FRR/ospf: demote/promote carp when no neighbors are found (#1460)

FRR: Inspired by OpenBSD's handling of carp demotion in ospfd (https://man.openbsd.org/ospfd.conf.5), this should lead to a similar result. Event handling is not complete yet, but the concept seems to be working.

- The basic idea is actually quite simple, create a ospf status monitor script to utilize our new carp hooks (https://docs.opnsense.org/development/backend/carp.html)
- Use Syslog-NG's functionality to filter messages and use those as events, so we can trigger "configctl interface update carp service_status" when our state changes

and carp should do the rest.

net/frr/src/etc/rc.carp_service_status.d/carp_frr_ospf

@@ -0,0 +1,25 @@
+#!/bin/sh
+if [ -f /etc/rc.conf.d/frr ]; then
+    . /etc/rc.conf.d/frr
+fi
+
+if [ "$frr_enable" == "YES" ] && (`echo "$frr_daemons" | /usr/bin/grep -F -q -w "ospfd"`) &&
+        (`echo "$frr_carp_demote" | /usr/bin/grep -F -q -w "ospfd"`)  ; then
+    # OSPF enabled
+    OSPF_NEIGHBOR=`echo "show ip ospf neighbor" | /usr/local/bin/vtysh 2>&1` IFS=
+    if [ "$?" -eq 0 ]; then
+        # running, check if we can find any neighbors
+        IFS=
+        neighbors_count=`echo $OSPF_NEIGHBOR |  grep "Full/" | wc -l`
+        unset IFS
+        if [ "$neighbors_count" -eq 0 ]; then
+            # no neighbors in state Full/* found
+            exit 2
+        else
+            exit 0
+        fi
+    else
+        # not running
+        exit 1
+    fi
+fi

net/frr/src/opnsense/mvc/app/controllers/OPNsense/Quagga/forms/ospf.xml

@@ -5,6 +5,16 @@
         <type>checkbox</type>
         <help>This will activate the OSPF service if routing protocols are enabled in "General".</help>
     </field>
+    <field>
+      <id>ospf.carp_demote</id>
+      <label>CARP demote</label>
+      <type>checkbox</type>
+      <help>
+            Register CARP status monitor, when no neighbors are found, consider this node less attractive.
+            This feature needs syslog enabled using "Debugging" logging to catch all relevant status events.
+            This option is not compatible with "Enable CARP Failover".
+      </help>
+    </field>
     <field>
         <id>ospf.routerid</id>
         <label>Router ID</label>

net/frr/src/opnsense/mvc/app/models/OPNsense/Quagga/OSPF.xml

@@ -7,6 +7,10 @@
             <default>0</default>
             <Required>Y</Required>
         </enabled>
+        <carp_demote type="BooleanField">
+            <default>0</default>
+            <Required>Y</Required>
+        </carp_demote>
         <routerid type="TextField">
             <default></default>
             <Required>N</Required>

net/frr/src/opnsense/service/templates/OPNsense/Quagga/+TARGETS

@@ -5,3 +5,4 @@ ripd.conf:/usr/local/etc/frr/ripd.conf
 frr:/etc/rc.conf.d/frr
 zebra.conf:/usr/local/etc/frr/zebra.conf
 vtysh.conf:/usr/local/etc/frr/vtysh.conf
+syslog-ng-frr-events.conf:/usr/local/etc/syslog-ng.conf.d/frr-events.conf

net/frr/src/opnsense/service/templates/OPNsense/Quagga/frr

@@ -11,6 +11,7 @@ if helpers.exists('OPNsense.quagga.bgp.enabled') and OPNsense.quagga.bgp.enabled
 if helpers.exists('OPNsense.quagga.ospf6.enabled') and OPNsense.quagga.ospf6.enabled == '1' %} ospf6d{% endif %}{%
 if helpers.exists('OPNsense.quagga.ripng.enabled') and OPNsense.quagga.ripng.enabled == '1' %} ripngd{% endif %}{%
 if helpers.exists('OPNsense.quagga.isis.enabled') and OPNsense.quagga.isis.enabled == '1' %} isisd{% endif %}"
+frr_carp_demote="{% if not helpers.empty('OPNsense.quagga.ospf.carp_demote') %} ospfd{% endif %}"
 {% else %}
 frr_enable="NO"
 {% endif %}

net/frr/src/opnsense/service/templates/OPNsense/Quagga/syslog-ng-frr-events.conf

@@ -0,0 +1,23 @@
+{% if not helpers.empty('OPNsense.quagga.general.enabled')
+  and not helpers.empty('OPNsense.quagga.ospf.enabled')
+  and not helpers.empty('OPNsense.quagga.ospf.carp_demote') %}
+destination d_frr_event {
+    program("/usr/local/sbin/configctl -e -t 0.5 interface update carp service_status");
+};
+
+filter f_frr_ospf {
+    program("ospfd") and (
+        (
+                level("info") or level("notice")
+        ) or (
+                level("debug") and message(".*EXT .*ospf_ext_link_ism_change.*")
+        )
+    );
+};
+
+log {
+    source(s_all);
+    filter(f_frr_ospf);
+    destination(d_frr_event);
+};
+{% endif %}