/*********************************************************************
 *
 * Filename:      irlap_frame.c
 * Version:       1.0
 * Description:   Build and transmit IrLAP frames
 * Status:        Stable
 * Author:        Dag Brattli <dagb@cs.uit.no>
 * Created at:    Tue Aug 19 10:27:26 1997
 * Modified at:   Wed Jan  5 08:59:04 2000
 * Modified by:   Dag Brattli <dagb@cs.uit.no>
 *
 *     Copyright (c) 1998-2000 Dag Brattli <dagb@cs.uit.no>,
 *     All Rights Reserved.
 *     Copyright (c) 2000-2003 Jean Tourrilhes <jt@hpl.hp.com>
 *
 *     This program is free software; you can redistribute it and/or
 *     modify it under the terms of the GNU General Public License as
 *     published by the Free Software Foundation; either version 2 of
 *     the License, or (at your option) any later version.
 *
 *     Neither Dag Brattli nor University of Tromsø admit liability nor
 *     provide warranty for any of this software. This material is
 *     provided "AS-IS" and at no charge.
 *
 ********************************************************************/

#include <linux/skbuff.h>
#include <linux/if.h>
#include <linux/if_ether.h>
#include <linux/netdevice.h>
#include <linux/irda.h>
#include <linux/slab.h>

#include <net/pkt_sched.h>
#include <net/sock.h>

#include <asm/byteorder.h>

#include <net/irda/irda.h>
#include <net/irda/irda_device.h>
#include <net/irda/irlap.h>
#include <net/irda/wrapper.h>
#include <net/irda/timer.h>
#include <net/irda/irlap_frame.h>
#include <net/irda/qos.h>

static void irlap_send_i_frame(struct irlap_cb *self, struct sk_buff *skb,
                               int command);

/*
 * Function irlap_insert_info (self, skb)
 *
 *    Insert minimum turnaround time and speed information into the skb. We
 *    need to do this since it's per packet relevant information. Safe to
 *    have this function inlined since it's only called from one place
 */
static inline void irlap_insert_info(struct irlap_cb *self,
                                     struct sk_buff *skb)
{
        struct irda_skb_cb *cb = (struct irda_skb_cb *) skb->cb;

        /*
         * Insert MTT (min. turn time) and speed into skb, so that the
         * device driver knows which settings to use
         */
        cb->magic = LAP_MAGIC;
        cb->mtt = self->mtt_required;
        cb->next_speed = self->speed;

        /* Reset */
        self->mtt_required = 0;

        /*
         * Delay equals negotiated BOFs count, plus the number of BOFs to
         * force the negotiated minimum turnaround time
         */
        cb->xbofs = self->bofs_count;
        cb->next_xbofs = self->next_bofs;
        cb->xbofs_delay = self->xbofs_delay;

        /* Reset XBOF's delay (used only for getting min turn time) */
        self->xbofs_delay = 0;
        /* Put the correct xbofs value for the next packet */
        self->bofs_count = self->next_bofs;
}

/*
 * Function irlap_queue_xmit (self, skb)
 *
 *    A little wrapper for dev_queue_xmit, so we can insert some common
 *    code into it.
 */
void irlap_queue_xmit(struct irlap_cb *self, struct sk_buff *skb)
{
        /* Some common init stuff */
        skb->dev = self->netdev;
        skb_reset_mac_header(skb);
        skb_reset_network_header(skb);
        skb_reset_transport_header(skb);
        skb->protocol = htons(ETH_P_IRDA);
        skb->priority = TC_PRIO_BESTEFFORT;

        irlap_insert_info(self, skb);

        if (unlikely(self->mode & IRDA_MODE_MONITOR)) {
                pr_debug("%s(): %s is in monitor mode\n", __func__,
                         self->netdev->name);
                dev_kfree_skb(skb);
                return;
        }

        dev_queue_xmit(skb);
}

/*
 * Function irlap_send_snrm_cmd (void)
 *
 *    Transmits a connect SNRM command frame
 */
void irlap_send_snrm_frame(struct irlap_cb *self, struct qos_info *qos)
{
        struct sk_buff *tx_skb;
        struct snrm_frame *frame;
        int ret;

        IRDA_ASSERT(self != NULL, return;);
        IRDA_ASSERT(self->magic == LAP_MAGIC, return;);

        /* Allocate frame */
        tx_skb = alloc_skb(sizeof(struct snrm_frame) +
                           IRLAP_NEGOCIATION_PARAMS_LEN,
                           GFP_ATOMIC);
        if (!tx_skb)
                return;

        frame = (struct snrm_frame *) skb_put(tx_skb, 2);

        /* Insert connection address field */
        if (qos)
                frame->caddr = CMD_FRAME | CBROADCAST;
        else
                frame->caddr = CMD_FRAME | self->caddr;

        /* Insert control field */
        frame->control = SNRM_CMD | PF_BIT;

        /*
         *  If we are establishing a connection then insert QoS parameters
         */
        if (qos) {
                skb_put(tx_skb, 9); /* 25 left */
                frame->saddr = cpu_to_le32(self->saddr);
                frame->daddr = cpu_to_le32(self->daddr);

                frame->ncaddr = self->caddr;

                ret = irlap_insert_qos_negotiation_params(self, tx_skb);
                if (ret < 0) {
                        dev_kfree_skb(tx_skb);
                        return;
                }
        }
        irlap_queue_xmit(self, tx_skb);
}

/*
 * Function irlap_recv_snrm_cmd (skb, info)
 *
 *    Received SNRM (Set Normal Response Mode) command frame
 *
 */
static void irlap_recv_snrm_cmd(struct irlap_cb *self, struct sk_buff *skb,
                                struct irlap_info *info)
{
        struct snrm_frame *frame;

        if (pskb_may_pull(skb,sizeof(struct snrm_frame))) {
                frame = (struct snrm_frame *) skb->data;

