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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 <net/llc.h>
  17 #include <net/llc_sap.h>
  18 #include <net/llc_conn.h>
  19 #include <net/llc_c_ac.h>
  20 #include <net/llc_s_ac.h>
  21 #include <net/llc_c_ev.h>
  22 #include <net/llc_c_st.h>
  23 #include <net/llc_s_ev.h>
  24 #include <net/llc_s_st.h>
  25 #include <net/llc_pdu.h>
  26
  27 /**
  28  * struct llc_station - LLC station component
  29  *
  30  * SAP and connection resource manager, one per adapter.
  31  *
  32  * @state - state of station
  33  * @xid_r_count - XID response PDU counter
  34  * @mac_sa - MAC source address
  35  * @sap_list - list of related SAPs
  36  * @ev_q - events entering state mach.
  37  * @mac_pdu_q - PDUs ready to send to MAC
  38  */
  39 struct llc_station {
  40         u8                          state;
  41         u8                          xid_r_count;
  42         struct timer_list           ack_timer;
  43         u8                          retry_count;
  44         u8                          maximum_retry;
  45         struct {
  46                 struct sk_buff_head list;
  47                 spinlock_t          lock;
  48         } ev_q;
  49         struct sk_buff_head         mac_pdu_q;
  50 };
  51
  52 #define LLC_STATION_ACK_TIME (3 * HZ)
  53
  54 int sysctl_llc_station_ack_timeout = LLC_STATION_ACK_TIME;
  55
  56 /* Types of events (possible values in 'ev->type') */
  57 #define LLC_STATION_EV_TYPE_SIMPLE      1
  58 #define LLC_STATION_EV_TYPE_CONDITION   2
  59 #define LLC_STATION_EV_TYPE_PRIM        3
  60 #define LLC_STATION_EV_TYPE_PDU         4       /* command/response PDU */
  61 #define LLC_STATION_EV_TYPE_ACK_TMR     5
  62 #define LLC_STATION_EV_TYPE_RPT_STATUS  6
  63
  64 /* Events */
  65 #define LLC_STATION_EV_ENABLE_WITH_DUP_ADDR_CHECK               1
  66 #define LLC_STATION_EV_ENABLE_WITHOUT_DUP_ADDR_CHECK            2
  67 #define LLC_STATION_EV_ACK_TMR_EXP_LT_RETRY_CNT_MAX_RETRY       3
  68 #define LLC_STATION_EV_ACK_TMR_EXP_EQ_RETRY_CNT_MAX_RETRY       4
  69 #define LLC_STATION_EV_RX_NULL_DSAP_XID_C                       5
  70 #define LLC_STATION_EV_RX_NULL_DSAP_0_XID_R_XID_R_CNT_EQ        6
  71 #define LLC_STATION_EV_RX_NULL_DSAP_1_XID_R_XID_R_CNT_EQ        7
  72 #define LLC_STATION_EV_RX_NULL_DSAP_TEST_C                      8
  73 #define LLC_STATION_EV_DISABLE_REQ                              9
  74
  75 struct llc_station_state_ev {
  76         u8               type;
  77         u8               prim;
  78         u8               prim_type;
  79         u8               reason;
  80         struct list_head node; /* node in station->ev_q.list */
  81 };
  82
  83 static __inline__ struct llc_station_state_ev *
  84                                         llc_station_ev(struct sk_buff *skb)
  85 {
  86         return (struct llc_station_state_ev *)skb->cb;
  87 }
  88
  89 typedef int (*llc_station_ev_t)(struct sk_buff *skb);
  90
  91 #define LLC_STATION_STATE_DOWN          1       /* initial state */
  92 #define LLC_STATION_STATE_DUP_ADDR_CHK  2
  93 #define LLC_STATION_STATE_UP            3
  94
  95 #define LLC_NBR_STATION_STATES          3       /* size of state table */
  96
  97 typedef int (*llc_station_action_t)(struct sk_buff *skb);
  98
  99 /* Station component state table structure */
