// SPDX-License-Identifier: GPL-2.0-or-later

  /*

   *
   * Copyright (C) Alan Cox GW4PTS (alan@lxorguk.ukuu.org.uk)
   * Copyright (C) Jonathan Naylor G4KLX (g4klx@g4klx.demon.co.uk)
   * Copyright (C) Joerg Reuter DL1BKE (jreuter@yaina.de)
   */

  #include <linux/errno.h>
  #include <linux/types.h>
  #include <linux/socket.h>
  #include <linux/in.h>
  #include <linux/kernel.h>

  #include <linux/module.h>

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

  #include <linux/slab.h>

  #include <net/ax25.h>
  #include <linux/inet.h>
  #include <linux/netdevice.h>
  #include <linux/skbuff.h>

  #include <net/sock.h>

  #include <linux/uaccess.h>

  #include <linux/fcntl.h>
  #include <linux/mm.h>
  #include <linux/interrupt.h>
  
  static DEFINE_SPINLOCK(ax25_frag_lock);
  
  ax25_cb *ax25_send_frame(struct sk_buff *skb, int paclen, ax25_address *src, ax25_address *dest, ax25_digi *digi, struct net_device *dev)
  {
  	ax25_dev *ax25_dev;
  	ax25_cb *ax25;
  
  	/*
  	 * Take the default packet length for the device if zero is
  	 * specified.
  	 */
  	if (paclen == 0) {
  		if ((ax25_dev = ax25_dev_ax25dev(dev)) == NULL)
  			return NULL;
  
  		paclen = ax25_dev->values[AX25_VALUES_PACLEN];
  	}
  
  	/*
  	 * Look for an existing connection.
  	 */
  	if ((ax25 = ax25_find_cb(src, dest, digi, dev)) != NULL) {
  		ax25_output(ax25, paclen, skb);
  		return ax25;		/* It already existed */
  	}
  
  	if ((ax25_dev = ax25_dev_ax25dev(dev)) == NULL)
  		return NULL;
  
  	if ((ax25 = ax25_create_cb()) == NULL)
  		return NULL;
  
  	ax25_fillin_cb(ax25, ax25_dev);
  
  	ax25->source_addr = *src;
  	ax25->dest_addr   = *dest;
  
  	if (digi != NULL) {

  		ax25->digipeat = kmemdup(digi, sizeof(*digi), GFP_ATOMIC);
  		if (ax25->digipeat == NULL) {

  			ax25_cb_put(ax25);
  			return NULL;
  		}

  	}
  
  	switch (ax25->ax25_dev->values[AX25_VALUES_PROTOCOL]) {
  	case AX25_PROTO_STD_SIMPLEX:
  	case AX25_PROTO_STD_DUPLEX:
  		ax25_std_establish_data_link(ax25);
  		break;
  
  #ifdef CONFIG_AX25_DAMA_SLAVE
  	case AX25_PROTO_DAMA_SLAVE:
  		if (ax25_dev->dama.slave)
  			ax25_ds_establish_data_link(ax25);
  		else
  			ax25_std_establish_data_link(ax25);
  		break;
  #endif
  	}

  	/*
  	 * There is one ref for the state machine; a caller needs
  	 * one more to put it back, just like with the existing one.
  	 */
  	ax25_cb_hold(ax25);

  	ax25_cb_add(ax25);
  
  	ax25->state = AX25_STATE_1;
  
  	ax25_start_heartbeat(ax25);
  
  	ax25_output(ax25, paclen, skb);
  
  	return ax25;			/* We had to create it */
  }

  EXPORT_SYMBOL(ax25_send_frame);

  /*
   *	All outgoing AX.25 I frames pass via this routine. Therefore this is
   *	where the fragmentation of frames takes place. If fragment is set to
   *	zero then we are not allowed to do fragmentation, even if the frame
   *	is too large.
   */
  void ax25_output(ax25_cb *ax25, int paclen, struct sk_buff *skb)
  {
  	struct sk_buff *skbn;
  	unsigned char *p;
  	int frontlen, len, fragno, ka9qfrag, first = 1;

  	if (paclen < 16) {
  		WARN_ON_ONCE(1);
  		kfree_skb(skb);
  		return;
  	}

  	if ((skb->len - 1) > paclen) {
  		if (*skb->data == AX25_P_TEXT) {
  			skb_pull(skb, 1); /* skip PID */
  			ka9qfrag = 0;
  		} else {
  			paclen -= 2;	/* Allow for fragment control info */
  			ka9qfrag = 1;
  		}
  