                /* Copy the new connection address ignoring the C/R bit */
                info->caddr = frame->ncaddr & 0xFE;

                /* Check if the new connection address is valid */
                if ((info->caddr == 0x00) || (info->caddr == 0xfe)) {
                        pr_debug("%s(), invalid connection address!\n",
                                 __func__);
                        return;
                }

                /* Copy peer device address */
                info->daddr = le32_to_cpu(frame->saddr);
                info->saddr = le32_to_cpu(frame->daddr);

                /* Only accept if addressed directly to us */
                if (info->saddr != self->saddr) {
                        pr_debug("%s(), not addressed to us!\n",
                                 __func__);
                        return;
                }
                irlap_do_event(self, RECV_SNRM_CMD, skb, info);
        } else {
                /* Signal that this SNRM frame does not contain and I-field */
                irlap_do_event(self, RECV_SNRM_CMD, skb, NULL);
        }
}

/*
 * Function irlap_send_ua_response_frame (qos)
 *
 *    Send UA (Unnumbered Acknowledgement) frame
 *
 */
void irlap_send_ua_response_frame(struct irlap_cb *self, struct qos_info *qos)
{
        struct sk_buff *tx_skb;
        struct ua_frame *frame;
        int ret;

        pr_debug("%s() <%ld>\n", __func__, jiffies);

        IRDA_ASSERT(self != NULL, return;);
        IRDA_ASSERT(self->magic == LAP_MAGIC, return;);

        /* Allocate frame */
        tx_skb = alloc_skb(sizeof(struct ua_frame) +
                           IRLAP_NEGOCIATION_PARAMS_LEN,
                           GFP_ATOMIC);
        if (!tx_skb)
                return;

        frame = (struct ua_frame *) skb_put(tx_skb, 10);

        /* Build UA response */
        frame->caddr = self->caddr;
        frame->control = UA_RSP | PF_BIT;

        frame->saddr = cpu_to_le32(self->saddr);
        frame->daddr = cpu_to_le32(self->daddr);

        /* Should we send QoS negotiation parameters? */
        if (qos) {
                ret = irlap_insert_qos_negotiation_params(self, tx_skb);
                if (ret < 0) {
                        dev_kfree_skb(tx_skb);
                        return;
                }
        }

        irlap_queue_xmit(self, tx_skb);
}


/*
 * Function irlap_send_dm_frame (void)
 *
 *    Send disconnected mode (DM) frame
 *
 */
void irlap_send_dm_frame( struct irlap_cb *self)
{
        struct sk_buff *tx_skb = NULL;
        struct dm_frame *frame;

        IRDA_ASSERT(self != NULL, return;);
        IRDA_ASSERT(self->magic == LAP_MAGIC, return;);

        tx_skb = alloc_skb(sizeof(struct dm_frame), GFP_ATOMIC);
        if (!tx_skb)
                return;

        frame = (struct dm_frame *)skb_put(tx_skb, 2);

        if (self->state == LAP_NDM)
                frame->caddr = CBROADCAST;
        else
                frame->caddr = self->caddr;

        frame->control = DM_RSP | PF_BIT;

        irlap_queue_xmit(self, tx_skb);
}

/*
 * Function irlap_send_disc_frame (void)
 *
 *    Send disconnect (DISC) frame
 *
 */
void irlap_send_disc_frame(struct irlap_cb *self)
{
        struct sk_buff *tx_skb = NULL;
        struct disc_frame *frame;

        IRDA_ASSERT(self != NULL, return;);
        IRDA_ASSERT(self->magic == LAP_MAGIC, return;);

        tx_skb = alloc_skb(sizeof(struct disc_frame), GFP_ATOMIC);
        if (!tx_skb)
                return;

        frame = (struct disc_frame *)skb_put(tx_skb, 2);

        frame->caddr = self->caddr | CMD_FRAME;
        frame->control = DISC_CMD | PF_BIT;

        irlap_queue_xmit(self, tx_skb);
}

/*
 * Function irlap_send_discovery_xid_frame (S, s, command)
 *
 *    Build and transmit a XID (eXchange station IDentifier) discovery
 *    frame.
 */
void irlap_send_discovery_xid_frame(struct irlap_cb *self, int S, __u8 s,
                                    __u8 command, discovery_t *discovery)
{
        struct sk_buff *tx_skb = NULL;
        struct xid_frame *frame;
        __u32 bcast = BROADCAST;
        __u8 *info;

        pr_debug("%s(), s=%d, S=%d, command=%d\n", __func__,
                 s, S, command);

        IRDA_ASSERT(self != NULL, return;);
        IRDA_ASSERT(self->magic == LAP_MAGIC, return;);
        IRDA_ASSERT(discovery != NULL, return;);

        tx_skb = alloc_skb(sizeof(struct xid_frame) + IRLAP_DISCOVERY_INFO_LEN,
                           GFP_ATOMIC);
        if (!tx_skb)
                return;

        skb_put(tx_skb, 14);
        frame = (struct xid_frame *) tx_skb->data;

        if (command) {
                frame->caddr = CBROADCAST | CMD_FRAME;
                frame->control =  XID_CMD | PF_BIT;
        } else {
                frame->caddr = CBROADCAST;
                frame->control =  XID_RSP | PF_BIT;
        }
        frame->ident = XID_FORMAT;

        frame->saddr = cpu_to_le32(self->saddr);

        if (command)
                frame->daddr = cpu_to_le32(bcast);
        else
                frame->daddr = cpu_to_le32(discovery->data.daddr);

        switch (S) {
        case 1:
                frame->flags = 0x00;
                break;
        case 6:
                frame->flags = 0x01;
                break;
        case 8:
                frame->flags = 0x02;
                break;
        case 16:
                frame->flags = 0x03;
                break;
        default:
                frame->flags = 0x02;
                break;
        }

        frame->slotnr = s;
        frame->version = 0x00;

