/*
   *	X.25 Packet Layer release 002
   *
   *	This is ALPHA test software. This code may break your machine,
   *	randomly fail to work with new releases, misbehave and/or generally
   *	screw up. It might even work.
   *
   *	This code REQUIRES 2.1.15 or higher
   *
   *	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
   *	X.25 001	Jonathan Naylor	  Started coding.
   *	X.25 002	Jonathan Naylor	  Centralised disconnection processing.
   *	mar/20/00	Daniela Squassoni Disabling/enabling of facilities
   *					  negotiation.
   *	jun/24/01	Arnaldo C. Melo	  use skb_queue_purge, cleanups
   *	apr/04/15	Shaun Pereira		Fast select with no
   *						restriction on response.
   */
  
  #define pr_fmt(fmt) "X25: " fmt
  
  #include <linux/slab.h>
  #include <linux/kernel.h>
  #include <linux/string.h>
  #include <linux/skbuff.h>
  #include <net/sock.h>
  #include <net/tcp_states.h>
  #include <net/x25.h>
  
  /*
   *	This routine purges all of the queues of frames.
   */
  void x25_clear_queues(struct sock *sk)
  {
  	struct x25_sock *x25 = x25_sk(sk);
  
  	skb_queue_purge(&sk->sk_write_queue);
  	skb_queue_purge(&x25->ack_queue);
  	skb_queue_purge(&x25->interrupt_in_queue);
  	skb_queue_purge(&x25->interrupt_out_queue);
  	skb_queue_purge(&x25->fragment_queue);
  }
  
  
  /*
   * This routine purges the input queue of those frames that have been
   * acknowledged. This replaces the boxes labelled "V(a) <- N(r)" on the
   * SDL diagram.
  */
  void x25_frames_acked(struct sock *sk, unsigned short nr)
  {
  	struct sk_buff *skb;
  	struct x25_sock *x25 = x25_sk(sk);
  	int modulus = x25->neighbour->extended ? X25_EMODULUS : X25_SMODULUS;
  
  	/*
  	 * Remove all the ack-ed frames from the ack queue.
  	 */
  	if (x25->va != nr)
  		while (skb_peek(&x25->ack_queue) && x25->va != nr) {
  			skb = skb_dequeue(&x25->ack_queue);
  			kfree_skb(skb);
  			x25->va = (x25->va + 1) % modulus;
  		}
  }
  
  void x25_requeue_frames(struct sock *sk)
  {
  	struct sk_buff *skb, *skb_prev = NULL;
  
  	/*
  	 * Requeue all the un-ack-ed frames on the output queue to be picked
  	 * up by x25_kick. This arrangement handles the possibility of an empty
  	 * output queue.
  	 */
  	while ((skb = skb_dequeue(&x25_sk(sk)->ack_queue)) != NULL) {
  		if (!skb_prev)
  			skb_queue_head(&sk->sk_write_queue, skb);
  		else
  			skb_append(skb_prev, skb, &sk->sk_write_queue);
  		skb_prev = skb;
  	}
  }
  
  /*
   *	Validate that the value of nr is between va and vs. Return true or
   *	false for testing.
   */
  int x25_validate_nr(struct sock *sk, unsigned short nr)
  {
  	struct x25_sock *x25 = x25_sk(sk);
  	unsigned short vc = x25->va;
  	int modulus = x25->neighbour->extended ? X25_EMODULUS : X25_SMODULUS;
  
  	while (vc != x25->vs) {
  		if (nr == vc)
  			return 1;
  		vc = (vc + 1) % modulus;
  	}
  
  	return nr == x25->vs ? 1 : 0;
  }
  
  /*
   *  This routine is called when the packet layer internally generates a
   *  control frame.
   */
  void x25_write_internal(struct sock *sk, int frametype)
  {
  	struct x25_sock *x25 = x25_sk(sk);
  	struct sk_buff *skb;
  	unsigned char  *dptr;
  	unsigned char  facilities[X25_MAX_FAC_LEN];
  	unsigned char  addresses[1 + X25_ADDR_LEN];
  	unsigned char  lci1, lci2;
  	/*
  	 *	Default safe frame size.
  	 */
  	int len = X25_MAX_L2_LEN + X25_EXT_MIN_LEN;
  
