/*
   *	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	Split from x25_subr.c
   *	mar/20/00	Daniela Squassoni Disabling/enabling of facilities
   *					  negotiation.
   *	apr/14/05	Shaun Pereira - Allow fast select with no restriction
   *					on response.
   */
  
  #define pr_fmt(fmt) "X25: " fmt
  
  #include <linux/kernel.h>
  #include <linux/string.h>
  #include <linux/skbuff.h>
  #include <net/sock.h>
  #include <net/x25.h>
  
  /**
   * x25_parse_facilities - Parse facilities from skb into the facilities structs
   *
   * @skb: sk_buff to parse
   * @facilities: Regular facilities, updated as facilities are found
   * @dte_facs: ITU DTE facilities, updated as DTE facilities are found
   * @vc_fac_mask: mask is updated with all facilities found
   *
   * Return codes:
   *  -1 - Parsing error, caller should drop call and clean up
   *   0 - Parse OK, this skb has no facilities
   *  >0 - Parse OK, returns the length of the facilities header
   *
   */
  int x25_parse_facilities(struct sk_buff *skb, struct x25_facilities *facilities,
  		struct x25_dte_facilities *dte_facs, unsigned long *vc_fac_mask)
  {
  	unsigned char *p;
  	unsigned int len;
  
  	*vc_fac_mask = 0;
  
  	/*
  	 * The kernel knows which facilities were set on an incoming call but
  	 * currently this information is not available to userspace.  Here we
  	 * give userspace who read incoming call facilities 0 length to indicate
  	 * it wasn't set.
  	 */
  	dte_facs->calling_len = 0;
  	dte_facs->called_len = 0;
  	memset(dte_facs->called_ae, '\0', sizeof(dte_facs->called_ae));
  	memset(dte_facs->calling_ae, '\0', sizeof(dte_facs->calling_ae));
  
  	if (!pskb_may_pull(skb, 1))
  		return 0;
  
  	len = skb->data[0];
  
  	if (!pskb_may_pull(skb, 1 + len))
  		return -1;
  
  	p = skb->data + 1;
  
  	while (len > 0) {
  		switch (*p & X25_FAC_CLASS_MASK) {
  		case X25_FAC_CLASS_A:
  			if (len < 2)
  				return -1;
  			switch (*p) {
  			case X25_FAC_REVERSE:
  				if((p[1] & 0x81) == 0x81) {
  					facilities->reverse = p[1] & 0x81;
  					*vc_fac_mask |= X25_MASK_REVERSE;
  					break;
  				}
  
  				if((p[1] & 0x01) == 0x01) {
  					facilities->reverse = p[1] & 0x01;
  					*vc_fac_mask |= X25_MASK_REVERSE;
  					break;
  				}
  
  				if((p[1] & 0x80) == 0x80) {
  					facilities->reverse = p[1] & 0x80;
  					*vc_fac_mask |= X25_MASK_REVERSE;
  					break;
  				}
  
  				if(p[1] == 0x00) {
  					facilities->reverse
  						= X25_DEFAULT_REVERSE;
  					*vc_fac_mask |= X25_MASK_REVERSE;
  					break;
  				}
  
