Adding upstream version 9.1.upstream/9.1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 655 insertions, 0 deletions

diff --git a/isisd/isis_ldp_sync.c b/isisd/isis_ldp_sync.c
new file mode 100644
index 0000000..53676ff
--- /dev/null
+++ b/isisd/isis_ldp_sync.c
@@ -0,0 +1,655 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/**
+ * isis_ldp_sync.c: ISIS LDP-IGP Sync  handling routines
+ * Copyright (C) 2020 Volta Networks, Inc.
+ */
+
+#include <zebra.h>
+#include <string.h>
+
+#include "monotime.h"
+#include "memory.h"
+#include "frrevent.h"
+#include "prefix.h"
+#include "table.h"
+#include "vty.h"
+#include "command.h"
+#include "plist.h"
+#include "log.h"
+#include "zclient.h"
+#include <lib/json.h>
+#include "defaults.h"
+#include "ldp_sync.h"
+
+#include "isisd/isis_constants.h"
+#include "isisd/isis_common.h"
+#include "isisd/isis_flags.h"
+#include "isisd/isis_circuit.h"
+#include "isisd/isis_lsp.h"
+#include "isisd/isis_pdu.h"
+#include "isisd/isis_network.h"
+#include "isisd/isis_misc.h"
+#include "isisd/isis_constants.h"
+#include "isisd/isis_adjacency.h"
+#include "isisd/isis_dr.h"
+#include "isisd/isisd.h"
+#include "isisd/isis_csm.h"
+#include "isisd/isis_events.h"
+#include "isisd/isis_te.h"
+#include "isisd/isis_mt.h"
+#include "isisd/isis_errors.h"
+#include "isisd/isis_tx_queue.h"
+#include "isisd/isis_nb.h"
+#include "isisd/isis_ldp_sync.h"
+
+extern struct zclient *zclient;
+
+/*
+ * LDP-SYNC msg between IGP and LDP
+ */
+int isis_ldp_sync_state_update(struct ldp_igp_sync_if_state state)
+{
+	struct interface *ifp;
+	struct isis_circuit *circuit = NULL;
+	struct isis_area *area;
+
+	/* lookup circuit */
+	ifp = if_lookup_by_index(state.ifindex, VRF_DEFAULT);
+	if (ifp == NULL)
+		return 0;
+
+	circuit = ifp->info;
+	if (circuit == NULL)
+		return 0;
+
+	/* if isis is not enabled or LDP-SYNC is not configured ignore */
+	area = circuit->area;
+	if (area == NULL
+	    || !CHECK_FLAG(area->ldp_sync_cmd.flags, LDP_SYNC_FLAG_ENABLE))
+		return 0;
+
+	/* received ldp-sync interface state from LDP */
+	ils_debug("%s: rcvd %s from LDP if %s", __func__,
+		  state.sync_start ? "sync-start" : "sync-complete", ifp->name);
+	if (state.sync_start)
+		isis_ldp_sync_if_start(circuit, false);
+	else
+		isis_ldp_sync_if_complete(circuit);
+
+	return 0;
+}
+
+int isis_ldp_sync_announce_update(struct ldp_igp_sync_announce announce)
+{
+	struct isis_area *area;
+	struct listnode *anode, *cnode;
+	struct isis_circuit *circuit;
+	struct isis *isis = isis_lookup_by_vrfid(VRF_DEFAULT);
+
+	/* if isis is not enabled ignore */
+	if (!isis)
+		return 0;
+
+	if (announce.proto != ZEBRA_ROUTE_LDP)
+		return 0;
+
+	ils_debug("%s: rcvd announce from LDP", __func__);
+
+	/* LDP just started up:
+	 *  set cost to LSInfinity
+	 *  send request to LDP for LDP-SYNC state for each interface
+	 */
+	for (ALL_LIST_ELEMENTS_RO(isis->area_list, anode, area)) {
+		if (!CHECK_FLAG(area->ldp_sync_cmd.flags, LDP_SYNC_FLAG_ENABLE))
+			continue;
