cnt_by_1,
 470        [2] = llc_station_ac_set_xid_r_cnt_0,
 471        [3] = llc_station_ac_send_null_dsap_xid_c,
 472        [4] = NULL,
 473};
 474
 475static struct llc_station_state_trans llc_stat_dupaddr_state_trans_4 = {
 476        .ev         = llc_stat_ev_ack_tmr_exp_lt_retry_cnt_max_retry,
 477        .next_state = LLC_STATION_STATE_DUP_ADDR_CHK,
 478        .ev_actions = llc_stat_dupaddr_state_actions_4,
 479};
 480
 481/* state transition for LLC_STATION_EV_ACK_TMR_EXP_EQ_RETRY_CNT_MAX_RETRY
 482 * event
 483 */
 484static llc_station_action_t llc_stat_dupaddr_state_actions_5[] = {
 485        [0] = llc_station_ac_report_status,     /* STATION UP */
 486        [1] = NULL,
 487};
 488
 489static struct llc_station_state_trans llc_stat_dupaddr_state_trans_5 = {
 490        .ev         = llc_stat_ev_ack_tmr_exp_eq_retry_cnt_max_retry,
 491        .next_state = LLC_STATION_STATE_UP,
 492        .ev_actions = llc_stat_dupaddr_state_actions_5,
 493};
 494
 495/* state transition for LLC_STATION_EV_DISABLE_REQ event */
 496static llc_station_action_t llc_stat_dupaddr_state_actions_6[] = {
 497        [0] = llc_station_ac_report_status,     /* STATION DOWN */
 498        [1] = NULL,
 499};
 500
 501static struct llc_station_state_trans llc_stat_dupaddr_state_trans_6 = {
 502        .ev         = llc_stat_ev_disable_req,
 503        .next_state = LLC_STATION_STATE_DOWN,
 504        .ev_actions = llc_stat_dupaddr_state_actions_6,
 505};
 506
 507/* array of pointers; one to each transition */
 508static struct llc_station_state_trans *llc_stat_dupaddr_state_trans[] = {
 509        [0] = &llc_stat_dupaddr_state_trans_6,  /* Request */
 510        [1] = &llc_stat_dupaddr_state_trans_4,  /* Timer */
 511        [2] = &llc_stat_dupaddr_state_trans_5,
 512        [3] = &llc_stat_dupaddr_state_trans_1,  /* Receive frame */
 513        [4] = &llc_stat_dupaddr_state_trans_2,
 514        [5] = &llc_stat_dupaddr_state_trans_3,
 515        [6] = &llc_stat_state_trans_end,
 516};
 517
 518static struct llc_station_state
 519                        llc_station_state_table[LLC_NBR_STATION_STATES] = {
 520        [LLC_STATION_STATE_DOWN - 1] = {
 521                .curr_state  = LLC_STATION_STATE_DOWN,
 522                .transitions = llc_stat_dwn_state_trans,
 523        },
 524        [LLC_STATION_STATE_DUP_ADDR_CHK - 1] = {
 525                .curr_state  = LLC_STATION_STATE_DUP_ADDR_CHK,
 526                .transitions = llc_stat_dupaddr_state_trans,
 527        },
 528        [LLC_STATION_STATE_UP - 1] = {
 529                .curr_state  = LLC_STATION_STATE_UP,
 530                .transitions = llc_stat_up_state_trans,
 531        },
 532};
 533
 534/**
 535 *      llc_exec_station_trans_actions - executes actions for transition
 536 *      @trans: Address of the transition
 537 *      @skb: Address of the event that caused the transition
 538 *
 539 *      Executes actions of a transition of the station state machine. Returns
 540 *      0 if all actions complete successfully, nonzero otherwise.
 541 */
 542static u16 llc_exec_station_trans_actions(struct llc_station_state_trans *trans,
 543                                          struct sk_buff *skb)
 544{
 545        u16 rc = 0;
 546        llc_station_action_t *next_action = trans->ev_actions;
 547
 548        for (; next_action && *next_action; next_action++)
 549                if ((*next_action)(skb))
 550                        rc = 1;
 551        return rc;
 552}
 553
 554/**
 555 *      llc_find_station_trans - finds transition for this event
 556 *      @skb: Address of the event
 557 *
 558 *      Search thru events of the current state of the station until list
 559 *      exhausted or it's obvious that the event is not valid for the current
 560 *      state. Returns the address of the transition if cound, %NULL otherwise.
 561 */
 562static struct llc_station_state_trans *
 563                                llc_find_station_trans(struct sk_buff *skb)
 564{
 565        int i = 0;
 566        struct llc_station_state_trans *rc = NULL;
 567        struct llc_station_state_trans **next_trans;
 568        struct llc_station_state *curr_state =
 569                                &llc_station_state_table[llc_main_station.state - 1];
 570
 571        for (next_trans = curr_state->transitions; next_trans[i]->ev; i++)
 572                if (!next_trans[i]->ev(skb)) {
 573                        rc = next_trans[i];
 574                        break;
 575                }
 576        return rc;
 577}
 578
 579/**
 580 *      llc_station_free_ev - frees an event
 581 *      @skb: Address of the event
 582 *
 583 *      Frees an event.
