/*
   * llc_conn.c - Driver routines for connection component.
   *
   * 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/slab.h>

  #include <net/llc_sap.h>
  #include <net/llc_conn.h>
  #include <net/sock.h>

  #include <net/tcp_states.h>

  #include <net/llc_c_ev.h>
  #include <net/llc_c_ac.h>
  #include <net/llc_c_st.h>
  #include <net/llc_pdu.h>
  
  #if 0
  #define dprintk(args...) printk(KERN_DEBUG args)
  #else
  #define dprintk(args...)
  #endif
  
  static int llc_find_offset(int state, int ev_type);
  static void llc_conn_send_pdus(struct sock *sk);
  static int llc_conn_service(struct sock *sk, struct sk_buff *skb);
  static int llc_exec_conn_trans_actions(struct sock *sk,
  				       struct llc_conn_state_trans *trans,
  				       struct sk_buff *ev);
  static struct llc_conn_state_trans *llc_qualify_conn_ev(struct sock *sk,
  							struct sk_buff *skb);
  
  /* Offset table on connection states transition diagram */
  static int llc_offset_table[NBR_CONN_STATES][NBR_CONN_EV];

  int sysctl_llc2_ack_timeout = LLC2_ACK_TIME * HZ;
  int sysctl_llc2_p_timeout = LLC2_P_TIME * HZ;
  int sysctl_llc2_rej_timeout = LLC2_REJ_TIME * HZ;
  int sysctl_llc2_busy_timeout = LLC2_BUSY_TIME * HZ;

  /**
   *	llc_conn_state_process - sends event to connection state machine
   *	@sk: connection
   *	@skb: occurred event
   *
   *	Sends an event to connection state machine. After processing event
   *	(executing it's actions and changing state), upper layer will be
   *	indicated or confirmed, if needed. Returns 0 for success, 1 for
   *	failure. The socket lock has to be held before calling this function.
   */
  int llc_conn_state_process(struct sock *sk, struct sk_buff *skb)
  {
  	int rc;

  	struct llc_sock *llc = llc_sk(skb->sk);

  	struct llc_conn_state_ev *ev = llc_conn_ev(skb);
  
  	/*
  	 * We have to hold the skb, because llc_conn_service will kfree it in
  	 * the sending path and we need to look at the skb->cb, where we encode
  	 * llc_conn_state_ev.
  	 */
  	skb_get(skb);
  	ev->ind_prim = ev->cfm_prim = 0;

  	/*
  	 * Send event to state machine
  	 */
  	rc = llc_conn_service(skb->sk, skb);

  	if (unlikely(rc != 0)) {

  		printk(KERN_ERR "%s: llc_conn_service failed
  ", __func__);

  		goto out_kfree_skb;
  	}

  	if (unlikely(!ev->ind_prim && !ev->cfm_prim)) {

  		/* indicate or confirm not required */

  		if (!skb->next)

  			goto out_kfree_skb;
  		goto out_skb_put;
  	}

  	if (unlikely(ev->ind_prim && ev->cfm_prim)) /* Paranoia */

  		skb_get(skb);
  
  	switch (ev->ind_prim) {
  	case LLC_DATA_PRIM:

  		llc_save_primitive(sk, skb, LLC_DATA_PRIM);
  		if (unlikely(sock_queue_rcv_skb(sk, skb))) {

  			/*
  			 * shouldn't happen
  			 */
  			printk(KERN_ERR "%s: sock_queue_rcv_skb failed!
  ",

  			       __func__);

  			kfree_skb(skb);
  		}
  		break;

  	case LLC_CONN_PRIM:

  		/*

  		 * Can't be sock_queue_rcv_skb, because we have to leave the
  		 * skb->sk pointing to the newly created struct sock in
  		 * llc_conn_handler. -acme

  		 */

  		skb_queue_tail(&sk->sk_receive_queue, skb);
  		sk->sk_state_change(sk);

  		break;
  	case LLC_DISC_PRIM:
  		sock_hold(sk);
  		if (sk->sk_type == SOCK_STREAM &&
  		    sk->sk_state == TCP_ESTABLISHED) {
  			sk->sk_shutdown       = SHUTDOWN_MASK;
  			sk->sk_socket->state  = SS_UNCONNECTED;
  			sk->sk_state          = TCP_CLOSE;
  			if (!sock_flag(sk, SOCK_DEAD)) {

  				sock_set_flag(sk, SOCK_DEAD);

  				sk->sk_state_change(sk);

  			}
  		}
  		kfree_skb(skb);
  		sock_put(sk);
  		break;
  	case LLC_RESET_PRIM:
  		/*
  		 * FIXME:
  		 * RESET is not being notified to upper layers for now
  		 */

  		printk(KERN_INFO "%s: received a reset ind!
  ", __func__);

  		kfree_skb(skb);
  		break;
  	default:
  		if (ev->ind_prim) {
  			printk(KERN_INFO "%s: received unknown %d prim!
  ",