  	/*
  	 *	Adjust frame size.
  	 */
  	switch (frametype) {
  	case X25_CALL_REQUEST:
  		len += 1 + X25_ADDR_LEN + X25_MAX_FAC_LEN + X25_MAX_CUD_LEN;
  		break;
  	case X25_CALL_ACCEPTED: /* fast sel with no restr on resp */
  		if (x25->facilities.reverse & 0x80) {
  			len += 1 + X25_MAX_FAC_LEN + X25_MAX_CUD_LEN;
  		} else {
  			len += 1 + X25_MAX_FAC_LEN;
  		}
  		break;
  	case X25_CLEAR_REQUEST:
  	case X25_RESET_REQUEST:
  		len += 2;
  		break;
  	case X25_RR:
  	case X25_RNR:
  	case X25_REJ:
  	case X25_CLEAR_CONFIRMATION:
  	case X25_INTERRUPT_CONFIRMATION:
  	case X25_RESET_CONFIRMATION:
  		break;
  	default:
  		pr_err("invalid frame type %02X
  ", frametype);
  		return;
  	}
  
  	if ((skb = alloc_skb(len, GFP_ATOMIC)) == NULL)
  		return;
  
  	/*
  	 *	Space for Ethernet and 802.2 LLC headers.
  	 */
  	skb_reserve(skb, X25_MAX_L2_LEN);
  
  	/*
  	 *	Make space for the GFI and LCI, and fill them in.
  	 */
  	dptr = skb_put(skb, 2);
  
  	lci1 = (x25->lci >> 8) & 0x0F;
  	lci2 = (x25->lci >> 0) & 0xFF;
  
  	if (x25->neighbour->extended) {
  		*dptr++ = lci1 | X25_GFI_EXTSEQ;
  		*dptr++ = lci2;
  	} else {
  		*dptr++ = lci1 | X25_GFI_STDSEQ;
  		*dptr++ = lci2;
  	}
  
  	/*
  	 *	Now fill in the frame type specific information.
  	 */
  	switch (frametype) {
  
  		case X25_CALL_REQUEST:
  			dptr    = skb_put(skb, 1);
  			*dptr++ = X25_CALL_REQUEST;
  			len     = x25_addr_aton(addresses, &x25->dest_addr,
  						&x25->source_addr);
  			dptr    = skb_put(skb, len);
  			memcpy(dptr, addresses, len);
  			len     = x25_create_facilities(facilities,
  					&x25->facilities,
  					&x25->dte_facilities,
  					x25->neighbour->global_facil_mask);
  			dptr    = skb_put(skb, len);
  			memcpy(dptr, facilities, len);
  			dptr = skb_put(skb, x25->calluserdata.cudlength);
  			memcpy(dptr, x25->calluserdata.cuddata,
  			       x25->calluserdata.cudlength);
  			x25->calluserdata.cudlength = 0;
  			break;
  
  		case X25_CALL_ACCEPTED:
  			dptr    = skb_put(skb, 2);
  			*dptr++ = X25_CALL_ACCEPTED;
  			*dptr++ = 0x00;		/* Address lengths */
  			len     = x25_create_facilities(facilities,
  							&x25->facilities,
  							&x25->dte_facilities,
  							x25->vc_facil_mask);
  			dptr    = skb_put(skb, len);
  			memcpy(dptr, facilities, len);
  
  			/* fast select with no restriction on response
  				allows call user data. Userland must
  				ensure it is ours and not theirs */
  			if(x25->facilities.reverse & 0x80) {
  				dptr = skb_put(skb,
  					x25->calluserdata.cudlength);
  				memcpy(dptr, x25->calluserdata.cuddata,
  				       x25->calluserdata.cudlength);
  			}
  			x25->calluserdata.cudlength = 0;
  			break;
  
  		case X25_CLEAR_REQUEST:
  			dptr    = skb_put(skb, 3);
  			*dptr++ = frametype;
  			*dptr++ = x25->causediag.cause;
  			*dptr++ = x25->causediag.diagnostic;
  			break;
  
  		case X25_RESET_REQUEST:
  			dptr    = skb_put(skb, 3);
  			*dptr++ = frametype;
  			*dptr++ = 0x00;		/* XXX */
  			*dptr++ = 0x00;		/* XXX */
  			break;
  
  		case X25_RR:
  		case X25_RNR:
  		case X25_REJ:
  			if (x25->neighbour->extended) {
  				dptr     = skb_put(skb, 2);
  				*dptr++  = frametype;
  				*dptr++  = (x25->vr << 1) & 0xFE;
  			} else {
  				dptr     = skb_put(skb, 1);
  				*dptr    = frametype;
  				*dptr++ |= (x25->vr << 5) & 0xE0;
  			}
  			break;
  
  		case X25_CLEAR_CONFIRMATION:
  		case X25_INTERRUPT_CONFIRMATION:
  		case X25_RESET_CONFIRMATION:
  			dptr  = skb_put(skb, 1);
  			*dptr = frametype;
  			break;
  	}
  
  	x25_transmit_link(skb, x25->neighbour);
  }
  
  /*
   *	Unpick the contents of the passed X.25 Packet Layer frame.
   */
  int x25_decode(struct sock *sk, struct sk_buff *skb, int *ns, int *nr, int *q,
  	       int *d, int *m)
  {
  	struct x25_sock *x25 = x25_sk(sk);
  	unsigned char *frame;
  
  	if (!pskb_may_pull(skb, X25_STD_MIN_LEN))
  		return X25_ILLEGAL;
  	frame = skb->data;
  
