zenoh: Add support for ROS2 Humble and earlier (#26619)

* Add support for hash-less Zenoh topic key expressions

- Add kConfig option ZENOH_KEY_TYPE_HASH to toggle the inclusion
- Update topic and liveliness generators

* chore: Update Zenoh kConfig param description and help message

* docs(zenoh): Document Zenoh configuration for Humble

* docs: Clarify PX4 ROS2 Interface library compatibility

docs/en/middleware/zenoh.md

@@ -48,6 +48,11 @@ ros2 run rmw_zenoh_cpp rmw_zenohd
 
 For more information about the Zenoh Router see the [rmw_zenoh](https://github.com/ros2/rmw_zenoh?tab=readme-ov-file#start-the-zenoh-router) documentation.
 
+::: note
+From ROS 2 Jazzy onward, `rmw_zenoh` topic key expressions include the message type hash (RIHS01, as defined in REP-2016). This prevents interoperability with ROS 2 Humble and earlier.
+For more information about key expressions, refer to the [rmw_zenoh design documentation](https://github.com/ros2/rmw_zenoh/blob/jazzy/docs/design.md#topic-and-service-name-mapping-to-zenoh-key-expressions).
+:::
+
 ## PX4 Zenoh-Pico Node Setup
 
 ### PX4 Firmware
@@ -78,6 +83,12 @@ You can check if Zenoh is present at runtime by using QGroundControl to [find th
 If present, the module is installed.
 :::
 
+::: warning
+Interoperability with ROS 2 Humble and earlier requires setting `CONFIG_ZENOH_KEY_TYPE_HASH=n` to disable the
+inclusion of the message type hash (RIHS01, as defined in REP-2016) in the Zenoh key expression.
+Note that this will break compatibility with ROS 2 Jazzy and later.
+:::
+
 ### Enable Zenoh on PX4 Startup
 