+
+		for (ALL_LIST_ELEMENTS_RO(area->circuit_list, cnode, circuit))
+			isis_ldp_sync_if_start(circuit, true);
+	}
+
+	return 0;
+}
+
+void isis_ldp_sync_state_req_msg(struct isis_circuit *circuit)
+{
+	struct ldp_igp_sync_if_state_req request;
+	struct interface *ifp = circuit->interface;
+
+	ils_debug("%s: send state request to LDP for %s", __func__, ifp->name);
+
+	memset(&request, 0, sizeof(request));
+	strlcpy(request.name, ifp->name, sizeof(ifp->name));
+	request.proto = LDP_IGP_SYNC_IF_STATE_REQUEST;
+	request.ifindex = ifp->ifindex;
+
+	zclient_send_opaque(zclient, LDP_IGP_SYNC_IF_STATE_REQUEST,
+		(uint8_t *)&request, sizeof(request));
+}
+
+/*
+ * LDP-SYNC general interface routines
+ */
+void isis_ldp_sync_if_start(struct isis_circuit *circuit,
+	bool send_state_req)
+{
+	struct ldp_sync_info *ldp_sync_info;
+
+	ldp_sync_info = circuit->ldp_sync_info;
+
+	/* Start LDP-SYNC on this interface:
+	 *  set cost of interface to LSInfinity so traffic will use different
+	 *  interface until LDP has learned all labels from peer
+	 *  start holddown timer if configured
+	 *  send msg to LDP to get LDP-SYNC state
+	 */
+	if (ldp_sync_info &&
+	    ldp_sync_info->enabled == LDP_IGP_SYNC_ENABLED &&
+	    ldp_sync_info->state != LDP_IGP_SYNC_STATE_NOT_REQUIRED) {
+		ils_debug("%s: start on if %s state: %s", __func__,
+			  circuit->interface->name, "Holding down until Sync");
+		ldp_sync_info->state = LDP_IGP_SYNC_STATE_REQUIRED_NOT_UP;
+		isis_ldp_sync_set_if_metric(circuit, true);
+		isis_ldp_sync_holddown_timer_add(circuit);
+
+		if (send_state_req)
+			isis_ldp_sync_state_req_msg(circuit);
+	}
+}
+
+void isis_ldp_sync_if_complete(struct isis_circuit *circuit)
+{
+	struct ldp_sync_info *ldp_sync_info;
+
+	ldp_sync_info = circuit->ldp_sync_info;
+
+	/* received sync-complete from LDP:
+	 *  set state to up
+	 *  stop timer
+	 *  restore interface cost to original value
+	 */
+	if (ldp_sync_info && ldp_sync_info->enabled == LDP_IGP_SYNC_ENABLED) {
+		if (ldp_sync_info->state == LDP_IGP_SYNC_STATE_REQUIRED_NOT_UP)
+			ldp_sync_info->state = LDP_IGP_SYNC_STATE_REQUIRED_UP;
+
+		EVENT_OFF(ldp_sync_info->t_holddown);
+
+		isis_ldp_sync_set_if_metric(circuit, true);
+	}
+}
+
+void isis_ldp_sync_ldp_fail(struct isis_circuit *circuit)
+{
+	struct ldp_sync_info *ldp_sync_info;
+
+	ldp_sync_info = circuit->ldp_sync_info;
+
+	/* LDP client close detected:
+	 *  stop holddown timer
+	 *  set cost of interface to LSInfinity so traffic will use different
+	 *  interface until LDP restarts and has learned all labels from peer
+	 */
+	if (ldp_sync_info &&
+	    ldp_sync_info->enabled == LDP_IGP_SYNC_ENABLED &&
+	    ldp_sync_info->state != LDP_IGP_SYNC_STATE_NOT_REQUIRED) {
+		EVENT_OFF(ldp_sync_info->t_holddown);
+		ldp_sync_info->state = LDP_IGP_SYNC_STATE_REQUIRED_NOT_UP;
+		isis_ldp_sync_set_if_metric(circuit, true);
+	}
+}
+
+static int isis_ldp_sync_adj_state_change(struct isis_adjacency *adj)
+{
+	struct isis_circuit *circuit = adj->circuit;
