[NET]: Avoid atomic xchg() for non-error case
[linux-2.6.git] / net / llc / llc_station.c
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/config.h>
15 #include <linux/init.h>
16 #include <linux/module.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  */
40 struct 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
55 int 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
76 struct 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
84 static __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
90 typedef 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
98 typedef int (*llc_station_action_t)(struct sk_buff *skb);
99
100 /* Station component state table structure */
101 struct llc_station_state_trans {
102         llc_station_ev_t ev;
103         u8 next_state;
104         llc_station_action_t *ev_actions;
105 };
106
107 struct llc_station_state {
108         u8 curr_state;
109         struct llc_station_state_trans **transitions;
110 };
111
112 static struct llc_station llc_main_station;
113
114 static 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
123 static 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
132 static 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
141 static 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
150 static 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
162 static 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
175 static 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
188 static 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
200 static 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  */
215 static 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
223 static 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
230 static 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
236 static 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
242 static 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
248 static 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
254 static 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);
258
259         if (!nskb)
260                 goto out;
261         llc_pdu_header_init(nskb, LLC_PDU_TYPE_U, 0, 0, LLC_PDU_CMD);
262         llc_pdu_init_as_xid_cmd(nskb, LLC_XID_NULL_CLASS_2, 127);
263         rc = llc_mac_hdr_init(nskb, llc_station_mac_sa, llc_station_mac_sa);
264         if (unlikely(rc))
265                 goto free;
266         llc_station_send_pdu(nskb);
267 out:
268         return rc;
269 free:
270         kfree_skb(skb);
271         goto out;
272 }
273
274 static int llc_station_ac_send_xid_r(struct sk_buff *skb)
275 {
276         u8 mac_da[ETH_ALEN], dsap;
277         int rc = 1;
278         struct sk_buff* nskb = llc_alloc_frame(NULL, skb->dev);
279
280         if (!nskb)
281                 goto out;
282         rc = 0;
283         llc_pdu_decode_sa(skb, mac_da);
284         llc_pdu_decode_ssap(skb, &dsap);
285         llc_pdu_header_init(nskb, LLC_PDU_TYPE_U, 0, dsap, LLC_PDU_RSP);
286         llc_pdu_init_as_xid_rsp(nskb, LLC_XID_NULL_CLASS_2, 127);
287         rc = llc_mac_hdr_init(nskb, llc_station_mac_sa, mac_da);
288         if (unlikely(rc))
289                 goto free;
290         llc_station_send_pdu(nskb);
291 out:
292         return rc;
293 free:
294         kfree_skb(skb);
295         goto out;
296 }
297
298 static int llc_station_ac_send_test_r(struct sk_buff *skb)
299 {
300         u8 mac_da[ETH_ALEN], dsap;
301         int rc = 1;
302         struct sk_buff *nskb = llc_alloc_frame(NULL, skb->dev);
303
304         if (!nskb)
305                 goto out;
306         rc = 0;
307         llc_pdu_decode_sa(skb, mac_da);
308         llc_pdu_decode_ssap(skb, &dsap);