  			case X25_FAC_THROUGHPUT:
  				facilities->throughput = p[1];
  				*vc_fac_mask |= X25_MASK_THROUGHPUT;
  				break;
  			case X25_MARKER:
  				break;
  			default:
  				pr_debug("unknown facility "
  				       "%02X, value %02X
  ",
  				       p[0], p[1]);
  				break;
  			}
  			p   += 2;
  			len -= 2;
  			break;
  		case X25_FAC_CLASS_B:
  			if (len < 3)
  				return -1;
  			switch (*p) {
  			case X25_FAC_PACKET_SIZE:
  				facilities->pacsize_in  = p[1];
  				facilities->pacsize_out = p[2];
  				*vc_fac_mask |= X25_MASK_PACKET_SIZE;
  				break;
  			case X25_FAC_WINDOW_SIZE:
  				facilities->winsize_in  = p[1];
  				facilities->winsize_out = p[2];
  				*vc_fac_mask |= X25_MASK_WINDOW_SIZE;
  				break;
  			default:
  				pr_debug("unknown facility "
  				       "%02X, values %02X, %02X
  ",
  				       p[0], p[1], p[2]);
  				break;
  			}
  			p   += 3;
  			len -= 3;
  			break;
  		case X25_FAC_CLASS_C:
  			if (len < 4)
  				return -1;
  			pr_debug("unknown facility %02X, "
  			       "values %02X, %02X, %02X
  ",
  			       p[0], p[1], p[2], p[3]);
  			p   += 4;
  			len -= 4;
  			break;
  		case X25_FAC_CLASS_D:
  			if (len < p[1] + 2)
  				return -1;
  			switch (*p) {
  			case X25_FAC_CALLING_AE:
  				if (p[1] > X25_MAX_DTE_FACIL_LEN || p[1] <= 1)
  					return -1;
  				if (p[2] > X25_MAX_AE_LEN)
  					return -1;
  				dte_facs->calling_len = p[2];
  				memcpy(dte_facs->calling_ae, &p[3], p[1] - 1);
  				*vc_fac_mask |= X25_MASK_CALLING_AE;
  				break;
  			case X25_FAC_CALLED_AE:
  				if (p[1] > X25_MAX_DTE_FACIL_LEN || p[1] <= 1)
  					return -1;
  				if (p[2] > X25_MAX_AE_LEN)
  					return -1;
  				dte_facs->called_len = p[2];
  				memcpy(dte_facs->called_ae, &p[3], p[1] - 1);
  				*vc_fac_mask |= X25_MASK_CALLED_AE;
  				break;
  			default:
  				pr_debug("unknown facility %02X,"
  					"length %d
  ", p[0], p[1]);
  				break;
  			}
  			len -= p[1] + 2;
  			p += p[1] + 2;
  			break;
  		}
  	}
  
  	return p - skb->data;
  }
  
  /*
   *	Create a set of facilities.
   */
  int x25_create_facilities(unsigned char *buffer,
  		struct x25_facilities *facilities,
  		struct x25_dte_facilities *dte_facs, unsigned long facil_mask)
  {
  	unsigned char *p = buffer + 1;
  	int len;
  
  	if (!facil_mask) {
  		/*
  		 * Length of the facilities field in call_req or
  		 * call_accept packets
  		 */
  		buffer[0] = 0;
  		len = 1; /* 1 byte for the length field */
  		return len;
  	}
  
  	if (facilities->reverse && (facil_mask & X25_MASK_REVERSE)) {
  		*p++ = X25_FAC_REVERSE;
  		*p++ = facilities->reverse;
  	}
  
  	if (facilities->throughput && (facil_mask & X25_MASK_THROUGHPUT)) {
  		*p++ = X25_FAC_THROUGHPUT;
  		*p++ = facilities->throughput;
  	}
  
  	if ((facilities->pacsize_in || facilities->pacsize_out) &&
  	    (facil_mask & X25_MASK_PACKET_SIZE)) {
  		*p++ = X25_FAC_PACKET_SIZE;
  		*p++ = facilities->pacsize_in ? : facilities->pacsize_out;
  		*p++ = facilities->pacsize_out ? : facilities->pacsize_in;
  	}
  
  	if ((facilities->winsize_in || facilities->winsize_out) &&
  	    (facil_mask & X25_MASK_WINDOW_SIZE)) {
  		*p++ = X25_FAC_WINDOW_SIZE;
  		*p++ = facilities->winsize_in ? : facilities->winsize_out;
  		*p++ = facilities->winsize_out ? : facilities->winsize_in;
  	}
  
  	if (facil_mask & (X25_MASK_CALLING_AE|X25_MASK_CALLED_AE)) {
  		*p++ = X25_MARKER;
  		*p++ = X25_DTE_SERVICES;
  	}
  
  	if (dte_facs->calling_len && (facil_mask & X25_MASK_CALLING_AE)) {
  		unsigned int bytecount = (dte_facs->calling_len + 1) >> 1;
  		*p++ = X25_FAC_CALLING_AE;
  		*p++ = 1 + bytecount;
  		*p++ = dte_facs->calling_len;
  		memcpy(p, dte_facs->calling_ae, bytecount);
  		p += bytecount;
  	}
  
