/* $Id: isdn_x25iface.c,v 1.2 2005/06/16 13:46:30 cgoh Exp $

 *
 * Linux ISDN subsystem, X.25 related functions
 *
 * This program 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, or (at your option)
 * any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 *
 *
 * stuff needed to support the Linux X.25 PLP code on top of devices that
 * can provide a lab_b service using the concap_proto mechanism.
 * This module supports a network interface wich provides lapb_sematics
 * -- as defined in ../../Documentation/networking/x25-iface.txt -- to
 * the upper layer and assumes that the lower layer provides a reliable
 * data link service by means of the concap_device_ops callbacks.
 *
 * Only protocol specific stuff goes here. Device specific stuff
 * goes to another -- device related -- concap_proto support source file.
 *
 */

/* #include <linux/isdn.h> */
#include <linux/netdevice.h>
#include <linux/concap.h>
#include <linux/wanrouter.h>
#include "isdn_x25iface.h"

/* for debugging messages not to cause an oops when device pointer is NULL*/
#define MY_DEVNAME(dev)  ( (dev) ? (dev)->name : "DEVICE UNSPECIFIED" )


typedef struct isdn_x25iface_proto_data {
	int magic;
	enum wan_states state;
	/* Private stuff, not to be accessed via proto_data. We provide the
	   other storage for the concap_proto instance here as well,
	   enabling us to allocate both with just one kmalloc(): */ 
	struct concap_proto priv;
} ix25_pdata_t;



/* is now in header file (extern): struct concap_proto * isdn_x25iface_proto_new(void); */
void isdn_x25iface_proto_del( struct concap_proto * );
int isdn_x25iface_proto_close( struct concap_proto * );
int isdn_x25iface_proto_restart( struct concap_proto *,
				 struct device *,
				 struct concap_device_ops *);
int isdn_x25iface_xmit( struct concap_proto *, struct sk_buff * );
int isdn_x25iface_receive( struct concap_proto *, struct sk_buff * );
int isdn_x25iface_connect_ind( struct concap_proto * );
int isdn_x25iface_disconn_ind( struct concap_proto * );


static struct concap_proto_ops ix25_pops = {
	&isdn_x25iface_proto_new,
	&isdn_x25iface_proto_del,
	&isdn_x25iface_proto_restart,
	&isdn_x25iface_proto_close,
	&isdn_x25iface_xmit,
	&isdn_x25iface_receive,
	&isdn_x25iface_connect_ind,
	&isdn_x25iface_disconn_ind
};

/* error message helper function */
static void illegal_state_warn( unsigned state, unsigned char firstbyte) 
{
	printk( KERN_WARNING "isdn_x25iface: firstbyte %x illegal in"
		"current state %d\n",firstbyte, state );
}

/* check protocol data field for consistency */
static int pdata_is_bad( ix25_pdata_t * pda ){

	if( pda  &&  pda -> magic == ISDN_X25IFACE_MAGIC ) return 0;
	printk( KERN_WARNING
		"isdn_x25iface_xxx: illegal pointer to proto data\n" );
	return 1;
}

/* create a new x25 interface protocol instance
 */
struct concap_proto * isdn_x25iface_proto_new()
{
	ix25_pdata_t * tmp = kmalloc(sizeof(ix25_pdata_t),GFP_KERNEL);
	IX25DEBUG("isdn_x25iface_proto_new\n");
	if( tmp ){
		tmp -> magic = ISDN_X25IFACE_MAGIC;
		tmp -> state = WAN_UNCONFIGURED;
		/* private data space used to hold the concap_proto data.
		   Only to be accessed via the returned pointer */
		tmp -> priv.dops       = NULL;
		tmp -> priv.net_dev    = NULL;
		tmp -> priv.pops       = &ix25_pops;
		tmp -> priv.flags      = 0;
		tmp -> priv.proto_data = tmp;
		return( &(tmp -> priv) );
	}
	return NULL;
};

