isisd: Start Label Manager safer

Initial attempt to connect to the Label Manager used an infinite loop with
a sleep statement which block isisd until Label Manager connection fire up.

This commit changes the way Label Manager connection is established and uses
a `thread_add_timer()` call to re-attempt to establish the connection in case
of failure (zebra or label manager not ready).

New variables are added to the SRDB in order to control the request of SRGB
and SRLB to the Label Manager to start Segment Routing in a safe way.

Signed-off-by: Olivier Dugeon <olivier.dugeon@orange.com>

1 files changed, 116 insertions, 39 deletions

diff --git a/isisd/isis_sr.c b/isisd/isis_sr.c
index 32de71cca..f27aca991 100644
--- a/isisd/isis_sr.c
+++ b/isisd/isis_sr.c
@@ -142,10 +142,20 @@ int isis_sr_cfg_srgb_update(struct isis_area *area, uint32_t lower_bound,
 	sr_debug("ISIS-Sr (%s): Update SRGB with new range [%u/%u]",
 		 area->area_tag, lower_bound, upper_bound);
 
-	/* First release the old SRGB. */
-	if (srdb->config.enabled)
-		isis_zebra_release_label_range(srdb->config.srgb_lower_bound,
+	/* Just store new SRGB values if Label Manager is not available.
+	 * SRGB will be configured later when SR start */
+	if (!isis_zebra_label_manager_ready()) {
+		srdb->config.srgb_lower_bound = lower_bound;
+		srdb->config.srgb_upper_bound = upper_bound;
+		return 0;
+	}
+
+	/* Label Manager is ready, start by releasing the old SRGB. */
+	if (srdb->srgb_active) {
+	        isis_zebra_release_label_range(srdb->config.srgb_lower_bound,
 					       srdb->config.srgb_upper_bound);
+	        srdb->srgb_active = false;
+	}
 
 	srdb->config.srgb_lower_bound = lower_bound;
 	srdb->config.srgb_upper_bound = upper_bound;
@@ -157,8 +167,12 @@ int isis_sr_cfg_srgb_update(struct isis_area *area, uint32_t lower_bound,
 		if (isis_zebra_request_label_range(
 			    srdb->config.srgb_lower_bound,
 			    srdb->config.srgb_upper_bound
-				    - srdb->config.srgb_lower_bound + 1))
+				    - srdb->config.srgb_lower_bound + 1) < 0) {
+			srdb->srgb_active = false;
 			return -1;
+		} else
+			srdb->srgb_active = true;
+
 
 		sr_debug("  |- Got new SRGB [%u/%u]",
 			 srdb->config.srgb_lower_bound,
@@ -175,8 +189,7 @@ int isis_sr_cfg_srgb_update(struct isis_area *area, uint32_t lower_bound,
 		lsp_regenerate_schedule(area, area->is_type, 0);
 	} else if (srdb->config.enabled) {
 		/* Try to enable SR again using the new SRGB. */
-		if (isis_sr_start(area) == 0)
-			area->srdb.enabled = true;
+		isis_sr_start(area);
 	}
 
 	return 0;
@@ -199,33 +212,39 @@ int isis_sr_cfg_srlb_update(struct isis_area *area, uint32_t lower_bound,
 	struct isis_sr_db *srdb = &area->srdb;
 	struct listnode *node, *nnode;
 	struct sr_adjacency *sra;
-	int rc;
 
 	sr_debug("ISIS-Sr (%s): Update SRLB with new range [%u/%u]",
 		 area->area_tag, lower_bound, upper_bound);
 
-	/* First Delete SRLB */
+	/* Just store new SRLB values if Label Manager is not available.
+	 * SRLB will be configured later when SR start */
+	if (!isis_zebra_label_manager_ready()) {
+		srdb->config.srlb_lower_bound = lower_bound;
+		srdb->config.srlb_upper_bound = upper_bound;
+		return 0;
+	}
+
+	/* LM is ready, start by deleting the old SRLB */
 	sr_local_block_delete(area);
 
 	srdb->config.srlb_lower_bound = lower_bound;
 	srdb->config.srlb_upper_bound = upper_bound;
 
