Instead of continuing to add more and more functionality to the
bsc_hack binary, we should have the new SGSN code run as a separate
executable.
After this commit we now build a 'osmo_sgsn' executable, using its
own osmo_sgsn.cfg config file.
However, the SGSN is not yet functional, mainly due to the fact that
the BSSGP and GMM code are written with the assumption that there
is a msgb->trx->bts and the according 'sturct gsm_bts' data model
around - which clearly is no longer the case outside of bsc_hack.
The ida of the Gb proxy is to aggregate Gb links with a number of BSS
and then present all the BSSGP-VC's together inside one NS-VC to the
actual SGSN.
The code is not yet expected to be complete.
According to TS 08.16, the BSSGP layer needs to specify NSEI and BVCI when
executing the NS UNITDATA REQUEST primitive of the underlying NS layer.
Rather than passing around a pointer to the 'struct gprs_nsvc', we now
have NSEI and BVCI as members of 'struct obsc_msgb_cb' and set them
when BSSGP hands a message down to NS.
NS then does a lookup of the 'gprs_nsvc' based on the NSEI parameter.
The explicit 'tlli, gmmh' members of struct msgb are gone from
current libosmocore and have been replaced by the more generic
'control buffer' mechanism.
Harald Welte