  				__func__, ev->ind_prim);

  			kfree_skb(skb);
  		}
  		/* No indication */
  		break;
  	}
  
  	switch (ev->cfm_prim) {
  	case LLC_DATA_PRIM:
  		if (!llc_data_accept_state(llc->state))
  			sk->sk_write_space(sk);
  		else
  			rc = llc->failed_data_req = 1;
  		break;
  	case LLC_CONN_PRIM:
  		if (sk->sk_type == SOCK_STREAM &&
  		    sk->sk_state == TCP_SYN_SENT) {
  			if (ev->status) {
  				sk->sk_socket->state = SS_UNCONNECTED;
  				sk->sk_state         = TCP_CLOSE;
  			} else {
  				sk->sk_socket->state = SS_CONNECTED;
  				sk->sk_state         = TCP_ESTABLISHED;
  			}
  			sk->sk_state_change(sk);
  		}
  		break;
  	case LLC_DISC_PRIM:
  		sock_hold(sk);
  		if (sk->sk_type == SOCK_STREAM && sk->sk_state == TCP_CLOSING) {
  			sk->sk_socket->state = SS_UNCONNECTED;
  			sk->sk_state         = TCP_CLOSE;
  			sk->sk_state_change(sk);
  		}
  		sock_put(sk);
  		break;
  	case LLC_RESET_PRIM:
  		/*
  		 * FIXME:
  		 * RESET is not being notified to upper layers for now
  		 */

  		printk(KERN_INFO "%s: received a reset conf!
  ", __func__);

  		break;
  	default:
  		if (ev->cfm_prim) {
  			printk(KERN_INFO "%s: received unknown %d prim!
  ",

  					__func__, ev->cfm_prim);

  			break;
  		}
  		goto out_skb_put; /* No confirmation */
  	}
  out_kfree_skb:
  	kfree_skb(skb);
  out_skb_put:
  	kfree_skb(skb);
  	return rc;
  }
  
  void llc_conn_send_pdu(struct sock *sk, struct sk_buff *skb)
  {
  	/* queue PDU to send to MAC layer */
  	skb_queue_tail(&sk->sk_write_queue, skb);
  	llc_conn_send_pdus(sk);
  }
  
  /**
   *	llc_conn_rtn_pdu - sends received data pdu to upper layer
   *	@sk: Active connection
   *	@skb: Received data frame
   *
   *	Sends received data pdu to upper layer (by using indicate function).
   *	Prepares service parameters (prim and prim_data). calling indication
   *	function will be done in llc_conn_state_process.
   */
  void llc_conn_rtn_pdu(struct sock *sk, struct sk_buff *skb)
  {
  	struct llc_conn_state_ev *ev = llc_conn_ev(skb);
  
  	ev->ind_prim = LLC_DATA_PRIM;
  }
  
  /**
   *	llc_conn_resend_i_pdu_as_cmd - resend all all unacknowledged I PDUs
   *	@sk: active connection
   *	@nr: NR
   *	@first_p_bit: p_bit value of first pdu
   *
   *	Resend all unacknowledged I PDUs, starting with the NR; send first as
   *	command PDU with P bit equal first_p_bit; if more than one send
   *	subsequent as command PDUs with P bit equal zero (0).
   */
  void llc_conn_resend_i_pdu_as_cmd(struct sock *sk, u8 nr, u8 first_p_bit)
  {
  	struct sk_buff *skb;
  	struct llc_pdu_sn *pdu;
  	u16 nbr_unack_pdus;
  	struct llc_sock *llc;
  	u8 howmany_resend = 0;
  
  	llc_conn_remove_acked_pdus(sk, nr, &nbr_unack_pdus);
  	if (!nbr_unack_pdus)
  		goto out;
  	/*
  	 * Process unack PDUs only if unack queue is not empty; remove
  	 * appropriate PDUs, fix them up, and put them on mac_pdu_q.
  	 */
  	llc = llc_sk(sk);
  
  	while ((skb = skb_dequeue(&llc->pdu_unack_q)) != NULL) {
  		pdu = llc_pdu_sn_hdr(skb);
  		llc_pdu_set_cmd_rsp(skb, LLC_PDU_CMD);
  		llc_pdu_set_pf_bit(skb, first_p_bit);
  		skb_queue_tail(&sk->sk_write_queue, skb);
  		first_p_bit = 0;
  		llc->vS = LLC_I_GET_NS(pdu);
  		howmany_resend++;
  	}
  	if (howmany_resend > 0)
  		llc->vS = (llc->vS + 1) % LLC_2_SEQ_NBR_MODULO;
  	/* any PDUs to re-send are queued up; start sending to MAC */
  	llc_conn_send_pdus(sk);
  out:;
  }
  
