net/llc/llc_station.c - kernel/msm-4.9 - Gitiles

 /*
  * llc_station.c - station component of LLC
  *
  * Copyright (c) 1997 by Procom Technology, Inc.
  * 		 2001-2003 by Arnaldo Carvalho de Melo <acme@conectiva.com.br>
  *
  * This program can be redistributed or modified under the terms of the
  * GNU General Public License as published by the Free Software Foundation.
  * This program is distributed without any warranty or implied warranty
  * of merchantability or fitness for a particular purpose.
  *
  * See the GNU General Public License for more details.
  */
 #include <linux/init.h>
 #include <linux/module.h>
 #include <linux/slab.h>
 #include <net/llc.h>
 #include <net/llc_sap.h>
 #include <net/llc_conn.h>
 #include <net/llc_c_ac.h>
 #include <net/llc_s_ac.h>
 #include <net/llc_c_ev.h>
 #include <net/llc_c_st.h>
 #include <net/llc_s_ev.h>
 #include <net/llc_s_st.h>
 #include <net/llc_pdu.h>

 /**
  * struct llc_station - LLC station component
  *
  * SAP and connection resource manager, one per adapter.
  *
  * @state: state of station
  * @xid_r_count: XID response PDU counter
  * @mac_sa: MAC source address
  * @sap_list: list of related SAPs
  * @ev_q: events entering state mach.
  * @mac_pdu_q: PDUs ready to send to MAC
  */
 struct llc_station {
 	u8			    state;
 	u8			    xid_r_count;
 	struct timer_list	    ack_timer;
 	u8			    retry_count;
 	u8			    maximum_retry;
 	struct {
 		struct sk_buff_head list;
 		spinlock_t	    lock;
 	} ev_q;
 	struct sk_buff_head	    mac_pdu_q;
 };

 #define LLC_STATION_ACK_TIME (3 * HZ)

 int sysctl_llc_station_ack_timeout = LLC_STATION_ACK_TIME;

 /* Types of events (possible values in 'ev->type') */
 #define LLC_STATION_EV_TYPE_SIMPLE	1
 #define LLC_STATION_EV_TYPE_CONDITION	2
 #define LLC_STATION_EV_TYPE_PRIM	3
 #define LLC_STATION_EV_TYPE_PDU		4       /* command/response PDU */
 #define LLC_STATION_EV_TYPE_ACK_TMR	5
 #define LLC_STATION_EV_TYPE_RPT_STATUS	6

 /* Events */
 #define LLC_STATION_EV_ENABLE_WITH_DUP_ADDR_CHECK		1
 #define LLC_STATION_EV_ENABLE_WITHOUT_DUP_ADDR_CHECK		2
 #define LLC_STATION_EV_ACK_TMR_EXP_LT_RETRY_CNT_MAX_RETRY	3
 #define LLC_STATION_EV_ACK_TMR_EXP_EQ_RETRY_CNT_MAX_RETRY	4
 #define LLC_STATION_EV_RX_NULL_DSAP_XID_C			5
 #define LLC_STATION_EV_RX_NULL_DSAP_0_XID_R_XID_R_CNT_EQ	6
 #define LLC_STATION_EV_RX_NULL_DSAP_1_XID_R_XID_R_CNT_EQ	7
 #define LLC_STATION_EV_RX_NULL_DSAP_TEST_C			8
 #define LLC_STATION_EV_DISABLE_REQ				9

 struct llc_station_state_ev {
 	u8		 type;
 	u8		 prim;
 	u8		 prim_type;
 	u8		 reason;
 	struct list_head node; /* node in station->ev_q.list */
 };

 static __inline__ struct llc_station_state_ev *
 					llc_station_ev(struct sk_buff *skb)
 {
 	return (struct llc_station_state_ev *)skb->cb;
 }

 typedef int (*llc_station_ev_t)(struct sk_buff *skb);

 #define LLC_STATION_STATE_DOWN		1	/* initial state */
 #define LLC_STATION_STATE_DUP_ADDR_CHK	2
 #define LLC_STATION_STATE_UP		3

 #define LLC_NBR_STATION_STATES		3	/* size of state table */

 typedef int (*llc_station_action_t)(struct sk_buff *skb);

 /* Station component state table structure */
 struct llc_station_state_trans {
 	llc_station_ev_t ev;
 	u8 next_state;
 	llc_station_action_t *ev_actions;
 };

 struct llc_station_state {
 	u8 curr_state;
 	struct llc_station_state_trans **transitions;
 };

 static struct llc_station llc_main_station;

 static int llc_stat_ev_enable_with_dup_addr_check(struct sk_buff *skb)
 {
 	struct llc_station_state_ev *ev = llc_station_ev(skb);

 	return ev->type == LLC_STATION_EV_TYPE_SIMPLE &&
 	       ev->prim_type ==
 			      LLC_STATION_EV_ENABLE_WITH_DUP_ADDR_CHECK ? 0 : 1;
 }

 static int llc_stat_ev_enable_without_dup_addr_check(struct sk_buff *skb)
 {
 	struct llc_station_state_ev *ev = llc_station_ev(skb);

 	return ev->type == LLC_STATION_EV_TYPE_SIMPLE &&
 	       ev->prim_type ==
 			LLC_STATION_EV_ENABLE_WITHOUT_DUP_ADDR_CHECK ? 0 : 1;
 }

 static int llc_stat_ev_ack_tmr_exp_lt_retry_cnt_max_retry(struct sk_buff *skb)
 {
 	struct llc_station_state_ev *ev = llc_station_ev(skb);

 	return ev->type == LLC_STATION_EV_TYPE_ACK_TMR &&
 		llc_main_station.retry_count <
 		llc_main_station.maximum_retry ? 0 : 1;
 }

 static int llc_stat_ev_ack_tmr_exp_eq_retry_cnt_max_retry(struct sk_buff *skb)
 {
 	struct llc_station_state_ev *ev = llc_station_ev(skb);

 	return ev->type == LLC_STATION_EV_TYPE_ACK_TMR &&
 		llc_main_station.retry_count ==
 		llc_main_station.maximum_retry ? 0 : 1;
 }

 static int llc_stat_ev_rx_null_dsap_xid_c(struct sk_buff *skb)
 {
 	struct llc_station_state_ev *ev = llc_station_ev(skb);
 	struct llc_pdu_un *pdu = llc_pdu_un_hdr(skb);

 	return ev->type == LLC_STATION_EV_TYPE_PDU &&
 	       LLC_PDU_IS_CMD(pdu) &&			/* command PDU */
 	       LLC_PDU_TYPE_IS_U(pdu) &&		/* U type PDU */
 	       LLC_U_PDU_CMD(pdu) == LLC_1_PDU_CMD_XID &&
 	       !pdu->dsap ? 0 : 1;			/* NULL DSAP value */
 }

 static int llc_stat_ev_rx_null_dsap_0_xid_r_xid_r_cnt_eq(struct sk_buff *skb)
 {
 	struct llc_station_state_ev *ev = llc_station_ev(skb);
 	struct llc_pdu_un *pdu = llc_pdu_un_hdr(skb);