        /*
         *  Provide info for final slot only in commands, and for all
         *  responses. Send the second byte of the hint only if the
         *  EXTENSION bit is set in the first byte.
         */
        if (!command || (frame->slotnr == 0xff)) {
                int len;

                if (discovery->data.hints[0] & HINT_EXTENSION) {
                        info = skb_put(tx_skb, 2);
                        info[0] = discovery->data.hints[0];
                        info[1] = discovery->data.hints[1];
                } else {
                        info = skb_put(tx_skb, 1);
                        info[0] = discovery->data.hints[0];
                }
                info = skb_put(tx_skb, 1);
                info[0] = discovery->data.charset;

                len = IRDA_MIN(discovery->name_len, skb_tailroom(tx_skb));
                info = skb_put(tx_skb, len);
                memcpy(info, discovery->data.info, len);
        }
        irlap_queue_xmit(self, tx_skb);
}

/*
 * Function irlap_recv_discovery_xid_rsp (skb, info)
 *
 *    Received a XID discovery response
 *
 */
static void irlap_recv_discovery_xid_rsp(struct irlap_cb *self,
                                         struct sk_buff *skb,
                                         struct irlap_info *info)
{
        struct xid_frame *xid;
        discovery_t *discovery = NULL;
        __u8 *discovery_info;
        char *text;

        IRDA_ASSERT(self != NULL, return;);
        IRDA_ASSERT(self->magic == LAP_MAGIC, return;);

        if (!pskb_may_pull(skb, sizeof(struct xid_frame))) {
                net_err_ratelimited("%s: frame too short!\n", __func__);
                return;
        }

        xid = (struct xid_frame *) skb->data;

        info->daddr = le32_to_cpu(xid->saddr);
        info->saddr = le32_to_cpu(xid->daddr);

        /* Make sure frame is addressed to us */
        if ((info->saddr != self->saddr) && (info->saddr != BROADCAST)) {
                pr_debug("%s(), frame is not addressed to us!\n",
                         __func__);
                return;
        }

        if ((discovery = kzalloc(sizeof(discovery_t), GFP_ATOMIC)) == NULL) {
                net_warn_ratelimited("%s: kmalloc failed!\n", __func__);
                return;
        }

        discovery->data.daddr = info->daddr;
        discovery->data.saddr = self->saddr;
        discovery->timestamp = jiffies;

        pr_debug("%s(), daddr=%08x\n", __func__,
                 discovery->data.daddr);

        discovery_info = skb_pull(skb, sizeof(struct xid_frame));

        /* Get info returned from peer */
        discovery->data.hints[0] = discovery_info[0];
        if (discovery_info[0] & HINT_EXTENSION) {
                pr_debug("EXTENSION\n");
                discovery->data.hints[1] = discovery_info[1];
                discovery->data.charset = discovery_info[2];
                text = (char *) &discovery_info[3];
        } else {
                discovery->data.hints[1] = 0;
                discovery->data.charset = discovery_info[1];
                text = (char *) &discovery_info[2];
        }
        /*
         *  Terminate info string, should be safe since this is where the
         *  FCS bytes resides.
         */
        skb->data[skb->len] = '\0';
        strncpy(discovery->data.info, text, NICKNAME_MAX_LEN);
        discovery->name_len = strlen(discovery->data.info);

        info->discovery = discovery;

        irlap_do_event(self, RECV_DISCOVERY_XID_RSP, skb, info);
}

/*
 * Function irlap_recv_discovery_xid_cmd (skb, info)
 *
 *    Received a XID discovery command
 *
 */
static void irlap_recv_discovery_xid_cmd(struct irlap_cb *self,
                                         struct sk_buff *skb,
                                         struct irlap_info *info)
{
        struct xid_frame *xid;
        discovery_t *discovery = NULL;
        __u8 *discovery_info;
        char *text;

        if (!pskb_may_pull(skb, sizeof(struct xid_frame))) {
                net_err_ratelimited("%s: frame too short!\n", __func__);
                return;
        }

        xid = (struct xid_frame *) skb->data;

        info->daddr = le32_to_cpu(xid->saddr);
        info->saddr = le32_to_cpu(xid->daddr);

        /* Make sure frame is addressed to us */
        if ((info->saddr != self->saddr) && (info->saddr != BROADCAST)) {
                pr_debug("%s(), frame is not addressed to us!\n",
                         __func__);
                return;
        }

        switch (xid->flags & 0x03) {
        case 0x00:
                info->S = 1;
                break;
        case 0x01:
                info->S = 6;
                break;
        case 0x02:
                info->S = 8;
                break;
        case 0x03:
                info->S = 16;
                break;
        default:
                /* Error!! */
                return;
        }
        info->s = xid->slotnr;

        discovery_info = skb_pull(skb, sizeof(struct xid_frame));

        /*
         *  Check if last frame
         */
        if (info->s == 0xff) {
                /* Check if things are sane at this point... */
                if((discovery_info == NULL) ||
                   !pskb_may_pull(skb, 3)) {
                        net_err_ratelimited("%s: discovery frame too short!\n",
                                            __func__);
                        return;
                }