  		fragno = skb->len / paclen;
  		if (skb->len % paclen == 0) fragno--;
  
  		frontlen = skb_headroom(skb);	/* Address space + CTRL */
  
  		while (skb->len > 0) {
  			spin_lock_bh(&ax25_frag_lock);
  			if ((skbn = alloc_skb(paclen + 2 + frontlen, GFP_ATOMIC)) == NULL) {
  				spin_unlock_bh(&ax25_frag_lock);
  				printk(KERN_CRIT "AX.25: ax25_output - out of memory
  ");
  				return;
  			}
  
  			if (skb->sk != NULL)
  				skb_set_owner_w(skbn, skb->sk);
  
  			spin_unlock_bh(&ax25_frag_lock);
  
  			len = (paclen > skb->len) ? skb->len : paclen;
  
  			if (ka9qfrag == 1) {
  				skb_reserve(skbn, frontlen + 2);

  				skb_set_network_header(skbn,
  						      skb_network_offset(skb));

  				skb_copy_from_linear_data(skb, skb_put(skbn, len), len);

  				p = skb_push(skbn, 2);
  
  				*p++ = AX25_P_SEGMENT;
  
  				*p = fragno--;
  				if (first) {
  					*p |= AX25_SEG_FIRST;
  					first = 0;
  				}
  			} else {
  				skb_reserve(skbn, frontlen + 1);

  				skb_set_network_header(skbn,
  						      skb_network_offset(skb));

  				skb_copy_from_linear_data(skb, skb_put(skbn, len), len);

  				p = skb_push(skbn, 1);
  				*p = AX25_P_TEXT;
  			}
  
  			skb_pull(skb, len);
  			skb_queue_tail(&ax25->write_queue, skbn); /* Throw it on the queue */
  		}
  
  		kfree_skb(skb);
  	} else {
  		skb_queue_tail(&ax25->write_queue, skb);	  /* Throw it on the queue */
  	}
  
  	switch (ax25->ax25_dev->values[AX25_VALUES_PROTOCOL]) {
  	case AX25_PROTO_STD_SIMPLEX:
  	case AX25_PROTO_STD_DUPLEX:
  		ax25_kick(ax25);
  		break;
  
  #ifdef CONFIG_AX25_DAMA_SLAVE
  	/*
  	 * A DAMA slave is _required_ to work as normal AX.25L2V2
  	 * if no DAMA master is available.
  	 */
  	case AX25_PROTO_DAMA_SLAVE:
  		if (!ax25->ax25_dev->dama.slave) ax25_kick(ax25);
  		break;
  #endif
  	}
  }
  
  /*
   *  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 ax25_send_iframe(ax25_cb *ax25, struct sk_buff *skb, int poll_bit)
  {
  	unsigned char *frame;
  
  	if (skb == NULL)
  		return;

  	skb_reset_network_header(skb);

  
  	if (ax25->modulus == AX25_MODULUS) {
  		frame = skb_push(skb, 1);
  
  		*frame = AX25_I;
  		*frame |= (poll_bit) ? AX25_PF : 0;
  		*frame |= (ax25->vr << 5);
  		*frame |= (ax25->vs << 1);
  	} else {
  		frame = skb_push(skb, 2);
  
  		frame[0] = AX25_I;
  		frame[0] |= (ax25->vs << 1);
  		frame[1] = (poll_bit) ? AX25_EPF : 0;
  		frame[1] |= (ax25->vr << 1);
  	}
  
  	ax25_start_idletimer(ax25);
  
  	ax25_transmit_buffer(ax25, skb, AX25_COMMAND);
  }
  
  void ax25_kick(ax25_cb *ax25)
  {
  	struct sk_buff *skb, *skbn;
  	int last = 1;
  	unsigned short start, end, next;
  
  	if (ax25->state != AX25_STATE_3 && ax25->state != AX25_STATE_4)
  		return;
  
  	if (ax25->condition & AX25_COND_PEER_RX_BUSY)
  		return;
  
  	if (skb_peek(&ax25->write_queue) == NULL)
  		return;
  
  	start = (skb_peek(&ax25->ack_queue) == NULL) ? ax25->va : ax25->vs;
  	end   = (ax25->va + ax25->window) % ax25->modulus;
  
  	if (start == end)
  		return;

  	/*
  	 * Transmit data until either we're out of data to send or
  	 * the window is full. Send a poll on the final I frame if
  	 * the window is filled.
  	 */
  
  	/*
  	 * Dequeue the frame and copy it.

