Changes

tcap loadshare: allow to define the fallback mechanism for unroutable TCAP messages

When a TCAP Continue/End/Abort message is received, but no TCAP session entry can be found
and no valid TCAP range is available for the dtid, the message can be either:

- rejected by returning an error with udts
- routed by round robin to all available ASP of this AS

To define the behaviour, a new vty option is introduced:
```
   tcap-unroutable-sessions (reject-udts | load-share-over-as)
```
Defaults to reject-udts.

Related: SYS#5432
Change-Id: Ic1c876da30b05065a476d3a7c1bbf0680adf55bd

tcap loadshare: move last_asp_idx_sent from cfg to runtime struct

The last_asp_idx_sent is a runtime information and not configurable.
Move it to the other runtime state.

Change-Id: Id52bb0f6c67949b5e03f7ad36996f37a0d25214a

vty-tests: Re-introduce the check on the help

With the support of regex within vty tests,
the help message can be checked again.

Depends-on: Iadcd7a8c3677548a6405e098fe53d0614ef2012c (osmo-python-tests)
Change-Id: I3fad268b7a8925f378f6331fcab073637bd80e08

tcap loadshare: Rework initial selection of a node

The original TCAP loadshare plan was to used the OTID of a TCAP Begin to select
the node.
However this should not be used anymore. Instead the correct one would be to
do a load-sharing across all available ASP and keep this relation ("sticky" sessions).

The counter SS7_AS_CTR_TCAP_ASP_FALLBACK will be re-used by a later patch.

Related: SYS#5432
Change-Id: I151e6acb59e1f3c481487e76d2b01236fcee755f

tcap loadshare: count all ENOKEY as a FAILED

The ASP should count all message which couldn't routed as failed.

Related: SYS#5432
Change-Id: I8bee6db5c75195855a3d378579e30886cd4d6fa8

ss7_as: fix indention

Related: SYS#5432
Change-Id: Id006f4fcbf9ae6b5b50be3d41fb216c7f9bb2dfb

tcap loadshare: Add session miss counter

When a non-starting TCAP message (Continue, End, Abort) is received and
no session can be associated with it, count these as session miss.

Those should not appear under normal operation, except after a restart of osmo-stp.

Related: SYS#5432
Change-Id: I23319294e899e6acb6421d89675ce456048f7475

vty-tests: remove help from expected output

Until the vty tests support regex, remove the help message
as it depends on the compile option TCAP Routing and can't
handle both compile options.

It will be re-introduced later

Change-Id: I0d8141c00525f49c0a9f9f63b73fee531f591e5c

tcap_as_loadshare: improve logging of lookup failures

Change-Id: I80878dfd080c705de28175260cb392186dafed6a

tcap_as_loadshare: improve log lines

Change-Id: Idffe9a02127c587aca4123f12f74b657d6911a80

tcap_as_loadshare: Don't fill in PC from M3UA

Filling in the point codes from M3UA breaks down on asymmetric MTP paths
where the reply is sent from a different PC than the original message
was addressed to.

If both calling and called_addr are not point codes then the compare in
tcap_trans_track_entry_find() will ignore them. It still matches on
otid/dtid.

Related: SYS#5423
Change-Id: I4f99fc87cd33ee3f2aad531710cc39a9b9c7e6d9

tcap_as_loadshare: Use tcap_trans_track_begin instead of *_entry_create

*_begin checks for a matching entry and reuses that (with an updated
timestamp). This avoids duplicate entries in the tcap cache.

Related: SYS#5423
Change-Id: Icbaab976ed8207843129291494176679db574304

tcap_as_loadshare: Route msg based on TCAP route if cache lookup fails

Related: SYS#5423
Change-Id: I2fd9068be8a0a512b17c8bd2365aa87c266e5669

tcap_as_loadshare: Clarify name of tcap asp selection function

Change-Id: I327ad282d2689be2bcf7d3da23026717923c9325