/*
   *	LAPB release 002
   *
   *	This code REQUIRES 2.1.15 or higher/ NET3.038
   *
   *	This module:
   *		This module 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.
   *
   *	History
   *	LAPB 001	Jonathan Naylor	Started Coding
   *	LAPB 002	Jonathan Naylor	New timer architecture.
   */
  
  #include <linux/errno.h>
  #include <linux/types.h>
  #include <linux/socket.h>
  #include <linux/in.h>
  #include <linux/kernel.h>

  #include <linux/timer.h>
  #include <linux/string.h>
  #include <linux/sockios.h>
  #include <linux/net.h>
  #include <linux/inet.h>
  #include <linux/skbuff.h>

  #include <linux/slab.h>

  #include <net/sock.h>
  #include <asm/uaccess.h>
  #include <asm/system.h>
  #include <linux/fcntl.h>
  #include <linux/mm.h>
  #include <linux/interrupt.h>
  #include <net/lapb.h>

  /*

   *  This procedure is passed a buffer descriptor for an iframe. It builds
   *  the rest of the control part of the frame and then writes it out.
   */
  static void lapb_send_iframe(struct lapb_cb *lapb, struct sk_buff *skb, int poll_bit)
  {
  	unsigned char *frame;
  
  	if (!skb)
  		return;
  
  	if (lapb->mode & LAPB_EXTENDED) {
  		frame = skb_push(skb, 2);
  
  		frame[0] = LAPB_I;
  		frame[0] |= lapb->vs << 1;
  		frame[1] = poll_bit ? LAPB_EPF : 0;
  		frame[1] |= lapb->vr << 1;
  	} else {
  		frame = skb_push(skb, 1);
  
  		*frame = LAPB_I;
  		*frame |= poll_bit ? LAPB_SPF : 0;
  		*frame |= lapb->vr << 5;
  		*frame |= lapb->vs << 1;
  	}
  
  #if LAPB_DEBUG > 1
  	printk(KERN_DEBUG "lapb: (%p) S%d TX I(%d) S%d R%d
  ",
  	       lapb->dev, lapb->state, poll_bit, lapb->vs, lapb->vr);
  #endif

  	lapb_transmit_buffer(lapb, skb, LAPB_COMMAND);

  }
  
  void lapb_kick(struct lapb_cb *lapb)
  {
  	struct sk_buff *skb, *skbn;
  	unsigned short modulus, start, end;
  
  	modulus = (lapb->mode & LAPB_EXTENDED) ? LAPB_EMODULUS : LAPB_SMODULUS;
  	start = !skb_peek(&lapb->ack_queue) ? lapb->va : lapb->vs;
  	end   = (lapb->va + lapb->window) % modulus;
  
  	if (!(lapb->condition & LAPB_PEER_RX_BUSY_CONDITION) &&
  	    start != end && skb_peek(&lapb->write_queue)) {
  		lapb->vs = start;
  
  		/*
  		 * Dequeue the frame and copy it.
  		 */
  		skb = skb_dequeue(&lapb->write_queue);
  
  		do {
  			if ((skbn = skb_clone(skb, GFP_ATOMIC)) == NULL) {
  				skb_queue_head(&lapb->write_queue, skb);
  				break;
  			}
  
  			if (skb->sk)
  				skb_set_owner_w(skbn, skb->sk);
  
  			/*
  			 * Transmit the frame copy.
  			 */
  			lapb_send_iframe(lapb, skbn, LAPB_POLLOFF);
  
  			lapb->vs = (lapb->vs + 1) % modulus;
  
  			/*
  			 * Requeue the original data frame.
  			 */
  			skb_queue_tail(&lapb->ack_queue, skb);
  
