isisd: link protection optional fallback in ti-lfa

The current implementation of TI-LFA computes link-protecting
repair paths (even when node protection is enabled) to have repair
paths to all destinations when no node-protecting repair has been
found. This may be desired or not. E.g. the link-protecting paths
may use the protected node and be, therefore, useless if the node
fails. Also, computing link-protecting repairs incurs extra
calculations.

With this patch, when node protection is enabled, link protecting
repair paths are only computed if "link-fallback" is specified in
the configuration, on a per interface and IS-IS level.

Signed-off-by: Fredi Raspall <fredi@voltanet.io>

diff --git a/isisd/isis_circuit.h b/isisd/isis_circuit.h
index 45c0a7e0ed0dba22c001e4eb0709ebcff1010cdc..84c3ca3ff2b43f47a7e5f843373fad4b8f74e5f8 100644 (file)
--- a/isisd/isis_circuit.h
+++ b/isisd/isis_circuit.h
@@ -152,6 +152,7 @@ struct isis_circuit {
        struct hash *lfa_excluded_ifaces[ISIS_LEVELS];
        bool tilfa_protection[ISIS_LEVELS];
        bool tilfa_node_protection[ISIS_LEVELS];
+       bool tilfa_link_fallback[ISIS_LEVELS];
        /*
         * Counters as in 10589--11.2.5.9
         */

diff --git a/isisd/isis_cli.c b/isisd/isis_cli.c
index 3e719df4bb218fccf08eefe67eb69d67c64fc7cf..f316e0279ce83394e2e30d717f2dbba3d19f1c4e 100644 (file)
--- a/isisd/isis_cli.c
+++ b/isisd/isis_cli.c
@@ -2647,6 +2647,7 @@ void cli_show_ip_isis_frr(struct vty *vty, struct lyd_node *dnode,
 {
        bool l1_enabled, l2_enabled;
        bool l1_node_protection, l2_node_protection;
+       bool l1_link_fallback, l2_link_fallback;
 
        /* Classic LFA */
        l1_enabled = yang_dnode_get_bool(dnode, "./level-1/lfa/enable");
@@ -2692,13 +2693,21 @@ void cli_show_ip_isis_frr(struct vty *vty, struct lyd_node *dnode,
                yang_dnode_get_bool(dnode, "./level-1/ti-lfa/node-protection");
        l2_node_protection =
                yang_dnode_get_bool(dnode, "./level-2/ti-lfa/node-protection");
+       l1_link_fallback =
+               yang_dnode_get_bool(dnode, "./level-1/ti-lfa/link-fallback");
+       l2_link_fallback =
+               yang_dnode_get_bool(dnode, "./level-2/ti-lfa/link-fallback");
+
 