  /**
   *	llc_conn_resend_i_pdu_as_rsp - Resend all unacknowledged I PDUs
   *	@sk: active connection.
   *	@nr: NR
   *	@first_f_bit: f_bit value of first pdu.
   *
   *	Resend all unacknowledged I PDUs, starting with the NR; send first as
   *	response PDU with F bit equal first_f_bit; if more than one send
   *	subsequent as response PDUs with F bit equal zero (0).
   */
  void llc_conn_resend_i_pdu_as_rsp(struct sock *sk, u8 nr, u8 first_f_bit)
  {
  	struct sk_buff *skb;
  	u16 nbr_unack_pdus;
  	struct llc_sock *llc = llc_sk(sk);
  	u8 howmany_resend = 0;
  
  	llc_conn_remove_acked_pdus(sk, nr, &nbr_unack_pdus);
  	if (!nbr_unack_pdus)
  		goto out;
  	/*
  	 * Process unack PDUs only if unack queue is not empty; remove
  	 * appropriate PDUs, fix them up, and put them on mac_pdu_q
  	 */
  	while ((skb = skb_dequeue(&llc->pdu_unack_q)) != NULL) {
  		struct llc_pdu_sn *pdu = llc_pdu_sn_hdr(skb);
  
  		llc_pdu_set_cmd_rsp(skb, LLC_PDU_RSP);
  		llc_pdu_set_pf_bit(skb, first_f_bit);
  		skb_queue_tail(&sk->sk_write_queue, skb);
  		first_f_bit = 0;
  		llc->vS = LLC_I_GET_NS(pdu);
  		howmany_resend++;
  	}
  	if (howmany_resend > 0)
  		llc->vS = (llc->vS + 1) % LLC_2_SEQ_NBR_MODULO;
  	/* any PDUs to re-send are queued up; start sending to MAC */
  	llc_conn_send_pdus(sk);
  out:;
  }
  
  /**
   *	llc_conn_remove_acked_pdus - Removes acknowledged pdus from tx queue
   *	@sk: active connection
   *	nr: NR
   *	how_many_unacked: size of pdu_unack_q after removing acked pdus
   *
   *	Removes acknowledged pdus from transmit queue (pdu_unack_q). Returns
   *	the number of pdus that removed from queue.
   */
  int llc_conn_remove_acked_pdus(struct sock *sk, u8 nr, u16 *how_many_unacked)
  {
  	int pdu_pos, i;
  	struct sk_buff *skb;
  	struct llc_pdu_sn *pdu;
  	int nbr_acked = 0;
  	struct llc_sock *llc = llc_sk(sk);
  	int q_len = skb_queue_len(&llc->pdu_unack_q);
  
  	if (!q_len)
  		goto out;
  	skb = skb_peek(&llc->pdu_unack_q);
  	pdu = llc_pdu_sn_hdr(skb);
  
  	/* finding position of last acked pdu in queue */
  	pdu_pos = ((int)LLC_2_SEQ_NBR_MODULO + (int)nr -
  			(int)LLC_I_GET_NS(pdu)) % LLC_2_SEQ_NBR_MODULO;
  
  	for (i = 0; i < pdu_pos && i < q_len; i++) {
  		skb = skb_dequeue(&llc->pdu_unack_q);

  		kfree_skb(skb);

  		nbr_acked++;
  	}
  out:
  	*how_many_unacked = skb_queue_len(&llc->pdu_unack_q);
  	return nbr_acked;
  }
  
  /**
   *	llc_conn_send_pdus - Sends queued PDUs
   *	@sk: active connection
   *
   *	Sends queued pdus to MAC layer for transmission.
   */
  static void llc_conn_send_pdus(struct sock *sk)
  {
  	struct sk_buff *skb;
  
  	while ((skb = skb_dequeue(&sk->sk_write_queue)) != NULL) {
  		struct llc_pdu_sn *pdu = llc_pdu_sn_hdr(skb);
  
  		if (LLC_PDU_TYPE_IS_I(pdu) &&
  		    !(skb->dev->flags & IFF_LOOPBACK)) {
  			struct sk_buff *skb2 = skb_clone(skb, GFP_ATOMIC);
  
  			skb_queue_tail(&llc_sk(sk)->pdu_unack_q, skb);
  			if (!skb2)
  				break;
  			skb = skb2;
  		}
  		dev_queue_xmit(skb);
  	}
  }
  
