zebra: Add CLI command to verify SRv6 Manager

Add a new CLI command `show segment-routing srv6 manager [json]` to
verify the overall SRv6 state. The current output displays only the
configured source address of outer encapsulating IPv6 header. The output
can be extended in the future to show more information, including
summary SRv6 information and supported capabilities.

Example:

```
r1# show segment-routing srv6 manager
Parameters:
  Encapsulation:
    Source Address:
      Configured: fc00:0:1::1

r1# show segment-routing srv6 manager json
{
  "parameters":{
    "encapsulation":{
      "sourceAddress":{
        "configured":"fc00:0:1::1"
      }
    }
  }
}
```

Signed-off-by: Carmine Scarpitta <[email protected]>

zebra/zebra_srv6_vty.c

@@ -68,6 +68,45 @@ static struct cmd_node srv6_encap_node = {
 	.prompt = "%s(config-srv6-encap)# "
 };
 
+DEFPY (show_srv6_manager,
+       show_srv6_manager_cmd,
+       "show segment-routing srv6 manager [json]",
+       SHOW_STR
+       "Segment Routing\n"
+       "Segment Routing SRv6\n"
+       "Verify SRv6 Manager\n"
+       JSON_STR)
+{
+	const bool uj = use_json(argc, argv);
+	struct zebra_srv6 *srv6 = zebra_srv6_get_default();
+	json_object *json = NULL;
+	json_object *json_parameters = NULL;
+	json_object *json_encapsulation = NULL;
+	json_object *json_source_address = NULL;
+
+	if (uj) {
+		json = json_object_new_object();
+		json_parameters = json_object_new_object();
+		json_object_object_add(json, "parameters", json_parameters);
+		json_encapsulation = json_object_new_object();
+		json_object_object_add(json_parameters, "encapsulation",
+				       json_encapsulation);
+		json_source_address = json_object_new_object();
+		json_object_object_add(json_encapsulation, "sourceAddress",
+				       json_source_address);
+		json_object_string_addf(json_source_address, "configured",
+					"%pI6", &srv6->encap_src_addr);
+		vty_json(vty, json);
+	} else {
+		vty_out(vty, "Parameters:\n");
+		vty_out(vty, "  Encapsulation:\n");
+		vty_out(vty, "    Source Address:\n");
+		vty_out(vty, "      Configured: %pI6\n", &srv6->encap_src_addr);
+	}
+
+	return CMD_SUCCESS;
+}
+
 DEFUN (show_srv6_locator,
        show_srv6_locator_cmd,
        "show segment-routing srv6 locator [json]",
@@ -508,4 +547,5 @@ void zebra_srv6_vty_init(void)
 	/* Command for operation */
 	install_element(VIEW_NODE, &show_srv6_locator_cmd);
 	install_element(VIEW_NODE, &show_srv6_locator_detail_cmd);
+	install_element(VIEW_NODE, &show_srv6_manager_cmd);
 }