 	return ev->type == LLC_STATION_EV_TYPE_PDU &&
 	       LLC_PDU_IS_RSP(pdu) &&			/* response PDU */
 	       LLC_PDU_TYPE_IS_U(pdu) &&		/* U type PDU */
 	       LLC_U_PDU_RSP(pdu) == LLC_1_PDU_CMD_XID &&
 	       !pdu->dsap &&				/* NULL DSAP value */
 	       !llc_main_station.xid_r_count ? 0 : 1;
 }

 static int llc_stat_ev_rx_null_dsap_1_xid_r_xid_r_cnt_eq(struct sk_buff *skb)
 {
 	struct llc_station_state_ev *ev = llc_station_ev(skb);
 	struct llc_pdu_un *pdu = llc_pdu_un_hdr(skb);

 	return ev->type == LLC_STATION_EV_TYPE_PDU &&
 	       LLC_PDU_IS_RSP(pdu) &&			/* response PDU */
 	       LLC_PDU_TYPE_IS_U(pdu) &&		/* U type PDU */
 	       LLC_U_PDU_RSP(pdu) == LLC_1_PDU_CMD_XID &&
 	       !pdu->dsap &&				/* NULL DSAP value */
 	       llc_main_station.xid_r_count == 1 ? 0 : 1;
 }

 static int llc_stat_ev_rx_null_dsap_test_c(struct sk_buff *skb)
 {
 	struct llc_station_state_ev *ev = llc_station_ev(skb);
 	struct llc_pdu_un *pdu = llc_pdu_un_hdr(skb);

 	return ev->type == LLC_STATION_EV_TYPE_PDU &&
 	       LLC_PDU_IS_CMD(pdu) &&			/* command PDU */
 	       LLC_PDU_TYPE_IS_U(pdu) &&		/* U type PDU */
 	       LLC_U_PDU_CMD(pdu) == LLC_1_PDU_CMD_TEST &&
 	       !pdu->dsap ? 0 : 1;			/* NULL DSAP */
 }

 static int llc_stat_ev_disable_req(struct sk_buff *skb)
 {
 	struct llc_station_state_ev *ev = llc_station_ev(skb);

 	return ev->type == LLC_STATION_EV_TYPE_PRIM &&
 	       ev->prim == LLC_DISABLE_PRIM &&
 	       ev->prim_type == LLC_PRIM_TYPE_REQ ? 0 : 1;
 }

 /**
  *	llc_station_send_pdu - queues PDU to send
  *	@skb: Address of the PDU
  *
  *	Queues a PDU to send to the MAC layer.
  */
 static void llc_station_send_pdu(struct sk_buff *skb)
 {
 	skb_queue_tail(&llc_main_station.mac_pdu_q, skb);
 	while ((skb = skb_dequeue(&llc_main_station.mac_pdu_q)) != NULL)
 		if (dev_queue_xmit(skb))
 			break;
 }

 static int llc_station_ac_start_ack_timer(struct sk_buff *skb)
 {
 	mod_timer(&llc_main_station.ack_timer,
 		  jiffies + sysctl_llc_station_ack_timeout);
 	return 0;
 }

 static int llc_station_ac_set_retry_cnt_0(struct sk_buff *skb)
 {
 	llc_main_station.retry_count = 0;
 	return 0;
 }

 static int llc_station_ac_inc_retry_cnt_by_1(struct sk_buff *skb)
 {
 	llc_main_station.retry_count++;
 	return 0;
 }

 static int llc_station_ac_set_xid_r_cnt_0(struct sk_buff *skb)
 {
 	llc_main_station.xid_r_count = 0;
 	return 0;
 }

 static int llc_station_ac_inc_xid_r_cnt_by_1(struct sk_buff *skb)
 {
 	llc_main_station.xid_r_count++;
 	return 0;
 }

 static int llc_station_ac_send_null_dsap_xid_c(struct sk_buff *skb)
 {
 	int rc = 1;
 	struct sk_buff *nskb = llc_alloc_frame(NULL, skb->dev, LLC_PDU_TYPE_U,
 					       sizeof(struct llc_xid_info));

 	if (!nskb)
 		goto out;
 	llc_pdu_header_init(nskb, LLC_PDU_TYPE_U, 0, 0, LLC_PDU_CMD);
 	llc_pdu_init_as_xid_cmd(nskb, LLC_XID_NULL_CLASS_2, 127);
 	rc = llc_mac_hdr_init(nskb, skb->dev->dev_addr, skb->dev->dev_addr);
 	if (unlikely(rc))
 		goto free;
 	llc_station_send_pdu(nskb);
 out:
 	return rc;
 free:
 	kfree_skb(nskb);
 	goto out;
 }

 static int llc_station_ac_send_xid_r(struct sk_buff *skb)
 {
 	u8 mac_da[ETH_ALEN], dsap;
 	int rc = 1;
 	struct sk_buff *nskb = llc_alloc_frame(NULL, skb->dev, LLC_PDU_TYPE_U,
 					       sizeof(struct llc_xid_info));

 	if (!nskb)
 		goto out;
 	rc = 0;
 	llc_pdu_decode_sa(skb, mac_da);
 	llc_pdu_decode_ssap(skb, &dsap);
 	llc_pdu_header_init(nskb, LLC_PDU_TYPE_U, 0, dsap, LLC_PDU_RSP);
 	llc_pdu_init_as_xid_rsp(nskb, LLC_XID_NULL_CLASS_2, 127);
 	rc = llc_mac_hdr_init(nskb, skb->dev->dev_addr, mac_da);
 	if (unlikely(rc))
 		goto free;
 	llc_station_send_pdu(nskb);
 out:
 	return rc;
 free:
 	kfree_skb(nskb);
 	goto out;
 }

 static int llc_station_ac_send_test_r(struct sk_buff *skb)
 {
 	u8 mac_da[ETH_ALEN], dsap;
 	int rc = 1;
 	u32 data_size;
 	struct sk_buff *nskb;

 	/* The test request command is type U (llc_len = 3) */
 	data_size = ntohs(eth_hdr(skb)->h_proto) - 3;
 	nskb = llc_alloc_frame(NULL, skb->dev, LLC_PDU_TYPE_U, data_size);

 	if (!nskb)
 		goto out;
 	rc = 0;
 	llc_pdu_decode_sa(skb, mac_da);
 	llc_pdu_decode_ssap(skb, &dsap);
 	llc_pdu_header_init(nskb, LLC_PDU_TYPE_U, 0, dsap, LLC_PDU_RSP);
 	llc_pdu_init_as_test_rsp(nskb, skb);
 	rc = llc_mac_hdr_init(nskb, skb->dev->dev_addr, mac_da);
 	if (unlikely(rc))
 		goto free;
 	llc_station_send_pdu(nskb);
 out:
 	return rc;
 free:
 	kfree_skb(nskb);
 	goto out;
 }

 static int llc_station_ac_report_status(struct sk_buff *skb)
 {
 	return 0;
 }

 /* COMMON STATION STATE transitions */

 /* dummy last-transition indicator; common to all state transition groups
  * last entry for this state
  * all members are zeros, .bss zeroes it
  */
 static struct llc_station_state_trans llc_stat_state_trans_end;

