isisd: Add support for isis hello padding sometimes

New configuration to pad ISIS hello packets during adjacency formation only.

Signed-off-by: Diogo Oliveira <14191454+dorDiogo@users.noreply.github.com>

9 files changed, 100 insertions, 30 deletions

diff --git a/isisd/isis_circuit.c b/isisd/isis_circuit.c
index dd5f921bef..ebf9901c52 100644
--- a/isisd/isis_circuit.c
+++ b/isisd/isis_circuit.c
@@ -107,7 +107,7 @@ struct isis_circuit *isis_circuit_new(struct interface *ifp, const char *tag)
 		"/frr-interface:lib/interface/frr-isisd:isis/circuit-type");
 	circuit->flags = 0;
 
-	circuit->pad_hellos = yang_get_default_bool(
+	circuit->pad_hellos = yang_get_default_enum(
 		"/frr-interface:lib/interface/frr-isisd:isis/hello/padding");
 	circuit->hello_interval[0] = yang_get_default_uint32(
 		"/frr-interface:lib/interface/frr-isisd:isis/hello/interval/level-1");
@@ -145,7 +145,7 @@ struct isis_circuit *isis_circuit_new(struct interface *ifp, const char *tag)
 #else
 	circuit->is_type_config = IS_LEVEL_1_AND_2;
 	circuit->flags = 0;
-	circuit->pad_hellos = 1;
+	circuit->pad_hellos = ISIS_HELLO_PADDING_ALWAYS;
 	for (i = 0; i < 2; i++) {
 		circuit->hello_interval[i] = DEFAULT_HELLO_INTERVAL;
 		circuit->hello_multiplier[i] = DEFAULT_HELLO_MULTIPLIER;
@@ -1029,7 +1029,8 @@ void isis_circuit_print_json(struct isis_circuit *circuit,
 					circuit->hello_multiplier[0]);
 				json_object_string_add(
 					hold_json, "pad",
-					(circuit->pad_hellos ? "yes" : "no"));
+					isis_hello_padding2string(
+						circuit->pad_hellos));
 				json_object_int_add(level_json, "cnsp-interval",
 						    circuit->csnp_interval[0]);
 				json_object_int_add(level_json, "psnp-interval",
@@ -1137,11 +1138,11 @@ void isis_circuit_print_vty(struct isis_circuit *circuit, struct vty *vty,
 				vty_out(vty, ", Active neighbors: %u\n",
 					circuit->upadjcount[0]);
 				vty_out(vty,
-					"      Hello interval: %u, Holddown count: %u %s\n",
+					"      Hello interval: %u, Holddown count: %u, Padding: %s\n",
 					circuit->hello_interval[0],
 					circuit->hello_multiplier[0],
-					(circuit->pad_hellos ? "(pad)"
-							     : "(no-pad)"));
+					isis_hello_padding2string(
+						circuit->pad_hellos));
 				vty_out(vty,
 					"      CNSP interval: %u, PSNP interval: %u\n",
 					circuit->csnp_interval[0],
@@ -1169,11 +1170,11 @@ void isis_circuit_print_vty(struct isis_circuit *circuit, struct vty *vty,
 				vty_out(vty, ", Active neighbors: %u\n",
 					circuit->upadjcount[1]);
 				vty_out(vty,
-					"      Hello interval: %u, Holddown count: %u %s\n",
+					"      Hello interval: %u, Holddown count: %u, Padding: %s\n",
 					circuit->hello_interval[1],
 					circuit->hello_multiplier[1],
-					(circuit->pad_hellos ? "(pad)"
-							     : "(no-pad)"));
+					isis_hello_padding2string(
+						circuit->pad_hellos));
 				vty_out(vty,
 					"      CNSP interval: %u, PSNP interval: %u\n",
 					circuit->csnp_interval[1],
@@ -1319,11 +1320,20 @@ static int isis_interface_config_write(struct vty *vty)
 				}
 			}
 
-			/* ISIS - Hello padding - Defaults to true so only
-			 * display if false */
-			if (circuit->pad_hellos == 0) {
+			/* ISIS - Hello padding - Defaults to always so only
+			 * display if not always */
+			switch (circuit->pad_hellos) {
+			case ISIS_HELLO_PADDING_DISABLED:
 				vty_out(vty, " no " PROTO_NAME " hello padding\n");
 				write++;
+				break;
+			case ISIS_HELLO_PADDING_SOMETIMES:
+				vty_out(vty, PROTO_NAME
+					" hello padding sometimes\n");
+				write++;
+				break;
+			case ISIS_HELLO_PADDING_ALWAYS:
+				break;
 			}
 
 			if (circuit->disable_threeway_adj) {
diff --git a/isisd/isis_circuit.h b/isisd/isis_circuit.h
index 494e96b697..58aa28195f 100644
--- a/isisd/isis_circuit.h
+++ b/isisd/isis_circuit.h
@@ -63,6 +63,15 @@ struct isis_circuit_arg {
 	struct isis_circuit *circuit;
 };
 