                /*
                 *  We now have some discovery info to deliver!
                 */
                discovery = kzalloc(sizeof(discovery_t), GFP_ATOMIC);
                if (!discovery)
                        return;

                discovery->data.daddr = info->daddr;
                discovery->data.saddr = self->saddr;
                discovery->timestamp = jiffies;

                discovery->data.hints[0] = discovery_info[0];
                if (discovery_info[0] & HINT_EXTENSION) {
                        discovery->data.hints[1] = discovery_info[1];
                        discovery->data.charset = discovery_info[2];
                        text = (char *) &discovery_info[3];
                } else {
                        discovery->data.hints[1] = 0;
                        discovery->data.charset = discovery_info[1];
                        text = (char *) &discovery_info[2];
                }
                /*
                 *  Terminate string, should be safe since this is where the
                 *  FCS bytes resides.
                 */
                skb->data[skb->len] = '\0';
                strncpy(discovery->data.info, text, NICKNAME_MAX_LEN);
                discovery->name_len = strlen(discovery->data.info);

                info->discovery = discovery;
        } else
                info->discovery = NULL;

        irlap_do_event(self, RECV_DISCOVERY_XID_CMD, skb, info);
}

/*
 * Function irlap_send_rr_frame (self, command)
 *
 *    Build and transmit RR (Receive Ready) frame. Notice that it is currently
 *    only possible to send RR frames with the poll bit set.
 */
void irlap_send_rr_frame(struct irlap_cb *self, int command)
{
        struct sk_buff *tx_skb;
        struct rr_frame *frame;

        tx_skb = alloc_skb(sizeof(struct rr_frame), GFP_ATOMIC);
        if (!tx_skb)
                return;

        frame = (struct rr_frame *)skb_put(tx_skb, 2);

        frame->caddr = self->caddr;
        frame->caddr |= (command) ? CMD_FRAME : 0;

        frame->control = RR | PF_BIT | (self->vr << 5);

        irlap_queue_xmit(self, tx_skb);
}

/*
 * Function irlap_send_rd_frame (self)
 *
 *    Request disconnect. Used by a secondary station to request the
 *    disconnection of the link.
 */
void irlap_send_rd_frame(struct irlap_cb *self)
{
        struct sk_buff *tx_skb;
        struct rd_frame *frame;

        tx_skb = alloc_skb(sizeof(struct rd_frame), GFP_ATOMIC);
        if (!tx_skb)
                return;

        frame = (struct rd_frame *)skb_put(tx_skb, 2);

        frame->caddr = self->caddr;
        frame->control = RD_RSP | PF_BIT;

        irlap_queue_xmit(self, tx_skb);
}

/*
 * Function irlap_recv_rr_frame (skb, info)
 *
 *    Received RR (Receive Ready) frame from peer station, no harm in
 *    making it inline since its called only from one single place
 *    (irlap_driver_rcv).
 */
static inline void irlap_recv_rr_frame(struct irlap_cb *self,
                                       struct sk_buff *skb,
                                       struct irlap_info *info, int command)
{
        info->nr = skb->data[1] >> 5;

        /* Check if this is a command or a response frame */
        if (command)
                irlap_do_event(self, RECV_RR_CMD, skb, info);
        else
                irlap_do_event(self, RECV_RR_RSP, skb, info);
}

/*
 * Function irlap_recv_rnr_frame (self, skb, info)
 *
 *    Received RNR (Receive Not Ready) frame from peer station
 *
 */
static void irlap_recv_rnr_frame(struct irlap_cb *self, struct sk_buff *skb,
                                 struct irlap_info *info, int command)
{
        info->nr = skb->data[1] >> 5;

        pr_debug("%s(), nr=%d, %ld\n", __func__, info->nr, jiffies);

        if (command)
                irlap_do_event(self, RECV_RNR_CMD, skb, info);
        else
                irlap_do_event(self, RECV_RNR_RSP, skb, info);
}

static void irlap_recv_rej_frame(struct irlap_cb *self, struct sk_buff *skb,
                                 struct irlap_info *info, int command)
{
        info->nr = skb->data[1] >> 5;

        /* Check if this is a command or a response frame */
        if (command)
                irlap_do_event(self, RECV_REJ_CMD, skb, info);
        else
                irlap_do_event(self, RECV_REJ_RSP, skb, info);
}

static void irlap_recv_srej_frame(struct irlap_cb *self, struct sk_buff *skb,
                                  struct irlap_info *info, int command)
{
        info->nr = skb->data[1] >> 5;

        /* Check if this is a command or a response frame */
        if (command)
                irlap_do_event(self, RECV_SREJ_CMD, skb, info);
        else
                irlap_do_event(self, RECV_SREJ_RSP, skb, info);
}

static void irlap_recv_disc_frame(struct irlap_cb *self, struct sk_buff *skb,
                                  struct irlap_info *info, int command)
{
        /* Check if this is a command or a response frame */
        if (command)
                irlap_do_event(self, RECV_DISC_CMD, skb, info);
        else
                irlap_do_event(self, RECV_RD_RSP, skb, info);
}

/*
 * Function irlap_recv_ua_frame (skb, frame)
 *
 *    Received UA (Unnumbered Acknowledgement) frame
 *
 */
static inline void irlap_recv_ua_frame(struct irlap_cb *self,
                                       struct sk_buff *skb,
                                       struct irlap_info *info)
{
        irlap_do_event(self, RECV_UA_RSP, skb, info);
}

/*
 * Function irlap_send_data_primary(self, skb)
 *
 *    Send I-frames as the primary station but without the poll bit set
 *
 */
void irlap_send_data_primary(struct irlap_cb *self, struct sk_buff *skb)
{
        struct sk_buff *tx_skb;

        if (skb->data[1] == I_FRAME) {

                /*
                 *  Insert frame sequence number (Vs) in control field before
                 *  inserting into transmit window queue.
                 */
                skb->data[1] = I_FRAME | (self->vs << 1);

