Cellular Network Infrastructure » cni-legacy » OpenBSC

The problem should be fixed now. First of all I have taken some actions to allow
zero length codec list. I have fixed both, the encoding and the decoding and
added a unit test for the zero length corner case.

See also: https://gerrit.osmocom.org/11373

The BSC uses the speech codec list decoding functionality once, I have fixed it
so that it now checks the length, before this it was relying on the fact that
the decoding function fails for the zero length case.

See also: https://gerrit.osmocom.org/#/c/osmo-bsc/+/11386

Then I have removed the check for zero length that the BSC does before it
generates the COMPLETE LAYER 3 INFORMATION message. It now sends a possibly
empty speech codec list to the encoder function that now happly encodecs it.

See also: https://gerrit.osmocom.org/#/c/osmo-bsc/+/11387

The last thing I added is optional. I am not sure if it is really needed or if
we should abandon it. I now again check for zero length codec list and if this
is the case the codec list will be completely excluded. I should be permitted
by the spec because in general the IE is optional, it is only required if the
network supports an IP based user-plane interface. If we have no codecs
available we effectively don't support an IP based user-plane interface and
therefore we may exclude the IE completely. I think in the end it is a matter
of taste what. Having a zero length speech codec element inside the
COMPLETE LAYER 3 INFORMATION message wouln't look that nice, but it still would
be spec compliant.

See also: https://gerrit.osmocom.org/#/c/osmo-bsc/+/11388

All patches are merged, I think we can close this.