 /* DOWN STATE transitions */

 /* state transition for LLC_STATION_EV_ENABLE_WITH_DUP_ADDR_CHECK event */
 static llc_station_action_t llc_stat_down_state_actions_1[] = {
 	[0] = llc_station_ac_start_ack_timer,
 	[1] = llc_station_ac_set_retry_cnt_0,
 	[2] = llc_station_ac_set_xid_r_cnt_0,
 	[3] = llc_station_ac_send_null_dsap_xid_c,
 	[4] = NULL,
 };

 static struct llc_station_state_trans llc_stat_down_state_trans_1 = {
 	.ev	    = llc_stat_ev_enable_with_dup_addr_check,
 	.next_state = LLC_STATION_STATE_DUP_ADDR_CHK,
 	.ev_actions = llc_stat_down_state_actions_1,
 };

 /* state transition for LLC_STATION_EV_ENABLE_WITHOUT_DUP_ADDR_CHECK event */
 static llc_station_action_t llc_stat_down_state_actions_2[] = {
 	[0] = llc_station_ac_report_status,	/* STATION UP */
 	[1] = NULL,
 };

 static struct llc_station_state_trans llc_stat_down_state_trans_2 = {
 	.ev	    = llc_stat_ev_enable_without_dup_addr_check,
 	.next_state = LLC_STATION_STATE_UP,
 	.ev_actions = llc_stat_down_state_actions_2,
 };

 /* array of pointers; one to each transition */
 static struct llc_station_state_trans *llc_stat_dwn_state_trans[] = {
 	[0] = &llc_stat_down_state_trans_1,
 	[1] = &llc_stat_down_state_trans_2,
 	[2] = &llc_stat_state_trans_end,
 };

 /* UP STATE transitions */
 /* state transition for LLC_STATION_EV_DISABLE_REQ event */
 static llc_station_action_t llc_stat_up_state_actions_1[] = {
 	[0] = llc_station_ac_report_status,	/* STATION DOWN */
 	[1] = NULL,
 };

 static struct llc_station_state_trans llc_stat_up_state_trans_1 = {
 	.ev	    = llc_stat_ev_disable_req,
 	.next_state = LLC_STATION_STATE_DOWN,
 	.ev_actions = llc_stat_up_state_actions_1,
 };

 /* state transition for LLC_STATION_EV_RX_NULL_DSAP_XID_C event */
 static llc_station_action_t llc_stat_up_state_actions_2[] = {
 	[0] = llc_station_ac_send_xid_r,
 	[1] = NULL,
 };

 static struct llc_station_state_trans llc_stat_up_state_trans_2 = {
 	.ev	    = llc_stat_ev_rx_null_dsap_xid_c,
 	.next_state = LLC_STATION_STATE_UP,
 	.ev_actions = llc_stat_up_state_actions_2,
 };

 /* state transition for LLC_STATION_EV_RX_NULL_DSAP_TEST_C event */
 static llc_station_action_t llc_stat_up_state_actions_3[] = {
 	[0] = llc_station_ac_send_test_r,
 	[1] = NULL,
 };

 static struct llc_station_state_trans llc_stat_up_state_trans_3 = {
 	.ev	    = llc_stat_ev_rx_null_dsap_test_c,
 	.next_state = LLC_STATION_STATE_UP,
 	.ev_actions = llc_stat_up_state_actions_3,
 };

 /* array of pointers; one to each transition */
 static struct llc_station_state_trans *llc_stat_up_state_trans [] = {
 	[0] = &llc_stat_up_state_trans_1,
 	[1] = &llc_stat_up_state_trans_2,
 	[2] = &llc_stat_up_state_trans_3,
 	[3] = &llc_stat_state_trans_end,
 };

 /* DUP ADDR CHK STATE transitions */
 /* state transition for LLC_STATION_EV_RX_NULL_DSAP_0_XID_R_XID_R_CNT_EQ
  * event
  */
 static llc_station_action_t llc_stat_dupaddr_state_actions_1[] = {
 	[0] = llc_station_ac_inc_xid_r_cnt_by_1,
 	[1] = NULL,
 };

 static struct llc_station_state_trans llc_stat_dupaddr_state_trans_1 = {
 	.ev	    = llc_stat_ev_rx_null_dsap_0_xid_r_xid_r_cnt_eq,
 	.next_state = LLC_STATION_STATE_DUP_ADDR_CHK,
 	.ev_actions = llc_stat_dupaddr_state_actions_1,
 };

 /* state transition for LLC_STATION_EV_RX_NULL_DSAP_1_XID_R_XID_R_CNT_EQ
  * event
  */
 static llc_station_action_t llc_stat_dupaddr_state_actions_2[] = {
 	[0] = llc_station_ac_report_status,	/* DUPLICATE ADDRESS FOUND */
 	[1] = NULL,
 };

 static struct llc_station_state_trans llc_stat_dupaddr_state_trans_2 = {
 	.ev	    = llc_stat_ev_rx_null_dsap_1_xid_r_xid_r_cnt_eq,
 	.next_state = LLC_STATION_STATE_DOWN,
 	.ev_actions = llc_stat_dupaddr_state_actions_2,
 };

 /* state transition for LLC_STATION_EV_RX_NULL_DSAP_XID_C event */
 static llc_station_action_t llc_stat_dupaddr_state_actions_3[] = {
 	[0] = llc_station_ac_send_xid_r,
 	[1] = NULL,
 };

 static struct llc_station_state_trans llc_stat_dupaddr_state_trans_3 = {
 	.ev	    = llc_stat_ev_rx_null_dsap_xid_c,
 	.next_state = LLC_STATION_STATE_DUP_ADDR_CHK,
 	.ev_actions = llc_stat_dupaddr_state_actions_3,
 };

 /* state transition for LLC_STATION_EV_ACK_TMR_EXP_LT_RETRY_CNT_MAX_RETRY
  * event
  */
 static llc_station_action_t llc_stat_dupaddr_state_actions_4[] = {
 	[0] = llc_station_ac_start_ack_timer,
 	[1] = llc_station_ac_inc_retry_cnt_by_1,
 	[2] = llc_station_ac_set_xid_r_cnt_0,
 	[3] = llc_station_ac_send_null_dsap_xid_c,
 	[4] = NULL,
 };

 static struct llc_station_state_trans llc_stat_dupaddr_state_trans_4 = {
 	.ev	    = llc_stat_ev_ack_tmr_exp_lt_retry_cnt_max_retry,
 	.next_state = LLC_STATION_STATE_DUP_ADDR_CHK,
 	.ev_actions = llc_stat_dupaddr_state_actions_4,
 };

 /* state transition for LLC_STATION_EV_ACK_TMR_EXP_EQ_RETRY_CNT_MAX_RETRY
  * event
  */
 static llc_station_action_t llc_stat_dupaddr_state_actions_5[] = {
 	[0] = llc_station_ac_report_status,	/* STATION UP */
 	[1] = NULL,
 };

 static struct llc_station_state_trans llc_stat_dupaddr_state_trans_5 = {
 	.ev	    = llc_stat_ev_ack_tmr_exp_eq_retry_cnt_max_retry,
 	.next_state = LLC_STATION_STATE_UP,
 	.ev_actions = llc_stat_dupaddr_state_actions_5,
 };