 100 struct llc_station_state_trans {
 101         llc_station_ev_t ev;
 102         u8 next_state;
 103         llc_station_action_t *ev_actions;
 104 };
 105
 106 struct llc_station_state {
 107         u8 curr_state;
 108         struct llc_station_state_trans **transitions;
 109 };
 110
 111 static struct llc_station llc_main_station;
 112
 113 static int llc_stat_ev_enable_with_dup_addr_check(struct sk_buff *skb)
 114 {
 115         struct llc_station_state_ev *ev = llc_station_ev(skb);
 116
 117         return ev->type == LLC_STATION_EV_TYPE_SIMPLE &&
 118                ev->prim_type ==
 119                               LLC_STATION_EV_ENABLE_WITH_DUP_ADDR_CHECK ? 0 : 1;
 120 }
 121
 122 static int llc_stat_ev_enable_without_dup_addr_check(struct sk_buff *skb)
 123 {
 124         struct llc_station_state_ev *ev = llc_station_ev(skb);
 125
 126         return ev->type == LLC_STATION_EV_TYPE_SIMPLE &&
 127                ev->prim_type ==
 128                         LLC_STATION_EV_ENABLE_WITHOUT_DUP_ADDR_CHECK ? 0 : 1;
 129 }
 130
 131 static int llc_stat_ev_ack_tmr_exp_lt_retry_cnt_max_retry(struct sk_buff *skb)
 132 {
 133         struct llc_station_state_ev *ev = llc_station_ev(skb);
 134
 135         return ev->type == LLC_STATION_EV_TYPE_ACK_TMR &&
 136                 llc_main_station.retry_count <
 137                 llc_main_station.maximum_retry ? 0 : 1;
 138 }
 139
 140 static int llc_stat_ev_ack_tmr_exp_eq_retry_cnt_max_retry(struct sk_buff *skb)
 141 {
 142         struct llc_station_state_ev *ev = llc_station_ev(skb);
 143
 144         return ev->type == LLC_STATION_EV_TYPE_ACK_TMR &&
 145                 llc_main_station.retry_count ==
 146                 llc_main_station.maximum_retry ? 0 : 1;
 147 }
 148
 149 static int llc_stat_ev_rx_null_dsap_xid_c(struct sk_buff *skb)
 150 {
 151         struct llc_station_state_ev *ev = llc_station_ev(skb);
 152         struct llc_pdu_un *pdu = llc_pdu_un_hdr(skb);
 153
 154         return ev->type == LLC_STATION_EV_TYPE_PDU &&
 155                LLC_PDU_IS_CMD(pdu) &&                   /* command PDU */
 156                LLC_PDU_TYPE_IS_U(pdu) &&                /* U type PDU */
 157                LLC_U_PDU_CMD(pdu) == LLC_1_PDU_CMD_XID &&
 158                !pdu->dsap ? 0 : 1;                      /* NULL DSAP value */
 159 }
 160
 161 static int llc_stat_ev_rx_null_dsap_0_xid_r_xid_r_cnt_eq(struct sk_buff *skb)
 162 {
 163         struct llc_station_state_ev *ev = llc_station_ev(skb);
 164         struct llc_pdu_un *pdu = llc_pdu_un_hdr(skb);
 165
 166         return ev->type == LLC_STATION_EV_TYPE_PDU &&
 167                LLC_PDU_IS_RSP(pdu) &&                   /* response PDU */
 168                LLC_PDU_TYPE_IS_U(pdu) &&                /* U type PDU */
 169                LLC_U_PDU_RSP(pdu) == LLC_1_PDU_CMD_XID &&
 170                !pdu->dsap &&                            /* NULL DSAP value */
 171                !llc_main_station.xid_r_count ? 0 : 1;
 172 }
 173
 174 static int llc_stat_ev_rx_null_dsap_1_xid_r_xid_r_cnt_eq(struct sk_buff *skb)
 175 {
 176         struct llc_station_state_ev *ev = llc_station_ev(skb);
 177         struct llc_pdu_un *pdu = llc_pdu_un_hdr(skb);
 178
 179         return ev->type == LLC_STATION_EV_TYPE_PDU &&
 180                LLC_PDU_IS_RSP(pdu) &&                   /* response PDU */