        if (l1_enabled || l2_enabled) {
                if (l1_enabled == l2_enabled
-                   && l1_node_protection == l2_node_protection) {
+                   && l1_node_protection == l2_node_protection
+                   && l1_link_fallback == l2_link_fallback) {
                        vty_out(vty, " isis fast-reroute ti-lfa");
                        if (l1_node_protection)
                                vty_out(vty, " node-protection");
+                       if (l1_link_fallback)
+                               vty_out(vty, " link-fallback");
                        vty_out(vty, "\n");
                } else {
                        if (l1_enabled) {
@@ -2706,6 +2715,8 @@ void cli_show_ip_isis_frr(struct vty *vty, struct lyd_node *dnode,
                                        " isis fast-reroute ti-lfa level-1");
                                if (l1_node_protection)
                                        vty_out(vty, " node-protection");
+                               if (l1_link_fallback)
+                                       vty_out(vty, " link-fallback");
                                vty_out(vty, "\n");
                        }
                        if (l2_enabled) {
@@ -2713,6 +2724,8 @@ void cli_show_ip_isis_frr(struct vty *vty, struct lyd_node *dnode,
                                        " isis fast-reroute ti-lfa level-2");
                                if (l2_node_protection)
                                        vty_out(vty, " node-protection");
+                               if (l2_link_fallback)
+                                       vty_out(vty, " link-fallback");
                                vty_out(vty, "\n");
                        }
                }
@@ -2917,14 +2930,15 @@ void cli_show_frr_remote_lfa_max_metric(struct vty *vty, struct lyd_node *dnode,
  * XPath: /frr-interface:lib/interface/frr-isisd:isis/fast-reroute/level-{1,2}/ti-lfa/enable
  */
 DEFPY(isis_ti_lfa, isis_ti_lfa_cmd,
-      "[no] isis fast-reroute ti-lfa [level-1|level-2]$level [node-protection$node_protection]",
+      "[no] isis fast-reroute ti-lfa [level-1|level-2]$level [node-protection$node_protection [link-fallback$link_fallback]]",
       NO_STR
       "IS-IS routing protocol\n"
       "Interface IP Fast-reroute configuration\n"
       "Enable TI-LFA computation\n"
       "Enable TI-LFA computation for Level 1 only\n"
       "Enable TI-LFA computation for Level 2 only\n"
-      "Protect against node failures\n")
+      "Protect against node failures\n"
+      "Enable link-protection fallback\n")
 {
        if (!level || strmatch(level, "level-1")) {
                if (no) {
@@ -2936,6 +2950,10 @@ DEFPY(isis_ti_lfa, isis_ti_lfa_cmd,
                                vty,
                                "./frr-isisd:isis/fast-reroute/level-1/ti-lfa/node-protection",
                                NB_OP_MODIFY, "false");
+                       nb_cli_enqueue_change(
+                               vty,
+                               "./frr-isisd:isis/fast-reroute/level-1/ti-lfa/link-fallback",
+                               NB_OP_MODIFY, "false");
                } else {
                        nb_cli_enqueue_change(
                                vty,
@@ -2946,6 +2964,10 @@ DEFPY(isis_ti_lfa, isis_ti_lfa_cmd,
                                "./frr-isisd:isis/fast-reroute/level-1/ti-lfa/node-protection",
                                NB_OP_MODIFY,
                                node_protection ? "true" : "false");
+                       nb_cli_enqueue_change(
+                               vty,
+                               "./frr-isisd:isis/fast-reroute/level-1/ti-lfa/link-fallback",
+                               NB_OP_MODIFY, link_fallback ? "true" : "false");
                }
        }
        if (!level || strmatch(level, "level-2")) {
@@ -2958,6 +2980,10 @@ DEFPY(isis_ti_lfa, isis_ti_lfa_cmd,
                                vty,
                                "./frr-isisd:isis/fast-reroute/level-2/ti-lfa/node-protection",
                                NB_OP_MODIFY, "false");
+                       nb_cli_enqueue_change(
+                               vty,
+                               "./frr-isisd:isis/fast-reroute/level-2/ti-lfa/link-fallback",
+                               NB_OP_MODIFY, "false");
                } else {
                        nb_cli_enqueue_change(
                                vty,
@@ -2968,6 +2994,10 @@ DEFPY(isis_ti_lfa, isis_ti_lfa_cmd,
                                "./frr-isisd:isis/fast-reroute/level-2/ti-lfa/node-protection",
                                NB_OP_MODIFY,
                                node_protection ? "true" : "false");
+                       nb_cli_enqueue_change(
+                               vty,
+                               "./frr-isisd:isis/fast-reroute/level-2/ti-lfa/link-fallback",
+                               NB_OP_MODIFY, link_fallback ? "true" : "false");
                }
        }
 

diff --git a/isisd/isis_lfa.c b/isisd/isis_lfa.c
index b535924e9364c1a4cf27c9d8dd5b34d015582a99..e033c28fefd345e86058c71b1f1eec4e6e8afc23 100644 (file)
--- a/isisd/isis_lfa.c
+++ b/isisd/isis_lfa.c
@@ -2258,6 +2258,11 @@ static void isis_spf_run_tilfa(struct isis_area *area,
                spftree_pc_node = isis_tilfa_compute(area, spftree,
                                                     spftree_reverse, resource);
                isis_spftree_del(spftree_pc_node);
+
+               /* don't do link protection unless link-fallback is configured
+                */
+               if (!circuit->tilfa_link_fallback[spftree->level - 1])
+                       return;
        }
 
        /* Compute link protecting repair paths. */

diff --git a/isisd/isis_nb.c b/isisd/isis_nb.c
index 4eac8de2cba7bb988c06ec146c2c782cb16a182e..ecad16229c18b63c2b0aadc9638618fc6c6cc443 100644 (file)
--- a/isisd/isis_nb.c
+++ b/isisd/isis_nb.c
@@ -977,6 +977,12 @@ const struct frr_yang_module_info frr_isisd_info = {
                                .modify = lib_interface_isis_fast_reroute_level_1_ti_lfa_node_protection_modify,
                        }
                },
+               {
+                       .xpath = "/frr-interface:lib/interface/frr-isisd:isis/fast-reroute/level-1/ti-lfa/link-fallback",
+                       .cbs = {
+                               .modify = lib_interface_isis_fast_reroute_level_1_ti_lfa_link_fallback_modify,
+                       }
+               },
                {
                        .xpath = "/frr-interface:lib/interface/frr-isisd:isis/fast-reroute/level-2/lfa/enable",
                        .cbs = {
@@ -1017,6 +1023,12 @@ const struct frr_yang_module_info frr_isisd_info = {
                                .modify = lib_interface_isis_fast_reroute_level_2_ti_lfa_node_protection_modify,
                        }
                },
+               {
+                       .xpath = "/frr-interface:lib/interface/frr-isisd:isis/fast-reroute/level-2/ti-lfa/link-fallback",
+                       .cbs = {
+                               .modify = lib_interface_isis_fast_reroute_level_2_ti_lfa_link_fallback_modify,
+                       }
+               },
                {
                        .xpath = "/frr-interface:lib/interface/state/frr-isisd:isis",
                        .cbs = {