  	 * Check for race with ax25_clear_queues().

  	 */
  	skb  = skb_dequeue(&ax25->write_queue);

  	if (!skb)
  		return;
  
  	ax25->vs = start;

  
  	do {
  		if ((skbn = skb_clone(skb, GFP_ATOMIC)) == NULL) {
  			skb_queue_head(&ax25->write_queue, skb);
  			break;
  		}
  
  		if (skb->sk != NULL)
  			skb_set_owner_w(skbn, skb->sk);
  
  		next = (ax25->vs + 1) % ax25->modulus;
  		last = (next == end);
  
  		/*
  		 * Transmit the frame copy.
  		 * bke 960114: do not set the Poll bit on the last frame
  		 * in DAMA mode.
  		 */
  		switch (ax25->ax25_dev->values[AX25_VALUES_PROTOCOL]) {
  		case AX25_PROTO_STD_SIMPLEX:
  		case AX25_PROTO_STD_DUPLEX:
  			ax25_send_iframe(ax25, skbn, (last) ? AX25_POLLON : AX25_POLLOFF);
  			break;
  
  #ifdef CONFIG_AX25_DAMA_SLAVE
  		case AX25_PROTO_DAMA_SLAVE:
  			ax25_send_iframe(ax25, skbn, AX25_POLLOFF);
  			break;
  #endif
  		}
  
  		ax25->vs = next;
  
  		/*
  		 * Requeue the original data frame.
  		 */
  		skb_queue_tail(&ax25->ack_queue, skb);
  
  	} while (!last && (skb = skb_dequeue(&ax25->write_queue)) != NULL);
  
  	ax25->condition &= ~AX25_COND_ACK_PENDING;
  
  	if (!ax25_t1timer_running(ax25)) {
  		ax25_stop_t3timer(ax25);
  		ax25_calculate_t1(ax25);
  		ax25_start_t1timer(ax25);
  	}
  }
  
  void ax25_transmit_buffer(ax25_cb *ax25, struct sk_buff *skb, int type)
  {
  	struct sk_buff *skbn;
  	unsigned char *ptr;
  	int headroom;
  
  	if (ax25->ax25_dev == NULL) {
  		ax25_disconnect(ax25, ENETUNREACH);
  		return;
  	}
  
  	headroom = ax25_addr_size(ax25->digipeat);
  
  	if (skb_headroom(skb) < headroom) {
  		if ((skbn = skb_realloc_headroom(skb, headroom)) == NULL) {
  			printk(KERN_CRIT "AX.25: ax25_transmit_buffer - out of memory
  ");
  			kfree_skb(skb);
  			return;
  		}
  
  		if (skb->sk != NULL)
  			skb_set_owner_w(skbn, skb->sk);

  		consume_skb(skb);

  		skb = skbn;
  	}
  
  	ptr = skb_push(skb, headroom);
  
  	ax25_addr_build(ptr, &ax25->source_addr, &ax25->dest_addr, ax25->digipeat, type, ax25->modulus);

  	ax25_queue_xmit(skb, ax25->ax25_dev->dev);

  }
  
  /*
   *	A small shim to dev_queue_xmit to add the KISS control byte, and do
   *	any packet forwarding in operation.
   */

  void ax25_queue_xmit(struct sk_buff *skb, struct net_device *dev)

  {
  	unsigned char *ptr;

  	skb->protocol = ax25_type_trans(skb, ax25_fwd_dev(dev));

  
  	ptr  = skb_push(skb, 1);
  	*ptr = 0x00;			/* KISS */
  
  	dev_queue_xmit(skb);
  }
  
  int ax25_check_iframes_acked(ax25_cb *ax25, unsigned short nr)
  {
  	if (ax25->vs == nr) {
  		ax25_frames_acked(ax25, nr);
  		ax25_calculate_rtt(ax25);
  		ax25_stop_t1timer(ax25);
  		ax25_start_t3timer(ax25);
  		return 1;
  	} else {
  		if (ax25->va != nr) {
  			ax25_frames_acked(ax25, nr);
  			ax25_calculate_t1(ax25);
  			ax25_start_t1timer(ax25);
  			return 1;
  		}
  	}
  	return 0;
  }