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..
.. SPDX-License-Identifier: GPL-2.0-or-later
..
.. June 19 2023, Christian Hopps <chopps@labn.net>
..
.. Copyright (c) 2023, LabN Consulting, L.L.C.
..
.. _mgmtd_dev:
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
<https://github.com/opensourcerouting/frr/wiki/Retrofitting-Configuration-Commands>`_
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:
1. Add YANG module file to ``mgmtd/subdir.am`` (e.g., ``yang/frr-staticd.c``)
2. Add YANG module description into array defined in ``mgmtd/mgmt_main.c``
3. Add CLI handler file[s] to ``mgmtd/subdir.am`` (e.g., ``staticd/static_vty.c``)
4. [if needed] Exclude (#ifndef) non-configuration CLI handlers from CLI source
file (e.g., inside ``staticd/static_vty.c``)
Back-End Interface:
5. 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.
.. code-block:: make
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``:
.. code-block:: 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:
.. code-block:: c
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:
.. code-block:: c
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
.. figure:: ../figures/cli-change-client.svg
:align: center
The server (mgmtd) side of a CLI change
.. figure:: ../figures/cli-change-mgmtd.svg
:align: center
|