+/*
+ * Hello padding types
+ */
+enum isis_hello_padding {
+	ISIS_HELLO_PADDING_ALWAYS,
+	ISIS_HELLO_PADDING_DISABLED,
+	ISIS_HELLO_PADDING_SOMETIMES
+};
+
 struct isis_circuit {
 	enum isis_circuit_state state;
 	uint8_t circuit_id;	  /* l1/l2 bcast CircuitID */
@@ -100,7 +109,7 @@ struct isis_circuit {
 		struct isis_p2p_info p2p;
 	} u;
 	uint8_t priority[ISIS_LEVELS]; /* l1/2 IS configured priority */
-	int pad_hellos;     /* add padding to Hello PDUs ? */
+	enum isis_hello_padding pad_hellos; /* type of Hello PDUs padding */
 	char ext_domain;    /* externalDomain   (boolean) */
 	int lsp_regenerate_pending[ISIS_LEVELS];
 	uint64_t lsp_error_counter;
diff --git a/isisd/isis_cli.c b/isisd/isis_cli.c
index 5c7f610881..f430ded745 100644
--- a/isisd/isis_cli.c
+++ b/isisd/isis_cli.c
@@ -2239,15 +2239,22 @@ void cli_show_ip_isis_threeway_shake(struct vty *vty,
 /*
  * XPath: /frr-interface:lib/interface/frr-isisd:isis/hello/padding
  */
-DEFPY_YANG(isis_hello_padding, isis_hello_padding_cmd, "[no] isis hello padding",
-      NO_STR
-      "IS-IS routing protocol\n"
-      "Add padding to IS-IS hello packets\n"
-      "Pad hello packets\n")
+DEFPY_YANG(isis_hello_padding, isis_hello_padding_cmd,
+	   "[no] isis hello padding [sometimes]$padding_type",
+	   NO_STR
+	   "IS-IS routing protocol\n"
+	   "Type of padding for IS-IS hello packets\n"
+	   "Pad hello packets\n"
+	   "Add padding to hello packets during adjacency formation only.\n")
 {
-	nb_cli_enqueue_change(vty, "./frr-isisd:isis/hello/padding",
-			      NB_OP_MODIFY, no ? "false" : "true");
-
+	if (no) {
+		nb_cli_enqueue_change(vty, "./frr-isisd:isis/hello/padding",
+				      NB_OP_MODIFY, "disabled");
+	} else {
+		nb_cli_enqueue_change(vty, "./frr-isisd:isis/hello/padding",
+				      NB_OP_MODIFY,
+				      padding_type ? padding_type : "always");
+	}
 	return nb_cli_apply_changes(vty, NULL);
 }
 
@@ -2255,10 +2262,13 @@ void cli_show_ip_isis_hello_padding(struct vty *vty,
 				    const struct lyd_node *dnode,
 				    bool show_defaults)
 {
-	if (!yang_dnode_get_bool(dnode, NULL))
+	int hello_padding_type = yang_dnode_get_enum(dnode, NULL);
+	if (hello_padding_type == ISIS_HELLO_PADDING_DISABLED)
 		vty_out(vty, " no");
-
-	vty_out(vty, " isis hello padding\n");
+	vty_out(vty, " isis hello padding");
+	if (hello_padding_type == ISIS_HELLO_PADDING_SOMETIMES)
+		vty_out(vty, " sometimes");
+	vty_out(vty, "\n");
 }
 
 /*
diff --git a/isisd/isis_misc.c b/isisd/isis_misc.c
index 4a490ab5ac..7c6d600362 100644
--- a/isisd/isis_misc.c
+++ b/isisd/isis_misc.c
@@ -294,6 +294,19 @@ const char *syst2string(int type)
 	return NULL; /* not reached */
 }
 