+	struct ldp_sync_info *ldp_sync_info = circuit->ldp_sync_info;
+	struct isis_area *area = circuit->area;
+
+	if (!CHECK_FLAG(area->ldp_sync_cmd.flags, LDP_SYNC_FLAG_ENABLE)
+	    || circuit->interface->vrf->vrf_id != VRF_DEFAULT
+	    || if_is_loopback(circuit->interface))
+		return 0;
+
+	if (ldp_sync_info->enabled != LDP_IGP_SYNC_ENABLED)
+		return 0;
+
+	if (adj->adj_state == ISIS_ADJ_UP) {
+		if (circuit->circ_type == CIRCUIT_T_P2P ||
+		    if_is_pointopoint(circuit->interface)) {
+			/* If LDP-SYNC is configure on interface then start */
+			ldp_sync_info->state =
+				LDP_IGP_SYNC_STATE_REQUIRED_NOT_UP;
+			isis_ldp_sync_if_start(circuit, true);
+		} else {
+			/* non ptop link so don't run ldp-sync */
+			ldp_sync_info->state = LDP_IGP_SYNC_STATE_NOT_REQUIRED;
+			isis_ldp_sync_set_if_metric(circuit, true);
+		}
+	} else {
+		/* If LDP-SYNC is configure on this interface then stop it */
+		if (circuit->circ_type == CIRCUIT_T_P2P ||
+		    if_is_pointopoint(circuit->interface))
+			ldp_sync_info->state =
+				LDP_IGP_SYNC_STATE_REQUIRED_NOT_UP;
+		else
+			ldp_sync_info->state = LDP_IGP_SYNC_STATE_NOT_REQUIRED;
+
+		ils_debug("%s: down on if %s", __func__,
+			  circuit->interface->name);
+		ldp_sync_if_down(circuit->ldp_sync_info);
+	}
+
+	return 0;
+}
+
+bool isis_ldp_sync_if_metric_config(struct isis_circuit *circuit, int level,
+				    int metric)
+{
+	struct ldp_sync_info *ldp_sync_info = circuit->ldp_sync_info;
+	struct isis_area *area = circuit->area;
+
+	/* configured interface metric has been changed:
+	 *   if LDP-IGP Sync is running and metric has been set to LSInfinity
+	 *   change saved value so when ldp-sync completes proper metric is
+	 *   restored
+	 */
+	if (area && CHECK_FLAG(area->ldp_sync_cmd.flags, LDP_SYNC_FLAG_ENABLE)
+	    && ldp_sync_info != NULL) {
+
+		if (CHECK_FLAG(ldp_sync_info->flags,
+			       LDP_SYNC_FLAG_SET_METRIC)) {
+			ldp_sync_info->metric[level-1] = metric;
+			ldp_sync_info->metric[level-1] = metric;
+			return false;
+		}
+	}
+	return true;
+}
+
+void isis_ldp_sync_set_if_metric(struct isis_circuit *circuit, bool run_regen)
+{
+	struct ldp_sync_info *ldp_sync_info;
+
+	/* set interface metric:
+	 *   if LDP-IGP Sync is starting set metric so interface
+	 *   is used only as last resort
+	 *   else restore metric to original value
+	 */
+	if (circuit->ldp_sync_info == NULL || circuit->area == NULL)
+		return;
+
+	ldp_sync_info = circuit->ldp_sync_info;
+	if (ldp_sync_if_is_enabled(ldp_sync_info)) {
+		/* if metric already set to LSInfinity just return */
+		if (CHECK_FLAG(ldp_sync_info->flags, LDP_SYNC_FLAG_SET_METRIC))
+			return;
+
+		SET_FLAG(ldp_sync_info->flags, LDP_SYNC_FLAG_SET_METRIC);
+		if (circuit->is_type & IS_LEVEL_1) {
+			if (circuit->area->newmetric) {
+				ldp_sync_info->metric[0] =
+					circuit->te_metric[0];
+				circuit->te_metric[0] =
+					ISIS_WIDE_METRIC_INFINITY;
+			} else {
+				ldp_sync_info->metric[0] = circuit->metric[0];
+				circuit->metric[0] =
