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net: lwm2m: Correctly Support Bootstrap-Delete Operation #29964

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broglep-work opened this issue Nov 12, 2020 · 1 comment · Fixed by #30200
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net: lwm2m: Correctly Support Bootstrap-Delete Operation #29964

broglep-work opened this issue Nov 12, 2020 · 1 comment · Fixed by #30200
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@rlubos
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area: LWM2M Enhancement Changes/Updates/Additions to existing features

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@broglep-work
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broglep-work commented Nov 12, 2020 •
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Summary

  • DELETE / is implemented as DELETE /0
  • DELETE /and DELETE /x for x != 0 is not supported/implemented

Background

Zephyr client should support bootstrap-delete according to the specification.
Currently the support is only implementing partially and that part not according to the specification:

  • If the client is in bootstrap mode and bootstrap server sends a DELETE request without Uri-Path option, then bootstrap_delete will be executed (wm2m_engine.c:3344)
  • bootstrap_delete deletes SECURITY instances > 0

Given bootstrap_delete is called when no uri option is set, the assumed contract of that method is that it should correspond to DELETE / where all Instances of all Objects in the LwM2M Client MUST be removed (except for the two cases mentioned above) where The two exceptions are the LwM2M Bootstrap-Server Account, potentially including an associated Instance of an OSCORE Object ID:21, and the single Instance of the mandatory Device Object (ID:3), which are not affected by any Delete operation.

Proposal

  1. Fix: Adjust current code to delete all other object instances as well
  2. Enhancement: Support both no Uri-Path header and empty Uri-Path header, and treat them the same way
  3. Enhancement: Support deletion of all instance of a particular object

Side Note

Sending a DELETE /x request to the client in bootstrap mode is executed as DELETE /x/0 (goes through regular delete request handler that does not check if uri path has length >=2 as it is not allowed by the spec outside of bootstrap, object and instance id must be set)
@broglep-work broglep-work added the Enhancement Changes/Updates/Additions to existing features label Nov 12, 2020
@rlubos rlubos mentioned this issue Nov 23, 2020
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rlubos commented Nov 23, 2020 •
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@broglep-work Thanks for reporting. Indeed the current implementation oversimplified a lot. I've pushed a PR with proposed changes: #30200

I've verified that DELETE / and DELETE /x works as expected, I wasn't able to verify DELETE /x/y though as the bootstrap serves I tried with did not issue such operation. I'm not expecting any surprises there though since the same bootstrap_delete handler shall be called then, which implements single resource removal in a straightforward way.

During the rework I've also realized that bootstrap DISCOVER operation is totally broken, but that's a story for a separate PR.

rlubos added a commit to rlubos/zephyr that referenced this issue Nov 24, 2020
@rlubos
net: lwm2m: Rework bootstrap DELETE operation
d0d32d5 
Rework the bootstrap DELETE operation, to support deletion of multiple
resources.

Current implementation had several oversimplifications, making it not
spec-compliant:
* DELETE `/` removed only Security object instances (!= 0)
* DELETE `/x` was handled as DELETE `/x/0`, therefore not removing all
  of the object instances.

Since the above is only supported during bootstrap and not regular
Device management, this functionality was implemented in the
`bootstrap_delete` function, which now will be called for all DELETE
operations initiated during bootstrap. The regular LwM2M DELETE handler
will only be called during regular Device management, as it has more
strict limitations on what can be deleted.

Additionally, handle empty URI Path option as `/`, therefore indicating
deletion of all resources.

Fixes zephyrproject-rtos#29964

Signed-off-by: Robert Lubos <[email protected]>
nashif pushed a commit that referenced this issue Dec 1, 2020
@rlubos @nashif
net: lwm2m: Rework bootstrap DELETE operation
1c8f52a 
Rework the bootstrap DELETE operation, to support deletion of multiple
resources.

Current implementation had several oversimplifications, making it not
spec-compliant:
* DELETE `/` removed only Security object instances (!= 0)
* DELETE `/x` was handled as DELETE `/x/0`, therefore not removing all
  of the object instances.

Since the above is only supported during bootstrap and not regular
Device management, this functionality was implemented in the
`bootstrap_delete` function, which now will be called for all DELETE
operations initiated during bootstrap. The regular LwM2M DELETE handler
will only be called during regular Device management, as it has more
strict limitations on what can be deleted.

Additionally, handle empty URI Path option as `/`, therefore indicating
deletion of all resources.

Fixes #29964

Signed-off-by: Robert Lubos <[email protected]>
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net: lwm2m: Rework bootstrap DELETE operation rlubos/zephyr
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@broglep-work @carlescufi @rlubos