 181                LLC_PDU_TYPE_IS_U(pdu) &&                /* U type PDU */
 182                LLC_U_PDU_RSP(pdu) == LLC_1_PDU_CMD_XID &&
 183                !pdu->dsap &&                            /* NULL DSAP value */
 184                llc_main_station.xid_r_count == 1 ? 0 : 1;
 185 }
 186
 187 static int llc_stat_ev_rx_null_dsap_test_c(struct sk_buff *skb)
 188 {
 189         struct llc_station_state_ev *ev = llc_station_ev(skb);
 190         struct llc_pdu_un *pdu = llc_pdu_un_hdr(skb);
 191
 192         return ev->type == LLC_STATION_EV_TYPE_PDU &&
 193                LLC_PDU_IS_CMD(pdu) &&                   /* command PDU */
 194                LLC_PDU_TYPE_IS_U(pdu) &&                /* U type PDU */
 195                LLC_U_PDU_CMD(pdu) == LLC_1_PDU_CMD_TEST &&
 196                !pdu->dsap ? 0 : 1;                      /* NULL DSAP */
 197 }
 198
 199 static int llc_stat_ev_disable_req(struct sk_buff *skb)
 200 {
 201         struct llc_station_state_ev *ev = llc_station_ev(skb);
 202
 203         return ev->type == LLC_STATION_EV_TYPE_PRIM &&
 204                ev->prim == LLC_DISABLE_PRIM &&
 205                ev->prim_type == LLC_PRIM_TYPE_REQ ? 0 : 1;
 206 }
 207
 208 /**
 209  *      llc_station_send_pdu - queues PDU to send
 210  *      @skb: Address of the PDU
 211  *
 212  *      Queues a PDU to send to the MAC layer.
 213  */
 214 static void llc_station_send_pdu(struct sk_buff *skb)
 215 {
 216         skb_queue_tail(&llc_main_station.mac_pdu_q, skb);
 217         while ((skb = skb_dequeue(&llc_main_station.mac_pdu_q)) != NULL)
 218                 if (dev_queue_xmit(skb))
 219                         break;
 220 }
 221
 222 static int llc_station_ac_start_ack_timer(struct sk_buff *skb)
 223 {
 224         mod_timer(&llc_main_station.ack_timer,
 225                   jiffies + sysctl_llc_station_ack_timeout);
 226         return 0;
 227 }
 228
 229 static int llc_station_ac_set_retry_cnt_0(struct sk_buff *skb)
 230 {
 231         llc_main_station.retry_count = 0;
 232         return 0;
 233 }
 234
 235 static int llc_station_ac_inc_retry_cnt_by_1(struct sk_buff *skb)
 236 {
 237         llc_main_station.retry_count++;
 238         return 0;
 239 }
 240
 241 static int llc_station_ac_set_xid_r_cnt_0(struct sk_buff *skb)
 242 {
 243         llc_main_station.xid_r_count = 0;
 244         return 0;
 245 }
 246
 247 static int llc_station_ac_inc_xid_r_cnt_by_1(struct sk_buff *skb)
 248 {
 249         llc_main_station.xid_r_count++;
 250         return 0;
 251 }
 252
 253 static int llc_station_ac_send_null_dsap_xid_c(struct sk_buff *skb)
 254 {
 255         int rc = 1;
 256         struct sk_buff *nskb = llc_alloc_frame(NULL, skb->dev);
 257
 258         if (!nskb)
 259                 goto out;
 260         llc_pdu_header_init(nskb, LLC_PDU_TYPE_U, 0, 0, LLC_PDU_CMD);
 261         llc_pdu_init_as_xid_cmd(nskb, LLC_XID_NULL_CLASS_2, 127);
 262         rc = llc_mac_hdr_init(nskb, llc_station_mac_sa, llc_station_mac_sa);
 263         if (unlikely(rc))
 264                 goto free;
 265         llc_station_send_pdu(nskb);
 266 out:
 267         return rc;
 268 free:
 269         kfree_skb(skb);
 270         goto out;
 271 }
 272
 273 static int llc_station_ac_send_xid_r(struct sk_buff *skb)
 274 {
 275         u8 mac_da[ETH_ALEN], dsap;
 276         int rc = 1;
 277         struct sk_buff* nskb = llc_alloc_frame(NULL, skb->dev);
 278