                /*
                 *  Insert frame in store, in case of retransmissions
                 *  Increase skb reference count, see irlap_do_event()
                 */
                skb_get(skb);
                skb_queue_tail(&self->wx_list, skb);

                /* Copy buffer */
                tx_skb = skb_clone(skb, GFP_ATOMIC);
                if (tx_skb == NULL) {
                        return;
                }

                self->vs = (self->vs + 1) % 8;
                self->ack_required = FALSE;
                self->window -= 1;

                irlap_send_i_frame( self, tx_skb, CMD_FRAME);
        } else {
                pr_debug("%s(), sending unreliable frame\n", __func__);
                irlap_send_ui_frame(self, skb_get(skb), self->caddr, CMD_FRAME);
                self->window -= 1;
        }
}
/*
 * Function irlap_send_data_primary_poll (self, skb)
 *
 *    Send I(nformation) frame as primary with poll bit set
 */
void irlap_send_data_primary_poll(struct irlap_cb *self, struct sk_buff *skb)
{
        struct sk_buff *tx_skb;
        int transmission_time;

        /* Stop P timer */
        del_timer(&self->poll_timer);

        /* Is this reliable or unreliable data? */
        if (skb->data[1] == I_FRAME) {

                /*
                 *  Insert frame sequence number (Vs) in control field before
                 *  inserting into transmit window queue.
                 */
                skb->data[1] = I_FRAME | (self->vs << 1);

                /*
                 *  Insert frame in store, in case of retransmissions
                 *  Increase skb reference count, see irlap_do_event()
                 */
                skb_get(skb);
                skb_queue_tail(&self->wx_list, skb);

                /* Copy buffer */
                tx_skb = skb_clone(skb, GFP_ATOMIC);
                if (tx_skb == NULL) {
                        return;
                }

                /*
                 *  Set poll bit if necessary. We do this to the copied
                 *  skb, since retransmitted need to set or clear the poll
                 *  bit depending on when they are sent.
                 */
                tx_skb->data[1] |= PF_BIT;

                self->vs = (self->vs + 1) % 8;
                self->ack_required = FALSE;

                irlap_next_state(self, LAP_NRM_P);
                irlap_send_i_frame(self, tx_skb, CMD_FRAME);
        } else {
                pr_debug("%s(), sending unreliable frame\n", __func__);

                if (self->ack_required) {
                        irlap_send_ui_frame(self, skb_get(skb), self->caddr, CMD_FRAME);
                        irlap_next_state(self, LAP_NRM_P);
                        irlap_send_rr_frame(self, CMD_FRAME);
                        self->ack_required = FALSE;
                } else {
                        skb->data[1] |= PF_BIT;
                        irlap_next_state(self, LAP_NRM_P);
                        irlap_send_ui_frame(self, skb_get(skb), self->caddr, CMD_FRAME);
                }
        }

        /* How much time we took for transmission of all frames.
         * We don't know, so let assume we used the full window. Jean II */
        transmission_time = self->final_timeout;

        /* Reset parameter so that we can fill next window */
        self->window = self->window_size;

#ifdef CONFIG_IRDA_DYNAMIC_WINDOW
        /* Remove what we have not used. Just do a prorata of the
         * bytes left in window to window capacity.
         * See max_line_capacities[][] in qos.c for details. Jean II */
        transmission_time -= (self->final_timeout * self->bytes_left
                              / self->line_capacity);
        pr_debug("%s() adjusting transmission_time : ft=%d, bl=%d, lc=%d -> tt=%d\n",
                 __func__, self->final_timeout, self->bytes_left,
                 self->line_capacity, transmission_time);

        /* We are allowed to transmit a maximum number of bytes again. */
        self->bytes_left = self->line_capacity;
#endif /* CONFIG_IRDA_DYNAMIC_WINDOW */

        /*
         * The network layer has a intermediate buffer between IrLAP
         * and the IrDA driver which can contain 8 frames. So, even
         * though IrLAP is currently sending the *last* frame of the
         * tx-window, the driver most likely has only just started
         * sending the *first* frame of the same tx-window.
         * I.e. we are always at the very beginning of or Tx window.
         * Now, we are supposed to set the final timer from the end
         * of our tx-window to let the other peer reply. So, we need
         * to add extra time to compensate for the fact that we
         * are really at the start of tx-window, otherwise the final timer
         * might expire before he can answer...
         * Jean II
         */
        irlap_start_final_timer(self, self->final_timeout + transmission_time);

        /*
         * The clever amongst you might ask why we do this adjustement
         * only here, and not in all the other cases in irlap_event.c.
         * In all those other case, we only send a very short management
         * frame (few bytes), so the adjustement would be lost in the
         * noise...
         * The exception of course is irlap_resend_rejected_frame().
         * Jean II */
}

/*
 * Function irlap_send_data_secondary_final (self, skb)
 *
 *    Send I(nformation) frame as secondary with final bit set
 *
 */
void irlap_send_data_secondary_final(struct irlap_cb *self,
                                     struct sk_buff *skb)
{
        struct sk_buff *tx_skb = NULL;

        IRDA_ASSERT(self != NULL, return;);
        IRDA_ASSERT(self->magic == LAP_MAGIC, return;);
        IRDA_ASSERT(skb != NULL, return;);

        /* Is this reliable or unreliable data? */
        if (skb->data[1] == I_FRAME) {

                /*
                 *  Insert frame sequence number (Vs) in control field before
                 *  inserting into transmit window queue.
                 */
                skb->data[1] = I_FRAME | (self->vs << 1);