+					ISIS_NARROW_METRIC_INFINITY;
+			}
+		}
+		if (circuit->is_type & IS_LEVEL_2) {
+			if (circuit->area->newmetric) {
+				ldp_sync_info->metric[1] =
+					circuit->te_metric[1];
+				circuit->te_metric[1] =
+					ISIS_WIDE_METRIC_INFINITY;
+			} else {
+				ldp_sync_info->metric[1] = circuit->metric[1];
+				circuit->metric[1] =
+					ISIS_NARROW_METRIC_INFINITY;
+			}
+		}
+	} else {
+		/* if metric already restored just return */
+		if (!CHECK_FLAG(ldp_sync_info->flags, LDP_SYNC_FLAG_SET_METRIC))
+			return;
+
+		UNSET_FLAG(ldp_sync_info->flags, LDP_SYNC_FLAG_SET_METRIC);
+		if (circuit->is_type & IS_LEVEL_1) {
+			circuit->te_metric[0] = ldp_sync_info->metric[0];
+			circuit->metric[0] = ldp_sync_info->metric[0];
+		}
+		if (circuit->is_type & IS_LEVEL_2) {
+			circuit->te_metric[1] = ldp_sync_info->metric[1];
+			circuit->metric[1] = ldp_sync_info->metric[1];
+		}
+	}
+
+	if (run_regen)
+		lsp_regenerate_schedule(circuit->area, circuit->is_type, 0);
+}
+
+
+/*
+ * LDP-SYNC holddown timer routines
+ */
+static void isis_ldp_sync_holddown_timer(struct event *thread)
+{
+	struct isis_circuit *circuit;
+	struct ldp_sync_info *ldp_sync_info;
+
+	/* holddown timer expired:
+	 *  didn't receive msg from LDP indicating sync-complete
+	 *  restore interface cost to original value
+	 */
+	circuit = EVENT_ARG(thread);
+	if (circuit->ldp_sync_info == NULL)
+		return;
+
+	ldp_sync_info = circuit->ldp_sync_info;
+
+	ldp_sync_info->state = LDP_IGP_SYNC_STATE_REQUIRED_UP;
+	ldp_sync_info->t_holddown = NULL;
+
+	ils_debug("%s: holddown timer expired for %s state:sync achieved",
+		  __func__, circuit->interface->name);
+
+	isis_ldp_sync_set_if_metric(circuit, true);
+}
+
+void isis_ldp_sync_holddown_timer_add(struct isis_circuit *circuit)
+{
+	struct ldp_sync_info *ldp_sync_info;
+
+	ldp_sync_info = circuit->ldp_sync_info;
+
+	/* Start holddown timer:
+	 *  this timer is used to keep interface cost at LSInfinity
+	 *  once expires returns cost to original value
+	 *  if timer is already running or holddown time is off just return
+	 */
+	if (ldp_sync_info->t_holddown ||
+	    ldp_sync_info->holddown == LDP_IGP_SYNC_HOLDDOWN_DEFAULT)
+		return;
+
+	ils_debug("%s: start holddown timer for %s time %d", __func__,
+		  circuit->interface->name, ldp_sync_info->holddown);
+
+	event_add_timer(master, isis_ldp_sync_holddown_timer, circuit,
+			ldp_sync_info->holddown, &ldp_sync_info->t_holddown);
+}
+
+/*
+ * LDP-SYNC handle client close routine
+ */
+void isis_ldp_sync_handle_client_close(struct zapi_client_close_info *info)
+{
+	struct isis_area *area;
+	struct listnode *anode, *cnode;
+	struct isis_circuit *circuit;
+	struct isis *isis = isis_lookup_by_vrfid(VRF_DEFAULT);
+
+	/* if isis is not enabled ignore */
+	if (!isis)
+		return;
+
+	/* Check if the LDP main client session closed */
+	if (info->proto != ZEBRA_ROUTE_LDP || info->session_id == 0)
+		return;
+
+	/* Handle the zebra notification that the LDP client session closed.