  /**
   *	llc_conn_service - finds transition and changes state of connection
   *	@sk: connection
   *	@skb: happened event
   *
   *	This function finds transition that matches with happened event, then
   *	executes related actions and finally changes state of connection.
   *	Returns 0 for success, 1 for failure.
   */
  static int llc_conn_service(struct sock *sk, struct sk_buff *skb)
  {
  	int rc = 1;
  	struct llc_sock *llc = llc_sk(sk);
  	struct llc_conn_state_trans *trans;
  
  	if (llc->state > NBR_CONN_STATES)
  		goto out;
  	rc = 0;
  	trans = llc_qualify_conn_ev(sk, skb);
  	if (trans) {
  		rc = llc_exec_conn_trans_actions(sk, trans, skb);
  		if (!rc && trans->next_state != NO_STATE_CHANGE) {
  			llc->state = trans->next_state;
  			if (!llc_data_accept_state(llc->state))
  				sk->sk_state_change(sk);
  		}
  	}
  out:
  	return rc;
  }
  
  /**
   *	llc_qualify_conn_ev - finds transition for event
   *	@sk: connection
   *	@skb: happened event
   *
   *	This function finds transition that matches with happened event.
   *	Returns pointer to found transition on success, %NULL otherwise.
   */
  static struct llc_conn_state_trans *llc_qualify_conn_ev(struct sock *sk,
  							struct sk_buff *skb)
  {
  	struct llc_conn_state_trans **next_trans;
  	llc_conn_ev_qfyr_t *next_qualifier;
  	struct llc_conn_state_ev *ev = llc_conn_ev(skb);
  	struct llc_sock *llc = llc_sk(sk);
  	struct llc_conn_state *curr_state =
  					&llc_conn_state_table[llc->state - 1];
  
  	/* search thru events for this state until
  	 * list exhausted or until no more
  	 */
  	for (next_trans = curr_state->transitions +
  		llc_find_offset(llc->state - 1, ev->type);
  	     (*next_trans)->ev; next_trans++) {
  		if (!((*next_trans)->ev)(sk, skb)) {
  			/* got POSSIBLE event match; the event may require
  			 * qualification based on the values of a number of
  			 * state flags; if all qualifications are met (i.e.,
  			 * if all qualifying functions return success, or 0,
  			 * then this is THE event we're looking for
  			 */
  			for (next_qualifier = (*next_trans)->ev_qualifiers;
  			     next_qualifier && *next_qualifier &&
  			     !(*next_qualifier)(sk, skb); next_qualifier++)
  				/* nothing */;
  			if (!next_qualifier || !*next_qualifier)
  				/* all qualifiers executed successfully; this is
  				 * our transition; return it so we can perform
  				 * the associated actions & change the state
  				 */
  				return *next_trans;
  		}
  	}
  	return NULL;
  }
  
  /**
   *	llc_exec_conn_trans_actions - executes related actions
   *	@sk: connection
   *	@trans: transition that it's actions must be performed
   *	@skb: event
   *
   *	Executes actions that is related to happened event. Returns 0 for
   *	success, 1 to indicate failure of at least one action.
   */
  static int llc_exec_conn_trans_actions(struct sock *sk,
  				       struct llc_conn_state_trans *trans,
  				       struct sk_buff *skb)
  {
  	int rc = 0;
  	llc_conn_action_t *next_action;
  
  	for (next_action = trans->ev_actions;
  	     next_action && *next_action; next_action++) {
  		int rc2 = (*next_action)(sk, skb);
  
  		if (rc2 == 2) {
  			rc = rc2;
  			break;
  		} else if (rc2)
  			rc = 1;
  	}
  	return rc;
  }

  static inline bool llc_estab_match(const struct llc_sap *sap,
  				   const struct llc_addr *daddr,
  				   const struct llc_addr *laddr,
  				   const struct sock *sk)
  {
  	struct llc_sock *llc = llc_sk(sk);
  
  	return llc->laddr.lsap == laddr->lsap &&
  		llc->daddr.lsap == daddr->lsap &&
  		llc_mac_match(llc->laddr.mac, laddr->mac) &&
  		llc_mac_match(llc->daddr.mac, daddr->mac);
  }

  /**

   *	__llc_lookup_established - Finds connection for the remote/local sap/mac

   *	@sap: SAP
   *	@daddr: address of remote LLC (MAC + SAP)
   *	@laddr: address of local LLC (MAC + SAP)
   *
   *	Search connection list of the SAP and finds connection using the remote
   *	mac, remote sap, local mac, and local sap. Returns pointer for
   *	connection found, %NULL otherwise.

   *	Caller has to make sure local_bh is disabled.