 279         if (!nskb)
 280                 goto out;
 281         rc = 0;
 282         llc_pdu_decode_sa(skb, mac_da);
 283         llc_pdu_decode_ssap(skb, &dsap);
 284         llc_pdu_header_init(nskb, LLC_PDU_TYPE_U, 0, dsap, LLC_PDU_RSP);
 285         llc_pdu_init_as_xid_rsp(nskb, LLC_XID_NULL_CLASS_2, 127);
 286         rc = llc_mac_hdr_init(nskb, llc_station_mac_sa, mac_da);
 287         if (unlikely(rc))
 288                 goto free;
 289         llc_station_send_pdu(nskb);
 290 out:
 291         return rc;
 292 free:
 293         kfree_skb(skb);
 294         goto out;
 295 }
 296
 297 static int llc_station_ac_send_test_r(struct sk_buff *skb)
 298 {
 299         u8 mac_da[ETH_ALEN], dsap;
 300         int rc = 1;
 301         struct sk_buff *nskb = llc_alloc_frame(NULL, skb->dev);
 302
 303         if (!nskb)
 304                 goto out;
 305         rc = 0;
 306         llc_pdu_decode_sa(skb, mac_da);
 307         llc_pdu_decode_ssap(skb, &dsap);
 308         llc_pdu_header_init(nskb, LLC_PDU_TYPE_U, 0, dsap, LLC_PDU_RSP);
 309         llc_pdu_init_as_test_rsp(nskb, skb);
 310         rc = llc_mac_hdr_init(nskb, llc_station_mac_sa, mac_da);
 311         if (unlikely(rc))
 312                 goto free;
 313         llc_station_send_pdu(nskb);
 314 out:
 315         return rc;
 316 free:
 317         kfree_skb(skb);
 318         goto out;
 319 }
 320
 321 static int llc_station_ac_report_status(struct sk_buff *skb)
 322 {
 323         return 0;
 324 }
 325
 326 /* COMMON STATION STATE transitions */
 327
 328 /* dummy last-transition indicator; common to all state transition groups
 329  * last entry for this state
 330  * all members are zeros, .bss zeroes it
 331  */
 332 static struct llc_station_state_trans llc_stat_state_trans_end;
 333
 334 /* DOWN STATE transitions */
 335
 336 /* state transition for LLC_STATION_EV_ENABLE_WITH_DUP_ADDR_CHECK event */
 337 static llc_station_action_t llc_stat_down_state_actions_1[] = {
 338         [0] = llc_station_ac_start_ack_timer,
 339         [1] = llc_station_ac_set_retry_cnt_0,
 340         [2] = llc_station_ac_set_xid_r_cnt_0,
 341         [3] = llc_station_ac_send_null_dsap_xid_c,
 342         [4] = NULL,
 343 };
 344
 345 static struct llc_station_state_trans llc_stat_down_state_trans_1 = {
 346         .ev         = llc_stat_ev_enable_with_dup_addr_check,
 347         .next_state = LLC_STATION_STATE_DUP_ADDR_CHK,
 348         .ev_actions = llc_stat_down_state_actions_1,
 349 };
 350
 351 /* state transition for LLC_STATION_EV_ENABLE_WITHOUT_DUP_ADDR_CHECK event */
 352 static llc_station_action_t llc_stat_down_state_actions_2[] = {
 353         [0] = llc_station_ac_report_status,     /* STATION UP */
 354         [1] = NULL,
 355 };
 356
 357 static struct llc_station_state_trans llc_stat_down_state_trans_2 = {
 358         .ev         = llc_stat_ev_enable_without_dup_addr_check,
 359         .next_state = LLC_STATION_STATE_UP,
 360         .ev_actions = llc_stat_down_state_actions_2,
 361 };
 362
 363 /* array of pointers; one to each transition */
 364 static struct llc_station_state_trans *llc_stat_dwn_state_trans[] = {
 365         [0] = &llc_stat_down_state_trans_1,
 366         [1] = &llc_stat_down_state_trans_2,
 367         [2] = &llc_stat_state_trans_end,
 368 };
 369
 370 /* UP STATE transitions */
 371 /* state transition for LLC_STATION_EV_DISABLE_REQ event */
