Unable to Create Parent Node Using lyd_new_path (Version 3.4.2)

[msps25]

I am trying to create an XML path using lyd_new_path in libyang 3.4.2:
/module-name:module-list/listItem[id="1"]/name

My goal is to create the parent node first and then use it to create a child node.
I am using the following code to create the parent node:

lyd_new_path(NULL, sr_acquire_context(sr_session_get_connection(sess)), 
             "/module-name:module-list", NULL, 0, parent);

However, I am encountering a segmentation fault, and the parent node is not being created successfully.

Issue:

1. lyd_new_path is causing a segmentation fault when trying to create a nested list.
2. I need guidance on how to properly create a list with keys and ensure the parent node is valid before adding child nodes.

Can anyone please help me understand the correct way to create a nested list using lyd_new_path?

Thanks in advance! 🙏

[michalvasko]

Can you please post the YANG module and ideally also a code example that can be compiled that reproduces the crash?

[msps25]

Setup Details:
Netopeer2 Version: netopeer2-2.2.28
Sysrepo Version: sysrepo-2.10.1
YANG Module: https://github.com/OpenROADM/OpenROADM_MSA_Public/blob/master/model/Common/org-openroadm-alarm.yang
Subscription Function Used in sysrepo

sr_oper_get_subscribe(session, "org-openroadm-alarm", 
                      "/org-openroadm-alarm:active-alarm-list", 
                      alarm_state_cb, NULL, SR_SUBSCR_ENABLED, &subscription);

Relevant Code Snippet (alarm_state_cb)

static int 
alarm_state_cb(sr_session_ctx_t *session, const char *module_name, const char *path, const char *request_xpath,
        uint32_t request_id, struct lyd_node **parent, void *private_data)
{
    (void)session;
    (void)module_name;
    (void)path;
    (void)request_xpath;
    (void)request_id;
    (void)private_data;

    Alarm alarm_node;
    alarm_node.get_alarms_from_db();

    LY_ERR return_node_err;

    // Attempt to create the parent node
    return_node_err = lyd_new_path(NULL, sr_acquire_context(sr_session_get_connection(sess)), 
                                   "/org-openroadm-alarm:active-alarm-list", NULL, 0, parent);
    if (return_node_err) {
        zlog_error(zlog_categ, "Error occurred while inserting parent node in sysrepo");
        return SR_ERR_INTERNAL;
    }

    // Populate the activeAlarms list
    for (auto x : alarm_node.SYSTEM_ALARMS) {
        string alarm_id = x.id;
        string cause = x.cause;
        string severity = x.severity;
        string raiseTime = x.raiseTime;

        char *alarm_raiseTime_path;
        char *alarm_severity_path;
        char *alarm_cause_path;
        
        asprintf(&alarm_raiseTime_path, "/org-openroadm-alarm:active-alarm-list/activeAlarms[id='%s']/raiseTime", alarm_id.c_str());
        asprintf(&alarm_severity_path, "/org-openroadm-alarm:active-alarm-list/activeAlarms[id='%s']/severity", alarm_id.c_str());
        asprintf(&alarm_cause_path, "/org-openroadm-alarm:active-alarm-list/activeAlarms[id='%s']/probableCause/cause", alarm_id.c_str());

        return_node_err = lyd_new_path(*parent, NULL, alarm_raiseTime_path, raiseTime.c_str(), NULL, 0);
        if (return_node_err) zlog_error(zlog_categ, "Error occurred while inserting raiseTime in sysrepo");

        return_node_err = lyd_new_path(*parent, NULL, alarm_severity_path, severity.c_str(), NULL, 0);
        if (return_node_err) zlog_error(zlog_categ, "Error occurred while inserting severity in sysrepo");

        return_node_err = lyd_new_path(*parent, NULL, alarm_cause_path, cause.c_str(), NULL, 0);
        if (return_node_err) zlog_error(zlog_categ, "Error occurred while inserting cause in sysrepo");

        free(alarm_raiseTime_path);
        free(alarm_severity_path);
        free(alarm_cause_path);
    }

    zlog_error(zlog_categ, "Leaving alarm state callback\n");
    return SR_ERR_OK;
}

[michalvasko]

The code looks mostly fine and when I tested it, it worked as expected. So, I have made a few changes, but I have kept the same lyd_new_path() calls so there is no problem there. My main issue would be with

sr_acquire_context(sr_session_get_connection(sess));

What is sess? The session in the parameters is called session. Also, every sr_acquire_context() function call requires a matching sr_release_context() call. There is also sr_session_acquire_context().

[msps25]

sess is global session sr_session_ctx_t for sysrepo-plugin.

I have tried with both sess and session variable but nothing worked out for me.

[michalvasko]

Have you tried running sysrepo-plugind with valgrind?

[msps25]

I have cross-compiled these libraries for my device. However, the system libraries on the device are stripped, preventing me from running and testing them with Valgrind.

Could you suggest an alternative method to insert read-only data for org-openroadm-alarm.yang

[jktjkt]

You can either build your binaries with debug symbols and without striping them away, or you can try to reproduce the problem without cross-compilation. Both approaches have worked well in our experience when building our internal SW (also DWDM related, btw) for ARM.