309         llc_pdu_header_init(nskb, LLC_PDU_TYPE_U, 0, dsap, LLC_PDU_RSP);
310         llc_pdu_init_as_test_rsp(nskb, skb);
311         rc = llc_mac_hdr_init(nskb, llc_station_mac_sa, mac_da);
312         if (unlikely(rc))
313                 goto free;
314         llc_station_send_pdu(nskb);
315 out:
316         return rc;
317 free:
318         kfree_skb(skb);
319         goto out;
320 }
321
322 static int llc_station_ac_report_status(struct sk_buff *skb)
323 {
324         return 0;
325 }
326
327 /* COMMON STATION STATE transitions */
328
329 /* dummy last-transition indicator; common to all state transition groups
330  * last entry for this state
331  * all members are zeros, .bss zeroes it
332  */
333 static struct llc_station_state_trans llc_stat_state_trans_end;
334
335 /* DOWN STATE transitions */
336
337 /* state transition for LLC_STATION_EV_ENABLE_WITH_DUP_ADDR_CHECK event */
338 static llc_station_action_t llc_stat_down_state_actions_1[] = {
339         [0] = llc_station_ac_start_ack_timer,
340         [1] = llc_station_ac_set_retry_cnt_0,
341         [2] = llc_station_ac_set_xid_r_cnt_0,
342         [3] = llc_station_ac_send_null_dsap_xid_c,
343         [4] = NULL,
344 };
345
346 static struct llc_station_state_trans llc_stat_down_state_trans_1 = {
347         .ev         = llc_stat_ev_enable_with_dup_addr_check,
348         .next_state = LLC_STATION_STATE_DUP_ADDR_CHK,
349         .ev_actions = llc_stat_down_state_actions_1,
350 };
351
352 /* state transition for LLC_STATION_EV_ENABLE_WITHOUT_DUP_ADDR_CHECK event */
353 static llc_station_action_t llc_stat_down_state_actions_2[] = {
354         [0] = llc_station_ac_report_status,     /* STATION UP */
355         [1] = NULL,
356 };
357
358 static struct llc_station_state_trans llc_stat_down_state_trans_2 = {
359         .ev         = llc_stat_ev_enable_without_dup_addr_check,
360         .next_state = LLC_STATION_STATE_UP,
361         .ev_actions = llc_stat_down_state_actions_2,
362 };
363
364 /* array of pointers; one to each transition */
365 static struct llc_station_state_trans *llc_stat_dwn_state_trans[] = {
366         [0] = &llc_stat_down_state_trans_1,
367         [1] = &llc_stat_down_state_trans_2,
368         [2] = &llc_stat_state_trans_end,
369 };
370
371 /* UP STATE transitions */
372 /* state transition for LLC_STATION_EV_DISABLE_REQ event */
373 static llc_station_action_t llc_stat_up_state_actions_1[] = {
374         [0] = llc_station_ac_report_status,     /* STATION DOWN */
375         [1] = NULL,
376 };
377
378 static struct llc_station_state_trans llc_stat_up_state_trans_1 = {
379         .ev         = llc_stat_ev_disable_req,
380         .next_state = LLC_STATION_STATE_DOWN,
381         .ev_actions = llc_stat_up_state_actions_1,
382 };
383
384 /* state transition for LLC_STATION_EV_RX_NULL_DSAP_XID_C event */
385 static llc_station_action_t llc_stat_up_state_actions_2[] = {
386         [0] = llc_station_ac_send_xid_r,
387         [1] = NULL,
388 };
389
390 static struct llc_station_state_trans llc_stat_up_state_trans_2 = {
391         .ev         = llc_stat_ev_rx_null_dsap_xid_c,
392         .next_state = LLC_STATION_STATE_UP,
393         .ev_actions = llc_stat_up_state_actions_2,
394 };
395
396 /* state transition for LLC_STATION_EV_RX_NULL_DSAP_TEST_C event */
397 static llc_station_action_t llc_stat_up_state_actions_3[] = {
398         [0] = llc_station_ac_send_test_r,
399         [1] = NULL,
400 };
401
402 static struct llc_station_state_trans llc_stat_up_state_trans_3 = {
403         .ev         = llc_stat_ev_rx_null_dsap_test_c,
404         .next_state = LLC_STATION_STATE_UP,
405         .ev_actions = llc_stat_up_state_actions_3,