diff --git a/isisd/isis_nb.h b/isisd/isis_nb.h
index 94aa00c9758527b26b2b16e13cd430be03f64874..0c2f7b6b7e5acecace3d54c560be82429d6fb50c 100644 (file)
--- a/isisd/isis_nb.h
+++ b/isisd/isis_nb.h
@@ -319,6 +319,8 @@ int lib_interface_isis_fast_reroute_level_1_ti_lfa_enable_modify(
        struct nb_cb_modify_args *args);
 int lib_interface_isis_fast_reroute_level_1_ti_lfa_node_protection_modify(
        struct nb_cb_modify_args *args);
+int lib_interface_isis_fast_reroute_level_1_ti_lfa_link_fallback_modify(
+       struct nb_cb_modify_args *args);
 int lib_interface_isis_fast_reroute_level_2_lfa_enable_modify(
        struct nb_cb_modify_args *args);
 int lib_interface_isis_fast_reroute_level_2_lfa_exclude_interface_create(
@@ -335,6 +337,8 @@ int lib_interface_isis_fast_reroute_level_2_ti_lfa_enable_modify(
        struct nb_cb_modify_args *args);
 int lib_interface_isis_fast_reroute_level_2_ti_lfa_node_protection_modify(
        struct nb_cb_modify_args *args);
+int lib_interface_isis_fast_reroute_level_2_ti_lfa_link_fallback_modify(
+       struct nb_cb_modify_args *args);
 struct yang_data *
 lib_interface_state_isis_get_elem(struct nb_cb_get_elem_args *args);
 const void *lib_interface_state_isis_adjacencies_adjacency_get_next(

diff --git a/isisd/isis_nb_config.c b/isisd/isis_nb_config.c
index f9028bdd9f79b1301b5e73694160b215c221359b..5ca2329dd34e2e1adb08341f921d920b2a70fb14 100644 (file)
--- a/isisd/isis_nb_config.c
+++ b/isisd/isis_nb_config.c
@@ -3516,6 +3516,30 @@ int lib_interface_isis_fast_reroute_level_1_ti_lfa_node_protection_modify(
        return NB_OK;
 }
 
+/*
+ * XPath:
+ * /frr-interface:lib/interface/frr-isisd:isis/fast-reroute/level-1/ti-lfa/link-fallback
+ */
+int lib_interface_isis_fast_reroute_level_1_ti_lfa_link_fallback_modify(
+       struct nb_cb_modify_args *args)
+{
+       struct isis_area *area;
+       struct isis_circuit *circuit;
+
+       if (args->event != NB_EV_APPLY)
+               return NB_OK;
+
+       circuit = nb_running_get_entry(args->dnode, NULL, true);
+       circuit->tilfa_link_fallback[0] =
+               yang_dnode_get_bool(args->dnode, NULL);
+
+       area = circuit->area;
+       if (area)
+               lsp_regenerate_schedule(area, area->is_type, 0);
+
+       return NB_OK;
+}
+
 /*
  * XPath:
  * /frr-interface:lib/interface/frr-isisd:isis/fast-reroute/level-2/lfa/enable
@@ -3720,3 +3744,27 @@ int lib_interface_isis_fast_reroute_level_2_ti_lfa_node_protection_modify(
 
        return NB_OK;
 }
+
+/*
+ * XPath:
+ * /frr-interface:lib/interface/frr-isisd:isis/fast-reroute/level-2/ti-lfa/link-fallback
+ */
+int lib_interface_isis_fast_reroute_level_2_ti_lfa_link_fallback_modify(
+       struct nb_cb_modify_args *args)
+{
+       struct isis_area *area;
+       struct isis_circuit *circuit;
+
+       if (args->event != NB_EV_APPLY)
+               return NB_OK;
+
+       circuit = nb_running_get_entry(args->dnode, NULL, true);
+       circuit->tilfa_link_fallback[1] =
+               yang_dnode_get_bool(args->dnode, NULL);
+
+       area = circuit->area;
+       if (area)
+               lsp_regenerate_schedule(area, area->is_type, 0);
+
+       return NB_OK;
+}

diff --git a/yang/frr-isisd.yang b/yang/frr-isisd.yang
index 46ad8d39715f7cb03575f86edc26cd443b273f51..4653e6f009a3d41c2687a8a7a6d1856e1cc4a058 100644 (file)
--- a/yang/frr-isisd.yang
+++ b/yang/frr-isisd.yang
@@ -493,6 +493,13 @@ module frr-isisd {
         description
           "Node protection is provided by the alternate.";
       }
+      leaf link-fallback {
+        type boolean;
+        must ". = 'false' or ../enable = 'true'";
+        default false;
+        description
+          "Fallback to link protection.";
+      }
     }
   }