Allow unknown TLVs to pass through

[puddly]

Unknown TLVs should not be a hard parsing failure (in this case we were missing DURATION = 23), they are inevitable and the TLV structure allows them to be passed through and re-serialized untouched.

#209 will add the missing TLVs.

[puddly]

This will also fix home-assistant/addons#4357

[agners]

Seems sensible to me!

[TheZoker]

Would be amazing, if this can be merged/releases rather quickly since my boarder router does not work because of this issue and I can't use my matter via thread devices. Thanks!

[lkm]

I've tried to patch my live installation with this and run into this exception instead.

Traceback (most recent call last):
  File "/usr/src/homeassistant/homeassistant/config_entries.py", line 762, in __async_setup_with_context
    result = await component.async_setup_entry(hass, self)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/src/homeassistant/homeassistant/components/otbr/__init__.py", line 73, in async_setup_entry
    await update_issues(hass, otbrdata, dataset_tlvs)
  File "/usr/src/homeassistant/homeassistant/components/otbr/util.py", line 268, in update_issues
    _warn_on_default_network_settings(hass, otbrdata, dataset_tlvs)
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/src/homeassistant/homeassistant/components/otbr/util.py", line 224, in _warn_on_default_network_settings
    dataset = tlv_parser.parse_tlv(dataset_tlvs.hex())
  File "/usr/local/lib/python3.13/site-packages/python_otbr_api/tlv_parser.py", line 187, in parse_tlv
    raise TLVError(f"expected {_len} bytes for tag {tag!r}, got {length - pos}")
python_otbr_api.tlv_parser.TLVError: expected 162 bytes for tag 61, got 6

UPDATE: I think this has to do with the fact that my OTBR docker instance had dropped it's active dataset entirely and reconfiguring via the UI didn't reapply it, however, manually setting the active dataset to the backed up value via ot-ctl did fix it.

[emontnemery]

Why do we modify the existing tests instead of adding new tests?
Also, is all the the new code covered by tests?

Edit: The only added code not covered is the handling of duplicated tags

[emontnemery]

Considering the point of the PR it to let unknown tags pass through, I'm not sure we should log a warning? I'd suggest to lower severity to debug since this shouldn't matter to the user.

[emontnemery]

I discussed this with @puddly and we decided to merge this PR as is and improve the tests in a follow-up to ensure this PR is included in Home Assistant Core 2026.2.0 which is released tomorrow.