                /*
                 *  Insert frame in store, in case of retransmissions
                 *  Increase skb reference count, see irlap_do_event()
                 */
                skb_get(skb);
                skb_queue_tail(&self->wx_list, skb);

                tx_skb = skb_clone(skb, GFP_ATOMIC);
                if (tx_skb == NULL) {
                        return;
                }

                tx_skb->data[1] |= PF_BIT;

                self->vs = (self->vs + 1) % 8;
                self->ack_required = FALSE;

                irlap_send_i_frame(self, tx_skb, RSP_FRAME);
        } else {
                if (self->ack_required) {
                        irlap_send_ui_frame(self, skb_get(skb), self->caddr, RSP_FRAME);
                        irlap_send_rr_frame(self, RSP_FRAME);
                        self->ack_required = FALSE;
                } else {
                        skb->data[1] |= PF_BIT;
                        irlap_send_ui_frame(self, skb_get(skb), self->caddr, RSP_FRAME);
                }
        }

        self->window = self->window_size;
#ifdef CONFIG_IRDA_DYNAMIC_WINDOW
        /* We are allowed to transmit a maximum number of bytes again. */
        self->bytes_left = self->line_capacity;
#endif /* CONFIG_IRDA_DYNAMIC_WINDOW */

        irlap_start_wd_timer(self, self->wd_timeout);
}

/*
 * Function irlap_send_data_secondary (self, skb)
 *
 *    Send I(nformation) frame as secondary without final bit set
 *
 */
void irlap_send_data_secondary(struct irlap_cb *self, struct sk_buff *skb)
{
        struct sk_buff *tx_skb = NULL;

        /* Is this reliable or unreliable data? */
        if (skb->data[1] == I_FRAME) {

                /*
                 *  Insert frame sequence number (Vs) in control field before
                 *  inserting into transmit window queue.
                 */
                skb->data[1] = I_FRAME | (self->vs << 1);

                /*
                 *  Insert frame in store, in case of retransmissions
                 *  Increase skb reference count, see irlap_do_event()
                 */
                skb_get(skb);
                skb_queue_tail(&self->wx_list, skb);

                tx_skb = skb_clone(skb, GFP_ATOMIC);
                if (tx_skb == NULL) {
                        return;
                }

                self->vs = (self->vs + 1) % 8;
                self->ack_required = FALSE;
                self->window -= 1;

                irlap_send_i_frame(self, tx_skb, RSP_FRAME);
        } else {
                irlap_send_ui_frame(self, skb_get(skb), self->caddr, RSP_FRAME);
                self->window -= 1;
        }
}

/*
 * Function irlap_resend_rejected_frames (nr)
 *
 *    Resend frames which has not been acknowledged. Should be safe to
 *    traverse the list without locking it since this function will only be
 *    called from interrupt context (BH)
 */
void irlap_resend_rejected_frames(struct irlap_cb *self, int command)
{
        struct sk_buff *tx_skb;
        struct sk_buff *skb;

        IRDA_ASSERT(self != NULL, return;);
        IRDA_ASSERT(self->magic == LAP_MAGIC, return;);

        /*  Resend unacknowledged frame(s) */
        skb_queue_walk(&self->wx_list, skb) {
                irlap_wait_min_turn_around(self, &self->qos_tx);

                /* We copy the skb to be retransmitted since we will have to
                 * modify it. Cloning will confuse packet sniffers
                 */
                /* tx_skb = skb_clone( skb, GFP_ATOMIC); */
                tx_skb = skb_copy(skb, GFP_ATOMIC);
                if (!tx_skb) {
                        pr_debug("%s(), unable to copy\n", __func__);
                        return;
                }

                /* Clear old Nr field + poll bit */
                tx_skb->data[1] &= 0x0f;

                /*
                 *  Set poll bit on the last frame retransmitted
                 */
                if (skb_queue_is_last(&self->wx_list, skb))

                        tx_skb->data[1] |= PF_BIT; /* Set p/f bit */
                else
                        tx_skb->data[1] &= ~PF_BIT; /* Clear p/f bit */

                irlap_send_i_frame(self, tx_skb, command);
        }
#if 0 /* Not yet */
        /*
         *  We can now fill the window with additional data frames
         */
        while (!skb_queue_empty(&self->txq)) {

                pr_debug("%s(), sending additional frames!\n", __func__);
                if (self->window > 0) {
                        skb = skb_dequeue( &self->txq);
                        IRDA_ASSERT(skb != NULL, return;);

                        /*
                         *  If send window > 1 then send frame with pf
                         *  bit cleared
                         */
                        if ((self->window > 1) &&
                            !skb_queue_empty(&self->txq)) {
                                irlap_send_data_primary(self, skb);
                        } else {
                                irlap_send_data_primary_poll(self, skb);
                        }
                        kfree_skb(skb);
                }
        }
#endif
}

void irlap_resend_rejected_frame(struct irlap_cb *self, int command)
{
        struct sk_buff *tx_skb;
        struct sk_buff *skb;

        IRDA_ASSERT(self != NULL, return;);
        IRDA_ASSERT(self->magic == LAP_MAGIC, return;);

        /*  Resend unacknowledged frame(s) */
        skb = skb_peek(&self->wx_list);
        if (skb != NULL) {
                irlap_wait_min_turn_around(self, &self->qos_tx);

                /* We copy the skb to be retransmitted since we will have to
                 * modify it. Cloning will confuse packet sniffers
                 */
                /* tx_skb = skb_clone( skb, GFP_ATOMIC); */
                tx_skb = skb_copy(skb, GFP_ATOMIC);
                if (!tx_skb) {
                        pr_debug("%s(), unable to copy\n", __func__);
                        return;
                }

                /* Clear old Nr field + poll bit */
                tx_skb->data[1] &= 0x0f;