 372 static llc_station_action_t llc_stat_up_state_actions_1[] = {
 373         [0] = llc_station_ac_report_status,     /* STATION DOWN */
 374         [1] = NULL,
 375 };
 376
 377 static struct llc_station_state_trans llc_stat_up_state_trans_1 = {
 378         .ev         = llc_stat_ev_disable_req,
 379         .next_state = LLC_STATION_STATE_DOWN,
 380         .ev_actions = llc_stat_up_state_actions_1,
 381 };
 382
 383 /* state transition for LLC_STATION_EV_RX_NULL_DSAP_XID_C event */
 384 static llc_station_action_t llc_stat_up_state_actions_2[] = {
 385         [0] = llc_station_ac_send_xid_r,
 386         [1] = NULL,
 387 };
 388
 389 static struct llc_station_state_trans llc_stat_up_state_trans_2 = {
 390         .ev         = llc_stat_ev_rx_null_dsap_xid_c,
 391         .next_state = LLC_STATION_STATE_UP,
 392         .ev_actions = llc_stat_up_state_actions_2,
 393 };
 394
 395 /* state transition for LLC_STATION_EV_RX_NULL_DSAP_TEST_C event */
 396 static llc_station_action_t llc_stat_up_state_actions_3[] = {
 397         [0] = llc_station_ac_send_test_r,
 398         [1] = NULL,
 399 };
 400
 401 static struct llc_station_state_trans llc_stat_up_state_trans_3 = {
 402         .ev         = llc_stat_ev_rx_null_dsap_test_c,
 403         .next_state = LLC_STATION_STATE_UP,
 404         .ev_actions = llc_stat_up_state_actions_3,
 405 };
 406
 407 /* array of pointers; one to each transition */
 408 static struct llc_station_state_trans *llc_stat_up_state_trans [] = {
 409         [0] = &llc_stat_up_state_trans_1,
 410         [1] = &llc_stat_up_state_trans_2,
 411         [2] = &llc_stat_up_state_trans_3,
 412         [3] = &llc_stat_state_trans_end,
 413 };
 414
 415 /* DUP ADDR CHK STATE transitions */
 416 /* state transition for LLC_STATION_EV_RX_NULL_DSAP_0_XID_R_XID_R_CNT_EQ
 417  * event
 418  */
 419 static llc_station_action_t llc_stat_dupaddr_state_actions_1[] = {
 420         [0] = llc_station_ac_inc_xid_r_cnt_by_1,
 421         [1] = NULL,
 422 };
 423
 424 static struct llc_station_state_trans llc_stat_dupaddr_state_trans_1 = {
 425         .ev         = llc_stat_ev_rx_null_dsap_0_xid_r_xid_r_cnt_eq,
 426         .next_state = LLC_STATION_STATE_DUP_ADDR_CHK,
 427         .ev_actions = llc_stat_dupaddr_state_actions_1,
 428 };
 429
 430 /* state transition for LLC_STATION_EV_RX_NULL_DSAP_1_XID_R_XID_R_CNT_EQ
 431  * event
 432  */
 433 static llc_station_action_t llc_stat_dupaddr_state_actions_2[] = {
 434         [0] = llc_station_ac_report_status,     /* DUPLICATE ADDRESS FOUND */
 435         [1] = NULL,
 436 };
 437
 438 static struct llc_station_state_trans llc_stat_dupaddr_state_trans_2 = {
 439         .ev         = llc_stat_ev_rx_null_dsap_1_xid_r_xid_r_cnt_eq,
 440         .next_state = LLC_STATION_STATE_DOWN,
 441         .ev_actions = llc_stat_dupaddr_state_actions_2,
 442 };
 443
 444 /* state transition for LLC_STATION_EV_RX_NULL_DSAP_XID_C event */
 445 static llc_station_action_t llc_stat_dupaddr_state_actions_3[] = {
 446         [0] = llc_station_ac_send_xid_r,
 447         [1] = NULL,
 448 };
 449
 450 static struct llc_station_state_trans llc_stat_dupaddr_state_trans_3 = {
 451         .ev         = llc_stat_ev_rx_null_dsap_xid_c,
 452         .next_state = LLC_STATION_STATE_DUP_ADDR_CHK,
 453         .ev_actions = llc_stat_dupaddr_state_actions_3,
 454 };
 455