  		} while (lapb->vs != end && (skb = skb_dequeue(&lapb->write_queue)) != NULL);
  
  		lapb->condition &= ~LAPB_ACK_PENDING_CONDITION;
  
  		if (!lapb_t1timer_running(lapb))
  			lapb_start_t1timer(lapb);
  	}
  }
  
  void lapb_transmit_buffer(struct lapb_cb *lapb, struct sk_buff *skb, int type)
  {
  	unsigned char *ptr;
  
  	ptr = skb_push(skb, 1);
  
  	if (lapb->mode & LAPB_MLP) {
  		if (lapb->mode & LAPB_DCE) {
  			if (type == LAPB_COMMAND)
  				*ptr = LAPB_ADDR_C;
  			if (type == LAPB_RESPONSE)
  				*ptr = LAPB_ADDR_D;
  		} else {
  			if (type == LAPB_COMMAND)
  				*ptr = LAPB_ADDR_D;
  			if (type == LAPB_RESPONSE)
  				*ptr = LAPB_ADDR_C;
  		}
  	} else {
  		if (lapb->mode & LAPB_DCE) {
  			if (type == LAPB_COMMAND)
  				*ptr = LAPB_ADDR_A;
  			if (type == LAPB_RESPONSE)
  				*ptr = LAPB_ADDR_B;
  		} else {
  			if (type == LAPB_COMMAND)
  				*ptr = LAPB_ADDR_B;
  			if (type == LAPB_RESPONSE)
  				*ptr = LAPB_ADDR_A;
  		}
  	}
  
  #if LAPB_DEBUG > 2
  	printk(KERN_DEBUG "lapb: (%p) S%d TX %02X %02X %02X
  ",
  	       lapb->dev, lapb->state,
  	       skb->data[0], skb->data[1], skb->data[2]);
  #endif
  
  	if (!lapb_data_transmit(lapb, skb))
  		kfree_skb(skb);
  }
  
  void lapb_establish_data_link(struct lapb_cb *lapb)
  {
  	lapb->condition = 0x00;
  	lapb->n2count   = 0;
  
  	if (lapb->mode & LAPB_EXTENDED) {
  #if LAPB_DEBUG > 1
  		printk(KERN_DEBUG "lapb: (%p) S%d TX SABME(1)
  ",
  		       lapb->dev, lapb->state);
  #endif
  		lapb_send_control(lapb, LAPB_SABME, LAPB_POLLON, LAPB_COMMAND);
  	} else {
  #if LAPB_DEBUG > 1
  		printk(KERN_DEBUG "lapb: (%p) S%d TX SABM(1)
  ",
  		       lapb->dev, lapb->state);
  #endif
  		lapb_send_control(lapb, LAPB_SABM, LAPB_POLLON, LAPB_COMMAND);
  	}
  
  	lapb_start_t1timer(lapb);
  	lapb_stop_t2timer(lapb);
  }
  
  void lapb_enquiry_response(struct lapb_cb *lapb)
  {
  #if LAPB_DEBUG > 1
  	printk(KERN_DEBUG "lapb: (%p) S%d TX RR(1) R%d
  ",
  	       lapb->dev, lapb->state, lapb->vr);
  #endif
  
  	lapb_send_control(lapb, LAPB_RR, LAPB_POLLON, LAPB_RESPONSE);
  
  	lapb->condition &= ~LAPB_ACK_PENDING_CONDITION;
  }
  
  void lapb_timeout_response(struct lapb_cb *lapb)
  {
  #if LAPB_DEBUG > 1
  	printk(KERN_DEBUG "lapb: (%p) S%d TX RR(0) R%d
  ",
  	       lapb->dev, lapb->state, lapb->vr);
  #endif
  	lapb_send_control(lapb, LAPB_RR, LAPB_POLLOFF, LAPB_RESPONSE);
  
  	lapb->condition &= ~LAPB_ACK_PENDING_CONDITION;
  }
  
  void lapb_check_iframes_acked(struct lapb_cb *lapb, unsigned short nr)
  {
  	if (lapb->vs == nr) {
  		lapb_frames_acked(lapb, nr);
  		lapb_stop_t1timer(lapb);
  		lapb->n2count = 0;
  	} else if (lapb->va != nr) {
  		lapb_frames_acked(lapb, nr);
  		lapb_start_t1timer(lapb);
  	}
  }
  
  void lapb_check_need_response(struct lapb_cb *lapb, int type, int pf)
  {
  	if (type == LAPB_COMMAND && pf)
  		lapb_enquiry_response(lapb);
  }