  	if (dte_facs->called_len && (facil_mask & X25_MASK_CALLED_AE)) {
  		unsigned int bytecount = (dte_facs->called_len % 2) ?
  		dte_facs->called_len / 2 + 1 :
  		dte_facs->called_len / 2;
  		*p++ = X25_FAC_CALLED_AE;
  		*p++ = 1 + bytecount;
  		*p++ = dte_facs->called_len;
  		memcpy(p, dte_facs->called_ae, bytecount);
  		p+=bytecount;
  	}
  
  	len       = p - buffer;
  	buffer[0] = len - 1;
  
  	return len;
  }
  
  /*
   *	Try to reach a compromise on a set of facilities.
   *
   *	The only real problem is with reverse charging.
   */
  int x25_negotiate_facilities(struct sk_buff *skb, struct sock *sk,
  		struct x25_facilities *new, struct x25_dte_facilities *dte)
  {
  	struct x25_sock *x25 = x25_sk(sk);
  	struct x25_facilities *ours = &x25->facilities;
  	struct x25_facilities theirs;
  	int len;
  
  	memset(&theirs, 0, sizeof(theirs));
  	memcpy(new, ours, sizeof(*new));
  
  	len = x25_parse_facilities(skb, &theirs, dte, &x25->vc_facil_mask);
  	if (len < 0)
  		return len;
  
  	/*
  	 *	They want reverse charging, we won't accept it.
  	 */
  	if ((theirs.reverse & 0x01 ) && (ours->reverse & 0x01)) {
  		SOCK_DEBUG(sk, "X.25: rejecting reverse charging request
  ");
  		return -1;
  	}
  
  	new->reverse = theirs.reverse;
  
  	if (theirs.throughput) {
  		int theirs_in =  theirs.throughput & 0x0f;
  		int theirs_out = theirs.throughput & 0xf0;
  		int ours_in  = ours->throughput & 0x0f;
  		int ours_out = ours->throughput & 0xf0;
  		if (!ours_in || theirs_in < ours_in) {
  			SOCK_DEBUG(sk, "X.25: inbound throughput negotiated
  ");
  			new->throughput = (new->throughput & 0xf0) | theirs_in;
  		}
  		if (!ours_out || theirs_out < ours_out) {
  			SOCK_DEBUG(sk,
  				"X.25: outbound throughput negotiated
  ");
  			new->throughput = (new->throughput & 0x0f) | theirs_out;
  		}
  	}
  
  	if (theirs.pacsize_in && theirs.pacsize_out) {
  		if (theirs.pacsize_in < ours->pacsize_in) {
  			SOCK_DEBUG(sk, "X.25: packet size inwards negotiated down
  ");
  			new->pacsize_in = theirs.pacsize_in;
  		}
  		if (theirs.pacsize_out < ours->pacsize_out) {
  			SOCK_DEBUG(sk, "X.25: packet size outwards negotiated down
  ");
  			new->pacsize_out = theirs.pacsize_out;
  		}
  	}
  
  	if (theirs.winsize_in && theirs.winsize_out) {
  		if (theirs.winsize_in < ours->winsize_in) {
  			SOCK_DEBUG(sk, "X.25: window size inwards negotiated down
  ");
  			new->winsize_in = theirs.winsize_in;
  		}
  		if (theirs.winsize_out < ours->winsize_out) {
  			SOCK_DEBUG(sk, "X.25: window size outwards negotiated down
  ");
  			new->winsize_out = theirs.winsize_out;
  		}
  	}
  
  	return len;
  }
  
  /*
   *	Limit values of certain facilities according to the capability of the
   *      currently attached x25 link.
   */
  void x25_limit_facilities(struct x25_facilities *facilities,
  			  struct x25_neigh *nb)
  {
  
  	if (!nb->extended) {
  		if (facilities->winsize_in  > 7) {
  			pr_debug("incoming winsize limited to 7
  ");
  			facilities->winsize_in = 7;
  		}
  		if (facilities->winsize_out > 7) {
  			facilities->winsize_out = 7;
  			pr_debug("outgoing winsize limited to 7
  ");
  		}
  	}
  }