 456 /* state transition for LLC_STATION_EV_ACK_TMR_EXP_LT_RETRY_CNT_MAX_RETRY
 457  * event
 458  */
 459 static llc_station_action_t llc_stat_dupaddr_state_actions_4[] = {
 460         [0] = llc_station_ac_start_ack_timer,
 461         [1] = llc_station_ac_inc_retry_cnt_by_1,
 462         [2] = llc_station_ac_set_xid_r_cnt_0,
 463         [3] = llc_station_ac_send_null_dsap_xid_c,
 464         [4] = NULL,
 465 };
 466
 467 static struct llc_station_state_trans llc_stat_dupaddr_state_trans_4 = {
 468         .ev         = llc_stat_ev_ack_tmr_exp_lt_retry_cnt_max_retry,
 469         .next_state = LLC_STATION_STATE_DUP_ADDR_CHK,
 470         .ev_actions = llc_stat_dupaddr_state_actions_4,
 471 };
 472
 473 /* state transition for LLC_STATION_EV_ACK_TMR_EXP_EQ_RETRY_CNT_MAX_RETRY
 474  * event
 475  */
 476 static llc_station_action_t llc_stat_dupaddr_state_actions_5[] = {
 477         [0] = llc_station_ac_report_status,     /* STATION UP */
 478         [1] = NULL,
 479 };
 480
 481 static struct llc_station_state_trans llc_stat_dupaddr_state_trans_5 = {
 482         .ev         = llc_stat_ev_ack_tmr_exp_eq_retry_cnt_max_retry,
 483         .next_state = LLC_STATION_STATE_UP,
 484         .ev_actions = llc_stat_dupaddr_state_actions_5,
 485 };
 486
 487 /* state transition for LLC_STATION_EV_DISABLE_REQ event */
 488 static llc_station_action_t llc_stat_dupaddr_state_actions_6[] = {
 489         [0] = llc_station_ac_report_status,     /* STATION DOWN */
 490         [1] = NULL,
 491 };
 492
 493 static struct llc_station_state_trans llc_stat_dupaddr_state_trans_6 = {
 494         .ev         = llc_stat_ev_disable_req,
 495         .next_state = LLC_STATION_STATE_DOWN,
 496         .ev_actions = llc_stat_dupaddr_state_actions_6,
 497 };
 498
 499 /* array of pointers; one to each transition */
 500 static struct llc_station_state_trans *llc_stat_dupaddr_state_trans[] = {
 501         [0] = &llc_stat_dupaddr_state_trans_6,  /* Request */
 502         [1] = &llc_stat_dupaddr_state_trans_4,  /* Timer */
 503         [2] = &llc_stat_dupaddr_state_trans_5,
 504         [3] = &llc_stat_dupaddr_state_trans_1,  /* Receive frame */
 505         [4] = &llc_stat_dupaddr_state_trans_2,
 506         [5] = &llc_stat_dupaddr_state_trans_3,
 507         [6] = &llc_stat_state_trans_end,
 508 };
 509
 510 static struct llc_station_state
 511                         llc_station_state_table[LLC_NBR_STATION_STATES] = {
 512         [LLC_STATION_STATE_DOWN - 1] = {
 513                 .curr_state  = LLC_STATION_STATE_DOWN,
 514                 .transitions = llc_stat_dwn_state_trans,
 515         },
 516         [LLC_STATION_STATE_DUP_ADDR_CHK - 1] = {
 517                 .curr_state  = LLC_STATION_STATE_DUP_ADDR_CHK,
 518                 .transitions = llc_stat_dupaddr_state_trans,
 519         },
 520         [LLC_STATION_STATE_UP - 1] = {
 521                 .curr_state  = LLC_STATION_STATE_UP,
 522                 .transitions = llc_stat_up_state_trans,
 523         },
 524 };
 525
 526 /**
 527  *      llc_exec_station_trans_actions - executes actions for transition
 528  *      @trans: Address of the transition
 529  *      @skb: Address of the event that caused the transition
 530  *
 531  *      Executes actions of a transition of the station state machine. Returns
 532  *      0 if all actions complete successfully, nonzero otherwise.