 /* state transition for LLC_STATION_EV_DISABLE_REQ event */
 static llc_station_action_t llc_stat_dupaddr_state_actions_6[] = {
 	[0] = llc_station_ac_report_status,	/* STATION DOWN */
 	[1] = NULL,
 };

 static struct llc_station_state_trans llc_stat_dupaddr_state_trans_6 = {
 	.ev	    = llc_stat_ev_disable_req,
 	.next_state = LLC_STATION_STATE_DOWN,
 	.ev_actions = llc_stat_dupaddr_state_actions_6,
 };

 /* array of pointers; one to each transition */
 static struct llc_station_state_trans *llc_stat_dupaddr_state_trans[] = {
 	[0] = &llc_stat_dupaddr_state_trans_6,	/* Request */
 	[1] = &llc_stat_dupaddr_state_trans_4,	/* Timer */
 	[2] = &llc_stat_dupaddr_state_trans_5,
 	[3] = &llc_stat_dupaddr_state_trans_1,	/* Receive frame */
 	[4] = &llc_stat_dupaddr_state_trans_2,
 	[5] = &llc_stat_dupaddr_state_trans_3,
 	[6] = &llc_stat_state_trans_end,
 };

 static struct llc_station_state
 			llc_station_state_table[LLC_NBR_STATION_STATES] = {
 	[LLC_STATION_STATE_DOWN - 1] = {
 		.curr_state  = LLC_STATION_STATE_DOWN,
 		.transitions = llc_stat_dwn_state_trans,
 	},
 	[LLC_STATION_STATE_DUP_ADDR_CHK - 1] = {
 		.curr_state  = LLC_STATION_STATE_DUP_ADDR_CHK,
 		.transitions = llc_stat_dupaddr_state_trans,
 	},
 	[LLC_STATION_STATE_UP - 1] = {
 		.curr_state  = LLC_STATION_STATE_UP,
 		.transitions = llc_stat_up_state_trans,
 	},
 };

 /**
  *	llc_exec_station_trans_actions - executes actions for transition
  *	@trans: Address of the transition
  *	@skb: Address of the event that caused the transition
  *
  *	Executes actions of a transition of the station state machine. Returns
  *	0 if all actions complete successfully, nonzero otherwise.
  */
 static u16 llc_exec_station_trans_actions(struct llc_station_state_trans *trans,
 					  struct sk_buff *skb)
 {
 	u16 rc = 0;
 	llc_station_action_t *next_action = trans->ev_actions;

 	for (; next_action && *next_action; next_action++)
 		if ((*next_action)(skb))
 			rc = 1;
 	return rc;
 }

 /**
  *	llc_find_station_trans - finds transition for this event
  *	@skb: Address of the event
  *
  *	Search thru events of the current state of the station until list
  *	exhausted or it's obvious that the event is not valid for the current
  *	state. Returns the address of the transition if cound, %NULL otherwise.
  */
 static struct llc_station_state_trans *
 				llc_find_station_trans(struct sk_buff *skb)
 {
 	int i = 0;
 	struct llc_station_state_trans *rc = NULL;
 	struct llc_station_state_trans **next_trans;
 	struct llc_station_state *curr_state =
 				&llc_station_state_table[llc_main_station.state - 1];

 	for (next_trans = curr_state->transitions; next_trans[i]->ev; i++)
 		if (!next_trans[i]->ev(skb)) {
 			rc = next_trans[i];
 			break;
 		}
 	return rc;
 }

 /**
  *	llc_station_free_ev - frees an event
  *	@skb: Address of the event
  *
  *	Frees an event.
  */
 static void llc_station_free_ev(struct sk_buff *skb)
 {
 	struct llc_station_state_ev *ev = llc_station_ev(skb);

 	if (ev->type == LLC_STATION_EV_TYPE_PDU)
 		kfree_skb(skb);
 }

 /**
  *	llc_station_next_state - processes event and goes to the next state
  *	@skb: Address of the event
  *
  *	Processes an event, executes any transitions related to that event and
  *	updates the state of the station.
  */
 static u16 llc_station_next_state(struct sk_buff *skb)
 {
 	u16 rc = 1;
 	struct llc_station_state_trans *trans;

 	if (llc_main_station.state > LLC_NBR_STATION_STATES)
 		goto out;
 	trans = llc_find_station_trans(skb);
 	if (trans) {
 		/* got the state to which we next transition; perform the
 		 * actions associated with this transition before actually
 		 * transitioning to the next state
 		 */
 		rc = llc_exec_station_trans_actions(trans, skb);
 		if (!rc)
 			/* transition station to next state if all actions
 			 * execute successfully; done; wait for next event
 			 */
 			llc_main_station.state = trans->next_state;
 	} else
 		/* event not recognized in current state; re-queue it for
 		 * processing again at a later time; return failure
 		 */
 		rc = 0;
 out:
 	llc_station_free_ev(skb);
 	return rc;
 }

 /**
  *	llc_station_service_events - service events in the queue
  *
  *	Get an event from the station event queue (if any); attempt to service
  *	the event; if event serviced, get the next event (if any) on the event
  *	queue; if event not service, re-queue the event on the event queue and
  *	attempt to service the next event; when serviced all events in queue,
  *	finished; if don't transition to different state, just service all
  *	events once; if transition to new state, service all events again.
  *	Caller must hold llc_main_station.ev_q.lock.
  */
 static void llc_station_service_events(void)
 {
 	struct sk_buff *skb;

 	while ((skb = skb_dequeue(&llc_main_station.ev_q.list)) != NULL)
 		llc_station_next_state(skb);
 }

 /**
  *	llc_station_state_process - queue event and try to process queue.
  *	@skb: Address of the event
  *
  *	Queues an event (on the station event queue) for handling by the
  *	station state machine and attempts to process any queued-up events.
  */
 static void llc_station_state_process(struct sk_buff *skb)
 {
 	spin_lock_bh(&llc_main_station.ev_q.lock);
 	skb_queue_tail(&llc_main_station.ev_q.list, skb);
 	llc_station_service_events();
 	spin_unlock_bh(&llc_main_station.ev_q.lock);
 }

 static void llc_station_ack_tmr_cb(unsigned long timeout_data)
 {
 	struct sk_buff *skb = alloc_skb(0, GFP_ATOMIC);

 	if (skb) {
 		struct llc_station_state_ev *ev = llc_station_ev(skb);

 		ev->type = LLC_STATION_EV_TYPE_ACK_TMR;
 		llc_station_state_process(skb);
 	}
 }

