/*
 * 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.
 *
 *      This function always consumes a reference to the skb.
 */
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);

        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\n", __func__);
                goto out_skb_put;
        }

        switch (ev->ind_prim) {
        case LLC_DATA_PRIM:
                skb_get(skb);
                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!\n",
                               __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_get(skb);
                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);
                        }
                }
                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!\n", __func__);
                break;
        default:
                if (ev->ind_prim)
                        printk(KERN_INFO "%s: received unknown %d prim!\n",
                                __func__, ev->ind_prim);
                /* 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!\n", __func__);
                break;
        default:
                if (ev->cfm_prim)
                        printk(KERN_INFO "%s: received unknown %d prim!\n",
                                        __func__, ev->cfm_prim);
                /* No confirmation */
                break;
        }
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;
        const 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;
        const 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 &&
                ether_addr_equal(llc->laddr.mac, laddr->mac) &&
                ether_addr_equal(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_TYPESAFE_BY_RCU */
                        if (unlikely(!refcount_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 &&
                ether_addr_equal(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_TYPESAFE_BY_RCU */
                        if (unlikely(!refcount_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);
        sock_set_flag(sk, SOCK_RCU_FREE);
        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, 0);
        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_orphan(skb);
                sock_hold(sk);
                skb->sk = sk;
                skb->destructor = sock_efree;
        }
        if (!sock_owned_by_user(sk))
                llc_conn_rcv(sk, skb);
        else {
                dprintk("%s: adding to backlog...\n", __func__);
                llc_set_backlog_type(skb, LLC_PACKET);
                if (sk_add_backlog(sk, skb, READ_ONCE(sk->sk_rcvbuf)))
                        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\n", __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;

        timer_setup(&llc->ack_timer.timer, llc_conn_ack_tmr_cb, 0);
        llc->ack_timer.expire         = sysctl_llc2_ack_timeout;

        timer_setup(&llc->pf_cycle_timer.timer, llc_conn_pf_cycle_tmr_cb, 0);
        llc->pf_cycle_timer.expire         = sysctl_llc2_p_timeout;

        timer_setup(&llc->rej_sent_timer.timer, llc_conn_rej_tmr_cb, 0);
        llc->rej_sent_timer.expire         = sysctl_llc2_rej_timeout;

        timer_setup(&llc->busy_state_timer.timer, llc_conn_busy_tmr_cb, 0);
        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, int kern)
{
        struct sock *sk = sk_alloc(net, family, priority, prot, kern);

        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\n", sk,
                __func__, atomic_read(&llc_sock_nr));
#endif
out:
        return sk;
}

void llc_sk_stop_all_timers(struct sock *sk, bool sync)
{
        struct llc_sock *llc = llc_sk(sk);

        if (sync) {
                del_timer_sync(&llc->pf_cycle_timer.timer);
                del_timer_sync(&llc->ack_timer.timer);
                del_timer_sync(&llc->rej_sent_timer.timer);
                del_timer_sync(&llc->busy_state_timer.timer);
        } else {
                del_timer(&llc->pf_cycle_timer.timer);
                del_timer(&llc->ack_timer.timer);
                del_timer(&llc->rej_sent_timer.timer);
                del_timer(&llc->busy_state_timer.timer);
        }

        llc->ack_must_be_send = 0;
        llc->ack_pf = 0;
}

/**
 *      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_sk_stop_all_timers(sk, true);
#ifdef DEBUG_LLC_CONN_ALLOC
        printk(KERN_INFO "%s: unackq=%d, txq=%d\n", __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 (refcount_read(&sk->sk_refcnt) != 1) {
                printk(KERN_DEBUG "Destruction of LLC sock %p delayed in %s, cnt=%d\n",
                        sk, __func__, refcount_read(&sk->sk_refcnt));
                printk(KERN_DEBUG "%d LLC sockets are still alive\n",
                        atomic_read(&llc_sock_nr));
        } else {
                atomic_dec(&llc_sock_nr);
                printk(KERN_DEBUG "LLC socket %p released in %s, %d are still alive\n", 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;
}