Changes

nokia: make Rx diversity configurable

The config structure sent to the BTS with BTS_CONF_DATA includes
an IE that enables or disables Rx diversity.  In the original code
this setting was hard-coded to enabled state; make it configurable
via vty.

Change-Id: I73bd91b717a8c8b338bacb6ed9db73bb07245c12

nokia bts-reset-timer: raise the maximum to 300 s

The previous vty tuning range for this timer (allowing up to 100 s)
is not sufficient for Flexi Multiradio BTS, where we need 120 s
minimum or 130 s for some margin.  Raise the upper limit for vty
config of this parameter to 5 min, which should be long enough
to not require further revisiting.

Change-Id: Ie5b784c9cce56e27800084471a7fb0b867cc0c69

nokia: respond to BTS_COMMISS_TEST_REQ

In some cases, Flexi Multiradio BTS sends us BTS_COMMISS_TEST_REQ
during its init process, and expects us to respond with
BTS_COMMISS_TEST_COMPL, indicating that we did the requested
commissioning tests.  While we don't do any actual tests currently,
and we have not yet reached an understanding of the exact conditions
as to when the BTS makes this query of us, if it does send us
BTS_COMMISS_TEST_REQ, we need to respond with BTS_COMMISS_TEST_COMPL
to make it happy.

Change-Id: I0f2710c3cdb38a9e5b37e40ca5584237a730a902

rsl: don't send legacy Chan Ident IE for Nokia BTS

The description of CHAN ACTIV command message in TS 48.058
section 8.4.1 lists Channel Identification as an optional IE,
with a note that reads "Included if compatibility with phase1
is required."  This note may have been misinterpreted as
referring to compatibility with Phase 1 phones - but since
this network-internal Abis detail is invisible to phones,
the real intent of GSM spec authors here must have been
compatibility with Phase 1 BTS.

Previous versions of OsmoBSC would always include this IE,
and it appears that all previously supported BTS models
would simply ignore it.  However, newer Nokia BTS models
(observed on Flexi Multiradio at least) dislike this IE
and return CHAN ACTIV NACK with an optional IE error cause
if it is included.

To avoid changing OsmoBSC behavior for other users, let us
conditionalize removal of this legacy IE on Nokia BTS for now.
This change has been tested on InSite, MetroSite and Flexi
Multiradio - no adverse effects on previously supported
*Site models.

Change-Id: Ibce7a841907ac87ae378ded3ddb174d38b70b7b7

nokia: add support for Flexi Multiradio

Previous support existed for Nokia MetroSite, UltraSite and InSite
models, resulting in BTS model name "nokia_site".  However, there
exist newer Nokia BTS models that also support E1 Abis and can be
supported by OsmoBSC with relatively small changes: Flexi EDGE,
Flexi Multiradio and Flexi Multiradio 10.  Out of these newer
models, American 2G Cooperative (the present patch author's current
organization) has only Flexi MR at the present time - hence this
model shall be the first "new" Nokia BTS to be supported.

The first change required in order to support Flexi MR is ability
to receive long OML messages that have been segmented by the BTS:
the new BTS sends a much longer BTS_CONF_REQ message, and we have
to handle it correctly.

Change-Id: Icd429552c3b5e90d6c5d3ae5f52afd6550e3cebc

nokia vty: change help strings away from "*Site"

Support for Nokia BTS in OsmoBSC is being expanded from just *Site
family to also include Flexi Multiradio - therefore, help strings
and error messages in vty should be changed accordingly.

FIXME: names of Nokia-specific vty settings still begin with
nokia_site, ditto for the name of the BTS model.  TODO: decide
on a proper long-term solution.

Change-Id: I55556b7b5aa5bc6efcbee815e9011497a933697c

nokia skip-reset: make consistent with other vty settings

All other Nokia-specific vty settings use is_nokia_bts() helper
function, while the code for skip-reset directly compares
bts->type against GSM_BTS_TYPE_NOKIA_SITE.  Change to use the
helper function: it is consistent with other vty settings,
and avoids one more place that erroneously refers to *Site
instead of all Nokia BTS.

Change-Id: Ie8cdac51f82185e2d4f37a8da00acba633670052

Cosmetic: bts_nokia_site: fix comment formatting

Ensure each line of a multiline comment starts with " * ".

Related: https://gerrit.osmocom.org/c/osmo-bsc/+/42712/comment/6aa80188_f56f2265/
Change-Id: I83ed16ec09fb66076dc2ba6a49ef272657b09407

handover_fsm: send_handover_performed(): check lchan != NULL

The target lchan is expected to be valid on HO_RESULT_OK, but it's
still safer to check it against NULL before dereferencing.

Change-Id: Iee734c98dc79681808e7d75360c208a941cc6821
Related: 107391d8c ("handover_fsm: fix send_handover_performed() using wrong lchan")

assignment_fsm: ipacc_chan_mode_supported(): log unsupported chan_mode

Change-Id: I1718994e25ff1349618bdb4660afbe735c5c3977
Related: aa959d74f ("assignment_fsm: check ipaccess channel mode support")