 533  */
 534 static u16 llc_exec_station_trans_actions(struct llc_station_state_trans *trans,
 535                                           struct sk_buff *skb)
 536 {
 537         u16 rc = 0;
 538         llc_station_action_t *next_action = trans->ev_actions;
 539
 540         for (; next_action && *next_action; next_action++)
 541                 if ((*next_action)(skb))
 542                         rc = 1;
 543         return rc;
 544 }
 545
 546 /**
 547  *      llc_find_station_trans - finds transition for this event
 548  *      @skb: Address of the event
 549  *
 550  *      Search thru events of the current state of the station until list
 551  *      exhausted or it's obvious that the event is not valid for the current
 552  *      state. Returns the address of the transition if cound, %NULL otherwise.
 553  */
 554 static struct llc_station_state_trans *
 555                                 llc_find_station_trans(struct sk_buff *skb)
 556 {
 557         int i = 0;
 558         struct llc_station_state_trans *rc = NULL;
 559         struct llc_station_state_trans **next_trans;
 560         struct llc_station_state *curr_state =
 561                                 &llc_station_state_table[llc_main_station.state - 1];
 562
 563         for (next_trans = curr_state->transitions; next_trans[i]->ev; i++)
 564                 if (!next_trans[i]->ev(skb)) {
 565                         rc = next_trans[i];
 566                         break;
 567                 }
 568         return rc;
 569 }
 570
 571 /**
 572  *      llc_station_free_ev - frees an event
 573  *      @skb: Address of the event
 574  *
 575  *      Frees an event.
 576  */
 577 static void llc_station_free_ev(struct sk_buff *skb)
 578 {
 579         struct llc_station_state_ev *ev = llc_station_ev(skb);
 580
 581         if (ev->type == LLC_STATION_EV_TYPE_PDU)
 582                 kfree_skb(skb);
 583 }
 584
 585 /**
 586  *      llc_station_next_state - processes event and goes to the next state
 587  *      @skb: Address of the event
 588  *
 589  *      Processes an event, executes any transitions related to that event and
 590  *      updates the state of the station.
 591  */
 592 static u16 llc_station_next_state(struct sk_buff *skb)
 593 {
 594         u16 rc = 1;
 595         struct llc_station_state_trans *trans;
 596
 597         if (llc_main_station.state > LLC_NBR_STATION_STATES)
 598                 goto out;
 599         trans = llc_find_station_trans(skb);
 600         if (trans) {
 601                 /* got the state to which we next transition; perform the
 602                  * actions associated with this transition before actually
 603                  * transitioning to the next state
 604                  */
 605                 rc = llc_exec_station_trans_actions(trans, skb);
 606                 if (!rc)
 607                         /* transition station to next state if all actions
 608                          * execute successfully; done; wait for next event
 609                          */
 610                         llc_main_station.state = trans->next_state;
 611         } else
 612                 /* event not recognized in current state; re-queue it for
 613                  * processing again at a later time; return failure
 614                  */
 615                 rc = 0;
 616 out:
 617         llc_station_free_ev(skb);
 618         return rc;
 619 }
 620
 621 /**
 622  *      llc_station_service_events - service events in the queue
 623  *
 624  *      Get an event from the station event queue (if any); attempt to service
 625  *      the event; if event serviced, get the next event (if any) on the event
 626  *      queue; if event not service, re-queue the event on the event queue and
 627  *      attempt to service the next event; when serviced all events in queue,
 628  *      finished; if don't transition to different state, just service all
 629  *      events once; if transition to new state, service all events again.
