Conference help::decnet-osi_for_vms

3936.0. "NCB with Invalid Buff Length?" by BACHUS::GOOVAERTS () Fri Apr 18 1997 03:07

	<Crossposted X25psi and decnet-osi> 
 Hello,

 I need some assistance with X25 programming on VMS/VAX
 We have a customer who has a program which runs
 on several sites except on one
 They have problems with the  IO$_ACCESS|IO$M_ACCEPT call.
 In the IOSB we get Invalid buffer length,which
 indicates that there is something with the ncb,but on all
 other sites its works.
 Any Hints?
	
 The failing call is :


/*
**      NCB descriptor for accepting incoming calls
*/
static  call_accept_ncb_t ncb     = { { sizeof(struct incoming_call_id_t),
                                        psi$c_ncb_ici,
                                        0 },
                                        { sizeof(struct packet_size),
                                        psi$c_ncb_pktsize,
                                        0 } };

static  struct dsc$descriptor ncb_desc = { sizeof (ncb),
        DSC$K_DTYPE_VT,
        DSC$K_CLASS_VS,
        &ncb };
/*
**  Initialize the NCB descriptor with the incoming call id
*/
    ncb.incoming_call_id.s = g_ppacbs[a_line_no].inc_call_id;
    ncb.pack_size.s        = LN_PACKET_SIZE_512;

/*
**  Make the CALL ACCEPT packet
*/
    status = SYS$QIOW  ( 0,                         /* Issus QIO and wait      
                        a_psi_channel,              /* to network device       
                        IO$_ACCESS|IO$M_ACCEPT,     /* function is make a call 
                        &iosb,                      /* pointer to the I/O statu
                        0,                          /* ast to decode the conten
                        0,                          /* parameter to the ast rou
                        0,
                        &ncb_desc,                  /* call NCB descriptor     
                        0,
                        0,
                        0,
                        0);

 The field status contains : '1',
 but iosb.status contains  :   844 / 0 / 19 / 0 (its 4 words)

 844 => SS$_IVBUFLEN
 



Contents of ncb_desc :

   word    : 14       length
   byte    : 37       type
   byte    : 11       class
   pointer : 2643120  pointer to data


 ncb : call_accept_ncb_t is defined :

typedef struct call_accept_ncb_t
{
    struct incoming_call_id_t incoming_call_id ;
    struct packet_size        pack_size;

}   call_accept_ncb_t;

typedef struct call_clear_ncb_t
{
    struct incoming_call_id_t {                             /* incoming call id
            short len;
            short code;
            int   s;                                        /* integer         
    } incoming_call_id ;

    ...

}   call_clear_ncb_t;

/*
**      NCB for a CALL REQUEST PACKET for PSI
*/
typedef struct call_ncb_t
{
    ...

    struct packet_size {                            /* packet size          */
            short len;
            short code;
            unsigned short s;
    } packet_size ;

    ...

} call_ncb_t;

 ncb contains :

            short len        8
            short code         11
            int   s            507

            short len          6
            short code         21
            unsigned short s   512

    What if the call can't use a packet size of 512? (E.g. the DTE max
    packet size if <512 or the incoming call requested a packet size <512)?