 /**
  *	llc_station_rcv - send received pdu to the station state machine
  *	@skb: received frame.
  *
  *	Sends data unit to station state machine.
  */
 static void llc_station_rcv(struct sk_buff *skb)
 {
 	struct llc_station_state_ev *ev = llc_station_ev(skb);

 	ev->type   = LLC_STATION_EV_TYPE_PDU;
 	ev->reason = 0;
 	llc_station_state_process(skb);
 }

 void __init llc_station_init(void)
 {
 	skb_queue_head_init(&llc_main_station.mac_pdu_q);
 	skb_queue_head_init(&llc_main_station.ev_q.list);
 	spin_lock_init(&llc_main_station.ev_q.lock);
 	setup_timer(&llc_main_station.ack_timer, llc_station_ack_tmr_cb,
 			(unsigned long)&llc_main_station);
 	llc_main_station.ack_timer.expires  = jiffies +
 						sysctl_llc_station_ack_timeout;
 	llc_main_station.maximum_retry	= 1;
 	llc_main_station.state		= LLC_STATION_STATE_UP;
 	llc_set_station_handler(llc_station_rcv);
 }

 void llc_station_exit(void)
 {
 	llc_set_station_handler(NULL);
 }
	/*
	* llc_station.c - station component of LLC
	*
	* Copyright (c) 1997 by Procom Technology, Inc.
	* 2001-2003 by Arnaldo Carvalho de Melo <acme@conectiva.com.br>
	*
	* This program can be redistributed or modified under the terms of the
	* GNU General Public License as published by the Free Software Foundation.
	* This program is distributed without any warranty or implied warranty
	* of merchantability or fitness for a particular purpose.
	*
	* See the GNU General Public License for more details.
	*/
	#include <linux/init.h>
	#include <linux/module.h>
	#include <linux/slab.h>
	#include <net/llc.h>
	#include <net/llc_sap.h>
	#include <net/llc_conn.h>
	#include <net/llc_c_ac.h>
	#include <net/llc_s_ac.h>
	#include <net/llc_c_ev.h>
	#include <net/llc_c_st.h>
	#include <net/llc_s_ev.h>
	#include <net/llc_s_st.h>
	#include <net/llc_pdu.h>

	/**
	* struct llc_station - LLC station component
	*
	* SAP and connection resource manager, one per adapter.
	*
	* @state: state of station
	* @xid_r_count: XID response PDU counter
	* @mac_sa: MAC source address
	* @sap_list: list of related SAPs
	* @ev_q: events entering state mach.
	* @mac_pdu_q: PDUs ready to send to MAC
	*/
	struct llc_station {
	u8 state;
	u8 xid_r_count;
	struct timer_list ack_timer;
	u8 retry_count;
	u8 maximum_retry;
	struct {
	struct sk_buff_head list;
	spinlock_t lock;
	} ev_q;
	struct sk_buff_head mac_pdu_q;
	};

	#define LLC_STATION_ACK_TIME (3 * HZ)

	int sysctl_llc_station_ack_timeout = LLC_STATION_ACK_TIME;

	/* Types of events (possible values in 'ev->type') */
	#define LLC_STATION_EV_TYPE_SIMPLE 1
	#define LLC_STATION_EV_TYPE_CONDITION 2
	#define LLC_STATION_EV_TYPE_PRIM 3
	#define LLC_STATION_EV_TYPE_PDU 4 /* command/response PDU */
	#define LLC_STATION_EV_TYPE_ACK_TMR 5
	#define LLC_STATION_EV_TYPE_RPT_STATUS 6

	/* Events */
	#define LLC_STATION_EV_ENABLE_WITH_DUP_ADDR_CHECK 1
	#define LLC_STATION_EV_ENABLE_WITHOUT_DUP_ADDR_CHECK 2
	#define LLC_STATION_EV_ACK_TMR_EXP_LT_RETRY_CNT_MAX_RETRY 3
	#define LLC_STATION_EV_ACK_TMR_EXP_EQ_RETRY_CNT_MAX_RETRY 4
	#define LLC_STATION_EV_RX_NULL_DSAP_XID_C 5
	#define LLC_STATION_EV_RX_NULL_DSAP_0_XID_R_XID_R_CNT_EQ 6
	#define LLC_STATION_EV_RX_NULL_DSAP_1_XID_R_XID_R_CNT_EQ 7
	#define LLC_STATION_EV_RX_NULL_DSAP_TEST_C 8
	#define LLC_STATION_EV_DISABLE_REQ 9

	struct llc_station_state_ev {
	u8 type;
	u8 prim;
	u8 prim_type;
	u8 reason;
	struct list_head node; /* node in station->ev_q.list */
	};

	static __inline__ struct llc_station_state_ev *
	llc_station_ev(struct sk_buff *skb)
	{
	return (struct llc_station_state_ev *)skb->cb;
	}

	typedef int (llc_station_ev_t)(struct sk_buff skb);

	#define LLC_STATION_STATE_DOWN 1 /* initial state */
	#define LLC_STATION_STATE_DUP_ADDR_CHK 2
	#define LLC_STATION_STATE_UP 3

	#define LLC_NBR_STATION_STATES 3 /* size of state table */

	typedef int (llc_station_action_t)(struct sk_buff skb);

	/* Station component state table structure */
	struct llc_station_state_trans {
	llc_station_ev_t ev;
	u8 next_state;
	llc_station_action_t *ev_actions;
	};

	struct llc_station_state {
	u8 curr_state;
	struct llc_station_state_trans **transitions;
	};

	static struct llc_station llc_main_station;

	static int llc_stat_ev_enable_with_dup_addr_check(struct sk_buff *skb)
	{
	struct llc_station_state_ev *ev = llc_station_ev(skb);

	return ev->type == LLC_STATION_EV_TYPE_SIMPLE &&
	ev->prim_type ==
	LLC_STATION_EV_ENABLE_WITH_DUP_ADDR_CHECK ? 0 : 1;
	}

	static int llc_stat_ev_enable_without_dup_addr_check(struct sk_buff *skb)
	{
	struct llc_station_state_ev *ev = llc_station_ev(skb);

	return ev->type == LLC_STATION_EV_TYPE_SIMPLE &&
	ev->prim_type ==
	LLC_STATION_EV_ENABLE_WITHOUT_DUP_ADDR_CHECK ? 0 : 1;
	}

	static int llc_stat_ev_ack_tmr_exp_lt_retry_cnt_max_retry(struct sk_buff *skb)
	{
	struct llc_station_state_ev *ev = llc_station_ev(skb);

	return ev->type == LLC_STATION_EV_TYPE_ACK_TMR &&
	llc_main_station.retry_count <
	llc_main_station.maximum_retry ? 0 : 1;
	}

	static int llc_stat_ev_ack_tmr_exp_eq_retry_cnt_max_retry(struct sk_buff *skb)
	{
	struct llc_station_state_ev *ev = llc_station_ev(skb);

	return ev->type == LLC_STATION_EV_TYPE_ACK_TMR &&
	llc_main_station.retry_count ==
	llc_main_station.maximum_retry ? 0 : 1;
	}

	static int llc_stat_ev_rx_null_dsap_xid_c(struct sk_buff *skb)
	{
	struct llc_station_state_ev *ev = llc_station_ev(skb);
	struct llc_pdu_un *pdu = llc_pdu_un_hdr(skb);

	return ev->type == LLC_STATION_EV_TYPE_PDU &&
	LLC_PDU_IS_CMD(pdu) && /* command PDU */
	LLC_PDU_TYPE_IS_U(pdu) && /* U type PDU */
	LLC_U_PDU_CMD(pdu) == LLC_1_PDU_CMD_XID &&
	!pdu->dsap ? 0 : 1; /* NULL DSAP value */
	}