 630  *      Caller must hold llc_main_station.ev_q.lock.
 631  */
 632 static void llc_station_service_events(void)
 633 {
 634         struct sk_buff *skb;
 635
 636         while ((skb = skb_dequeue(&llc_main_station.ev_q.list)) != NULL)
 637                 llc_station_next_state(skb);
 638 }
 639
 640 /**
 641  *      llc_station_state_process: queue event and try to process queue.
 642  *      @skb: Address of the event
 643  *
 644  *      Queues an event (on the station event queue) for handling by the
 645  *      station state machine and attempts to process any queued-up events.
 646  */
 647 static void llc_station_state_process(struct sk_buff *skb)
 648 {
 649         spin_lock_bh(&llc_main_station.ev_q.lock);
 650         skb_queue_tail(&llc_main_station.ev_q.list, skb);
 651         llc_station_service_events();
 652         spin_unlock_bh(&llc_main_station.ev_q.lock);
 653 }
 654
 655 static void llc_station_ack_tmr_cb(unsigned long timeout_data)
 656 {
 657         struct sk_buff *skb = alloc_skb(0, GFP_ATOMIC);
 658
 659         if (skb) {
 660                 struct llc_station_state_ev *ev = llc_station_ev(skb);
 661
 662                 ev->type = LLC_STATION_EV_TYPE_ACK_TMR;
 663                 llc_station_state_process(skb);
 664         }
 665 }
 666
 667 /*
 668  *      llc_station_rcv - send received pdu to the station state machine
 669  *      @skb: received frame.
 670  *
 671  *      Sends data unit to station state machine.
 672  */
 673 static void llc_station_rcv(struct sk_buff *skb)
 674 {
 675         struct llc_station_state_ev *ev = llc_station_ev(skb);
 676
 677         ev->type   = LLC_STATION_EV_TYPE_PDU;
 678         ev->reason = 0;
 679         llc_station_state_process(skb);
 680 }
 681
 682 int __init llc_station_init(void)
 683 {
 684         u16 rc = -ENOBUFS;
 685         struct sk_buff *skb;
 686         struct llc_station_state_ev *ev;
 687
 688         skb_queue_head_init(&llc_main_station.mac_pdu_q);
 689         skb_queue_head_init(&llc_main_station.ev_q.list);
 690         spin_lock_init(&llc_main_station.ev_q.lock);
 691         init_timer(&llc_main_station.ack_timer);
 692         llc_main_station.ack_timer.data     = (unsigned long)&llc_main_station;
 693         llc_main_station.ack_timer.function = llc_station_ack_tmr_cb;
 694         llc_main_station.ack_timer.expires  = jiffies +
 695                                                 sysctl_llc_station_ack_timeout;
 696         skb = alloc_skb(0, GFP_ATOMIC);
 697         if (!skb)
 698                 goto out;
 699         rc = 0;
 700         llc_set_station_handler(llc_station_rcv);
 701         ev = llc_station_ev(skb);
 702         memset(ev, 0, sizeof(*ev));
 703         llc_main_station.maximum_retry  = 1;
 704         llc_main_station.state          = LLC_STATION_STATE_DOWN;
 705         ev->type        = LLC_STATION_EV_TYPE_SIMPLE;
 706         ev->prim_type   = LLC_STATION_EV_ENABLE_WITHOUT_DUP_ADDR_CHECK;
 707         rc = llc_station_next_state(skb);
 708 out:
 709         return rc;
 710 }
 711
 712 void __exit llc_station_exit(void)
 713 {
 714         llc_set_station_handler(NULL);
 715 }