This OpenBTS socket interface was originally added to enable GPRS
capabilitie with a forked version of OpenBTS, at a time when the public
OpenBTS release didn't yet have any GPRS support.
Meanwhile, the later OpenBTS releases included their own version of
GPRS, without any external PCU/SGSN/GGSN, so this interface is no longer
needed.
This also means that the OsmoBTS socket interface is now the default at
compilation time. There is no other interface.
This also renames the --enable-sysmbts option to --enable-osmobts
This socket interface was nevery sysmoBTS specific, but it is a generic
socket interface to any OsmoBTS supported layer1/hardware. So it was a
mis-nomer so far.
In order to use this feature, sysmoBTS requires option "-M", otherwise
the traffic is forwarded through socket interface.
This is essential, if PCU runs on processor of sysmoBTS. The reaction
time and delay of PDTCH frames could heavily degrade proper packet flow.
Merge is based on jolly_new branch with two modifications.
1. Modified PCU L1 interface.
pcu_l1_if.cpp - common functions for tx and rx messages on L1 interface.
sysmo_sock.cpp - SYSMO-PCU socket functions.
openbts_sock.cpp - OpenBTS-PCU socket functions.
pcuif_proto.h - L1 interface's primitives.
2. Modified encoding of RLC/MAC Control messages, now we use structures and encode_gsm_rlcmac_downlink() function for encode control blocks (without hand-coding).
Harald Welte
Holger Hans Peter Freyther