MGMTD Development¶

Overview¶

mgmtd (Management Daemon) is a new centralized management daemon for FRR.

Previously, vtysh was the only centralized management service provided. Internally vtysh connects to each daemon and sends CLI commands (both configuration and operational state queries) over a socket connection. This service only supports CLI which is no longer sufficient.

An important next step was made with the addition of YANG support. A YANG infrastructure was added through a new development called northbound. This northbound interface added the capability of daemons to be configured and queried using YANG models. However, this interface was per daemon and not centralized, which is not sufficient.

mgmtd harnesses this new northbound interface to provide a centralized interface for all daemons. It utilizes the daemons YANG models to interact with each daemon. mgmtd currently provides the CLI interface for each daemon that has been converted to it, but in the future RESTCONF and NETCONF servers can easily be added as front-ends to mgmtd to support those protocols as well.

Converting A Daemon to MGMTD¶

A daemon must first be transitioned to the new northbound interface if that has not already been done (see this northbound conversion documentation for how to do this). Once this is done a few simple steps are all that is required move the daemon over to mgmtd control.

Overview of Changes¶

Adding support for a northbound converted daemon involves very little work. It requires enabling frontend (CLI and YANG) and backend (YANG) support. mgmtd was designed to keep this as simple as possible.

Front-End Interface:

Add YANG module file to mgmtd/subdir.am (e.g., yang/frr-staticd.c)
Add YANG module description into array defined in mgmtd/mgmt_main.c
Add CLI handler file[s] to mgmtd/subdir.am (e.g., staticd/static_vty.c)
[if needed] Exclude (#ifndef) non-configuration CLI handlers from CLI source file (e.g., inside staticd/static_vty.c)

Back-End Interface:

Add XPATHs mappings to a couple arrays to direct mgmtd at your daemon in mgmtd/mgmt_be_adapter.c

Add YANG and CLI into MGMTD¶

As an example here is the addition made to mgmtd/subdir.am for adding staticd support.

if STATICD
nodist_mgmtd_mgmtd_SOURCES += \
     yang/frr-staticd.yang.c \
     yang/frr-bfdd.yang.c \
     # end
nodist_mgmtd_libmgmt_be_nb_la_SOURCES += staticd/static_vty.c
endif

An here is the addition to the modules array in mgmtd/mgmt_main.c:

static const struct frr_yang_module_info *const mgmt_yang_modules[] = {
        &frr_filter_info,
        ...
#ifdef HAVE_STATICD
        &(struct frr_yang_module_info){.name = "frr-staticd",
                                      .ignore_cbs = true},
#endif
}

CLI Handlers¶

The daemon’s CLI handlers for configuration (which having been converted to northbound now simply generate YANG changes) will be linked directly into mgmtd.

If the operational and debug CLI commands are kept in files separate from the daemon’s configuration CLI commands then no extra work is required. Otherwise some CPP #ifndef’s will be required.

Currently mgmtd supports configuration CLI but not operational state so if both types of CLI handlers are present in a single file (e.g. a xxx_vty.c or xxx_cli.c file ) then #ifndef will be used to exclude these non-configuration CLI handlers from mgmtd. The same goes for debug CLI handlers. For example:

DEFPY(daemon_one_config, daemon_one_config_cmd,
      "daemon one [optional-arg]"
      ...
{
      ...
}

#ifndef INCLUDE_MGMTD_CMDDEFS_ONLY
DEFPY(daemon_show_oepr, daemon_show_oepr_cmd,
      "show daemon oper [all]"
      ...
{
      ...
}
#endif /* ifndef INCLUDE_MGMTD_CMDDEFS_ONLY */

void daemon_vty_init(void)
{
      install_element(CONFIG_NODE, &daemon_one_config_cmd);
      ...

#ifndef INCLUDE_MGMTD_CMDDEFS_ONLY
        install_element(ENABLE_NODE, &daemon_show_oper_cmd);
#endif /* ifndef INCLUDE_MGMTD_CMDDEFS_ONLY */

}

Add Back-End XPATH mappings¶

In order for mgmtd to direct configuration to your daemon you need to add some XPATH mappings to mgmtd/mgmt_be_adapter.c. These XPATHs determine which configuration changes get sent over the back-end interface to your daemon.

Below are the strings added for staticd support:

static const struct mgmt_be_xpath_map_init mgmt_xpath_map_init[] = {
    {
        .xpath_regexp = "/frr-vrf:lib/*",
        .subscr_info =
            {
#if HAVE_STATICD
                [MGMTD_BE_CLIENT_ID_STATICD] =
                    MGMT_SUBSCR_VALIDATE_CFG |
                    MGMT_SUBSCR_NOTIFY_CFG,
#endif
            },
    },
    ...
    {
        .xpath_regexp =
            "/frr-routing:routing/control-plane-protocols/control-plane-protocol/frr-staticd:staticd/*",
        .subscr_info =
            {
#if HAVE_STATICD
                [MGMTD_BE_CLIENT_ID_STATICD] =
                    MGMT_SUBSCR_VALIDATE_CFG |
                    MGMT_SUBSCR_NOTIFY_CFG,
#endif
            },
    },
};

#if HAVE_STATICD
static struct mgmt_be_client_xpath staticd_xpaths[] = {
    {
        .xpath = "/frr-vrf:lib/*",
        .subscribed = MGMT_SUBSCR_VALIDATE_CFG | MGMT_SUBSCR_NOTIFY_CFG,
    },
    ...
    {
        .xpath =
            "/frr-routing:routing/control-plane-protocols/control-plane-protocol/frr-staticd:staticd/*",
        .subscribed = MGMT_SUBSCR_VALIDATE_CFG | MGMT_SUBSCR_NOTIFY_CFG,
    },
};
#endif

static struct mgmt_be_client_xpath_map
    mgmt_client_xpaths[MGMTD_BE_CLIENT_ID_MAX] = {
#ifdef HAVE_STATICD
        [MGMTD_BE_CLIENT_ID_STATICD] = {staticd_xpaths,
                        array_size(staticd_xpaths)},
#endif
};

MGMTD Internals¶

This section will describe the internal functioning of mgmtd, for now a couple diagrams are included to aide in source code perusal.

The client side of a CLI change

The server (mgmtd) side of a CLI change