# isdn_x25iface.c

    /* $Id$
     * 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.
     *
     * $Log$
     * Revision 1.4  1998/06/17 19:51:00  he
     * merged with 2.1.10[34] (cosmetics and udelay() -> mdelay())
     * brute force fix to avoid Ugh's in isdn_tty_write()
     * cleaned up some dead code
     *
     * Revision 1.3  1998/02/20 17:25:20  fritz
     * Changes for recent kernels.
     *
     * Revision 1.2  1998/01/31 22:49:22  keil
     * correct comments
     *
     * Revision 1.1  1998/01/31 22:27:58  keil
     * New files from Henner Eisen for X.25 support
     *
     */

    /* #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 fuction */
    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;
    		        cprot -> dops -> connect_req(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;
    }