11.12. Migrating from Anjay 3.4

11.12.1. Introduction

Since Anjay 3.5.0, the code flow of delivering notifications has been refactored so that user handler callbacks may be called in a different order. This only affects direct users of avs_coap APIs (e.g. when communicating over raw CoAP protocol).

11.12.2. Changed flow of cancelling observations in case of errors

CoAP observations are implicitly cancelled if a notification bearing a 4.xx or 5.xx error code is delivered. If an attempt to deliver a confirmable notification times out, CoAP observation is not cancelled by default anymore. It can be adjusted by WITH_AVS_COAP_OBSERVE_CANCEL_ON_TIMEOUT.

In Anjay 3.4.x and earlier, this cancellation (which involves calling the avs_coap_observe_cancel_handler_t callback) was performed before calling the avs_coap_delivery_status_handler_t callback for the specific notification. Since Anjay 3.5.0, this order is reversed, so any code that relies on this logic may break.

This change is only relevant if you are using avs_coap APIs directly (e.g. when communicating over raw CoAP protocol) and in case of notifications intended to be delivered as confirmable. The LwM2M Observe/Notify implementation in Anjay has been updated accordingly.

11.12.3. Addition of resource_instance_remove handler

LwM2M TS 1.2 introduced possibility to delete a Resource Instance, so one additional data model handler had to be added.

New resource_instance_remove handler (and its associated anjay_dm_resource_instance_remove_t function type) has been introduced. It is analogous to the instance_remove handler; its job is to remove a specific Resource Instance from a multiple-instance Resource.

Its implementation is required in objects that include at least one writeable multiple-instance Resource, if the client application aims for compliance with LwM2M 1.2.

11.12.4. Limiting the maximum Hold Off Time for Bootstrap

A limit has been introduced on the maximum Hold Off Time (LwM2M Security Object, Resource ID: 11) to avoid excessive delays when initiating the Bootstrap process. Previously, the upper bound was implicitly 120 seconds, but it is now explicitly limited to 20 seconds by default.

This behavior can be customized at build time using the MAX_HOLDOFF_TIME macro.

11.12.5. Handling of Trust Store for certain Certificate Usages settings

avs_commons 5.5.0 that is used by Anjay 3.11.0 does not pass the configured Trust Store (whether manually provided or acquired through the EST process) to Mbed TLS when the certificate usage is set to DANE-TA or DANE-EE, if the Data Model already contains a Server certificate intended for verifying the Server during a secure connection.

If the Server certificate is missing from the Data Model, Anjay falls back to PKIX verification, provided that a Trust Store is available, even when the certificate usage is set to DANE-TA or DANE-EE.

For more information on how Anjay manages the Trust Store and the Certificate Usage resource, see Certificate Usage.

11.12.6. Python environment isolation

All Python-based tools (e.g. integration tests) must be executed within a Python virtual environment. See Virtual environments for more information.