406 };
407
408 /* array of pointers; one to each transition */
409 static struct llc_station_state_trans *llc_stat_up_state_trans [] = {
410         [0] = &llc_stat_up_state_trans_1,
411         [1] = &llc_stat_up_state_trans_2,
412         [2] = &llc_stat_up_state_trans_3,
413         [3] = &llc_stat_state_trans_end,
414 };
415
416 /* DUP ADDR CHK STATE transitions */
417 /* state transition for LLC_STATION_EV_RX_NULL_DSAP_0_XID_R_XID_R_CNT_EQ
418  * event
419  */
420 static llc_station_action_t llc_stat_dupaddr_state_actions_1[] = {
421         [0] = llc_station_ac_inc_xid_r_cnt_by_1,
422         [1] = NULL,
423 };
424
425 static struct llc_station_state_trans llc_stat_dupaddr_state_trans_1 = {
426         .ev         = llc_stat_ev_rx_null_dsap_0_xid_r_xid_r_cnt_eq,
427         .next_state = LLC_STATION_STATE_DUP_ADDR_CHK,
428         .ev_actions = llc_stat_dupaddr_state_actions_1,
429 };
430
431 /* state transition for LLC_STATION_EV_RX_NULL_DSAP_1_XID_R_XID_R_CNT_EQ
432  * event
433  */
434 static llc_station_action_t llc_stat_dupaddr_state_actions_2[] = {
435         [0] = llc_station_ac_report_status,     /* DUPLICATE ADDRESS FOUND */
436         [1] = NULL,
437 };
438
439 static struct llc_station_state_trans llc_stat_dupaddr_state_trans_2 = {
440         .ev         = llc_stat_ev_rx_null_dsap_1_xid_r_xid_r_cnt_eq,
441         .next_state = LLC_STATION_STATE_DOWN,
442         .ev_actions = llc_stat_dupaddr_state_actions_2,
443 };
444
445 /* state transition for LLC_STATION_EV_RX_NULL_DSAP_XID_C event */
446 static llc_station_action_t llc_stat_dupaddr_state_actions_3[] = {
447         [0] = llc_station_ac_send_xid_r,
448         [1] = NULL,
449 };
450
451 static struct llc_station_state_trans llc_stat_dupaddr_state_trans_3 = {
452         .ev         = llc_stat_ev_rx_null_dsap_xid_c,
453         .next_state = LLC_STATION_STATE_DUP_ADDR_CHK,
454         .ev_actions = llc_stat_dupaddr_state_actions_3,
455 };
456
457 /* state transition for LLC_STATION_EV_ACK_TMR_EXP_LT_RETRY_CNT_MAX_RETRY
458  * event
459  */
460 static llc_station_action_t llc_stat_dupaddr_state_actions_4[] = {
461         [0] = llc_station_ac_start_ack_timer,
462         [1] = llc_station_ac_inc_retry_cnt_by_1,
463         [2] = llc_station_ac_set_xid_r_cnt_0,
464         [3] = llc_station_ac_send_null_dsap_xid_c,
465         [4] = NULL,
466 };
467
468 static struct llc_station_state_trans llc_stat_dupaddr_state_trans_4 = {
469         .ev         = llc_stat_ev_ack_tmr_exp_lt_retry_cnt_max_retry,
470         .next_state = LLC_STATION_STATE_DUP_ADDR_CHK,
471         .ev_actions = llc_stat_dupaddr_state_actions_4,
472 };
473
474 /* state transition for LLC_STATION_EV_ACK_TMR_EXP_EQ_RETRY_CNT_MAX_RETRY
475  * event
476  */
477 static llc_station_action_t llc_stat_dupaddr_state_actions_5[] = {
478         [0] = llc_station_ac_report_status,     /* STATION UP */
479         [1] = NULL,
480 };
481
482 static struct llc_station_state_trans llc_stat_dupaddr_state_trans_5 = {
483         .ev         = llc_stat_ev_ack_tmr_exp_eq_retry_cnt_max_retry,
484         .next_state = LLC_STATION_STATE_UP,
485         .ev_actions = llc_stat_dupaddr_state_actions_5,
486 };
487
488 /* state transition for LLC_STATION_EV_DISABLE_REQ event */
489 static llc_station_action_t llc_stat_dupaddr_state_actions_6[] = {
490         [0] = llc_station_ac_report_status,     /* STATION DOWN */
491         [1] = NULL,
492 };
493
494 static struct llc_station_state_trans llc_stat_dupaddr_state_trans_6 = {
495         .ev         = llc_stat_ev_disable_req,
496         .next_state = LLC_STATION_STATE_DOWN,
497         .ev_actions = llc_stat_dupaddr_state_actions_6,
498 };
499
