isisd: Add support for SRv6 Adjacency SIDs

An SRv6 adjacency SID is a SID that is associated with a particular
adjacency. Adjacency SIDs are advertised using the SRv6 End.X SID
Sub-TLV (RFC 9352 section #8.1) or SRv6 LAN End.X SID Sub-TLV (RFC 9352
section #8.2).

This commit defines the following Adj SIDs management functions:
* srv6_endx_sid_add_single: add a new SRv6 Adjacency SID
* srv6_endx_sid_del: delete an SRv6 Adjacency SID
* isis_srv6_endx_sid_find: lookup SRv6 End.X SID by type

It also attaches some callbacks to the hooks isis_adj_state_change_hook,
isis_adj_ip_enabled_hook, isis_adj_ip_disabled_hook, which are
responsible for installing/removing an SRv6 Adjacency SID automatically
when the state of an IS-IS adjacency changes.

Signed-off-by: Carmine Scarpitta <carmine.scarpitta@uniroma2.it>

isisd/isis_adjacency.h

@@ -98,6 +98,8 @@ struct isis_adjacency {
 	struct list *adj_sids; /* Segment Routing Adj-SIDs. */
 	uint32_t snmp_idx;
 	struct listnode *snmp_list_node;
+
+	struct list *srv6_endx_sids; /* SRv6 End.X SIDs. */
 };
 
 struct isis_threeway_adj;

isisd/isis_srv6.c

@@ -11,14 +11,18 @@
 
 #include "srv6.h"
 #include "termtable.h"
+#include "lib/lib_errors.h"
 
 #include "isisd/isisd.h"
+#include "isisd/isis_adjacency.h"
 #include "isisd/isis_misc.h"
+#include "isisd/isis_route.h"
 #include "isisd/isis_srv6.h"
 #include "isisd/isis_zebra.h"
 
 /* Local variables and functions */
 DEFINE_MTYPE_STATIC(ISISD, ISIS_SRV6_SID, "ISIS SRv6 Segment ID");
+DEFINE_MTYPE_STATIC(ISISD, ISIS_SRV6_INFO, "ISIS SRv6 information");
 
 /**
  * Fill in SRv6 SID Structure Sub-Sub-TLV with information from an SRv6 SID.
@@ -97,6 +101,7 @@ bool isis_srv6_locator_unset(struct isis_area *area)
 	struct listnode *node, *nnode;
 	struct srv6_locator_chunk *chunk;
 	struct isis_srv6_sid *sid;
+	struct srv6_adjacency *sra;
 
 	if (strncmp(area->srv6db.config.srv6_locator_name, "",
 		    sizeof(area->srv6db.config.srv6_locator_name)) == 0) {
@@ -119,6 +124,10 @@ bool isis_srv6_locator_unset(struct isis_area *area)
 		isis_srv6_sid_free(sid);
 	}
 
+	/* Uninstall all local Adjacency-SIDs. */
+	for (ALL_LIST_ELEMENTS(area->srv6db.srv6_endx_sids, node, nnode, sra))
+		srv6_endx_sid_del(sra);
+
 	/* Inform Zebra that we are releasing the SRv6 locator */
 	ret = isis_zebra_srv6_manager_release_locator_chunk(
 		area->srv6db.config.srv6_locator_name);
@@ -298,6 +307,296 @@ void isis_srv6_sid_free(struct isis_srv6_sid *sid)
 	XFREE(MTYPE_ISIS_SRV6_SID, sid);
 }
 
