MFD:ifXTable:Data Structures - Revision history

Wes at 21:53, 13 July 2011

2011-07-13T21:53:38Z

Wes: /* MFD: ifXTable Data Structures */

2011-07-13T21:53:12Z

‎MFD: ifXTable Data Structures

Wes: moved MFD:IF-MIB:Data Structures to MFD:ifXTable:Data Structures

2011-07-13T17:17:27Z

moved MFD:IF-MIB:Data Structures to MFD:ifXTable:Data Structures

Wes: Created page with "{{MFDTutorial}} == MFD: ifXTable Data Structures == Let's take a look in `ifXTable.h`. Since we will be using the netsnmp access routines to get the interface data, w..."

2011-07-13T17:13:17Z

Created page with "{{MFDTutorial}} == MFD: ifXTable Data Structures == Let's take a look in <var>ifXTable.h</var>. Since we will be using the netsnmp access routines to get the interface data, w..."

New page

{{MFDTutorial}}

== MFD: ifXTable Data Structures ==

Let's take a look in <var>ifXTable.h</var>. Since we will be using
the netsnmp access routines to get the interface data, we specified
<var>netsnmp_interface_entry</var> as our data context. You might
expect to run into it a lot in the code. Instead, the code uses
a typedef:

<table><tr><td width=20></td>
<td><td bgcolor=CCCCCC>
/*
* data context
*/
typedef <font color=red>netsnmp_interface_entry</font> ifXTable_data;
</td></tr></table>

Whenever you see <var>ifXTable_data</var>, remember that it is
simply a typedef for <var>netsnmp_interface_entry</var>. As we will
see in a moment, the the row request context has a pointer to an
<var>ifXTable_data</var> structure. The first edit we need to make
is to include the interface access header file:

<table><tr><td width=20></td>
<td><td bgcolor=CCCCCC>
#include <net-snmp/library/asn1.h><font color=blue>
#include <net-snmp/data_access/interface.h></font>
</td></tr></table>

However, the <var>netsnmp_interface_entry</var> does not contain all
the information we need to implement all the ifXTable columns.
In particluar, the ifLinkUpDownTrapEnable and ifAlias columns are
specific to the ifXTable, and not kept in the netsnmp_interface_entry
structure. To keep track of them, we'll add them to the
<var>rowrequest_context</var>. Because we specified a type for our
data context, mib2c did not generate storage for any columns. So
we need to add storage. For consistency's sake, we'll use mib2c to
generate a data context. We specify <em>dummy</em> as the output file
name, so that it won't get confused with the other ifXTable
implementation files.

<table><tr><td width=20></td>
<td><td bgcolor=CCCCCC>
$ <font color=blue>mib2c -f dummy -c mib2c.column_storage.conf ifXTable</font>
</td></tr></table>

Then we copy the definitions we need from <var>dummy_storage.h</var>
to the <var>rowrequest_context</var> in <var>ifXTable.h</var>:

<table><tr><td width=20></td>
<td><td bgcolor=CCCCCC>
/*
*********************************************************************
* Row request context
* When your functions are called, you will be passed a
* ifXTable_rowreq_ctx pointer.
*/
typedef struct ifXTable_rowreq_ctx_s {

/** this must be first for container compare to work */
netsnmp_index oid_idx;
oid oid_tmp[MAX_OID_LEN]; /* xxx-rks: shrink this */

ifXTable_mib_index tbl_idx;

ifXTable_data *data;
ifXTable_undo_data *undo;

/** implementor's context pointer provided during registration */
ifXTable_registration_ptr ifXTable_reg;

/*
* TODO:
* add any other useful data
* (e.g. flags for when a column has been set)
*/<font color=blue>
/** ifLinkUpDownTrapEnable(14)/INTEGER/ASN_INTEGER/long(u_long)//l/A/W/E/r/d/h */
u_long ifLinkUpDownTrapEnable;

/** ifAlias(18)/DisplayString/ASN_OCTET_STR/char(char)//L/A/W/e/R/d/H */
char ifAlias[64];
size_t ifAlias_len; /* # of char elements, not bytes */
</font>
/*
* storage for future expansion
*/
netsnmp_data_list *ifXTable_data_list;

} ifXTable_rowreq_ctx;
</td>
</tr>
</table>

@@ Line 83: / Line 83: @@
          char            ifAlias[64];
          size_t          ifAlias_len;        /* # of char elements, not bytes */
-</font>
+ </font>
          /*
           * storage for future expansion

@@ Line 59: / Line 59: @@
       */
      typedef struct ifXTable_rowreq_ctx_s {
-−
      /** this must be first for container compare to work */
          netsnmp_index   oid_idx;
          oid             oid_tmp[MAX_OID_LEN];   /* xxx-rks: shrink this */
-−
          ifXTable_mib_index tbl_idx;
-−
          ifXTable_data  *data;
          ifXTable_undo_data *undo;
-−
      /** implementor's context pointer provided during registration */
          ifXTable_registration_ptr ifXTable_reg;
-−
          /*
           * TODO:
@@ Line 79: / Line 79: @@
          /** ifLinkUpDownTrapEnable(14)/INTEGER/ASN_INTEGER/long(u_long)//l/A/W/E/r/d/h */
          u_long          ifLinkUpDownTrapEnable;
-−
          /** ifAlias(18)/DisplayString/ASN_OCTET_STR/char(char)//L/A/W/e/R/d/H */
          char            ifAlias[64];
@@ Line 88: / Line 88: @@
           */
          netsnmp_data_list *ifXTable_data_list;
-−
      } ifXTable_rowreq_ctx;
 </td>
          </tr>
      </table>

← Older revision	Revision as of 17:17, 13 July 2011
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MFD:ifXTable:Data Structures - Revision history

Wes at 21:53, 13 July 2011

Wes: /* MFD: ifXTable Data Structures */

Wes: moved MFD:IF-MIB:Data Structures to MFD:ifXTable:Data Structures

Wes: Created page with "{{MFDTutorial}} == MFD: ifXTable Data Structures == Let's take a look in ifXTable.h. Since we will be using the netsnmp access routines to get the interface data, w..."

Wes: Created page with "{{MFDTutorial}} == MFD: ifXTable Data Structures == Let's take a look in `ifXTable.h`. Since we will be using the netsnmp access routines to get the interface data, w..."