500 /* array of pointers; one to each transition */
501 static struct llc_station_state_trans *llc_stat_dupaddr_state_trans[] = {
502         [0] = &llc_stat_dupaddr_state_trans_6,  /* Request */
503         [1] = &llc_stat_dupaddr_state_trans_4,  /* Timer */
504         [2] = &llc_stat_dupaddr_state_trans_5,
505         [3] = &llc_stat_dupaddr_state_trans_1,  /* Receive frame */
506         [4] = &llc_stat_dupaddr_state_trans_2,
507         [5] = &llc_stat_dupaddr_state_trans_3,
508         [6] = &llc_stat_state_trans_end,
509 };
510
511 static struct llc_station_state
512                         llc_station_state_table[LLC_NBR_STATION_STATES] = {
513         [LLC_STATION_STATE_DOWN - 1] = {
514                 .curr_state  = LLC_STATION_STATE_DOWN,
515                 .transitions = llc_stat_dwn_state_trans,
516         },
517         [LLC_STATION_STATE_DUP_ADDR_CHK - 1] = {
518                 .curr_state  = LLC_STATION_STATE_DUP_ADDR_CHK,
519                 .transitions = llc_stat_dupaddr_state_trans,
520         },
521         [LLC_STATION_STATE_UP - 1] = {
522                 .curr_state  = LLC_STATION_STATE_UP,
523                 .transitions = llc_stat_up_state_trans,
524         },
525 };
526
527 /**
528  *      llc_exec_station_trans_actions - executes actions for transition
529  *      @trans: Address of the transition
530  *      @skb: Address of the event that caused the transition
531  *
532  *      Executes actions of a transition of the station state machine. Returns
533  *      0 if all actions complete successfully, nonzero otherwise.
534  */
535 static u16 llc_exec_station_trans_actions(struct llc_station_state_trans *trans,
536                                           struct sk_buff *skb)
537 {
538         u16 rc = 0;
539         llc_station_action_t *next_action = trans->ev_actions;
540
541         for (; next_action && *next_action; next_action++)
542                 if ((*next_action)(skb))
543                         rc = 1;
544         return rc;
545 }
546
547 /**
548  *      llc_find_station_trans - finds transition for this event
549  *      @skb: Address of the event
550  *
551  *      Search thru events of the current state of the station until list
552  *      exhausted or it's obvious that the event is not valid for the current
553  *      state. Returns the address of the transition if cound, %NULL otherwise.
554  */
555 static struct llc_station_state_trans *
556                                 llc_find_station_trans(struct sk_buff *skb)
557 {
558         int i = 0;
559         struct llc_station_state_trans *rc = NULL;
560         struct llc_station_state_trans **next_trans;
561         struct llc_station_state *curr_state =
562                                 &llc_station_state_table[llc_main_station.state - 1];
563
564         for (next_trans = curr_state->transitions; next_trans[i]->ev; i++)
565                 if (!next_trans[i]->ev(skb)) {
566                         rc = next_trans[i];
567                         break;
568                 }
569         return rc;
570 }
571
572 /**
573  *      llc_station_free_ev - frees an event
574  *      @skb: Address of the event
575  *
576  *      Frees an event.
577  */
578 static void llc_station_free_ev(struct sk_buff *skb)
579 {
580         struct llc_station_state_ev *ev = llc_station_ev(skb);
581
582         if (ev->type == LLC_STATION_EV_TYPE_PDU)
583                 kfree_skb(skb);
584 }
585
586 /**
587  *      llc_station_next_state - processes event and goes to the next state
588  *      @skb: Address of the event
589  *
590  *      Processes an event, executes any transitions related to that event and
591  *      updates the state of the station.
