/************************************************************************
**                                                                      *
** Copyright © 1996 Digital Equipment Corporation.                      *
** All rights reserved.                                                 *
**                                                                      *
** Redistribution and use in source and binary forms are permitted      *
** provided that the above copyright notice and this paragraph are      *
** duplicated in all such forms and that any documentation,             *
** advertising materials, and other materials related to such           *
** distribution and use acknowledge that the software was developed     *
** by Digital Equipment Corporation.  The name of the                   *
** Corporation may not be used to endorse or promote products derived   *
** from this software without specific prior written permission.        *
** THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR       *
** IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED       *
** WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.  *
**                                                                      *
*************************************************************************
**                                                                      *
**      Important Note:                                                 *
**                                                                      *
**         This coding example uses privileged OpenVMS interfaces.      *
**         OpenVMS does not guarantee that these interfaces will        *
**         be supported indefinitely, and may change these interfaces   *
**         without prior notice.                                        *
**                                                                      *
*************************************************************************
**++
**  FACILITY:
**
**         PPPD
**
**  ABSTRACT:
**
**        This moudle implements a callback routine to start a protocol
**        a protocol running over PPP.   The routine is called when a user
**        types the "CONNECT" command in the PPPD utility.   It is
**        registered via the "SET NETWORK" command with the
**        /pppd_callout switch.
**
**        The code assumes that the sample exe (in this case IP_VCM.EXE)
**        contains pointer to the rotuine to the start the protocol in
**        the first longword of the nonpaged base section of the image.
**        A protocol doesn't have to be implemented this way, it was
**        just one of the ways it can be done.
**
**  AUTHORS:
**
**      Patrick Crilly,   Networks Engineering (Australia).
**
**  CREATION DATE:
**
**      5-March-1996
**
**  MODIFICATION HISTORY:
**
**      17-December-1996  Barry W. Kierstein
**                        Replaced the standard Digital copyright with
**                        one compatible with the CMU copyright.
**
**	 1-October-1996	  Forrest A. Kenney
**			  Remove 4 character device name restriction also make
**			  string is null terminated.
**
**       1-August-1996    Barry W. Kierstein
**                        Added "Important Note" disclaimer.
**
**      24-July-1996      Barry W. Kierstein
**                        Corrected copyright notice.
**
**      5-March-1996      Original version.
**
**--
*/

/*
**
** import definitions:
**        SS$_xxx
**
*/
#include "ssdef.h"

/*
**
** import definitions:
**        printf
**
*/
#include "stdio.h"

/*
**
** import definitions:
**        descriptors
**
*/
#include "descrip.h"

/*
**
** import definitions:
**        strncmp
**
*/
#include "string.h"

/*
**
** import definitions:
**        ldrimg defintions
**
*/
#include "ldrimgdef.h"

#define MIN( a, b ) ((a) < (b) ? (a) : (b))

/*
** External variables
*/
extern void *LDR$GQ_IMAGE_LIST;



/*
** Callback routine to start the protocol
**
** It accepts the name of the TTAx: device to start the protocol on
** as an input parameter.
**
** The callback routine is fairly straight forward.  It hunts down the
** list of loaded execlets to find IP_VCM.EXE.  The first longword of
** IP_VCM.EXE contains a pointer to the routine which causes the VCM
** to start the protocol.   When the IP_VCM image is found a pointer to the
** routine to start the protocol is saved.   The routine is then called.
**
** One thing to note is that the routine to start the protocol in the sample
** VCM doesn't accept device names greater than 5 characters (not including the
** NULL).  Check out the comments in ip_vcm.c
*/
int PPPD$OPEN_CONNECT(struct dsc$descriptor *devName )
{
    int status = SS$_NORMAL;
    LDRIMG *imageP;          /* pointer to executive image     */
    void   *rtnAddr = NULL;  /* pointer to routine             */
    char ttDevName[20]; /* startProtocol won't let it be longer than 4 bytes */
    int (*startProtocol)( char * ); /* pointer to startRoutine in VCM */

    /*
     ** Set-up the name of the TTAx: device to use
     */
    if ( devName->dsc$w_length >= sizeof(ttDevName) )
    {
        return ( SS$_BUFFEROVF );
    }
    strncpy( ttDevName, devName->dsc$a_pointer, devName->dsc$w_length );
    ttDevName[devName->dsc$w_length]  = '\0';

    /*
     ** Find the IP_VCM.EXE execlet.
     */
    for ( imageP = (LDRIMG *)LDR$GQ_IMAGE_LIST;
          imageP != (LDRIMG *)&LDR$GQ_IMAGE_LIST;
          imageP = imageP->ldrimg$l_flink )
    {
        if ( !strncmp(imageP->ldrimg$t_imgnam, "IP_VCM.EXE",
                      MIN(imageP->ldrimg$b_imgnamlen, strlen("IP_VCM.EXE"))))
        {
            rtnAddr = *(void **)imageP->ldrimg$l_nonpag_w_base;
        }
    }

    /* Call the routine in the test VCM which starts the protocol */
    startProtocol =   (int (*)())rtnAddr;
    if ( startProtocol )
    {
    	status = (*startProtocol)( ttDevName );
    }
    else
    {
	status = SS$_ABORT;
    }
    return (status);
}