                /*  Set poll/final bit */
                tx_skb->data[1] |= PF_BIT; /* Set p/f bit */

                irlap_send_i_frame(self, tx_skb, command);
        }
}

/*
 * Function irlap_send_ui_frame (self, skb, command)
 *
 *    Contruct and transmit an Unnumbered Information (UI) frame
 *
 */
void irlap_send_ui_frame(struct irlap_cb *self, struct sk_buff *skb,
                         __u8 caddr, int command)
{
        IRDA_ASSERT(self != NULL, return;);
        IRDA_ASSERT(self->magic == LAP_MAGIC, return;);
        IRDA_ASSERT(skb != NULL, return;);

        /* Insert connection address */
        skb->data[0] = caddr | ((command) ? CMD_FRAME : 0);

        irlap_queue_xmit(self, skb);
}

/*
 * Function irlap_send_i_frame (skb)
 *
 *    Contruct and transmit Information (I) frame
 */
static void irlap_send_i_frame(struct irlap_cb *self, struct sk_buff *skb,
                               int command)
{
        /* Insert connection address */
        skb->data[0] = self->caddr;
        skb->data[0] |= (command) ? CMD_FRAME : 0;

        /* Insert next to receive (Vr) */
        skb->data[1] |= (self->vr << 5);  /* insert nr */

        irlap_queue_xmit(self, skb);
}

/*
 * Function irlap_recv_i_frame (skb, frame)
 *
 *    Receive and parse an I (Information) frame, no harm in making it inline
 *    since it's called only from one single place (irlap_driver_rcv).
 */
static inline void irlap_recv_i_frame(struct irlap_cb *self,
                                      struct sk_buff *skb,
                                      struct irlap_info *info, int command)
{
        info->nr = skb->data[1] >> 5;          /* Next to receive */
        info->pf = skb->data[1] & PF_BIT;      /* Final bit */
        info->ns = (skb->data[1] >> 1) & 0x07; /* Next to send */

        /* Check if this is a command or a response frame */
        if (command)
                irlap_do_event(self, RECV_I_CMD, skb, info);
        else
                irlap_do_event(self, RECV_I_RSP, skb, info);
}

/*
 * Function irlap_recv_ui_frame (self, skb, info)
 *
 *    Receive and parse an Unnumbered Information (UI) frame
 *
 */
static void irlap_recv_ui_frame(struct irlap_cb *self, struct sk_buff *skb,
                                struct irlap_info *info)
{
        info->pf = skb->data[1] & PF_BIT;      /* Final bit */

        irlap_do_event(self, RECV_UI_FRAME, skb, info);
}

/*
 * Function irlap_recv_frmr_frame (skb, frame)
 *
 *    Received Frame Reject response.
 *
 */
static void irlap_recv_frmr_frame(struct irlap_cb *self, struct sk_buff *skb,
                                  struct irlap_info *info)
{
        __u8 *frame;
        int w, x, y, z;

        IRDA_ASSERT(self != NULL, return;);
        IRDA_ASSERT(self->magic == LAP_MAGIC, return;);
        IRDA_ASSERT(skb != NULL, return;);
        IRDA_ASSERT(info != NULL, return;);

        if (!pskb_may_pull(skb, 4)) {
                net_err_ratelimited("%s: frame too short!\n", __func__);
                return;
        }

        frame = skb->data;

        info->nr = frame[2] >> 5;          /* Next to receive */
        info->pf = frame[2] & PF_BIT;      /* Final bit */
        info->ns = (frame[2] >> 1) & 0x07; /* Next to send */

        w = frame[3] & 0x01;
        x = frame[3] & 0x02;
        y = frame[3] & 0x04;
        z = frame[3] & 0x08;

        if (w) {
                pr_debug("Rejected control field is undefined or not implemented\n");
        }
        if (x) {
                pr_debug("Rejected control field was invalid because it contained a non permitted I field\n");
        }
        if (y) {
                pr_debug("Received I field exceeded the maximum negotiated for the existing connection or exceeded the maximum this station supports if no connection exists\n");
        }
        if (z) {
                pr_debug("Rejected control field control field contained an invalid Nr count\n");
        }
        irlap_do_event(self, RECV_FRMR_RSP, skb, info);
}

/*
 * Function irlap_send_test_frame (self, daddr)
 *
 *    Send a test frame response
 *
 */
void irlap_send_test_frame(struct irlap_cb *self, __u8 caddr, __u32 daddr,
                           struct sk_buff *cmd)
{
        struct sk_buff *tx_skb;
        struct test_frame *frame;
        __u8 *info;

        tx_skb = alloc_skb(cmd->len + sizeof(struct test_frame), GFP_ATOMIC);
        if (!tx_skb)
                return;

        /* Broadcast frames must include saddr and daddr fields */
        if (caddr == CBROADCAST) {
                frame = (struct test_frame *)
                        skb_put(tx_skb, sizeof(struct test_frame));

                /* Insert the swapped addresses */
                frame->saddr = cpu_to_le32(self->saddr);
                frame->daddr = cpu_to_le32(daddr);
        } else
                frame = (struct test_frame *) skb_put(tx_skb, LAP_ADDR_HEADER + LAP_CTRL_HEADER);

        frame->caddr = caddr;
        frame->control = TEST_RSP | PF_BIT;

        /* Copy info */
        info = skb_put(tx_skb, cmd->len);
        memcpy(info, cmd->data, cmd->len);

        /* Return to sender */
        irlap_wait_min_turn_around(self, &self->qos_tx);
        irlap_queue_xmit(self, tx_skb);
}

