libmsc/ran_msg_iu.c: fix: properly handle SAPI IE of RANAP_DirectTransfer
The RANAP DirectTransfer message may contain an optional SAPI IE.
Thanks to our TTCN-3 tests (and Wireshark!), it was discovered
that this IE is ignored, so even if the MO SMS related messages
arrive on SAPI 3 (as per GSM TS 04.11, section 2.3) OsmoMSC sends
MT messages on SAPI 0.
In ran_iu_decode_l3() we need to check if the SAPI IE is present,
and tag the NAS PDU message buffer with a proper DLCI value.
This change makes the failing SMS related test cases pass.
Change-Id: I728b55b04e87fc23be6d4f8735e8cad82b6f640e
1 file changed