ospf6d: add support for NSSA totally stub areas

Add a knob to turn a NSSA area into a totally stub area. In this
configuration a Type-3 default summary route is generated by default.

Syntax: `area A.B.C.D nssa no-summary`.

Signed-off-by: Renato Westphal <renato@opensourcerouting.org>

doc/user/ospf6d.rst

@@ -176,9 +176,9 @@ OSPF6 area
     The `not-advertise` option, when present, prevents the summary route from
     being advertised, effectively filtering the summarized routes.
 
-.. clicmd:: area A.B.C.D nssa
+.. clicmd:: area A.B.C.D nssa [no-summary]
 
-.. clicmd:: area (0-4294967295) nssa
+.. clicmd:: area (0-4294967295) nssa [no-summary]
 
    Configure the area to be a NSSA (Not-So-Stubby Area).
 
@@ -194,6 +194,10 @@ OSPF6 area
    4. Support for NSSA Translator functionality when there are multiple NSSA
       ABR in an area.
 
+   An NSSA ABR can be configured with the `no-summary` option to prevent the
+   advertisement of summaries into the area. In that case, a single Type-3 LSA
+   containing a default route is originated into the NSSA.
+
 .. _ospf6-interface:
 
 OSPF6 interface

ospf6d/ospf6_abr.c

@@ -748,7 +748,15 @@ void ospf6_abr_defaults_to_stub(struct ospf6 *o)
 	def->path.cost = metric_value(o, type, 0);
 
 	for (ALL_LIST_ELEMENTS(o->area_list, node, nnode, oa)) {
-		if (!IS_AREA_STUB(oa)) {
+		if (IS_AREA_STUB(oa) || (IS_AREA_NSSA(oa) && oa->no_summary)) {
+			/* announce defaults to stubby areas */
+			if (IS_OSPF6_DEBUG_ABR)
+				zlog_debug(
+					"Announcing default route into stubby area %s",
+					oa->name);
+			UNSET_FLAG(def->flag, OSPF6_ROUTE_REMOVE);
+			ospf6_abr_originate_summary_to_area(def, oa);
+		} else {
 			/* withdraw defaults when an area switches from stub to
 			 * non-stub */
 			route = ospf6_route_lookup(&def->prefix,
@@ -762,14 +770,6 @@ void ospf6_abr_defaults_to_stub(struct ospf6 *o)
 				SET_FLAG(def->flag, OSPF6_ROUTE_REMOVE);
 				ospf6_abr_originate_summary_to_area(def, oa);
 			}
-		} else {
-			/* announce defaults to stubby areas */
-			if (IS_OSPF6_DEBUG_ABR)
-				zlog_debug(
-					"Announcing default route into stubby area %s",
-					oa->name);
-			UNSET_FLAG(def->flag, OSPF6_ROUTE_REMOVE);
-			ospf6_abr_originate_summary_to_area(def, oa);
 		}
 	}
 	ospf6_route_delete(def);

ospf6d/ospf6_area.c

@@ -46,6 +46,9 @@
 #include "ospf6d.h"
 #include "lib/json.h"
 #include "ospf6_nssa.h"
+#ifndef VTYSH_EXTRACT_PL
+#include "ospf6d/ospf6_area_clippy.c"
+#endif
 
 DEFINE_MTYPE_STATIC(OSPF6D, OSPF6_AREA,      "OSPF6 area");
 DEFINE_MTYPE_STATIC(OSPF6D, OSPF6_PLISTNAME, "Prefix list name");
@@ -643,8 +646,12 @@ void ospf6_area_config_write(struct vty *vty, struct ospf6 *ospf6)
 			else
 				vty_out(vty, " area %s stub\n", oa->name);
 		}
-		if (IS_AREA_NSSA(oa))
+		if (IS_AREA_NSSA(oa)) {
-			vty_out(vty, " area %s nssa\n", oa->name);
+			vty_out(vty, " area %s nssa", oa->name);
+			if (oa->no_summary)
+				vty_out(vty, " no-summary");
+			vty_out(vty, "\n");
+		}
 		if (PREFIX_NAME_IN(oa))
 			vty_out(vty, " area %s filter-list prefix %s in\n",
 				oa->name, PREFIX_NAME_IN(oa));
@@ -1250,18 +1257,18 @@ DEFUN (no_ospf6_area_stub_no_summary,
 	return CMD_SUCCESS;
 }
 
