bsc: improve encryption testing config TestHdlrEncrParams

Clean up: absorb pars.encr_exp_enc_alg into TestHdlrEncrParams as
pars.encr.alg_expect.

Remove the automagic encr alg choice from test procedures, instead put
all magic in the pars.encr configuration setup; like this all encr alg
values remain fixed through the tests, less confusing.

Add separate alg_chosen for BSSMAP: So far, we have only one algorithm
field for both the mask of permitted algorithms in the Encryption
Information IS and the Chosen Encryption Algorithm IE. However, in the
Chosen Enc Alg there must be only one bit set. Thus we cannot easily run
a test where more than one alg is permitted and where the BSSMAP Chosen
Enc Alg IE is involved.

We've recently come to realize that the Chosen Encryption Algorithm IE
may also be omitted from BSSMAP messages, in which case osmo-bsc should
still work. To be able to test BSSMAP messages with omitted Chosen
Encryption Algorithm, allow to set alg_chosen == omit.

Keep t_EncrParams() in a way that all current tests (that set only one
bit in alg_permitted) still run the same as they always did.

Add t_EncrParams2() for a proper template.
Add a convenience function to configure encryption testing.

Related: SYS#5839
Change-Id: I6590ecf4a146dbed494d9d72f5a79441877e9010
2 files changed