   */

  static struct sock *__llc_lookup_established(struct llc_sap *sap,
  					     struct llc_addr *daddr,
  					     struct llc_addr *laddr)

  {
  	struct sock *rc;

  	struct hlist_nulls_node *node;

  	int slot = llc_sk_laddr_hashfn(sap, laddr);
  	struct hlist_nulls_head *laddr_hb = &sap->sk_laddr_hash[slot];

  
  	rcu_read_lock();
  again:

  	sk_nulls_for_each_rcu(rc, node, laddr_hb) {

  		if (llc_estab_match(sap, daddr, laddr, rc)) {
  			/* Extra checks required by SLAB_DESTROY_BY_RCU */
  			if (unlikely(!atomic_inc_not_zero(&rc->sk_refcnt)))
  				goto again;
  			if (unlikely(llc_sk(rc)->sap != sap ||
  				     !llc_estab_match(sap, daddr, laddr, rc))) {
  				sock_put(rc);
  				continue;
  			}

  			goto found;
  		}
  	}
  	rc = NULL;

  	/*
  	 * if the nulls value we got at the end of this lookup is
  	 * not the expected one, we must restart lookup.
  	 * We probably met an item that was moved to another chain.
  	 */
  	if (unlikely(get_nulls_value(node) != slot))
  		goto again;

  found:

  	rcu_read_unlock();

  	return rc;
  }

  struct sock *llc_lookup_established(struct llc_sap *sap,
  				    struct llc_addr *daddr,
  				    struct llc_addr *laddr)
  {
  	struct sock *sk;
  
  	local_bh_disable();
  	sk = __llc_lookup_established(sap, daddr, laddr);
  	local_bh_enable();
  	return sk;
  }

  static inline bool llc_listener_match(const struct llc_sap *sap,
  				      const struct llc_addr *laddr,
  				      const struct sock *sk)
  {
  	struct llc_sock *llc = llc_sk(sk);
  
  	return sk->sk_type == SOCK_STREAM && sk->sk_state == TCP_LISTEN &&
  		llc->laddr.lsap == laddr->lsap &&

  		llc_mac_match(llc->laddr.mac, laddr->mac);

  }

  static struct sock *__llc_lookup_listener(struct llc_sap *sap,
  					  struct llc_addr *laddr)

  {
  	struct sock *rc;

  	struct hlist_nulls_node *node;

  	int slot = llc_sk_laddr_hashfn(sap, laddr);
  	struct hlist_nulls_head *laddr_hb = &sap->sk_laddr_hash[slot];

  
  	rcu_read_lock();
  again:

  	sk_nulls_for_each_rcu(rc, node, laddr_hb) {

  		if (llc_listener_match(sap, laddr, rc)) {
  			/* Extra checks required by SLAB_DESTROY_BY_RCU */
  			if (unlikely(!atomic_inc_not_zero(&rc->sk_refcnt)))
  				goto again;
  			if (unlikely(llc_sk(rc)->sap != sap ||
  				     !llc_listener_match(sap, laddr, rc))) {
  				sock_put(rc);
  				continue;
  			}

  			goto found;
  		}
  	}
  	rc = NULL;

  	/*
  	 * if the nulls value we got at the end of this lookup is
  	 * not the expected one, we must restart lookup.
  	 * We probably met an item that was moved to another chain.
  	 */
  	if (unlikely(get_nulls_value(node) != slot))
  		goto again;

  found:

  	rcu_read_unlock();

  	return rc;
  }

  /**
   *	llc_lookup_listener - Finds listener for local MAC + SAP
   *	@sap: SAP
   *	@laddr: address of local LLC (MAC + SAP)
   *
   *	Search connection list of the SAP and finds connection listening on
   *	local mac, and local sap. Returns pointer for parent socket found,
   *	%NULL otherwise.
   *	Caller has to make sure local_bh is disabled.
   */
  static struct sock *llc_lookup_listener(struct llc_sap *sap,
  					struct llc_addr *laddr)
  {
  	static struct llc_addr null_addr;
  	struct sock *rc = __llc_lookup_listener(sap, laddr);
  
  	if (!rc)
  		rc = __llc_lookup_listener(sap, &null_addr);
  
  	return rc;
  }

  static struct sock *__llc_lookup(struct llc_sap *sap,
  				 struct llc_addr *daddr,
  				 struct llc_addr *laddr)
  {
  	struct sock *sk = __llc_lookup_established(sap, daddr, laddr);
  
  	return sk ? : llc_lookup_listener(sap, laddr);
  }

  /**
   *	llc_data_accept_state - designates if in this state data can be sent.
   *	@state: state of connection.
   *
   *	Returns 0 if data can be sent, 1 otherwise.
   */
  u8 llc_data_accept_state(u8 state)
  {
  	return state != LLC_CONN_STATE_NORMAL && state != LLC_CONN_STATE_BUSY &&
  	       state != LLC_CONN_STATE_REJ;
  }
  
  /**

   *	llc_find_next_offset - finds offset for next category of transitions

   *	@state: state table.
   *	@offset: start offset.
   *
   *	Finds offset of next category of transitions in transition table.
   *	Returns the start index of next category.
   */

  static u16 __init llc_find_next_offset(struct llc_conn_state *state, u16 offset)