+/**
+ * Delete all backup SRv6 End.X SIDs.
+ *
+ * @param area	IS-IS area
+ * @param level	IS-IS level
+ */
+void isis_area_delete_backup_srv6_endx_sids(struct isis_area *area, int level)
+{
+	struct srv6_adjacency *sra;
+	struct listnode *node, *nnode;
+
+	for (ALL_LIST_ELEMENTS(area->srv6db.srv6_endx_sids, node, nnode, sra))
+		if (sra->type == ISIS_SRV6_LAN_BACKUP &&
+		    (sra->adj->level & level))
+			srv6_endx_sid_del(sra);
+}
+
+/* --- SRv6 End.X SID management functions ------------------- */
+
+/**
+ * Add new local End.X SID.
+ *
+ * @param adj	   IS-IS Adjacency
+ * @param backup   True to initialize backup Adjacency SID
+ * @param nexthops List of backup nexthops (for backup End.X SIDs only)
+ */
+void srv6_endx_sid_add_single(struct isis_adjacency *adj, bool backup,
+			      struct list *nexthops)
+{
+	struct isis_circuit *circuit = adj->circuit;
+	struct isis_area *area = circuit->area;
+	struct srv6_adjacency *sra;
+	struct isis_srv6_endx_sid_subtlv *adj_sid;
+	struct isis_srv6_lan_endx_sid_subtlv *ladj_sid;
+	struct in6_addr nexthop;
+	uint8_t flags = 0;
+	struct srv6_locator_chunk *chunk;
+	uint32_t behavior;
+
+	if (!area || !area->srv6db.srv6_locator_chunks ||
+	    list_isempty(area->srv6db.srv6_locator_chunks))
+		return;
+
+	sr_debug("ISIS-SRv6 (%s): Add %s End.X SID", area->area_tag,
+		 backup ? "Backup" : "Primary");
+
+	/* Determine nexthop IP address */
+	if (!circuit->ipv6_router || !adj->ll_ipv6_count)
+		return;
+
+	chunk = (struct srv6_locator_chunk *)listgetdata(
+		listhead(area->srv6db.srv6_locator_chunks));
+	if (!chunk)
+		return;
+
+	nexthop = adj->ll_ipv6_addrs[0];
+
+	/* Prepare SRv6 End.X as per RFC9352 section #8.1 */
+	if (backup)
+		SET_FLAG(flags, EXT_SUBTLV_LINK_SRV6_ENDX_SID_BFLG);
+
+	if (circuit->ext == NULL)
+		circuit->ext = isis_alloc_ext_subtlvs();
+
+	behavior = (CHECK_FLAG(chunk->flags, SRV6_LOCATOR_USID))
+			   ? SRV6_ENDPOINT_BEHAVIOR_END_X_NEXT_CSID
+			   : SRV6_ENDPOINT_BEHAVIOR_END_X;
+
+	sra = XCALLOC(MTYPE_ISIS_SRV6_INFO, sizeof(*sra));
+	sra->type = backup ? ISIS_SRV6_LAN_BACKUP : ISIS_SRV6_ADJ_NORMAL;
+	sra->behavior = behavior;
+	sra->locator = chunk;
+	sra->structure.loc_block_len = chunk->block_bits_length;
+	sra->structure.loc_node_len = chunk->node_bits_length;
+	sra->structure.func_len = chunk->function_bits_length;
+	sra->structure.arg_len = chunk->argument_bits_length;
+	sra->nexthop = nexthop;
+
+	sra->sid = srv6_locator_request_sid(area, chunk, -1);
+	if (IPV6_ADDR_SAME(&sra->sid, &in6addr_any)) {
+		XFREE(MTYPE_ISIS_SRV6_INFO, sra);
+		return;
+	}
+
+	switch (circuit->circ_type) {
+	/* SRv6 LAN End.X SID for Broadcast interface section #8.2 */
+	case CIRCUIT_T_BROADCAST:
+		ladj_sid = XCALLOC(MTYPE_ISIS_SUBTLV, sizeof(*ladj_sid));
+		memcpy(ladj_sid->neighbor_id, adj->sysid,
+		       sizeof(ladj_sid->neighbor_id));
+		ladj_sid->flags = flags;
+		ladj_sid->algorithm = SR_ALGORITHM_SPF;
+		ladj_sid->weight = 0;
+		ladj_sid->behavior = sra->behavior;