/*
 * Function irlap_recv_test_frame (self, skb)
 *
 *    Receive a test frame
 *
 */
static void irlap_recv_test_frame(struct irlap_cb *self, struct sk_buff *skb,
                                  struct irlap_info *info, int command)
{
        struct test_frame *frame;

        if (!pskb_may_pull(skb, sizeof(*frame))) {
                net_err_ratelimited("%s: frame too short!\n", __func__);
                return;
        }
        frame = (struct test_frame *) skb->data;

        /* Broadcast frames must carry saddr and daddr fields */
        if (info->caddr == CBROADCAST) {
                if (skb->len < sizeof(struct test_frame)) {
                        pr_debug("%s() test frame too short!\n",
                                 __func__);
                        return;
                }

                /* Read and swap addresses */
                info->daddr = le32_to_cpu(frame->saddr);
                info->saddr = le32_to_cpu(frame->daddr);

                /* Make sure frame is addressed to us */
                if ((info->saddr != self->saddr) &&
                    (info->saddr != BROADCAST)) {
                        return;
                }
        }

        if (command)
                irlap_do_event(self, RECV_TEST_CMD, skb, info);
        else
                irlap_do_event(self, RECV_TEST_RSP, skb, info);
}

/*
 * Function irlap_driver_rcv (skb, netdev, ptype)
 *
 *    Called when a frame is received. Dispatches the right receive function
 *    for processing of the frame.
 *
 * Note on skb management :
 * After calling the higher layers of the IrDA stack, we always
 * kfree() the skb, which drop the reference count (and potentially
 * destroy it).
 * If a higher layer of the stack want to keep the skb around (to put
 * in a queue or pass it to the higher layer), it will need to use
 * skb_get() to keep a reference on it. This is usually done at the
 * LMP level in irlmp.c.
 * Jean II
 */
int irlap_driver_rcv(struct sk_buff *skb, struct net_device *dev,
                     struct packet_type *ptype, struct net_device *orig_dev)
{
        struct irlap_info info;
        struct irlap_cb *self;
        int command;
        __u8 control;
        int ret = -1;

        if (!net_eq(dev_net(dev), &init_net))
                goto out;

        /* FIXME: should we get our own field? */
        self = (struct irlap_cb *) dev->atalk_ptr;

        /* If the net device is down, then IrLAP is gone! */
        if (!self || self->magic != LAP_MAGIC)
                goto err;

        /* We are no longer an "old" protocol, so we need to handle
         * share and non linear skbs. This should never happen, so
         * we don't need to be clever about it. Jean II */
        if ((skb = skb_share_check(skb, GFP_ATOMIC)) == NULL) {
                net_err_ratelimited("%s: can't clone shared skb!\n", __func__);
                goto err;
        }

        /* Check if frame is large enough for parsing */
        if (!pskb_may_pull(skb, 2)) {
                net_err_ratelimited("%s: frame too short!\n", __func__);
                goto err;
        }

        command    = skb->data[0] & CMD_FRAME;
        info.caddr = skb->data[0] & CBROADCAST;

        info.pf      = skb->data[1] &  PF_BIT;
        info.control = skb->data[1] & ~PF_BIT; /* Mask away poll/final bit */

        control = info.control;

        /*  First we check if this frame has a valid connection address */
        if ((info.caddr != self->caddr) && (info.caddr != CBROADCAST)) {
                pr_debug("%s(), wrong connection address!\n",
                         __func__);
                goto out;
        }
        /*
         *  Optimize for the common case and check if the frame is an
         *  I(nformation) frame. Only I-frames have bit 0 set to 0
         */
        if (~control & 0x01) {
                irlap_recv_i_frame(self, skb, &info, command);
                goto out;
        }
        /*
         *  We now check is the frame is an S(upervisory) frame. Only
         *  S-frames have bit 0 set to 1 and bit 1 set to 0
         */
        if (~control & 0x02) {
                /*
                 *  Received S(upervisory) frame, check which frame type it is
                 *  only the first nibble is of interest
                 */
                switch (control & 0x0f) {
                case RR:
                        irlap_recv_rr_frame(self, skb, &info, command);
                        break;
                case RNR:
                        irlap_recv_rnr_frame(self, skb, &info, command);
                        break;
                case REJ:
                        irlap_recv_rej_frame(self, skb, &info, command);
                        break;
                case SREJ:
                        irlap_recv_srej_frame(self, skb, &info, command);
                        break;
                default:
                        net_warn_ratelimited("%s: Unknown S-frame %02x received!\n",
                                             __func__, info.control);
                        break;
                }
                goto out;
        }
        /*
         *  This must be a C(ontrol) frame
         */
        switch (control) {
        case XID_RSP:
                irlap_recv_discovery_xid_rsp(self, skb, &info);
                break;
        case XID_CMD:
                irlap_recv_discovery_xid_cmd(self, skb, &info);
                break;
        case SNRM_CMD:
                irlap_recv_snrm_cmd(self, skb, &info);
                break;
        case DM_RSP:
                irlap_do_event(self, RECV_DM_RSP, skb, &info);
                break;
        case DISC_CMD: /* And RD_RSP since they have the same value */
                irlap_recv_disc_frame(self, skb, &info, command);
                break;
        case TEST_CMD:
                irlap_recv_test_frame(self, skb, &info, command);
                break;
        case UA_RSP:
                irlap_recv_ua_frame(self, skb, &info);
                break;
        case FRMR_RSP:
                irlap_recv_frmr_frame(self, skb, &info);
                break;
        case UI_FRAME:
                irlap_recv_ui_frame(self, skb, &info);
                break;
        default:
                net_warn_ratelimited("%s: Unknown frame %02x received!\n",
                                     __func__, info.control);
                break;
        }
out:
        ret = 0;
err:
        /* Always drop our reference on the skb */
        dev_kfree_skb(skb);
        return ret;
}