BSSGP stores a pointer to the Cell Identifier IE in msgb->cb, which
is later used by the GMM layer to identify the cell that has sent a
given message.
This now also means that the gsm_04_08_gprs.c code is free of any
legacy references to msg->trx or struct gsm_bts.
We now expect the highest level (actual SGSN GMM code) to know
all identifiers for every element in the protocol stack, i.e.
TLLI, SAPI, BVCI and NSEI. The layer-inetrnal state is looked
up based on those identifiers.
The reason for this is to ensure only the highest level state
needs to be persistent, while everything else can be regenerated
dynamically (e.g. in a SGSN restart)
In the old code
l3h = BSSGP, l4h = LLC, cb[gmmh] = 04.08
Now, this has been changed to
cb[bssgph] = BSSGP, cb[llch] = LLC, l3h = 04.08
This way, GSM general 04.08 and GPRS 04.08 code can expect a
GSM 04.08 header at msgb->l3h
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.
* move UDP listener code for NSIP from input/ipaccess.c and into gprs_ns.c
* add PDU type, IE and CAUSE values for later IP based 3GPP TS 48.016
* support multiple NS-VCs and their lookup based on NSVC and sockaddr_in
* maintain the remote_state (blocked/alive) for each NSVC
* introduce the concept of GPRS_NS instances, move all global vars to instance
* remove hardcoded calls to gprs_bssgp_rcvmsg() and replace it by callback
WARNING: This is not finished code. While it will compile, it will not work
yet, as BSSGP needs to be converted to properly indicate the NSVC to which it
needs to send data.
The explicit 'tlli, gmmh' members of struct msgb are gone from
current libosmocore and have been replaced by the more generic
'control buffer' mechanism.
While doing 'nm' on a VTY-using object file I noticed that all
cmd_elements are global symbols, which is not good.
Unfortuantely there are some vty-internal cmd_elements that need
to span across object files, so I had to introduce gDEFUN()
and gALIAS(). The old macros now all declare static structures.
Harald Welte
Holger Hans Peter Freyther