  	*ns = *nr = *q = *d = *m = 0;
  
  	switch (frame[2]) {
  	case X25_CALL_REQUEST:
  	case X25_CALL_ACCEPTED:
  	case X25_CLEAR_REQUEST:
  	case X25_CLEAR_CONFIRMATION:
  	case X25_INTERRUPT:
  	case X25_INTERRUPT_CONFIRMATION:
  	case X25_RESET_REQUEST:
  	case X25_RESET_CONFIRMATION:
  	case X25_RESTART_REQUEST:
  	case X25_RESTART_CONFIRMATION:
  	case X25_REGISTRATION_REQUEST:
  	case X25_REGISTRATION_CONFIRMATION:
  	case X25_DIAGNOSTIC:
  		return frame[2];
  	}
  
  	if (x25->neighbour->extended) {
  		if (frame[2] == X25_RR  ||
  		    frame[2] == X25_RNR ||
  		    frame[2] == X25_REJ) {
  			if (!pskb_may_pull(skb, X25_EXT_MIN_LEN))
  				return X25_ILLEGAL;
  			frame = skb->data;
  
  			*nr = (frame[3] >> 1) & 0x7F;
  			return frame[2];
  		}
  	} else {
  		if ((frame[2] & 0x1F) == X25_RR  ||
  		    (frame[2] & 0x1F) == X25_RNR ||
  		    (frame[2] & 0x1F) == X25_REJ) {
  			*nr = (frame[2] >> 5) & 0x07;
  			return frame[2] & 0x1F;
  		}
  	}
  
  	if (x25->neighbour->extended) {
  		if ((frame[2] & 0x01) == X25_DATA) {
  			if (!pskb_may_pull(skb, X25_EXT_MIN_LEN))
  				return X25_ILLEGAL;
  			frame = skb->data;
  
  			*q  = (frame[0] & X25_Q_BIT) == X25_Q_BIT;
  			*d  = (frame[0] & X25_D_BIT) == X25_D_BIT;
  			*m  = (frame[3] & X25_EXT_M_BIT) == X25_EXT_M_BIT;
  			*nr = (frame[3] >> 1) & 0x7F;
  			*ns = (frame[2] >> 1) & 0x7F;
  			return X25_DATA;
  		}
  	} else {
  		if ((frame[2] & 0x01) == X25_DATA) {
  			*q  = (frame[0] & X25_Q_BIT) == X25_Q_BIT;
  			*d  = (frame[0] & X25_D_BIT) == X25_D_BIT;
  			*m  = (frame[2] & X25_STD_M_BIT) == X25_STD_M_BIT;
  			*nr = (frame[2] >> 5) & 0x07;
  			*ns = (frame[2] >> 1) & 0x07;
  			return X25_DATA;
  		}
  	}
  
  	pr_debug("invalid PLP frame %02X %02X %02X
  ",
  	       frame[0], frame[1], frame[2]);
  
  	return X25_ILLEGAL;
  }
  
  void x25_disconnect(struct sock *sk, int reason, unsigned char cause,
  		    unsigned char diagnostic)
  {
  	struct x25_sock *x25 = x25_sk(sk);
  
  	x25_clear_queues(sk);
  	x25_stop_timer(sk);
  
  	x25->lci   = 0;
  	x25->state = X25_STATE_0;
  
  	x25->causediag.cause      = cause;
  	x25->causediag.diagnostic = diagnostic;
  
  	sk->sk_state     = TCP_CLOSE;
  	sk->sk_err       = reason;
  	sk->sk_shutdown |= SEND_SHUTDOWN;
  
  	if (!sock_flag(sk, SOCK_DEAD)) {
  		sk->sk_state_change(sk);
  		sock_set_flag(sk, SOCK_DEAD);
  	}
  }
  
  /*
   * Clear an own-rx-busy condition and tell the peer about this, provided
   * that there is a significant amount of free receive buffer space available.
   */
  void x25_check_rbuf(struct sock *sk)
  {
  	struct x25_sock *x25 = x25_sk(sk);
  
  	if (atomic_read(&sk->sk_rmem_alloc) < (sk->sk_rcvbuf >> 1) &&
  	    (x25->condition & X25_COND_OWN_RX_BUSY)) {
  		x25->condition &= ~X25_COND_OWN_RX_BUSY;
  		x25->condition &= ~X25_COND_ACK_PENDING;
  		x25->vl         = x25->vr;
  		x25_write_internal(sk, X25_RR);
  		x25_stop_timer(sk);
  	}
  }