+	 *  set cost to LSInfinity
+	 *  send request to LDP for LDP-SYNC state for each interface
+	 */
+	zlog_err("%s: LDP down", __func__);
+
+	for (ALL_LIST_ELEMENTS_RO(isis->area_list, anode, area)) {
+		if (!CHECK_FLAG(area->ldp_sync_cmd.flags, LDP_SYNC_FLAG_ENABLE))
+			continue;
+
+		for (ALL_LIST_ELEMENTS_RO(area->circuit_list, cnode, circuit))
+			isis_ldp_sync_ldp_fail(circuit);
+	}
+}
+
+/*
+ * LDP-SYNC routes used by set commands.
+ */
+
+void isis_area_ldp_sync_enable(struct isis_area *area)
+{
+	struct isis_circuit *circuit;
+	struct listnode *node;
+
+	if (!CHECK_FLAG(area->ldp_sync_cmd.flags, LDP_SYNC_FLAG_ENABLE)) {
+		SET_FLAG(area->ldp_sync_cmd.flags, LDP_SYNC_FLAG_ENABLE);
+
+		for (ALL_LIST_ELEMENTS_RO(area->circuit_list, node, circuit))
+			isis_if_ldp_sync_enable(circuit);
+	}
+}
+
+void isis_area_ldp_sync_disable(struct isis_area *area)
+{
+	struct isis_circuit *circuit;
+	struct listnode *node;
+
+	if (CHECK_FLAG(area->ldp_sync_cmd.flags, LDP_SYNC_FLAG_ENABLE)) {
+		for (ALL_LIST_ELEMENTS_RO(area->circuit_list, node, circuit))
+			isis_if_ldp_sync_disable(circuit);
+
+		UNSET_FLAG(area->ldp_sync_cmd.flags, LDP_SYNC_FLAG_ENABLE);
+
+		UNSET_FLAG(area->ldp_sync_cmd.flags, LDP_SYNC_FLAG_HOLDDOWN);
+		area->ldp_sync_cmd.holddown = LDP_IGP_SYNC_HOLDDOWN_DEFAULT;
+	}
+}
+
+void isis_area_ldp_sync_set_holddown(struct isis_area *area, uint16_t holddown)
+{
+	struct isis_circuit *circuit;
+	struct listnode *node;
+
+	if (holddown == LDP_IGP_SYNC_HOLDDOWN_DEFAULT)
+		UNSET_FLAG(area->ldp_sync_cmd.flags, LDP_SYNC_FLAG_HOLDDOWN);
+	else
+		SET_FLAG(area->ldp_sync_cmd.flags, LDP_SYNC_FLAG_HOLDDOWN);
+
+	area->ldp_sync_cmd.holddown = holddown;
+
+	for (ALL_LIST_ELEMENTS_RO(area->circuit_list, node, circuit))
+		isis_if_set_ldp_sync_holddown(circuit);
+}
+
+void isis_if_ldp_sync_enable(struct isis_circuit *circuit)
+{
+	struct ldp_sync_info *ldp_sync_info = circuit->ldp_sync_info;
+	struct isis_area *area = circuit->area;
+
+	/* called when setting LDP-SYNC at the global level:
+	 *  specified on interface overrides global config
+	 *  if ptop link send msg to LDP indicating ldp-sync enabled
+	 */
+	if (if_is_loopback(circuit->interface))
+		return;
+
+	if (circuit->interface->vrf->vrf_id != VRF_DEFAULT)