 Set the [ZENOH_ENABLE](../advanced_config/parameter_reference.md#ZENOH_ENABLE) parameter to `1` to enable Zenoh on PX4 startup.
@@ -93,7 +104,7 @@ If you're using a different IP for the Zenoh daemon, run the following command (
 zenoh config net client tcp/10.41.10.1:7447#iface=eth0
 ```
 
-Note that for the simulation target with Zeroh (`px4_sitl_zenoh`) you won't need to make any changes because the default IP address of the Zenoh daemon is set to `localhost`.
+Note that for the simulation target with Zenoh (`px4_sitl_zenoh`) you won't need to make any changes because the default IP address of the Zenoh daemon is set to `localhost`.
 
 :::warning
 Any changes to the network configuration require a PX4 system reboot to take effect.
@@ -198,3 +209,7 @@ Subscription count: 0
 The [PX4 ROS 2 Interface Library](../ros2/px4_ros2_interface_lib.md) works out of the box with Zenoh as a transport backend.
 This means you can publish and subscribe to PX4 topics over Zenoh without changing your ROS 2 nodes or dealing with DDS configuration.
 For setup details and supported message types, refer to the [PX4 ROS 2 Interface Library](../ros2/px4_ros2_interface_lib.md).
+
+::: info
+The PX4 ROS 2 Interface Library is not compatible with ROS 2 Humble and earlier, as it requires the message type hash (RIHS01, as defined in REP-2016) to be included in the Zenoh key expression.
+:::

docs/en/ros2/px4_ros2_interface_lib.md

@@ -6,6 +6,10 @@
 At the time of writing, parts of the PX4 ROS 2 Interface Library are experimental, and hence subject to change.
 :::
 
+:::info
+When using `rmw_zenoh`, the PX4 ROS 2 Interface Library requires ROS 2 Jazzy or later, and is not compatible with ROS 2 Humble or earlier.
+:::
+
 The [PX4 ROS 2 Interface Library](https://github.com/Auterion/px4-ros2-interface-lib) is a C++ library (with Python bindings) that simplifies controlling and interacting with PX4 from ROS 2.
 
 The library provides three high-level interfaces for developers:

src/modules/zenoh/Kconfig

@@ -35,6 +35,13 @@ if MODULES_ZENOH
                 Uses the Zenoh matching feature to check whether a publisher has subscribers.
                 If so, only then publish the data. This is still experimental
 
+    config ZENOH_KEY_TYPE_HASH
+        bool "Include the type hash in Zenoh key expression"
+        default y
+        ---help---
+                Uses the message type hash (RIHS01, as defined in REP-2016) in the Zenoh key
+                expression (supported by ROS2 Jazzy and later).
+                Set to false to use in ROS2 Humble and earlier.
 
     # Choose exactly one item
     choice ZENOH_PUBSUB_SELECTION

src/modules/zenoh/zenoh.cpp

@@ -115,6 +115,8 @@ int ZENOH::generate_rmw_zenoh_topic_keyexpr(const char *topic, const uint8_t *ri
 	if (type_name) {
 		strncpy(type, type_name, TOPIC_INFO_SIZE);
 		toCamelCase(type); // Convert uORB type to camel case
+
+#ifdef CONFIG_ZENOH_KEY_TYPE_HASH
 		return snprintf(keyexpr, KEYEXPR_SIZE, "%" PRId32 "%s/"
 				KEYEXPR_MSG_NAME "%s_/RIHS01_"
 				"%02x%02x%02x%02x%02x%02x%02x%02x"
@@ -131,6 +133,11 @@ int ZENOH::generate_rmw_zenoh_topic_keyexpr(const char *topic, const uint8_t *ri
 				rihs_hash[24], rihs_hash[25], rihs_hash[26], rihs_hash[27],
 				rihs_hash[28], rihs_hash[29], rihs_hash[30], rihs_hash[31]
 			       );
+#else
+		return snprintf(keyexpr, KEYEXPR_SIZE, "%" PRId32 "%s/"
+				KEYEXPR_MSG_NAME "%s_/TypeHashNotSupported",
+				_zenoh_domain_id.get(), topic, type);
+#endif
 	}
 
 	return -1;
@@ -155,6 +162,7 @@ int ZENOH::generate_rmw_zenoh_topic_liveliness_keyexpr(const z_id_t *id, const c
 		str++;
 	}
 
+#ifdef CONFIG_ZENOH_KEY_TYPE_HASH
 	return snprintf(keyexpr, KEYEXPR_SIZE,
 			"@ros2_lv/%" PRId32 "/"
 			"%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x/"
@@ -184,6 +192,25 @@ int ZENOH::generate_rmw_zenoh_topic_liveliness_keyexpr(const z_id_t *id, const c
 			rihs_hash[24], rihs_hash[25], rihs_hash[26], rihs_hash[27],
 			rihs_hash[28], rihs_hash[29], rihs_hash[30], rihs_hash[31]
 		       );
+#else
+	return snprintf(keyexpr, KEYEXPR_SIZE,
+			"@ros2_lv/%" PRId32 "/"
+			"%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x/"
+			"0/11/%s/%%/%%/px4_%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x/%s/"
+			KEYEXPR_MSG_NAME "%s_/TypeHashNotSupported"
+			"/::,7:,:,:,,",
+			_zenoh_domain_id.get(),
+			id->id[0], id->id[1],  id->id[2], id->id[3], id->id[4], id->id[5], id->id[6],
+			id->id[7], id->id[8],  id->id[9], id->id[10], id->id[11], id->id[12], id->id[13],
+			id->id[14], id->id[15],
+			entity_str,
+			_px4_guid[0], _px4_guid[1], _px4_guid[2], _px4_guid[3],
+			_px4_guid[4], _px4_guid[5], _px4_guid[6], _px4_guid[7],
+			_px4_guid[8], _px4_guid[9], _px4_guid[10], _px4_guid[11],
+			_px4_guid[12], _px4_guid[13], _px4_guid[14], _px4_guid[15],
+			topic_lv, type_camel_case
+		       );
+#endif
 }
 
 int ZENOH::setupSession()