xmldb_get0 returns invalid candidate on startup transaction callbacks

[shmuelhazan]

Description

xmldb_get0 with "candidate" as db will yield invalid results if it has been called on a validate/commit callback in a context of the first backend transaction.

Instead of returning the startup config as expected, it will return the candidate state as it was on the previous backend run.

Example

Compile the following simple backend plugin:

#include <errno.h>
#include <fcntl.h>
#include <inttypes.h>
#include <signal.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/time.h>
#include <syslog.h>
#include <unistd.h>

/* clicon */
#include "cligen/cligen.h"

/* Clicon library functions. */
#include "clixon/clixon.h"

/* These include signatures for plugin and transaction callbacks. */
#include "clixon/clixon_backend.h"

void dump_datastore(clicon_handle h, const char *datastore) {
  cxobj *obj;
  ret = xmldb_get0(h, datastore, NULL, NULL, 0, &obj, NULL);

  clicon_xml2file(stdout, obj, 0, 1);
}

int main_validate(clicon_handle h, transaction_data td) {
  clicon_debug(1, "%s", __FUNCTION__);
  transaction_log(h, td, 1, __FUNCTION__);
  dump_datastore(h, "candidate");
  return 0;
}

/*! Example callback:
 *  This is called on commit. Identify modifications and adjust machine state
 */
int main_commit(clicon_handle h, transaction_data td) {
  clicon_debug(1, "%s", __FUNCTION__);
  transaction_log(h, td, 1, __FUNCTION__);
  dump_datastore(h, "candidate");

  return 0;
}

clixon_plugin_api *clixon_plugin_init(clicon_handle h);

static clixon_plugin_api api = {
    "core",             /* name */
    clixon_plugin_init, /* init - must be called clixon_plugin_init */
    .ca_trans_validate = main_validate, /* trans validate */
    .ca_trans_commit = main_commit,     /* trans commit */
};
clixon_plugin_api *clixon_plugin_init(clicon_handle h) { return &api; }

Open clixon cli, write:

set parameter A value B
commit
copy running startup
set parameter A value A

Restart backend.

Expected result:

Aug 11 07:03:20: transaction_log 0 main_validate add: <table xmlns="urn:example:clixon"><parameter><name>A</name><value>B</value></parameter></table>
<config>
   <table xmlns="urn:example:clixon">
      <parameter>
         <name>A</name>
         <value>B</value>
      </parameter>
   </table>
</config>
Aug 11 07:03:20: transaction_log 0 main_commit add: <table xmlns="urn:example:clixon"><parameter><name>A</name><value>B</value></parameter></table>
<config>
   <table xmlns="urn:example:clixon">
      <parameter>
         <name>A</name>
         <value>B</value>
      </parameter>
   </table>
</config>

Actual:

Aug 11 07:03:20: transaction_log 0 main_validate add: <table xmlns="urn:example:clixon"><parameter><name>A</name><value>B</value></parameter></table>
<config>
   <table xmlns="urn:example:clixon">
      <parameter>
         <name>A</name>
         <value>A</value>
      </parameter>
   </table>
</config>
Aug 11 07:03:20: transaction_log 0 main_commit add: <table xmlns="urn:example:clixon"><parameter><name>A</name><value>B</value></parameter></table>
<config>
   <table xmlns="urn:example:clixon">
      <parameter>
         <name>A</name>
         <value>A</value>
      </parameter>
   </table>
</config>

Notes

Looks like simply clearing the candidate database on plugin init solves the issue.

[olofhagsand]

Fixed by always clearing db on startup.
Actually, this wasnt really an error, since candidate is not really a part of the startup mechanism, but I agree it could cause side-effect problems that candidate retained state from the previous run.
Please verify?

[dima1308]

@shmuelhazan did you verified it?

[shmuelhazan]

Looking good now, thanks.