	static int llc_stat_ev_rx_null_dsap_0_xid_r_xid_r_cnt_eq(struct sk_buff *skb)
	{
	struct llc_station_state_ev *ev = llc_station_ev(skb);
	struct llc_pdu_un *pdu = llc_pdu_un_hdr(skb);

	return ev->type == LLC_STATION_EV_TYPE_PDU &&
	LLC_PDU_IS_RSP(pdu) && /* response PDU */
	LLC_PDU_TYPE_IS_U(pdu) && /* U type PDU */
	LLC_U_PDU_RSP(pdu) == LLC_1_PDU_CMD_XID &&
	!pdu->dsap && /* NULL DSAP value */
	!llc_main_station.xid_r_count ? 0 : 1;
	}

	static int llc_stat_ev_rx_null_dsap_1_xid_r_xid_r_cnt_eq(struct sk_buff *skb)
	{
	struct llc_station_state_ev *ev = llc_station_ev(skb);
	struct llc_pdu_un *pdu = llc_pdu_un_hdr(skb);

	return ev->type == LLC_STATION_EV_TYPE_PDU &&
	LLC_PDU_IS_RSP(pdu) && /* response PDU */
	LLC_PDU_TYPE_IS_U(pdu) && /* U type PDU */
	LLC_U_PDU_RSP(pdu) == LLC_1_PDU_CMD_XID &&
	!pdu->dsap && /* NULL DSAP value */
	llc_main_station.xid_r_count == 1 ? 0 : 1;
	}

	static int llc_stat_ev_rx_null_dsap_test_c(struct sk_buff *skb)
	{
	struct llc_station_state_ev *ev = llc_station_ev(skb);
	struct llc_pdu_un *pdu = llc_pdu_un_hdr(skb);

	return ev->type == LLC_STATION_EV_TYPE_PDU &&
	LLC_PDU_IS_CMD(pdu) && /* command PDU */
	LLC_PDU_TYPE_IS_U(pdu) && /* U type PDU */
	LLC_U_PDU_CMD(pdu) == LLC_1_PDU_CMD_TEST &&
	!pdu->dsap ? 0 : 1; /* NULL DSAP */
	}

	static int llc_stat_ev_disable_req(struct sk_buff *skb)
	{
	struct llc_station_state_ev *ev = llc_station_ev(skb);

	return ev->type == LLC_STATION_EV_TYPE_PRIM &&
	ev->prim == LLC_DISABLE_PRIM &&
	ev->prim_type == LLC_PRIM_TYPE_REQ ? 0 : 1;
	}

	/**
	* llc_station_send_pdu - queues PDU to send
	* @skb: Address of the PDU
	*
	* Queues a PDU to send to the MAC layer.
	*/
	static void llc_station_send_pdu(struct sk_buff *skb)
	{
	skb_queue_tail(&llc_main_station.mac_pdu_q, skb);
	while ((skb = skb_dequeue(&llc_main_station.mac_pdu_q)) != NULL)
	if (dev_queue_xmit(skb))
	break;
	}

	static int llc_station_ac_start_ack_timer(struct sk_buff *skb)
	{
	mod_timer(&llc_main_station.ack_timer,
	jiffies + sysctl_llc_station_ack_timeout);
	return 0;
	}

	static int llc_station_ac_set_retry_cnt_0(struct sk_buff *skb)
	{
	llc_main_station.retry_count = 0;
	return 0;
	}

	static int llc_station_ac_inc_retry_cnt_by_1(struct sk_buff *skb)
	{
	llc_main_station.retry_count++;
	return 0;
	}

	static int llc_station_ac_set_xid_r_cnt_0(struct sk_buff *skb)
	{
	llc_main_station.xid_r_count = 0;
	return 0;
	}

	static int llc_station_ac_inc_xid_r_cnt_by_1(struct sk_buff *skb)
	{
	llc_main_station.xid_r_count++;
	return 0;
	}

	static int llc_station_ac_send_null_dsap_xid_c(struct sk_buff *skb)
	{
	int rc = 1;
	struct sk_buff *nskb = llc_alloc_frame(NULL, skb->dev, LLC_PDU_TYPE_U,
	sizeof(struct llc_xid_info));

	if (!nskb)
	goto out;
	llc_pdu_header_init(nskb, LLC_PDU_TYPE_U, 0, 0, LLC_PDU_CMD);
	llc_pdu_init_as_xid_cmd(nskb, LLC_XID_NULL_CLASS_2, 127);
	rc = llc_mac_hdr_init(nskb, skb->dev->dev_addr, skb->dev->dev_addr);
	if (unlikely(rc))
	goto free;
	llc_station_send_pdu(nskb);
	out:
	return rc;
	free:
	kfree_skb(nskb);
	goto out;
	}

	static int llc_station_ac_send_xid_r(struct sk_buff *skb)
	{
	u8 mac_da[ETH_ALEN], dsap;
	int rc = 1;
	struct sk_buff *nskb = llc_alloc_frame(NULL, skb->dev, LLC_PDU_TYPE_U,
	sizeof(struct llc_xid_info));

	if (!nskb)
	goto out;
	rc = 0;
	llc_pdu_decode_sa(skb, mac_da);
	llc_pdu_decode_ssap(skb, &dsap);
	llc_pdu_header_init(nskb, LLC_PDU_TYPE_U, 0, dsap, LLC_PDU_RSP);
	llc_pdu_init_as_xid_rsp(nskb, LLC_XID_NULL_CLASS_2, 127);
	rc = llc_mac_hdr_init(nskb, skb->dev->dev_addr, mac_da);
	if (unlikely(rc))
	goto free;
	llc_station_send_pdu(nskb);
	out:
	return rc;
	free:
	kfree_skb(nskb);
	goto out;
	}

	static int llc_station_ac_send_test_r(struct sk_buff *skb)
	{
	u8 mac_da[ETH_ALEN], dsap;
	int rc = 1;
	u32 data_size;
	struct sk_buff *nskb;

	/* The test request command is type U (llc_len = 3) */
	data_size = ntohs(eth_hdr(skb)->h_proto) - 3;
	nskb = llc_alloc_frame(NULL, skb->dev, LLC_PDU_TYPE_U, data_size);

	if (!nskb)
	goto out;
	rc = 0;
	llc_pdu_decode_sa(skb, mac_da);
	llc_pdu_decode_ssap(skb, &dsap);
	llc_pdu_header_init(nskb, LLC_PDU_TYPE_U, 0, dsap, LLC_PDU_RSP);
	llc_pdu_init_as_test_rsp(nskb, skb);
	rc = llc_mac_hdr_init(nskb, skb->dev->dev_addr, mac_da);
	if (unlikely(rc))
	goto free;
	llc_station_send_pdu(nskb);
	out:
	return rc;
	free:
	kfree_skb(nskb);
	goto out;
	}

	static int llc_station_ac_report_status(struct sk_buff *skb)
	{
	return 0;
	}

	/* COMMON STATION STATE transitions */

	/* dummy last-transition indicator; common to all state transition groups
	* last entry for this state
	* all members are zeros, .bss zeroes it
	*/
	static struct llc_station_state_trans llc_stat_state_trans_end;