+		ladj_sid->sid = sra->sid;
+		ladj_sid->subsubtlvs = isis_alloc_subsubtlvs(
+			ISIS_CONTEXT_SUBSUBTLV_SRV6_ENDX_SID);
+		ladj_sid->subsubtlvs->srv6_sid_structure = XCALLOC(
+			MTYPE_ISIS_SUBSUBTLV,
+			sizeof(*ladj_sid->subsubtlvs->srv6_sid_structure));
+		ladj_sid->subsubtlvs->srv6_sid_structure->loc_block_len =
+			sra->structure.loc_block_len;
+		ladj_sid->subsubtlvs->srv6_sid_structure->loc_node_len =
+			sra->structure.loc_node_len;
+		ladj_sid->subsubtlvs->srv6_sid_structure->func_len =
+			sra->structure.func_len;
+		ladj_sid->subsubtlvs->srv6_sid_structure->arg_len =
+			sra->structure.arg_len;
+		isis_tlvs_add_srv6_lan_endx_sid(circuit->ext, ladj_sid);
+		sra->u.lendx_sid = ladj_sid;
+		break;
+	/* SRv6 End.X SID for Point to Point interface section #8.1 */
+	case CIRCUIT_T_P2P:
+		adj_sid = XCALLOC(MTYPE_ISIS_SUBTLV, sizeof(*adj_sid));
+		adj_sid->flags = flags;
+		adj_sid->algorithm = SR_ALGORITHM_SPF;
+		adj_sid->weight = 0;
+		adj_sid->behavior = sra->behavior;
+		adj_sid->sid = sra->sid;
+		adj_sid->subsubtlvs = isis_alloc_subsubtlvs(
+			ISIS_CONTEXT_SUBSUBTLV_SRV6_ENDX_SID);
+		adj_sid->subsubtlvs->srv6_sid_structure = XCALLOC(
+			MTYPE_ISIS_SUBSUBTLV,
+			sizeof(*adj_sid->subsubtlvs->srv6_sid_structure));
+		adj_sid->subsubtlvs->srv6_sid_structure->loc_block_len =
+			sra->structure.loc_block_len;
+		adj_sid->subsubtlvs->srv6_sid_structure->loc_node_len =
+			sra->structure.loc_node_len;
+		adj_sid->subsubtlvs->srv6_sid_structure->func_len =
+			sra->structure.func_len;
+		adj_sid->subsubtlvs->srv6_sid_structure->arg_len =
+			sra->structure.arg_len;
+		isis_tlvs_add_srv6_endx_sid(circuit->ext, adj_sid);
+		sra->u.endx_sid = adj_sid;
+		break;
+	default:
+		flog_err(EC_LIB_DEVELOPMENT, "%s: unexpected circuit type: %u",
+			 __func__, circuit->circ_type);
+		exit(1);
+	}
+
+	/* Add Adjacency-SID in SRDB */
+	sra->adj = adj;
+	listnode_add(area->srv6db.srv6_endx_sids, sra);
+	listnode_add(adj->srv6_endx_sids, sra);
+
+	isis_zebra_srv6_adj_sid_install(sra);
+}
+
+/**
+ * Add Primary and Backup local SRv6 End.X SID.
+ *
+ * @param adj	  IS-IS Adjacency
+ */
+void srv6_endx_sid_add(struct isis_adjacency *adj)
+{
+	srv6_endx_sid_add_single(adj, false, NULL);
+}
+
+/**
+ * Delete local SRv6 End.X SID.
+ *
+ * @param sra	SRv6 Adjacency
+ */
+void srv6_endx_sid_del(struct srv6_adjacency *sra)
+{
+	struct isis_circuit *circuit = sra->adj->circuit;
+	struct isis_area *area = circuit->area;
+
+	sr_debug("ISIS-SRv6 (%s): Delete SRv6 End.X SID", area->area_tag);
+
+	isis_zebra_srv6_adj_sid_uninstall(sra);
+
+	/* Release dynamic SRv6 SID and remove subTLVs */
+	switch (circuit->circ_type) {
+	case CIRCUIT_T_BROADCAST:
+		isis_tlvs_del_srv6_lan_endx_sid(circuit->ext, sra->u.lendx_sid);
+		break;
+	case CIRCUIT_T_P2P:
+		isis_tlvs_del_srv6_endx_sid(circuit->ext, sra->u.endx_sid);
+		break;
+	default:
+		flog_err(EC_LIB_DEVELOPMENT, "%s: unexpected circuit type: %u",
+			 __func__, circuit->circ_type);
+		exit(1);
+	}
+