-DEFUN(ospf6_area_nssa, ospf6_area_nssa_cmd,
+DEFPY(ospf6_area_nssa, ospf6_area_nssa_cmd,
-      "area <A.B.C.D|(0-4294967295)> nssa",
+      "area <A.B.C.D|(0-4294967295)>$area_str nssa [no-summary$no_summary]",
       "OSPF6 area parameters\n"
       "OSPF6 area ID in IP address format\n"
       "OSPF6 area ID as a decimal value\n"
-      "Configure OSPF6 area as nssa\n")
+      "Configure OSPF6 area as nssa\n"
+      "Do not inject inter-area routes into area\n")
 {
-	int idx_ipv4_number = 1;
 	struct ospf6_area *area;
 
 	VTY_DECLVAR_CONTEXT(ospf6, ospf6);
-	OSPF6_CMD_AREA_GET(argv[idx_ipv4_number]->arg, area, ospf6);
+	OSPF6_CMD_AREA_GET(area_str, area, ospf6);
 
 	if (!ospf6_area_nssa_set(ospf6, area)) {
 		vty_out(vty,
@@ -1269,26 +1276,32 @@ DEFUN(ospf6_area_nssa, ospf6_area_nssa_cmd,
 		return CMD_WARNING_CONFIG_FAILED;
 	}
 
-	ospf6_area_no_summary_unset(ospf6, area);
+	if (no_summary)
+		ospf6_area_no_summary_set(ospf6, area);
+	else
+		ospf6_area_no_summary_unset(ospf6, area);
+	if (ospf6_check_and_set_router_abr(ospf6))
+		ospf6_abr_defaults_to_stub(ospf6);
 
 	return CMD_SUCCESS;
 }
 
-DEFUN(no_ospf6_area_nssa, no_ospf6_area_nssa_cmd,
+DEFPY(no_ospf6_area_nssa, no_ospf6_area_nssa_cmd,
-      "no area <A.B.C.D|(0-4294967295)> nssa",
+      "no area <A.B.C.D|(0-4294967295)>$area_str nssa [no-summary$no_summary]",
       NO_STR
       "OSPF6 area parameters\n"
       "OSPF6 area ID in IP address format\n"
       "OSPF6 area ID as a decimal value\n"
-      "Configure OSPF6 area as nssa\n")
+      "Configure OSPF6 area as nssa\n"
+      "Do not inject inter-area routes into area\n")
 {
-	int idx_ipv4_number = 2;
 	struct ospf6_area *area;
 
 	VTY_DECLVAR_CONTEXT(ospf6, ospf6);
-	OSPF6_CMD_AREA_GET(argv[idx_ipv4_number]->arg, area, ospf6);
+	OSPF6_CMD_AREA_GET(area_str, area, ospf6);
 
 	ospf6_area_nssa_unset(ospf6, area);
+	ospf6_area_no_summary_unset(ospf6, area);
 
 	return CMD_SUCCESS;
 }

ospf6d/ospf6_asbr.c

@@ -588,6 +588,32 @@ void ospf6_asbr_lsa_add(struct ospf6_lsa *lsa)
 		}
 	}
 
+	/*
+	 * RFC 3101 - Section 2.5:
+	 * "If the destination is a Type-7 default route (destination ID =
+	 * DefaultDestination) and one of the following is true, then do
+	 * nothing with this LSA and consider the next in the list:
+	 *
+	 *  o  The calculating router is a border router and the LSA has
+	 *     its P-bit clear.  Appendix E describes a technique
+	 *     whereby an NSSA border router installs a Type-7 default
+	 *     LSA without propagating it.
+	 *
+	 *  o  The calculating router is a border router and is
+	 *     suppressing the import of summary routes as Type-3
+	 *     summary-LSAs".
+	 */
+	if (ntohs(lsa->header->type) == OSPF6_LSTYPE_TYPE_7
+	    && external->prefix.prefix_length == 0
+	    && CHECK_FLAG(ospf6->flag, OSPF6_FLAG_ABR)
+	    && (CHECK_FLAG(external->prefix.prefix_options,
+			   OSPF6_PREFIX_OPTION_P)
+		|| oa->no_summary)) {
+		if (IS_OSPF6_DEBUG_EXAMIN(AS_EXTERNAL))
+			zlog_debug("Skipping Type-7 default route");
+		return;
+	}
+
 	/* Check the forwarding address */
 	if (CHECK_FLAG(external->bits_metric, OSPF6_ASBR_BIT_F)) {
 		offset = sizeof(*external)

ospf6d/subdir.am

@@ -92,6 +92,7 @@ ospf6d_ospf6d_snmp_la_LIBADD = lib/libfrrsnmp.la
 
 clippy_scan += \
 	ospf6d/ospf6_top.c \
+	ospf6d/ospf6_area.c \
 	ospf6d/ospf6_asbr.c \
 	ospf6d/ospf6_lsa.c \
 	ospf6d/ospf6_gr_helper.c \