 584 */
 585static void llc_station_free_ev(struct sk_buff *skb)
 586{
 587        struct llc_station_state_ev *ev = llc_station_ev(skb);
 588
 589        if (ev->type == LLC_STATION_EV_TYPE_PDU)
 590                kfree_skb(skb);
 591}
 592
 593/**
 594 *      llc_station_next_state - processes event and goes to the next state
 595 *      @skb: Address of the event
 596 *
 597 *      Processes an event, executes any transitions related to that event and
 598 *      updates the state of the station.
 599 */
 600static u16 llc_station_next_state(struct sk_buff *skb)
 601{
 602        u16 rc = 1;
 603        struct llc_station_state_trans *trans;
 604
 605        if (llc_main_station.state > LLC_NBR_STATION_STATES)
 606                goto out;
 607        trans = llc_find_station_trans(skb);
 608        if (trans) {
 609                /* got the state to which we next transition; perform the
 610                 * actions associated with this transition before actually
 611                 * transitioning to the next state
 612                 */
 613                rc = llc_exec_station_trans_actions(trans, skb);
 614                if (!rc)
 615                        /* transition station to next state if all actions
 616                         * execute successfully; done; wait for next event
 617                         */
 618                        llc_main_station.state = trans->next_state;
 619        } else
 620                /* event not recognized in current state; re-queue it for
 621                 * processing again at a later time; return failure
 622                 */
 623                rc = 0;
 624out:
 625        llc_station_free_ev(skb);
 626        return rc;
 627}
 628
 629/**
 630 *      llc_station_service_events - service events in the queue
 631 *
 632 *      Get an event from the station event queue (if any); attempt to service
 633 *      the event; if event serviced, get the next event (if any) on the event
 634 *      queue; if event not service, re-queue the event on the event queue and
 635 *      attempt to service the next event; when serviced all events in queue,
 636 *      finished; if don't transition to different state, just service all
 637 *      events once; if transition to new state, service all events again.
 638 *      Caller must hold llc_main_station.ev_q.lock.
 639 */
 640static void llc_station_service_events(void)
 641{
 642        struct sk_buff *skb;
 643
 644        while ((skb = skb_dequeue(&llc_main_station.ev_q.list)) != NULL)
 645                llc_station_next_state(skb);
 646}
 647
 648/**
 649 *      llc_station_state_process - queue event and try to process queue.
 650 *      @skb: Address of the event
 651 *
 652 *      Queues an event (on the station event queue) for handling by the
 653 *      station state machine and attempts to process any queued-up events.
 654 */
 655static void llc_station_state_process(struct sk_buff *skb)
 656{
 657        spin_lock_bh(&llc_main_station.ev_q.lock);
 658        skb_queue_tail(&llc_main_station.ev_q.list, skb);
 659        llc_station_service_events();
 660        spin_unlock_bh(&llc_main_station.ev_q.lock);
 661}
 662
 663static void llc_station_ack_tmr_cb(unsigned long timeout_data)
 664{
 665        struct sk_buff *skb = alloc_skb(0, GFP_ATOMIC);
 666
 667        if (skb) {
 668                struct llc_station_state_ev *ev = llc_station_ev(skb);
 669
 670                ev->type = LLC_STATION_EV_TYPE_ACK_TMR;
 671                llc_station_state_process(skb);
 672        }
 673}
 674
 675/**
 676 *      llc_station_rcv - send received pdu to the station state machine
 677 *      @skb: received frame.
 678 *
 679 *      Sends data unit to station state machine.
 680 */
 681static void llc_station_rcv(struct sk_buff *skb)
 682{
 683        struct llc_station_state_ev *ev = llc_station_ev(skb);
 684
 685        ev->type   = LLC_STATION_EV_TYPE_PDU;
 686        ev->reason = 0;
 687        llc_station_state_process(skb);
 688}
 689
 690void __init llc_station_init(void)
 691{
 692        skb_queue_head_init(&llc_main_station.mac_pdu_q);
 693        skb_queue_head_init(&llc_main_station.ev_q.list);
 694        spin_lock_init(&llc_main_station.ev_q.lock);
 695        setup_timer(&llc_main_station.ack_timer, llc_station_ack_tmr_cb,
 696                        (unsigned long)&llc_main_station);
 697        llc_main_station.ack_timer.expires  = jiffies +
 698                                                sysctl_llc_station_ack_timeout;
 699        llc_main_station.maximum_retry  = 1;
 700        llc_main_station.state          = LLC_STATION_STATE_UP;
 701        llc_set_station_handler(llc_station_rcv);
 702}
 703
 704void llc_station_exit(void)
 705{
 706        llc_set_station_handler(NULL);
 707}
 708
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