-	if (!srdb->enabled)
-		return 0;
-
-	/* Initialize new SRLB */
-	rc = sr_local_block_init(area);
-	if (rc !=0)
-		return rc;
-
-	/* Reinstall local Adjacency-SIDs with new labels. */
-	for (ALL_LIST_ELEMENTS(area->srdb.adj_sids, node, nnode, sra))
-		sr_adj_sid_update(sra, &srdb->srlb);
+	if (srdb->enabled) {
+		/* Initialize new SRLB */
+		if (sr_local_block_init(area) != 0)
+			return -1;
 
-	/* Update Router Capability */
+		/* Reinstall local Adjacency-SIDs with new labels. */
+		for (ALL_LIST_ELEMENTS(area->srdb.adj_sids, node, nnode, sra))
+			sr_adj_sid_update(sra, &srdb->srlb);
 
-	/* Update and Flood LSP */
-	lsp_regenerate_schedule(area, area->is_type, 0);
+		/* Update and Flood LSP */
+		lsp_regenerate_schedule(area, area->is_type, 0);
+	} else if (srdb->config.enabled) {
+		/* Try to enable SR again using the new SRLB. */
+		isis_sr_start(area);
+	}
 
 	return 0;
 }
@@ -1326,11 +1345,15 @@ static int sr_route_update(struct isis_area *area, struct prefix *prefix,
  *
  * @param area	IS-IS area
  */
-static void sr_local_block_init(struct isis_area *area)
+static int sr_local_block_init(struct isis_area *area)
 {
 	struct isis_sr_db *srdb = &area->srdb;
 	struct sr_local_block *srlb = &srdb->srlb;
 
+	/* Check if SRLB is not already configured */
+	if (srlb->active)
+		return 0;
+
 	/*
 	 * Request SRLB to the label manager. If the allocation fails, return
 	 * an error to disable SR until a new SRLB is successfully allocated.
@@ -1338,8 +1361,10 @@ static void sr_local_block_init(struct isis_area *area)
 	if (isis_zebra_request_label_range(
 		    srdb->config.srlb_lower_bound,
 		    srdb->config.srlb_upper_bound
-			    - srdb->config.srlb_lower_bound + 1))
-		return;
+			    - srdb->config.srlb_lower_bound + 1)) {
+		srlb->active = false;
+		return -1;
+	}
 
 	sr_debug("ISIS-Sr (%s): Got new SRLB [%u/%u]", area->area_tag,
 		 srdb->config.srlb_lower_bound, srdb->config.srlb_upper_bound);
@@ -1354,6 +1379,9 @@ static void sr_local_block_init(struct isis_area *area)
 		srlb->max_block++;
 	srlb->used_mark = XCALLOC(MTYPE_ISIS_SR_INFO,
 				  srlb->max_block * SRLB_BLOCK_SIZE);
+	srlb->active = true;
+
+	return 0;
 }
 
 /**
@@ -1366,6 +1394,10 @@ static void sr_local_block_delete(struct isis_area *area)
 	struct isis_sr_db *srdb = &area->srdb;
 	struct sr_local_block *srlb = &srdb->srlb;
 
+	/* Check if SRLB is not already delete */
+	if (!srlb->active)
+		return;
+
 	sr_debug("ISIS-Sr (%s): Remove SRLB [%u/%u]", area->area_tag,
 		 srlb->start, srlb->end);
 
@@ -1376,7 +1408,7 @@ static void sr_local_block_delete(struct isis_area *area)
 	/* Then reset SRLB structure */
 	if (srlb->used_mark != NULL)
 		XFREE(MTYPE_ISIS_SR_INFO, srlb->used_mark);
-	memset(srlb, 0, sizeof(struct sr_local_block));
+	srlb->active = false;
 }
 
 /**
@@ -2042,6 +2074,26 @@ DEFUN(show_sr_node, show_sr_node_cmd,
 /* --- IS-IS Segment Routing Management function ---------------------------- */
 