+const char *isis_hello_padding2string(int hello_padding_type)
+{
+	switch (hello_padding_type) {
+	case ISIS_HELLO_PADDING_DISABLED:
+		return "no";
+	case ISIS_HELLO_PADDING_SOMETIMES:
+		return "sometimes";
+	case ISIS_HELLO_PADDING_ALWAYS:
+		return "yes";
+	}
+	return NULL; /* not reached */
+}
+
 /*
  * Print functions - we print to static vars
  */
diff --git a/isisd/isis_misc.h b/isisd/isis_misc.h
index b8b4ebd280..01d9abe869 100644
--- a/isisd/isis_misc.h
+++ b/isisd/isis_misc.h
@@ -16,6 +16,7 @@ const char *circuit_t2string(int);
 const char *circuit_state2string(int state);
 const char *circuit_type2string(int type);
 const char *syst2string(int);
+const char *isis_hello_padding2string(int hello_padding_type);
 struct in_addr newprefix2inaddr(uint8_t *prefix_start, uint8_t prefix_masklen);
 /*
  * Converting input to memory stored format
diff --git a/isisd/isis_nb_config.c b/isisd/isis_nb_config.c
index ea021a4ff5..fbb237688b 100644
--- a/isisd/isis_nb_config.c
+++ b/isisd/isis_nb_config.c
@@ -2765,7 +2765,7 @@ int lib_interface_isis_hello_padding_modify(struct nb_cb_modify_args *args)
 		return NB_OK;
 
 	circuit = nb_running_get_entry(args->dnode, NULL, true);
-	circuit->pad_hellos = yang_dnode_get_bool(args->dnode, NULL);
+	circuit->pad_hellos = yang_dnode_get_enum(args->dnode, NULL);
 
 	return NB_OK;
 }
diff --git a/isisd/isis_pdu.c b/isisd/isis_pdu.c
index 70ec2426d3..9ddc427c13 100644
--- a/isisd/isis_pdu.c
+++ b/isisd/isis_pdu.c
@@ -1964,8 +1964,13 @@ int send_hello(struct isis_circuit *circuit, int level)
 		isis_tlvs_add_global_ipv6_addresses(tlvs,
 						    circuit->ipv6_non_link);
 
+	bool should_pad_hello =
+		circuit->pad_hellos == ISIS_HELLO_PADDING_ALWAYS ||
+		(circuit->pad_hellos == ISIS_HELLO_PADDING_SOMETIMES &&
+		 circuit->upadjcount[0] + circuit->upadjcount[1] == 0);
+
 	if (isis_pack_tlvs(tlvs, circuit->snd_stream, len_pointer,
-			   circuit->pad_hellos, false)) {
+			   should_pad_hello, false)) {
 		isis_free_tlvs(tlvs);
 		return ISIS_WARNING; /* XXX: Maybe Log TLV structure? */
 	}
diff --git a/isisd/isis_snmp.c b/isisd/isis_snmp.c
index ae570a0864..b4ae063639 100644
--- a/isisd/isis_snmp.c
+++ b/isisd/isis_snmp.c
@@ -2161,7 +2161,9 @@ static uint8_t *isis_snmp_find_circ(struct variable *v, oid *name,
 		/*
 		 * return false if lan hellos must be padded
 		 */
-		if (circuit->pad_hellos)
+		if (circuit->pad_hellos == ISIS_HELLO_PADDING_ALWAYS ||
+		    (circuit->pad_hellos == ISIS_HELLO_PADDING_SOMETIMES &&
+		     circuit->upadjcount[0] + circuit->upadjcount[1] == 0))
 			return SNMP_INTEGER(ISIS_SNMP_TRUTH_VALUE_FALSE);
 
 		return SNMP_INTEGER(ISIS_SNMP_TRUTH_VALUE_TRUE);
diff --git a/yang/frr-isisd.yang b/yang/frr-isisd.yang
index ff3ba5d12b..f2927339ad 100644
--- a/yang/frr-isisd.yang
+++ b/yang/frr-isisd.yang
@@ -116,6 +116,26 @@ module frr-isisd {
        associated with an interface.";
   }
 
+  typedef hello-padding-type {
+    type enumeration {
+      enum "always" {
+        value 0;
+        description
+          "Add padding to all hello packets.";
+      }
+      enum "disabled" {
+        value 1;
+        description
+          "Do not add any padding to hello packets.";
+      } 
+      enum "sometimes" {
+        value 2;
+        description
+          "Add padding to hello packets during adjacency formation only.";
+      }
+    }
+  }
+
   typedef network-type {
     type enumeration {
       enum "unknown" {
@@ -605,10 +625,10 @@ module frr-isisd {
       description
         "Parameters related to IS-IS hello PDUs.";
       leaf padding {
-        type boolean;
-        default "true";
+        type hello-padding-type;
+        default "always";
         description
-          "Add padding to IS-IS hello PDUs.";
+          "Type of padding for IS-IS hello packets.";
       }
 
       container interval {