  {
  	u16 cnt = 0;
  	struct llc_conn_state_trans **next_trans;
  
  	for (next_trans = state->transitions + offset;
  	     (*next_trans)->ev; next_trans++)
  		++cnt;
  	return cnt;
  }
  
  /**
   *	llc_build_offset_table - builds offset table of connection
   *
   *	Fills offset table of connection state transition table
   *	(llc_offset_table).
   */
  void __init llc_build_offset_table(void)
  {
  	struct llc_conn_state *curr_state;
  	int state, ev_type, next_offset;
  
  	for (state = 0; state < NBR_CONN_STATES; state++) {
  		curr_state = &llc_conn_state_table[state];
  		next_offset = 0;
  		for (ev_type = 0; ev_type < NBR_CONN_EV; ev_type++) {
  			llc_offset_table[state][ev_type] = next_offset;

  			next_offset += llc_find_next_offset(curr_state,
  							    next_offset) + 1;

  		}
  	}
  }
  
  /**
   *	llc_find_offset - finds start offset of category of transitions
   *	@state: state of connection
   *	@ev_type: type of happened event
   *
   *	Finds start offset of desired category of transitions. Returns the
   *	desired start offset.
   */
  static int llc_find_offset(int state, int ev_type)
  {
  	int rc = 0;
  	/* at this stage, llc_offset_table[..][2] is not important. it is for
  	 * init_pf_cycle and I don't know what is it.
  	 */
  	switch (ev_type) {
  	case LLC_CONN_EV_TYPE_PRIM:
  		rc = llc_offset_table[state][0]; break;
  	case LLC_CONN_EV_TYPE_PDU:
  		rc = llc_offset_table[state][4]; break;
  	case LLC_CONN_EV_TYPE_SIMPLE:
  		rc = llc_offset_table[state][1]; break;
  	case LLC_CONN_EV_TYPE_P_TMR:
  	case LLC_CONN_EV_TYPE_ACK_TMR:
  	case LLC_CONN_EV_TYPE_REJ_TMR:
  	case LLC_CONN_EV_TYPE_BUSY_TMR:
  		rc = llc_offset_table[state][3]; break;
  	}
  	return rc;
  }
  
  /**
   *	llc_sap_add_socket - adds a socket to a SAP
   *	@sap: SAP
   *	@sk: socket
   *

   *	This function adds a socket to the hash tables of a SAP.

   */
  void llc_sap_add_socket(struct llc_sap *sap, struct sock *sk)
  {

  	struct llc_sock *llc = llc_sk(sk);
  	struct hlist_head *dev_hb = llc_sk_dev_hash(sap, llc->dev->ifindex);

  	struct hlist_nulls_head *laddr_hb = llc_sk_laddr_hash(sap, &llc->laddr);

  	llc_sap_hold(sap);

  	llc_sk(sk)->sap = sap;

  
  	spin_lock_bh(&sap->sk_lock);

  	sap->sk_count++;
  	sk_nulls_add_node_rcu(sk, laddr_hb);

  	hlist_add_head(&llc->dev_hash_node, dev_hb);

  	spin_unlock_bh(&sap->sk_lock);

  }
  
  /**
   *	llc_sap_remove_socket - removes a socket from SAP
   *	@sap: SAP
   *	@sk: socket
   *

   *	This function removes a connection from the hash tables of a SAP if

   *	the connection was in this list.
   */
  void llc_sap_remove_socket(struct llc_sap *sap, struct sock *sk)
  {

  	struct llc_sock *llc = llc_sk(sk);

  	spin_lock_bh(&sap->sk_lock);
  	sk_nulls_del_node_init_rcu(sk);

  	hlist_del(&llc->dev_hash_node);

  	sap->sk_count--;

  	spin_unlock_bh(&sap->sk_lock);

  	llc_sap_put(sap);

  }
  
  /**
   *	llc_conn_rcv - sends received pdus to the connection state machine
   *	@sk: current connection structure.
   *	@skb: received frame.
   *
   *	Sends received pdus to the connection state machine.
   */
  static int llc_conn_rcv(struct sock* sk, struct sk_buff *skb)
  {
  	struct llc_conn_state_ev *ev = llc_conn_ev(skb);

  	ev->type   = LLC_CONN_EV_TYPE_PDU;
  	ev->reason = 0;
  	return llc_conn_state_process(sk, skb);
  }

  static struct sock *llc_create_incoming_sock(struct sock *sk,
  					     struct net_device *dev,
  					     struct llc_addr *saddr,
  					     struct llc_addr *daddr)
  {

  	struct sock *newsk = llc_sk_alloc(sock_net(sk), sk->sk_family, GFP_ATOMIC,

  					  sk->sk_prot);
  	struct llc_sock *newllc, *llc = llc_sk(sk);
  