+	if (sra->type == ISIS_SRV6_LAN_BACKUP && sra->backup_nexthops) {
+		sra->backup_nexthops->del =
+			(void (*)(void *))isis_nexthop_delete;
+		list_delete(&sra->backup_nexthops);
+	}
+
+	/* Remove Adjacency-SID from the SRDB */
+	listnode_delete(area->srv6db.srv6_endx_sids, sra);
+	listnode_delete(sra->adj->srv6_endx_sids, sra);
+	XFREE(MTYPE_ISIS_SRV6_INFO, sra);
+}
+
+/**
+ * Lookup SRv6 End.X SID by type.
+ *
+ * @param adj	  IS-IS Adjacency
+ * @param type    SRv6 End.X SID type
+ */
+struct srv6_adjacency *isis_srv6_endx_sid_find(struct isis_adjacency *adj,
+					       enum srv6_adj_type type)
+{
+	struct srv6_adjacency *sra;
+	struct listnode *node;
+
+	for (ALL_LIST_ELEMENTS_RO(adj->srv6_endx_sids, node, sra))
+		if (sra->type == type)
+			return sra;
+
+	return NULL;
+}
+
+/**
+ * Remove all SRv6 End.X SIDs associated to an adjacency that is going down.
+ *
+ * @param adj	IS-IS Adjacency
+ *
+ * @return	0
+ */
+static int srv6_adj_state_change(struct isis_adjacency *adj)
+{
+	struct srv6_adjacency *sra;
+	struct listnode *node, *nnode;
+
+	if (!adj->circuit->area->srv6db.config.enabled)
+		return 0;
+
+	if (adj->adj_state == ISIS_ADJ_UP)
+		return 0;
+
+	for (ALL_LIST_ELEMENTS(adj->srv6_endx_sids, node, nnode, sra))
+		srv6_endx_sid_del(sra);
+
+	return 0;
+}
+
+/**
+ * When IS-IS Adjacency got one or more IPv6 addresses, add new
+ * IPv6 address to corresponding SRv6 End.X SID accordingly.
+ *
+ * @param adj	  IS-IS Adjacency
+ * @param family  Inet Family (IPv4 or IPv6)
+ * @param global  Indicate if it concerns the Local or Global IPv6 addresses
+ *
+ * @return	  0
+ */
+static int srv6_adj_ip_enabled(struct isis_adjacency *adj, int family,
+			       bool global)
+{
+	if (!adj->circuit->area->srv6db.config.enabled || global ||
+	    family != AF_INET6)
+		return 0;
+
+	srv6_endx_sid_add(adj);
+
+	return 0;
+}
+
+/**
+ * When IS-IS Adjacency doesn't have any IPv6 addresses anymore,
+ * delete the corresponding SRv6 End.X SID(s) accordingly.
+ *
+ * @param adj	  IS-IS Adjacency
+ * @param family  Inet Family (IPv4 or IPv6)
+ * @param global  Indicate if it concerns the Local or Global IPv6 addresses
+ *
+ * @return	  0
+ */
+static int srv6_adj_ip_disabled(struct isis_adjacency *adj, int family,
+				bool global)
+{
+	struct srv6_adjacency *sra;
+	struct listnode *node, *nnode;
+
+	if (!adj->circuit->area->srv6db.config.enabled || global ||
+	    family != AF_INET6)
+		return 0;
+
+	for (ALL_LIST_ELEMENTS(adj->srv6_endx_sids, node, nnode, sra))
+		srv6_endx_sid_del(sra);
+
+	return 0;
+}
+
 /**
  * Show Segment Routing over IPv6 (SRv6) Node.
  *
@@ -444,6 +743,11 @@ void isis_srv6_area_term(struct isis_area *area)
 void isis_srv6_init(void)
 {
 	install_element(VIEW_NODE, &show_srv6_node_cmd);
+
+	/* Register hooks. */
+	hook_register(isis_adj_state_change_hook, srv6_adj_state_change);
+	hook_register(isis_adj_ip_enabled_hook, srv6_adj_ip_enabled);
+	hook_register(isis_adj_ip_disabled_hook, srv6_adj_ip_disabled);
 }
 