	/* DOWN STATE transitions */

	/* state transition for LLC_STATION_EV_ENABLE_WITH_DUP_ADDR_CHECK event */
	static llc_station_action_t llc_stat_down_state_actions_1[] = {
	[0] = llc_station_ac_start_ack_timer,
	[1] = llc_station_ac_set_retry_cnt_0,
	[2] = llc_station_ac_set_xid_r_cnt_0,
	[3] = llc_station_ac_send_null_dsap_xid_c,
	[4] = NULL,
	};

	static struct llc_station_state_trans llc_stat_down_state_trans_1 = {
	.ev = llc_stat_ev_enable_with_dup_addr_check,
	.next_state = LLC_STATION_STATE_DUP_ADDR_CHK,
	.ev_actions = llc_stat_down_state_actions_1,
	};

	/* state transition for LLC_STATION_EV_ENABLE_WITHOUT_DUP_ADDR_CHECK event */
	static llc_station_action_t llc_stat_down_state_actions_2[] = {
	[0] = llc_station_ac_report_status, /* STATION UP */
	[1] = NULL,
	};

	static struct llc_station_state_trans llc_stat_down_state_trans_2 = {
	.ev = llc_stat_ev_enable_without_dup_addr_check,
	.next_state = LLC_STATION_STATE_UP,
	.ev_actions = llc_stat_down_state_actions_2,
	};

	/* array of pointers; one to each transition */
	static struct llc_station_state_trans *llc_stat_dwn_state_trans[] = {
	[0] = &llc_stat_down_state_trans_1,
	[1] = &llc_stat_down_state_trans_2,
	[2] = &llc_stat_state_trans_end,
	};

	/* UP STATE transitions */
	/* state transition for LLC_STATION_EV_DISABLE_REQ event */
	static llc_station_action_t llc_stat_up_state_actions_1[] = {
	[0] = llc_station_ac_report_status, /* STATION DOWN */
	[1] = NULL,
	};

	static struct llc_station_state_trans llc_stat_up_state_trans_1 = {
	.ev = llc_stat_ev_disable_req,
	.next_state = LLC_STATION_STATE_DOWN,
	.ev_actions = llc_stat_up_state_actions_1,
	};

	/* state transition for LLC_STATION_EV_RX_NULL_DSAP_XID_C event */
	static llc_station_action_t llc_stat_up_state_actions_2[] = {
	[0] = llc_station_ac_send_xid_r,
	[1] = NULL,
	};

	static struct llc_station_state_trans llc_stat_up_state_trans_2 = {
	.ev = llc_stat_ev_rx_null_dsap_xid_c,
	.next_state = LLC_STATION_STATE_UP,
	.ev_actions = llc_stat_up_state_actions_2,
	};

	/* state transition for LLC_STATION_EV_RX_NULL_DSAP_TEST_C event */
	static llc_station_action_t llc_stat_up_state_actions_3[] = {
	[0] = llc_station_ac_send_test_r,
	[1] = NULL,
	};

	static struct llc_station_state_trans llc_stat_up_state_trans_3 = {
	.ev = llc_stat_ev_rx_null_dsap_test_c,
	.next_state = LLC_STATION_STATE_UP,
	.ev_actions = llc_stat_up_state_actions_3,
	};

	/* array of pointers; one to each transition */
	static struct llc_station_state_trans *llc_stat_up_state_trans [] = {
	[0] = &llc_stat_up_state_trans_1,
	[1] = &llc_stat_up_state_trans_2,
	[2] = &llc_stat_up_state_trans_3,
	[3] = &llc_stat_state_trans_end,
	};

	/* DUP ADDR CHK STATE transitions */
	/* state transition for LLC_STATION_EV_RX_NULL_DSAP_0_XID_R_XID_R_CNT_EQ
	* event
	*/
	static llc_station_action_t llc_stat_dupaddr_state_actions_1[] = {
	[0] = llc_station_ac_inc_xid_r_cnt_by_1,
	[1] = NULL,
	};

	static struct llc_station_state_trans llc_stat_dupaddr_state_trans_1 = {
	.ev = llc_stat_ev_rx_null_dsap_0_xid_r_xid_r_cnt_eq,
	.next_state = LLC_STATION_STATE_DUP_ADDR_CHK,
	.ev_actions = llc_stat_dupaddr_state_actions_1,
	};

	/* state transition for LLC_STATION_EV_RX_NULL_DSAP_1_XID_R_XID_R_CNT_EQ
	* event
	*/
	static llc_station_action_t llc_stat_dupaddr_state_actions_2[] = {
	[0] = llc_station_ac_report_status, /* DUPLICATE ADDRESS FOUND */
	[1] = NULL,
	};

	static struct llc_station_state_trans llc_stat_dupaddr_state_trans_2 = {
	.ev = llc_stat_ev_rx_null_dsap_1_xid_r_xid_r_cnt_eq,
	.next_state = LLC_STATION_STATE_DOWN,
	.ev_actions = llc_stat_dupaddr_state_actions_2,
	};

	/* state transition for LLC_STATION_EV_RX_NULL_DSAP_XID_C event */
	static llc_station_action_t llc_stat_dupaddr_state_actions_3[] = {
	[0] = llc_station_ac_send_xid_r,
	[1] = NULL,
	};

	static struct llc_station_state_trans llc_stat_dupaddr_state_trans_3 = {
	.ev = llc_stat_ev_rx_null_dsap_xid_c,
	.next_state = LLC_STATION_STATE_DUP_ADDR_CHK,
	.ev_actions = llc_stat_dupaddr_state_actions_3,
	};

	/* state transition for LLC_STATION_EV_ACK_TMR_EXP_LT_RETRY_CNT_MAX_RETRY
	* event
	*/
	static llc_station_action_t llc_stat_dupaddr_state_actions_4[] = {
	[0] = llc_station_ac_start_ack_timer,
	[1] = llc_station_ac_inc_retry_cnt_by_1,
	[2] = llc_station_ac_set_xid_r_cnt_0,
	[3] = llc_station_ac_send_null_dsap_xid_c,
	[4] = NULL,
	};

	static struct llc_station_state_trans llc_stat_dupaddr_state_trans_4 = {
	.ev = llc_stat_ev_ack_tmr_exp_lt_retry_cnt_max_retry,
	.next_state = LLC_STATION_STATE_DUP_ADDR_CHK,
	.ev_actions = llc_stat_dupaddr_state_actions_4,
	};

	/* state transition for LLC_STATION_EV_ACK_TMR_EXP_EQ_RETRY_CNT_MAX_RETRY
	* event
	*/
	static llc_station_action_t llc_stat_dupaddr_state_actions_5[] = {
	[0] = llc_station_ac_report_status, /* STATION UP */
	[1] = NULL,
	};

	static struct llc_station_state_trans llc_stat_dupaddr_state_trans_5 = {
	.ev = llc_stat_ev_ack_tmr_exp_eq_retry_cnt_max_retry,
	.next_state = LLC_STATION_STATE_UP,
	.ev_actions = llc_stat_dupaddr_state_actions_5,
	};