592  */
593 static u16 llc_station_next_state(struct sk_buff *skb)
594 {
595         u16 rc = 1;
596         struct llc_station_state_trans *trans;
597
598         if (llc_main_station.state > LLC_NBR_STATION_STATES)
599                 goto out;
600         trans = llc_find_station_trans(skb);
601         if (trans) {
602                 /* got the state to which we next transition; perform the
603                  * actions associated with this transition before actually
604                  * transitioning to the next state
605                  */
606                 rc = llc_exec_station_trans_actions(trans, skb);
607                 if (!rc)
608                         /* transition station to next state if all actions
609                          * execute successfully; done; wait for next event
610                          */
611                         llc_main_station.state = trans->next_state;
612         } else
613                 /* event not recognized in current state; re-queue it for
614                  * processing again at a later time; return failure
615                  */
616                 rc = 0;
617 out:
618         llc_station_free_ev(skb);
619         return rc;
620 }
621
622 /**
623  *      llc_station_service_events - service events in the queue
624  *
625  *      Get an event from the station event queue (if any); attempt to service
626  *      the event; if event serviced, get the next event (if any) on the event
627  *      queue; if event not service, re-queue the event on the event queue and
628  *      attempt to service the next event; when serviced all events in queue,
629  *      finished; if don't transition to different state, just service all
630  *      events once; if transition to new state, service all events again.
631  *      Caller must hold llc_main_station.ev_q.lock.
632  */
633 static void llc_station_service_events(void)
634 {
635         struct sk_buff *skb;
636
637         while ((skb = skb_dequeue(&llc_main_station.ev_q.list)) != NULL)
638                 llc_station_next_state(skb);
639 }
640
641 /**
642  *      llc_station_state_process: queue event and try to process queue.
643  *      @skb: Address of the event
644  *
645  *      Queues an event (on the station event queue) for handling by the
646  *      station state machine and attempts to process any queued-up events.
647  */
648 static void llc_station_state_process(struct sk_buff *skb)
649 {
650         spin_lock_bh(&llc_main_station.ev_q.lock);
651         skb_queue_tail(&llc_main_station.ev_q.list, skb);
652         llc_station_service_events();
653         spin_unlock_bh(&llc_main_station.ev_q.lock);
654 }
655
656 static void llc_station_ack_tmr_cb(unsigned long timeout_data)
657 {
658         struct sk_buff *skb = alloc_skb(0, GFP_ATOMIC);
659
660         if (skb) {
661                 struct llc_station_state_ev *ev = llc_station_ev(skb);
662
663                 ev->type = LLC_STATION_EV_TYPE_ACK_TMR;
664                 llc_station_state_process(skb);
665         }
666 }
667
668 /*
669  *      llc_station_rcv - send received pdu to the station state machine
670  *      @skb: received frame.
671  *
672  *      Sends data unit to station state machine.
673  */
674 static void llc_station_rcv(struct sk_buff *skb)
675 {
676         struct llc_station_state_ev *ev = llc_station_ev(skb);
677
678         ev->type   = LLC_STATION_EV_TYPE_PDU;
679         ev->reason = 0;
680         llc_station_state_process(skb);
681 }
682
683 int __init llc_station_init(void)
684 {
685         u16 rc = -ENOBUFS;
686         struct sk_buff *skb;
687         struct llc_station_state_ev *ev;
688
689         skb_queue_head_init(&llc_main_station.mac_pdu_q);
690         skb_queue_head_init(&llc_main_station.ev_q.list);
691         spin_lock_init(&llc_main_station.ev_q.lock);
692         init_timer(&llc_main_station.ack_timer);
693         llc_main_station.ack_timer.data     = (unsigned long)&llc_main_station;
694         llc_main_station.ack_timer.function = llc_station_ack_tmr_cb;
695         llc_main_station.ack_timer.expires  = jiffies +
696                                                 sysctl_llc_station_ack_timeout;
697         skb = alloc_skb(0, GFP_ATOMIC);
698         if (!skb)
699                 goto out;
700         rc = 0;
701         llc_set_station_handler(llc_station_rcv);
702         ev = llc_station_ev(skb);
703         memset(ev, 0, sizeof(*ev));
704         llc_main_station.maximum_retry  = 1;
705         llc_main_station.state          = LLC_STATION_STATE_DOWN;
706         ev->type        = LLC_STATION_EV_TYPE_SIMPLE;
707         ev->prim_type   = LLC_STATION_EV_ENABLE_WITHOUT_DUP_ADDR_CHECK;
708         rc = llc_station_next_state(skb);
709 out:
710         return rc;
711 }
712
713 void __exit llc_station_exit(void)
714 {
715         llc_set_station_handler(NULL);
716 }