 /**
@@ -451,4 +755,8 @@ void isis_srv6_init(void)
  */
 void isis_srv6_term(void)
 {
+	/* Unregister hooks. */
+	hook_unregister(isis_adj_state_change_hook, srv6_adj_state_change);
+	hook_unregister(isis_adj_ip_enabled_hook, srv6_adj_ip_enabled);
+	hook_unregister(isis_adj_ip_disabled_hook, srv6_adj_ip_disabled);
 }

isisd/isis_srv6.h

@@ -120,6 +120,9 @@ struct isis_srv6_db {
 	/* List of SRv6 SIDs allocated by the IS-IS instance */
 	struct list *srv6_sids;
 
+	/* List of SRv6 End.X SIDs allocated by the IS-IS instance */
+	struct list *srv6_endx_sids;
+
 	/* Area SRv6 configuration. */
 	struct {
 		/* Administrative status of SRv6 */
@@ -164,4 +167,12 @@ void isis_srv6_end_sid2subtlv(const struct isis_srv6_sid *sid,
 void isis_srv6_locator2tlv(const struct isis_srv6_locator *loc,
 			   struct isis_srv6_locator_tlv *loc_tlv);
 
+void srv6_endx_sid_add_single(struct isis_adjacency *adj, bool backup,
+			      struct list *nexthops);
+void srv6_endx_sid_add(struct isis_adjacency *adj);
+void srv6_endx_sid_del(struct srv6_adjacency *sra);
+struct srv6_adjacency *isis_srv6_endx_sid_find(struct isis_adjacency *adj,
+					       enum srv6_adj_type type);
+void isis_area_delete_backup_srv6_endx_sids(struct isis_area *area, int level);
+
 #endif /* _FRR_ISIS_SRV6_H */

isisd/isis_tlvs.c

@@ -7913,6 +7913,44 @@ void isis_tlvs_del_lan_adj_sid(struct isis_ext_subtlvs *exts,
 		UNSET_SUBTLV(exts, EXT_LAN_ADJ_SID);
 }
 