+		return;
+
+	ils_debug("%s: enable if %s", __func__, circuit->interface->name);
+
+	if (!CHECK_FLAG(area->ldp_sync_cmd.flags, LDP_SYNC_FLAG_ENABLE))
+		return;
+
+	/* config on interface, overrides global config. */
+	if (CHECK_FLAG(ldp_sync_info->flags, LDP_SYNC_FLAG_IF_CONFIG))
+		if (ldp_sync_info->enabled != LDP_IGP_SYNC_ENABLED)
+			return;
+
+	if (!CHECK_FLAG(ldp_sync_info->flags, LDP_SYNC_FLAG_HOLDDOWN))
+		ldp_sync_info->holddown = area->ldp_sync_cmd.holddown;
+
+	if (circuit->circ_type == CIRCUIT_T_P2P
+	    || if_is_pointopoint(circuit->interface)) {
+		ldp_sync_info->state = LDP_IGP_SYNC_STATE_REQUIRED_NOT_UP;
+		isis_ldp_sync_state_req_msg(circuit);
+	} else {
+		ldp_sync_info->state = LDP_IGP_SYNC_STATE_NOT_REQUIRED;
+		ils_debug("%s: Sync only runs on P2P links %s", __func__,
+			  circuit->interface->name);
+	}
+}
+
+void isis_if_ldp_sync_disable(struct isis_circuit *circuit)
+{
+	struct ldp_sync_info *ldp_sync_info = circuit->ldp_sync_info;
+	struct isis_area *area = circuit->area;
+
+	/* Stop LDP-SYNC on this interface:
+	 *  if holddown timer is running stop it
+	 *  delete ldp instance on interface
+	 *  restore metric
+	 */
+	if (if_is_loopback(circuit->interface))
+		return;
+
+	ils_debug("%s: remove if %s", __func__, circuit->interface->name);
+
+	if (!CHECK_FLAG(area->ldp_sync_cmd.flags, LDP_SYNC_FLAG_ENABLE))
+		return;
+
+	EVENT_OFF(ldp_sync_info->t_holddown);
+	ldp_sync_info->state = LDP_IGP_SYNC_STATE_NOT_REQUIRED;
+	isis_ldp_sync_set_if_metric(circuit, true);
+}
+
+void isis_if_set_ldp_sync_holddown(struct isis_circuit *circuit)
+{
+	struct ldp_sync_info *ldp_sync_info = circuit->ldp_sync_info;
+	struct isis_area *area = circuit->area;
+
+	/* called when setting LDP-SYNC at the global level:
+	 *  specified on interface overrides global config.
+	 */
+	if (if_is_loopback(circuit->interface))
+		return;
+
+	/* config on interface, overrides global config. */
+	if (CHECK_FLAG(ldp_sync_info->flags, LDP_SYNC_FLAG_HOLDDOWN))
+		return;
+	if (CHECK_FLAG(area->ldp_sync_cmd.flags, LDP_SYNC_FLAG_HOLDDOWN))
+		ldp_sync_info->holddown = area->ldp_sync_cmd.holddown;
+	else
+		ldp_sync_info->holddown = LDP_IGP_SYNC_HOLDDOWN_DEFAULT;
+}
+
+/*
+ * LDP-SYNC routines used by show commands.
