Osmocom Libraries » libosmo-sccp + libosmo-sigtran

if osmo_ss7_asp_find_or_create() finds the ASP by name but the
ports or protocol mismatch, it simply returns NULL. The SCCP init fails and we
have no clue that it's only because we picked a seemingly valid option:

If instead of 2905, I pick 2906 and m3ua:

cs7 instance 0
 point-code 0.23.1
 asp asp-clnt-OsmoMSC-A-Iu 2906 0 m3ua
  ! where to reach the STP:
  remote-ip 10.23.24.1

the default port 2905 mismatches 2906, osmo_ss7_asp_find_or_create() returns
NULL and the MSC doesn't start, but the user has no idea why:

<000a> ../../../../src/osmo-msc/src/osmo-msc/msc_main.c:373 CS7 Instance identifiers: A = Iu = 0
<002e> ../../../src/libosmo-sccp/src/sccp_user.c:374 OsmoMSC-A-Iu: Using SS7 instance 0, pc:0.23.1
<002e> ../../../src/libosmo-sccp/src/sccp_user.c:388 OsmoMSC-A-Iu: Creating AS instance
<002e> ../../../src/libosmo-sccp/src/sccp_user.c:398 OsmoMSC-A-Iu: Using AS instance as-clnt-OsmoMSC-A-Iu
<002e> ../../../src/libosmo-sccp/src/sccp_user.c:403 OsmoMSC-A-Iu: Creating default route
<002e> ../../../src/libosmo-sccp/src/sccp_user.c:418 OsmoMSC-A-Iu: Creating ASP instance
Setting up SCCP client failed.

Of course this only happens when the ASP's name exactly matches the default
name, but when we use config generated by 'show running-config' or 'write file'
and tweak that, this is actually a quite common case.