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isdn_x25iface.c

/* $Id: isdn_x25iface.c,v 1.1.2.2 2004/01/12 22:37:19 keil Exp $
 *
 * Linux ISDN subsystem, X.25 related functions
 *
 * This software may be used and distributed according to the terms
 * of the GNU General Public License, incorporated herein by reference.
 *
 * 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 which 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 <net/x25device.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); */
static void isdn_x25iface_proto_del( struct concap_proto * );
static int isdn_x25iface_proto_close( struct concap_proto * );
static int isdn_x25iface_proto_restart( struct concap_proto *,
                              struct net_device *,
                              struct concap_device_ops *);
static int isdn_x25iface_xmit( struct concap_proto *, struct sk_buff * );
static int isdn_x25iface_receive( struct concap_proto *, struct sk_buff * );
static int isdn_x25iface_connect_ind( struct concap_proto * );
static 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(void)
{
      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 */
            spin_lock_init(&tmp->priv.lock);
            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 
 */
static 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) );
      spin_lock_irqsave(&cprot->lock, flags);
      cprot -> dops    = NULL;
      cprot -> net_dev = NULL;
      tmp = cprot -> proto_data;
      if( pdata_is_bad( tmp ) ){
            ret = -1;
      } else {
            tmp -> state = WAN_UNCONFIGURED;
      }
      spin_unlock_irqrestore(&cprot->lock, flags);
      return ret;
}

/* Delete the x25iface encapsulation protocol instance
 */
static 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
 */
static int isdn_x25iface_proto_restart(struct concap_proto *cprot,
                              struct net_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;
      }
      spin_lock_irqsave(&cprot->lock, flags);
      cprot -> net_dev = ndev;
      cprot -> pops = &ix25_pops;
      cprot -> dops = dops;
      pda -> state = WAN_DISCONNECTED;
      spin_unlock_irqrestore(&cprot->lock, flags);
      return 0;
}

/* deliver a dl_data frame received from i4l HL driver to the network layer 
 */
static 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 ){
            if( skb_push(skb, 1)){
                  skb -> data[0]=0x00;
                  skb->protocol = x25_type_trans(skb, cprot->net_dev);
                  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 
 */
static int isdn_x25iface_connect_ind(struct concap_proto *cprot)
{
      struct sk_buff * skb;
      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;

      skb = dev_alloc_skb(1);
      if( skb ){
            *( skb_put(skb, 1) ) = 0x01;
            skb->protocol = x25_type_trans(skb, cprot->net_dev);
            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 
 */
static 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->protocol = x25_type_trans(skb, cprot->net_dev);
            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
   */
static int isdn_x25iface_xmit(struct concap_proto *cprot, struct sk_buff *skb)
{
      unsigned char firstbyte = skb->data[0];
      enum wan_states *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;
}

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