  	if (!newsk)
  		goto out;
  	newllc = llc_sk(newsk);
  	memcpy(&newllc->laddr, daddr, sizeof(newllc->laddr));
  	memcpy(&newllc->daddr, saddr, sizeof(newllc->daddr));
  	newllc->dev = dev;
  	dev_hold(dev);
  	llc_sap_add_socket(llc->sap, newsk);
  	llc_sap_hold(llc->sap);
  out:
  	return newsk;
  }

  void llc_conn_handler(struct llc_sap *sap, struct sk_buff *skb)
  {
  	struct llc_addr saddr, daddr;
  	struct sock *sk;
  
  	llc_pdu_decode_sa(skb, saddr.mac);
  	llc_pdu_decode_ssap(skb, &saddr.lsap);
  	llc_pdu_decode_da(skb, daddr.mac);
  	llc_pdu_decode_dsap(skb, &daddr.lsap);

  	sk = __llc_lookup(sap, &saddr, &daddr);
  	if (!sk)
  		goto drop;
  
  	bh_lock_sock(sk);
  	/*
  	 * This has to be done here and not at the upper layer ->accept
  	 * method because of the way the PROCOM state machine works:
  	 * it needs to set several state variables (see, for instance,
  	 * llc_adm_actions_2 in net/llc/llc_c_st.c) and send a packet to
  	 * the originator of the new connection, and this state has to be
  	 * in the newly created struct sock private area. -acme
  	 */
  	if (unlikely(sk->sk_state == TCP_LISTEN)) {
  		struct sock *newsk = llc_create_incoming_sock(sk, skb->dev,
  							      &saddr, &daddr);
  		if (!newsk)
  			goto drop_unlock;
  		skb_set_owner_r(skb, newsk);
  	} else {

  		/*

  		 * Can't be skb_set_owner_r, this will be done at the
  		 * llc_conn_state_process function, later on, when we will use
  		 * skb_queue_rcv_skb to send it to upper layers, this is
  		 * another trick required to cope with how the PROCOM state
  		 * machine works. -acme

  		 */

  		skb->sk = sk;

  	}

  	if (!sock_owned_by_user(sk))
  		llc_conn_rcv(sk, skb);
  	else {

  		dprintk("%s: adding to backlog...
  ", __func__);

  		llc_set_backlog_type(skb, LLC_PACKET);

  		if (sk_add_backlog(sk, skb))

  			goto drop_unlock;

  	}

  out:

  	bh_unlock_sock(sk);
  	sock_put(sk);
  	return;
  drop:
  	kfree_skb(skb);

  	return;
  drop_unlock:
  	kfree_skb(skb);
  	goto out;

  }
  
  #undef LLC_REFCNT_DEBUG
  #ifdef LLC_REFCNT_DEBUG
  static atomic_t llc_sock_nr;
  #endif
  
  /**

   *	llc_backlog_rcv - Processes rx frames and expired timers.
   *	@sk: LLC sock (p8022 connection)
   *	@skb: queued rx frame or event
   *
   *	This function processes frames that has received and timers that has
   *	expired during sending an I pdu (refer to data_req_handler).  frames
   *	queue by llc_rcv function (llc_mac.c) and timers queue by timer
   *	callback functions(llc_c_ac.c).
   */
  static int llc_backlog_rcv(struct sock *sk, struct sk_buff *skb)
  {
  	int rc = 0;
  	struct llc_sock *llc = llc_sk(sk);

  	if (likely(llc_backlog_type(skb) == LLC_PACKET)) {
  		if (likely(llc->state > 1)) /* not closed */

  			rc = llc_conn_rcv(sk, skb);
  		else
  			goto out_kfree_skb;
  	} else if (llc_backlog_type(skb) == LLC_EVENT) {
  		/* timer expiration event */

  		if (likely(llc->state > 1))  /* not closed */

  			rc = llc_conn_state_process(sk, skb);
  		else
  			goto out_kfree_skb;
  	} else {

  		printk(KERN_ERR "%s: invalid skb in backlog
  ", __func__);

  		goto out_kfree_skb;
  	}
  out:
  	return rc;
  out_kfree_skb:
  	kfree_skb(skb);
  	goto out;
  }
  