	/* state transition for LLC_STATION_EV_DISABLE_REQ event */
	static llc_station_action_t llc_stat_dupaddr_state_actions_6[] = {
	[0] = llc_station_ac_report_status, /* STATION DOWN */
	[1] = NULL,
	};

	static struct llc_station_state_trans llc_stat_dupaddr_state_trans_6 = {
	.ev = llc_stat_ev_disable_req,
	.next_state = LLC_STATION_STATE_DOWN,
	.ev_actions = llc_stat_dupaddr_state_actions_6,
	};

	/* array of pointers; one to each transition */
	static struct llc_station_state_trans *llc_stat_dupaddr_state_trans[] = {
	[0] = &llc_stat_dupaddr_state_trans_6, /* Request */
	[1] = &llc_stat_dupaddr_state_trans_4, /* Timer */
	[2] = &llc_stat_dupaddr_state_trans_5,
	[3] = &llc_stat_dupaddr_state_trans_1, /* Receive frame */
	[4] = &llc_stat_dupaddr_state_trans_2,
	[5] = &llc_stat_dupaddr_state_trans_3,
	[6] = &llc_stat_state_trans_end,
	};

	static struct llc_station_state
	llc_station_state_table[LLC_NBR_STATION_STATES] = {
	[LLC_STATION_STATE_DOWN - 1] = {
	.curr_state = LLC_STATION_STATE_DOWN,
	.transitions = llc_stat_dwn_state_trans,
	},
	[LLC_STATION_STATE_DUP_ADDR_CHK - 1] = {
	.curr_state = LLC_STATION_STATE_DUP_ADDR_CHK,
	.transitions = llc_stat_dupaddr_state_trans,
	},
	[LLC_STATION_STATE_UP - 1] = {
	.curr_state = LLC_STATION_STATE_UP,
	.transitions = llc_stat_up_state_trans,
	},
	};

	/**
	* llc_exec_station_trans_actions - executes actions for transition
	* @trans: Address of the transition
	* @skb: Address of the event that caused the transition
	*
	* Executes actions of a transition of the station state machine. Returns
	* 0 if all actions complete successfully, nonzero otherwise.
	*/
	static u16 llc_exec_station_trans_actions(struct llc_station_state_trans *trans,
	struct sk_buff *skb)
	{
	u16 rc = 0;
	llc_station_action_t *next_action = trans->ev_actions;

	for (; next_action && *next_action; next_action++)
	if ((*next_action)(skb))
	rc = 1;
	return rc;
	}

	/**
	* llc_find_station_trans - finds transition for this event
	* @skb: Address of the event
	*
	* Search thru events of the current state of the station until list
	* exhausted or it's obvious that the event is not valid for the current
	* state. Returns the address of the transition if cound, %NULL otherwise.
	*/
	static struct llc_station_state_trans *
	llc_find_station_trans(struct sk_buff *skb)
	{
	int i = 0;
	struct llc_station_state_trans *rc = NULL;
	struct llc_station_state_trans **next_trans;
	struct llc_station_state *curr_state =
	&llc_station_state_table[llc_main_station.state - 1];

	for (next_trans = curr_state->transitions; next_trans[i]->ev; i++)
	if (!next_trans[i]->ev(skb)) {
	rc = next_trans[i];
	break;
	}
	return rc;
	}

	/**
	* llc_station_free_ev - frees an event
	* @skb: Address of the event
	*
	* Frees an event.
	*/
	static void llc_station_free_ev(struct sk_buff *skb)
	{
	struct llc_station_state_ev *ev = llc_station_ev(skb);

	if (ev->type == LLC_STATION_EV_TYPE_PDU)
	kfree_skb(skb);
	}

	/**
	* llc_station_next_state - processes event and goes to the next state
	* @skb: Address of the event
	*
	* Processes an event, executes any transitions related to that event and
	* updates the state of the station.
	*/
	static u16 llc_station_next_state(struct sk_buff *skb)
	{
	u16 rc = 1;
	struct llc_station_state_trans *trans;

	if (llc_main_station.state > LLC_NBR_STATION_STATES)
	goto out;
	trans = llc_find_station_trans(skb);
	if (trans) {
	/* got the state to which we next transition; perform the
	* actions associated with this transition before actually
	* transitioning to the next state
	*/
	rc = llc_exec_station_trans_actions(trans, skb);
	if (!rc)
	/* transition station to next state if all actions
	* execute successfully; done; wait for next event
	*/
	llc_main_station.state = trans->next_state;
	} else
	/* event not recognized in current state; re-queue it for
	* processing again at a later time; return failure
	*/
	rc = 0;
	out:
	llc_station_free_ev(skb);
	return rc;
	}

	/**
	* llc_station_service_events - service events in the queue
	*
	* Get an event from the station event queue (if any); attempt to service
	* the event; if event serviced, get the next event (if any) on the event
	* queue; if event not service, re-queue the event on the event queue and
	* attempt to service the next event; when serviced all events in queue,
	* finished; if don't transition to different state, just service all
	* events once; if transition to new state, service all events again.
	* Caller must hold llc_main_station.ev_q.lock.
	*/
	static void llc_station_service_events(void)
	{
	struct sk_buff *skb;

	while ((skb = skb_dequeue(&llc_main_station.ev_q.list)) != NULL)
	llc_station_next_state(skb);
	}

	/**
	* llc_station_state_process - queue event and try to process queue.
	* @skb: Address of the event
	*
	* Queues an event (on the station event queue) for handling by the
	* station state machine and attempts to process any queued-up events.
	*/
	static void llc_station_state_process(struct sk_buff *skb)
	{
	spin_lock_bh(&llc_main_station.ev_q.lock);
	skb_queue_tail(&llc_main_station.ev_q.list, skb);
	llc_station_service_events();
	spin_unlock_bh(&llc_main_station.ev_q.lock);
	}

	static void llc_station_ack_tmr_cb(unsigned long timeout_data)
	{
	struct sk_buff *skb = alloc_skb(0, GFP_ATOMIC);

	if (skb) {
	struct llc_station_state_ev *ev = llc_station_ev(skb);

	ev->type = LLC_STATION_EV_TYPE_ACK_TMR;
	llc_station_state_process(skb);
	}
	}

	/**
	* llc_station_rcv - send received pdu to the station state machine
	* @skb: received frame.
	*
	* Sends data unit to station state machine.
	*/
	static void llc_station_rcv(struct sk_buff *skb)
	{
	struct llc_station_state_ev *ev = llc_station_ev(skb);

	ev->type = LLC_STATION_EV_TYPE_PDU;
	ev->reason = 0;
	llc_station_state_process(skb);
	}

	void __init llc_station_init(void)
	{
	skb_queue_head_init(&llc_main_station.mac_pdu_q);
	skb_queue_head_init(&llc_main_station.ev_q.list);
	spin_lock_init(&llc_main_station.ev_q.lock);
	setup_timer(&llc_main_station.ack_timer, llc_station_ack_tmr_cb,
	(unsigned long)&llc_main_station);
	llc_main_station.ack_timer.expires = jiffies +
	sysctl_llc_station_ack_timeout;
	llc_main_station.maximum_retry = 1;
	llc_main_station.state = LLC_STATION_STATE_UP;
	llc_set_station_handler(llc_station_rcv);
	}

	void llc_station_exit(void)
	{
	llc_set_station_handler(NULL);
	}