+ */
+
+static void isis_circuit_ldp_sync_print_vty(struct isis_circuit *circuit,
+	struct vty *vty)
+{
+	struct ldp_sync_info *ldp_sync_info;
+	const char *ldp_state;
+
+	if (circuit->ldp_sync_info == NULL ||
+	    if_is_loopback(circuit->interface))
+		return;
+
+	ldp_sync_info = circuit->ldp_sync_info;
+	vty_out(vty, "%-16s\n", circuit->interface->name);
+	if (circuit->state == C_STATE_CONF) {
+		vty_out(vty, "  Interface down\n");
+		return;
+	}
+
+	vty_out(vty, "  LDP-IGP Synchronization enabled: %s\n",
+		ldp_sync_info->enabled == LDP_IGP_SYNC_ENABLED
+		? "yes"
+		: "no");
+	vty_out(vty, "  holddown timer in seconds: %u\n",
+		ldp_sync_info->holddown);
+
+	switch (ldp_sync_info->state) {
+	case LDP_IGP_SYNC_STATE_REQUIRED_UP:
+		vty_out(vty, "  State: Sync achieved\n");
+		break;
+	case LDP_IGP_SYNC_STATE_REQUIRED_NOT_UP:
+		if (ldp_sync_info->t_holddown != NULL) {
+			struct timeval remain =
+				event_timer_remain(ldp_sync_info->t_holddown);
+			vty_out(vty,
+				"  Holddown timer is running %lld.%03lld remaining\n",
+				(long long)remain.tv_sec,
+				(long long)remain.tv_usec/1000);
+
+			vty_out(vty, "  State: Holding down until Sync\n");
+		} else
+			vty_out(vty, "  State: Sync not achieved\n");
+		break;
+	case LDP_IGP_SYNC_STATE_NOT_REQUIRED:
+	default:
+		if ((circuit->circ_type != CIRCUIT_T_P2P &&
+		     !if_is_pointopoint(circuit->interface)) &&
+		    circuit->circ_type != CIRCUIT_T_UNKNOWN)
+			ldp_state = "Sync not required: non-p2p link";
+		else
+			ldp_state = "Sync not required";
+		vty_out(vty, "  State: %s\n", ldp_state);
+		break;
+	}
+}
+
+DEFUN (show_isis_mpls_ldp_interface,
+       show_isis_mpls_ldp_interface_cmd,
+       "show " PROTO_NAME " mpls ldp-sync [interface <INTERFACE|all>]",
+       SHOW_STR
+       PROTO_HELP
+       MPLS_STR
+       "LDP-IGP Sync information\n"
+       "Interface information\n"
+       "Interface name\n"
+       "All interfaces\n")
+{
+	char *ifname = NULL;
+	int idx_intf = 0;
+	struct listnode *anode, *cnode;
+	struct isis_area *area;
+	struct isis_circuit *circuit;
+	struct isis *isis = isis_lookup_by_vrfid(VRF_DEFAULT);
+	bool found = false;
+
+	if (!isis) {
+		vty_out(vty, "IS-IS Routing Process not enabled\n");
+		return CMD_SUCCESS;
+	}
+
+	if (argv_find(argv, argc, "INTERFACE", &idx_intf))
+		ifname = argv[idx_intf]->arg;
+
+	for (ALL_LIST_ELEMENTS_RO(isis->area_list, anode, area)) {
+		for (ALL_LIST_ELEMENTS_RO(area->circuit_list, cnode, circuit))
+			if (!ifname)
+				isis_circuit_ldp_sync_print_vty(circuit, vty);
+			else if (strcmp(circuit->interface->name, ifname)
+				 == 0) {
+				isis_circuit_ldp_sync_print_vty(circuit, vty);
+				found = true;
+			}
+	}
+
+	if (found == false && ifname)
+		vty_out(vty, "%-16s\n  ISIS not enabled\n", ifname);
+
+	return CMD_SUCCESS;
+}
+
+void isis_ldp_sync_init(void)
+{
+
+	/* "show ip isis mpls ldp interface" commands. */
+	install_element(VIEW_NODE, &show_isis_mpls_ldp_interface_cmd);
+
+	/* register for adjacency state changes */
+	hook_register(isis_adj_state_change_hook,
+		      isis_ldp_sync_adj_state_change);
+}