x25_facilities.c

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/*
 *	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.
 */

#include <linux/config.h>
#if defined(CONFIG_X25) || defined(CONFIG_X25_MODULE)
#include <linux/errno.h>
#include <linux/types.h>
#include <linux/socket.h>
#include <linux/in.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/timer.h>
#include <linux/string.h>
#include <linux/sockios.h>
#include <linux/net.h>
#include <linux/inet.h>
#include <linux/netdevice.h>
#include <linux/skbuff.h>
#include <net/sock.h>
#include <asm/segment.h>
#include <asm/system.h>
#include <linux/fcntl.h>
#include <linux/mm.h>
#include <linux/interrupt.h>
#include <net/x25.h>

/*
 *	Parse a set of facilities into the facilities structure. Unrecognised
 *	facilities are written to the debug log file.
 */
int x25_parse_facilities(struct sk_buff *skb, struct x25_facilities *facilities, unsigned long *vc_fac_mask)
{
	unsigned int len;
	unsigned char *p = skb->data;

	len = *p++;
	*vc_fac_mask = 0;

	while (len > 0) {
		switch (*p & X25_FAC_CLASS_MASK) {
			case X25_FAC_CLASS_A:
				switch (*p) {
					case X25_FAC_REVERSE:
						facilities->reverse = (p[1] & 0x01);
						*vc_fac_mask |= X25_MASK_REVERSE;
						break;
					case X25_FAC_THROUGHPUT:
						facilities->throughput = p[1];
						*vc_fac_mask |= X25_MASK_THROUGHPUT;
						break;
					default:
						printk(KERN_DEBUG "X.25: unknown facility %02X, value %02X\n", p[0], p[1]);
						break;
				}
				p   += 2;
				len -= 2;
				break;

			case X25_FAC_CLASS_B:
				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:
						printk(KERN_DEBUG "X.25: unknown facility %02X, values %02X, %02X\n", p[0], p[1], p[2]);
						break;
				}
				p   += 3;
				len -= 3;
				break;

			case X25_FAC_CLASS_C:
				printk(KERN_DEBUG "X.25: unknown facility %02X, values %02X, %02X, %02X\n", p[0], p[1], p[2], p[3]);
				p   += 4;
				len -= 4;
				break;

			case X25_FAC_CLASS_D:
				printk(KERN_DEBUG "X.25: unknown facility %02X, length %d, values %02X, %02X, %02X, %02X\n", p[0], p[1], p[2], p[3], p[4], p[5]);
				p   += p[1] + 2;
				len -= p[1] + 2;
				break;
		}
	}

	return p - skb->data;
}

/*
 *	Create a set of facilities.
 */
int x25_create_facilities(unsigned char *buffer, struct x25_facilities *facilities, unsigned long facil_mask)
{
	unsigned char *p = buffer + 1;
	int len;

	if (facil_mask == 0) {
		buffer [0] = 0; /* length of the facilities field in call_req or call_accept packets */
		len = 1; /* 1 byte for the length field */
		return len;
	}

	if ((facilities->reverse != 0) && (facil_mask & X25_MASK_REVERSE)) {
		*p++ = X25_FAC_REVERSE;
		*p++ = (facilities->reverse) ? 0x01 : 0x00;
	}

	if ((facilities->throughput != 0) && (facil_mask & X25_MASK_THROUGHPUT)) {
		*p++ = X25_FAC_THROUGHPUT;
		*p++ = facilities->throughput;
	}

	if ((facilities->pacsize_in != 0 || facilities->pacsize_out != 0) && (facil_mask & X25_MASK_PACKET_SIZE)) {
		*p++ = X25_FAC_PACKET_SIZE;
		*p++ = (facilities->pacsize_in  == 0) ? facilities->pacsize_out : facilities->pacsize_in;
		*p++ = (facilities->pacsize_out == 0) ? facilities->pacsize_in  : facilities->pacsize_out;
	}

	if ((facilities->winsize_in != 0 || facilities->winsize_out != 0) && (facil_mask & X25_MASK_WINDOW_SIZE)) {
		*p++ = X25_FAC_WINDOW_SIZE;
		*p++ = (facilities->winsize_in  == 0) ? facilities->winsize_out : facilities->winsize_in;
		*p++ = (facilities->winsize_out == 0) ? facilities->winsize_in  : facilities->winsize_out;
	}

	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_facilities *ours;
	struct x25_facilities theirs;
	int len;

	memset(&theirs, 0x00, sizeof(struct x25_facilities));

	ours = &sk->protinfo.x25->facilities;

	*new = *ours;

	len = x25_parse_facilities(skb, &theirs, &sk->protinfo.x25->vc_facil_mask);

	/*
	 *	They want reverse charging, we won't accept it.
	 */
	if (theirs.reverse != 0 && ours->reverse == 0) {
		SOCK_DEBUG(sk, "X.25: rejecting reverse charging request");
		return -1;
	}

	new->reverse = theirs.reverse;

	if (theirs.throughput != 0) {
		if (theirs.throughput < ours->throughput) {
			SOCK_DEBUG(sk, "X.25: throughput negotiated down");
			new->throughput = theirs.throughput;
		}
	}

	if (theirs.pacsize_in != 0 && theirs.pacsize_out != 0) {
		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 != 0 && theirs.winsize_out != 0) {
		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 *neighbour)
{

	if( ! neighbour->extended ){
		if( facilities->winsize_in  > 7 ){
			printk(KERN_DEBUG "X.25: incoming winsize limited to 7\n");
			facilities->winsize_in = 7;
		}
		if( facilities->winsize_out > 7 ){
			facilities->winsize_out = 7;
			printk( KERN_DEBUG "X.25: outgoing winsize limited to 7\n");
		}
	}
}

#endif