  /**
   *     llc_sk_init - Initializes a socket with default llc values.
   *     @sk: socket to initialize.
   *
   *     Initializes a socket with default llc values.
   */
  static void llc_sk_init(struct sock* sk)
  {
  	struct llc_sock *llc = llc_sk(sk);
  
  	llc->state    = LLC_CONN_STATE_ADM;
  	llc->inc_cntr = llc->dec_cntr = 2;
  	llc->dec_step = llc->connect_step = 1;

  	setup_timer(&llc->ack_timer.timer, llc_conn_ack_tmr_cb,
  			(unsigned long)sk);

  	llc->ack_timer.expire	      = sysctl_llc2_ack_timeout;

  	setup_timer(&llc->pf_cycle_timer.timer, llc_conn_pf_cycle_tmr_cb,
  			(unsigned long)sk);

  	llc->pf_cycle_timer.expire	   = sysctl_llc2_p_timeout;

  	setup_timer(&llc->rej_sent_timer.timer, llc_conn_rej_tmr_cb,
  			(unsigned long)sk);

  	llc->rej_sent_timer.expire	   = sysctl_llc2_rej_timeout;

  	setup_timer(&llc->busy_state_timer.timer, llc_conn_busy_tmr_cb,
  			(unsigned long)sk);

  	llc->busy_state_timer.expire	     = sysctl_llc2_busy_timeout;

  
  	llc->n2 = 2;   /* max retransmit */
  	llc->k  = 2;   /* tx win size, will adjust dynam */
  	llc->rw = 128; /* rx win size (opt and equal to

  			* tx_win of remote LLC) */

  	skb_queue_head_init(&llc->pdu_unack_q);
  	sk->sk_backlog_rcv = llc_backlog_rcv;
  }
  
  /**
   *	llc_sk_alloc - Allocates LLC sock
   *	@family: upper layer protocol family
   *	@priority: for allocation (%GFP_KERNEL, %GFP_ATOMIC, etc)
   *
   *	Allocates a LLC sock and initializes it. Returns the new LLC sock
   *	or %NULL if there's no memory available for one
   */

  struct sock *llc_sk_alloc(struct net *net, int family, gfp_t priority, struct proto *prot)

  {

  	struct sock *sk = sk_alloc(net, family, priority, prot);

  
  	if (!sk)
  		goto out;
  	llc_sk_init(sk);
  	sock_init_data(NULL, sk);
  #ifdef LLC_REFCNT_DEBUG
  	atomic_inc(&llc_sock_nr);
  	printk(KERN_DEBUG "LLC socket %p created in %s, now we have %d alive
  ", sk,

  		__func__, atomic_read(&llc_sock_nr));

  #endif
  out:
  	return sk;
  }
  
  /**
   *	llc_sk_free - Frees a LLC socket
   *	@sk - socket to free
   *
   *	Frees a LLC socket
   */
  void llc_sk_free(struct sock *sk)
  {
  	struct llc_sock *llc = llc_sk(sk);
  
  	llc->state = LLC_CONN_OUT_OF_SVC;
  	/* Stop all (possibly) running timers */
  	llc_conn_ac_stop_all_timers(sk, NULL);
  #ifdef DEBUG_LLC_CONN_ALLOC

  	printk(KERN_INFO "%s: unackq=%d, txq=%d
  ", __func__,

  		skb_queue_len(&llc->pdu_unack_q),
  		skb_queue_len(&sk->sk_write_queue));
  #endif
  	skb_queue_purge(&sk->sk_receive_queue);
  	skb_queue_purge(&sk->sk_write_queue);
  	skb_queue_purge(&llc->pdu_unack_q);
  #ifdef LLC_REFCNT_DEBUG
  	if (atomic_read(&sk->sk_refcnt) != 1) {
  		printk(KERN_DEBUG "Destruction of LLC sock %p delayed in %s, cnt=%d
  ",

  			sk, __func__, atomic_read(&sk->sk_refcnt));

  		printk(KERN_DEBUG "%d LLC sockets are still alive
  ",
  			atomic_read(&llc_sock_nr));
  	} else {
  		atomic_dec(&llc_sock_nr);
  		printk(KERN_DEBUG "LLC socket %p released in %s, %d are still alive
  ", sk,

  			__func__, atomic_read(&llc_sock_nr));

  	}
  #endif
  	sock_put(sk);
  }
  
  /**
   *	llc_sk_reset - resets a connection
   *	@sk: LLC socket to reset
   *
   *	Resets a connection to the out of service state. Stops its timers
   *	and frees any frames in the queues of the connection.
   */
  void llc_sk_reset(struct sock *sk)
  {
  	struct llc_sock *llc = llc_sk(sk);
  
  	llc_conn_ac_stop_all_timers(sk, NULL);
  	skb_queue_purge(&sk->sk_write_queue);
  	skb_queue_purge(&llc->pdu_unack_q);
  	llc->remote_busy_flag	= 0;
  	llc->cause_flag		= 0;
  	llc->retry_count	= 0;
  	llc_conn_set_p_flag(sk, 0);
  	llc->f_flag		= 0;
  	llc->s_flag		= 0;
  	llc->ack_pf		= 0;
  	llc->first_pdu_Ns	= 0;
  	llc->ack_must_be_send	= 0;
  	llc->dec_step		= 1;
  	llc->inc_cntr		= 2;
  	llc->dec_cntr		= 2;
  	llc->X			= 0;
  	llc->failed_data_req	= 0 ;
  	llc->last_nr		= 0;
  }