confd: add must expression to verify ospf backbone is not nssa/stub

Silently drop any area-type setting for ospf backbone in a migrate
script to prevent any field issues after upgrading to this fix.

Fixes #1247

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

src/confd/share/migrate/1.6/30-ospf-backbone-area-type.sh

@@ -0,0 +1,28 @@
+#!/bin/sh
+# Remove area-type from OSPF backbone area (0.0.0.0)
+# The backbone area cannot be configured as stub or NSSA per RFC 2328/3101
+# Silently drop any area-type setting for area 0.0.0.0
+
+file=$1
+temp=${file}.tmp
+
+jq '
+if .["ietf-routing:routing"]?."control-plane-protocols"?."control-plane-protocol" then
+  .["ietf-routing:routing"]."control-plane-protocols"."control-plane-protocol" |= map(
+    if .["ietf-ospf:ospf"]?.areas?.area then
+      .["ietf-ospf:ospf"].areas.area |= map(
+        if (.["area-id"] == "0.0.0.0") and .["area-type"] then
+          # Remove area-type from backbone area
+          del(.["area-type"])
+        else
+          .
+        end
+      )
+    else
+      .
+    end
+  )
+else
+  .
+end
+' "$file" > "$temp" && mv "$temp" "$file"

src/confd/share/migrate/1.6/Makefile.am

@@ -1,3 +1,4 @@
 migratedir          = $(pkgdatadir)/migrate/1.6
 dist_migrate_DATA   = 10-dhcp-client-to-ipv4.sh \
-                      20-autoconf-to-presence.sh
+                      20-autoconf-to-presence.sh \
+                      30-ospf-backbone-area-type.sh

src/confd/yang/confd.inc

@@ -22,7 +22,7 @@ MODULES=(
 	"ieee802-dot1q-types@2022-10-29.yang"
 	"infix-ip@2025-11-02.yang"
 	"infix-if-type@2025-02-12.yang"
-	"infix-routing@2024-11-27.yang"
+	"infix-routing@2025-11-10.yang"
 	"ieee802-dot1ab-lldp@2022-03-15.yang"
 	"infix-lldp@2025-05-05.yang"
 	"infix-dhcp-common@2025-01-29.yang"

src/confd/yang/confd/infix-routing.yang

@@ -20,6 +20,10 @@ module infix-routing {
   contact      "kernelkit@googlegroups.com";
   description  "Deviations and augments for ietf-routing and ietf-ospf.";
 
+  revision 2025-11-10 {
+    description "Add must constraint to prevent backbone area as stub/NSSA";
+    reference "RFC 2328, RFC 3101";
+  }
   revision 2024-11-27 {
     description "Deviate address-family in OSPF";
     reference "internal";
@@ -348,6 +352,19 @@ module infix-routing {
   }
 
   /* OSPF Area */
+  deviation "/rt:routing/rt:control-plane-protocols/rt:control-plane-protocol/ospf:ospf/ospf:areas/ospf:area/ospf:area-type" {
+    deviate add {
+      must "(../ospf:area-id != '0.0.0.0') or "
+         + "(derived-from-or-self(., 'ospf:normal-area'))" {
+        error-message "Area 0.0.0.0 (backbone) cannot be configured as "
+                    + "stub or NSSA.";
+        description
+          "The backbone area (area 0.0.0.0) must be a normal area. "
+        + "It cannot be configured as a stub area or NSSA as per "
+        + "RFC 2328 and RFC 3101.";
+      }
+    }
+  }
   deviation "/rt:routing/rt:control-plane-protocols/rt:control-plane-protocol/ospf:ospf/ospf:areas/ospf:area/ospf:virtual-links" {
     deviate not-supported;
   }