 /**
+ * Thread function to re-attempt connection to the Label Manager and thus be
+ * able to start Segment Routing.
+ *
+ * @param start		Thread structure that contains area as argument
+ *
+ * @return		1 on success
+ */
+static int sr_start_label_manager(struct thread *start)
+{
+	struct isis_area *area;
+
+	area = THREAD_ARG(start);
+
+	/* re-attempt to start SR & Label Manager connection */
+	isis_sr_start(area);
+
+	return 1;
+}
+
+/**
  * Enable SR on the given IS-IS area.
  *
  * @param area	IS-IS area
@@ -2054,19 +2106,35 @@ int isis_sr_start(struct isis_area *area)
 	struct isis_circuit *circuit;
 	struct listnode *node;
 
-	/* Initialize the SRLB */
-	if (sr_local_block_init(area) != 0)
+	/* First start Label Manager if not ready */
+	if (!isis_zebra_label_manager_ready())
+		if (isis_zebra_label_manager_connect() < 0) {
+			/* Re-attempt to connect to Label Manager in 1 sec. */
+			thread_add_timer(master, sr_start_label_manager, area,
+					 1, &srdb->t_start_lm);
+			return -1;
+		}
+
+	/* Label Manager is ready, initialize the SRLB */
+	if (sr_local_block_init(area) < 0)
 		return -1;
 
 	/*
-	 * Request SGRB to the label manager. If the allocation fails, return
-	 * an error to disable SR until a new SRGB is successfully allocated.
+	 * Request SGRB to the label manager if not already active. If the
+	 * allocation fails, return an error to disable SR until a new SRGB
+	 * is successfully allocated.
 	 */
-	if (isis_zebra_request_label_range(
-		    srdb->config.srgb_lower_bound,
-		    srdb->config.srgb_upper_bound
-			    - srdb->config.srgb_lower_bound + 1))
-		return -1;
+	if (!srdb->srgb_active) {
+		if (isis_zebra_request_label_range(
+			    srdb->config.srgb_lower_bound,
+			    srdb->config.srgb_upper_bound
+				    - srdb->config.srgb_lower_bound + 1)
+		    < 0) {
+			srdb->srgb_active = false;
+			return -1;
+		} else
+			srdb->srgb_active = true;
+	}
 
 	sr_debug("ISIS-Sr: Starting Segment Routing for area %s",
 		 area->area_tag);
@@ -2102,6 +2170,8 @@ int isis_sr_start(struct isis_area *area)
 		}
 	}
 
+	area->srdb.enabled = true;
+
 	/* Regenerate LSPs to advertise Segment Routing capabilities. */
 	lsp_regenerate_schedule(area, area->is_type, 0);
 
@@ -2122,6 +2192,9 @@ void isis_sr_stop(struct isis_area *area)
 	sr_debug("ISIS-Sr: Stopping Segment Routing for area %s",
 		 area->area_tag);
 
+	/* Disable any re-attempt to connect to Label Manager */
+	THREAD_TIMER_OFF(srdb->t_start_lm);
+
 	/* Uninstall all local Adjacency-SIDs. */
 	for (ALL_LIST_ELEMENTS(area->srdb.adj_sids, node, nnode, sra))
 		sr_adj_sid_del(sra);
@@ -2136,13 +2209,18 @@ void isis_sr_stop(struct isis_area *area)
 		}
 	}
 
-	/* Release SRGB. */
-	isis_zebra_release_label_range(srdb->config.srgb_lower_bound,
-				       srdb->config.srgb_upper_bound);
+	/* Release SRGB if active. */
+	if (srdb->srgb_active) {
+		isis_zebra_release_label_range(srdb->config.srgb_lower_bound,
+					       srdb->config.srgb_upper_bound);
+		srdb->srgb_active = false;
+	}
 
 	/* Delete SRLB */
 	sr_local_block_delete(area);
 
+	area->srdb.enabled = false;
+
 	/* Regenerate LSPs to advertise that the Node is no more SR enable. */
 	lsp_regenerate_schedule(area, area->is_type, 0);
 }
@@ -2161,7 +2239,6 @@ void isis_sr_area_init(struct isis_area *area)
 
 	/* Initialize Segment Routing Data Base */
 	memset(srdb, 0, sizeof(*srdb));
-	srdb->enabled = false;
 	srdb->adj_sids = list_new();
 
 	for (int level = ISIS_LEVEL1; level <= ISIS_LEVELS; level++) {