/* close the x25iface encapsulation protocol 
 */
int isdn_x25iface_proto_close(struct concap_proto *cprot){

	ix25_pdata_t *tmp;
        int ret = 0;
	ulong flags;

	if( ! cprot ){
		printk( KERN_ERR "isdn_x25iface_proto_close: "
			"invalid concap_proto pointer\n" );
		return -1;
	}
	IX25DEBUG( "isdn_x25iface_proto_close %s \n", MY_DEVNAME(cprot -> net_dev) );
	save_flags(flags);
	cli();  /* avoid races with incoming events calling pops methods while
		 cprot members are inconsistent */  
	cprot -> dops    = NULL;
	cprot -> net_dev = NULL;
	tmp = cprot -> proto_data;
	if( pdata_is_bad( tmp ) ){
		ret = -1;
	} else {
		tmp -> state = WAN_UNCONFIGURED;
	}
	restore_flags(flags);

	return ret;
}

/* Delete the x25iface encapsulation protocol instance
 */
void isdn_x25iface_proto_del(struct concap_proto *cprot){

	ix25_pdata_t * tmp;
 
	IX25DEBUG( "isdn_x25iface_proto_del \n" );
	if( ! cprot ){
		printk( KERN_ERR "isdn_x25iface_proto_del: "
			"concap_proto pointer is NULL\n" );
		return;
	}
	tmp = cprot -> proto_data;
	if( tmp == NULL ){ 
		printk( KERN_ERR "isdn_x25iface_proto_del: inconsistent "
			"proto_data pointer (maybe already deleted?)\n"); 
		return;
	}
	/* close if the protocol is still open */
	if( cprot -> dops ) isdn_x25iface_proto_close(cprot);
	/* freeing the storage should be sufficient now. But some additional
	   settings might help to catch wild pointer bugs */
	tmp -> magic = 0;
	cprot -> proto_data = NULL;

	kfree( tmp );
	return;
}

/* (re-)initialize the data structures for x25iface encapsulation
 */
int isdn_x25iface_proto_restart(struct concap_proto *cprot,
				struct device *ndev, 
				struct concap_device_ops *dops)
{
	ix25_pdata_t * pda = cprot -> proto_data ;
	ulong flags;

	IX25DEBUG( "isdn_x25iface_proto_restart %s \n", MY_DEVNAME(ndev) );

	if ( pdata_is_bad( pda ) ) return -1;

	if( !( dops  && dops -> data_req && dops -> connect_req 
	       && dops -> disconn_req )  ){
		printk( KERN_WARNING "isdn_x25iface_restart: required dops"
			" missing\n" );
		isdn_x25iface_proto_close(cprot);
		return -1;
	}
	save_flags(flags);
	cli();  /* avoid races with incoming events calling pops methods while
		 cprot members are inconsistent */  
	cprot -> net_dev = ndev;
	cprot -> pops = &ix25_pops;
	cprot -> dops = dops;
	pda -> state = WAN_DISCONNECTED;
	restore_flags(flags);
	return 0;
}

/* deliver a dl_data frame received from i4l HL driver to the network layer 
 */
int isdn_x25iface_receive(struct concap_proto *cprot, struct sk_buff *skb)
{
  	IX25DEBUG( "isdn_x25iface_receive %s \n", MY_DEVNAME(cprot->net_dev) );
	if ( ( (ix25_pdata_t*) (cprot->proto_data) ) 
	     -> state == WAN_CONNECTED ){
		skb -> dev = cprot -> net_dev;
		skb -> protocol = htons(ETH_P_X25);
		skb -> pkt_type = PACKET_HOST;
		if( skb_push(skb, 1)){
			skb -> data[0]=0x00;
			skb -> mac.raw = skb -> data;
			netif_rx(skb);
			return 0;
		}
	}
	printk(KERN_WARNING "isdn_x25iface_receive %s: not connected, skb dropped\n", MY_DEVNAME(cprot->net_dev) );
	dev_kfree_skb(skb);
	return -1;
}

/* a connection set up is indicated by lower layer 
 */
int isdn_x25iface_connect_ind(struct concap_proto *cprot)
{
	struct sk_buff * skb = dev_alloc_skb(1);
	enum wan_states *state_p 
	  = &( ( (ix25_pdata_t*) (cprot->proto_data) ) -> state);
	IX25DEBUG( "isdn_x25iface_connect_ind %s \n"
		   , MY_DEVNAME(cprot->net_dev) );
	if( *state_p == WAN_UNCONFIGURED ){ 
		printk(KERN_WARNING 
		       "isdn_x25iface_connect_ind while unconfigured %s\n"
		       , MY_DEVNAME(cprot->net_dev) );
		return -1;
	}
	*state_p = WAN_CONNECTED;
	if( skb ){
		*( skb_put(skb, 1) ) = 0x01;
		skb -> mac.raw = skb -> data;
		skb -> dev  = cprot -> net_dev;
		skb -> protocol = htons(ETH_P_X25);
		skb -> pkt_type = PACKET_HOST;
		netif_rx(skb);
		return 0;
	} else {
		printk(KERN_WARNING "isdn_x25iface_connect_ind: "
		       " out of memory -- disconnecting\n");
		cprot -> dops -> disconn_req(cprot);
		return -1;
	}
}
	