+/* Add IS-IS SRv6 End.X SID subTLVs */
+void isis_tlvs_add_srv6_endx_sid(struct isis_ext_subtlvs *exts,
+				 struct isis_srv6_endx_sid_subtlv *adj)
+{
+	append_item(&exts->srv6_endx_sid, (struct isis_item *)adj);
+	SET_SUBTLV(exts, EXT_SRV6_ENDX_SID);
+}
+
+/* Delete IS-IS SRv6 End.X SID subTLVs */
+void isis_tlvs_del_srv6_endx_sid(struct isis_ext_subtlvs *exts,
+				 struct isis_srv6_endx_sid_subtlv *adj)
+{
+	isis_free_subsubtlvs(adj->subsubtlvs);
+	delete_item(&exts->srv6_endx_sid, (struct isis_item *)adj);
+	XFREE(MTYPE_ISIS_SUBTLV, adj);
+	if (exts->srv6_endx_sid.count == 0)
+		UNSET_SUBTLV(exts, EXT_SRV6_ENDX_SID);
+}
+
+/* Add IS-IS SRv6 LAN End.X SID subTLVs */
+void isis_tlvs_add_srv6_lan_endx_sid(struct isis_ext_subtlvs *exts,
+				     struct isis_srv6_lan_endx_sid_subtlv *lan)
+{
+	append_item(&exts->srv6_lan_endx_sid, (struct isis_item *)lan);
+	SET_SUBTLV(exts, EXT_SRV6_LAN_ENDX_SID);
+}
+
+/* Delete IS-IS SRv6 LAN End.X SID subTLVs */
+void isis_tlvs_del_srv6_lan_endx_sid(struct isis_ext_subtlvs *exts,
+				     struct isis_srv6_lan_endx_sid_subtlv *lan)
+{
+	isis_free_subsubtlvs(lan->subsubtlvs);
+	delete_item(&exts->srv6_lan_endx_sid, (struct isis_item *)lan);
+	XFREE(MTYPE_ISIS_SUBTLV, lan);
+	if (exts->srv6_lan_endx_sid.count == 0)
+		UNSET_SUBTLV(exts, EXT_SRV6_LAN_ENDX_SID);
+}
+
 void isis_tlvs_del_asla_flex_algo(struct isis_ext_subtlvs *ext,
 				  struct isis_asla_subtlvs *asla)
 {

isisd/isis_tlvs.h

@@ -891,4 +891,13 @@ void isis_subtlvs_add_srv6_end_sid(struct isis_subtlvs *subtlvs,
 				   struct isis_srv6_sid *sid);
 void isis_tlvs_add_srv6_locator(struct isis_tlvs *tlvs, uint16_t mtid,
 				struct isis_srv6_locator *loc);
+
+void isis_tlvs_add_srv6_endx_sid(struct isis_ext_subtlvs *exts,
+				 struct isis_srv6_endx_sid_subtlv *adj);
+void isis_tlvs_del_srv6_endx_sid(struct isis_ext_subtlvs *exts,
+				 struct isis_srv6_endx_sid_subtlv *adj);
+void isis_tlvs_add_srv6_lan_endx_sid(struct isis_ext_subtlvs *exts,
+				     struct isis_srv6_lan_endx_sid_subtlv *lan);
+void isis_tlvs_del_srv6_lan_endx_sid(struct isis_ext_subtlvs *exts,
+				     struct isis_srv6_lan_endx_sid_subtlv *lan);
 #endif

isisd/isis_zebra.c

@@ -1126,6 +1126,7 @@ static int isis_zebra_process_srv6_locator_chunk(ZAPI_CALLBACK_ARGS)
 	struct srv6_locator_chunk *c;
 	struct srv6_locator_chunk *chunk = srv6_locator_chunk_alloc();
 	struct isis_srv6_sid *sid;
+	struct isis_adjacency *adj;
 	enum srv6_endpoint_behavior_codepoint behavior;
 	bool allocated = false;
 
@@ -1181,6 +1182,12 @@ static int isis_zebra_process_srv6_locator_chunk(ZAPI_CALLBACK_ARGS)
 		/* Store the SID */
 		listnode_add(area->srv6db.srv6_sids, sid);
 
+		/* Create SRv6 End.X SIDs from existing IS-IS Adjacencies */
+		for (ALL_LIST_ELEMENTS_RO(area->adjacency_list, node, adj)) {
+			if (adj->ll_ipv6_count > 0)
+				srv6_endx_sid_add(adj);
+		}
+
 		/* Regenerate LSPs to advertise the new locator and the SID */
 		lsp_regenerate_schedule(area, area->is_type, 0);