OsmoBSC allows COMPLETE LAYER3 on SAPI !=0
GSM only supports SAPI0 (signalling) and SAPI3 (SMS). Other SAPIs are not in use.Furthermore,
- the initial establishment of the channel towards the MSC must happen on SAPI0
- the SABM command is only permitted to have L3 INFO on SAPI0 in uplink
- the BSSMAP COMPLETE LAYER3 INFO (as opposed to DTAP) doesn't have a SAPI/DLCI field
Yet, OsmoBSC permits a MS to establish e.g. SAPI1 on RSL/RLL and will happily report this as a COMPLETE L3 INFO to the MSC.
TC_rll_est_ind_inval_sapi1 in the TTCN-3 testsuite for this. But
TC_rll_est_ind_inval_sapi3 is also failing due to the same bug. SAPI3 can always only be established in addition to SAPI0 but never directly in a COMPLETE L3 INFO.