/* a disconnect is indicated by lower layer 
 */
int isdn_x25iface_disconn_ind(struct concap_proto *cprot)
{
	struct sk_buff *skb;
	enum wan_states *state_p 
	  = &( ( (ix25_pdata_t*) (cprot->proto_data) ) -> state);
	IX25DEBUG( "isdn_x25iface_disconn_ind %s \n", MY_DEVNAME(cprot -> net_dev) );
	if( *state_p == WAN_UNCONFIGURED ){ 
		printk(KERN_WARNING 
		       "isdn_x25iface_disconn_ind while unconfigured\n");
		return -1;
	}
	if(! cprot -> net_dev) return -1;
	*state_p = WAN_DISCONNECTED;
	skb = dev_alloc_skb(1);
	if( skb ){
		*( skb_put(skb, 1) ) = 0x02;
		skb -> mac.raw = skb -> data;
		skb -> dev  = cprot -> net_dev;
		skb -> protocol = htons(ETH_P_X25);
		skb -> pkt_type = PACKET_HOST;
		netif_rx(skb);
		return 0;
	} else {
		printk(KERN_WARNING "isdn_x25iface_disconn_ind:"
		       " out of memory\n");
		return -1;
	}
}

/* process a frame handed over to us from linux network layer. First byte
   semantics as defined in ../../Documentation/networking/x25-iface.txt 
   */
int isdn_x25iface_xmit(struct concap_proto *cprot, struct sk_buff *skb)
{
	unsigned char firstbyte = skb->data[0];
	unsigned *state = 
		&( ( (ix25_pdata_t*) (cprot -> proto_data) ) -> state  );
	int ret = 0;
	IX25DEBUG( "isdn_x25iface_xmit: %s first=%x state=%d \n", MY_DEVNAME(cprot -> net_dev), firstbyte, *state );
	switch ( firstbyte ){
	case 0x00: /* dl_data request */
		if( *state == WAN_CONNECTED ){
			skb_pull(skb, 1);
			cprot -> net_dev -> trans_start = jiffies;
			ret = ( cprot -> dops -> data_req(cprot, skb) );
			/* prepare for future retransmissions */
			if( ret ) skb_push(skb,1);
			return ret;
		}
		illegal_state_warn( *state, firstbyte ); 
		break;
	case 0x01: /* dl_connect request */
		if( *state == WAN_DISCONNECTED ){
			*state = WAN_CONNECTING;
		        ret = cprot -> dops -> connect_req(cprot);
			if(ret){
				/* reset state and notify upper layer about
				 * immidiatly failed attempts */
				isdn_x25iface_disconn_ind(cprot);
			}
		} else {
			illegal_state_warn( *state, firstbyte );
		}
		break;
	case 0x02: /* dl_disconnect request */
		switch ( *state ){
		case WAN_DISCONNECTED: 
			/* Should not happen. However, give upper layer a
			   chance to recover from inconstistency  but don't
			   trust the lower layer sending the disconn_confirm
			   when already disconnected */
			printk(KERN_WARNING "isdn_x25iface_xmit: disconnect "
			       " requested while disconnected\n" );
			isdn_x25iface_disconn_ind(cprot);
			break; /* prevent infinite loops */
		case WAN_CONNECTING:
		case WAN_CONNECTED:
			*state = WAN_DISCONNECTED;
			cprot -> dops -> disconn_req(cprot);
			break;
		default:
			illegal_state_warn( *state, firstbyte );
		}
		break;
	case 0x03: /* changing lapb parameters requested */
		printk(KERN_WARNING "isdn_x25iface_xmit: setting of lapb"
		       " options not yet supported\n");
		break;
	default:
		printk(KERN_WARNING "isdn_x25iface_xmit: frame with illegal"
		       " first byte %x ignored:\n", firstbyte);
	}
	dev_kfree_skb(skb);
	return 0;
}
