This is an implementation of SCCP as specified in ITO-T Q.71x,
particularly the SCRC (routing), SCLC (Connectionless) and SCOC
(Connection Oriented) portions. the elaborate state machines of
SCOC are implemented using osmo_fsm, with one state machine for each
connection.
Interfaces to the top (user application) are the SCCP-USER-SAP and on
the bottom (network) side the MTP-USER-SAP as provided by osmo_ss7.
Contrary to a straight-forward implementation, the code internally
always uses a SUA representation of all messages (in struct xua_msg).
This enables us to have one common implementation of all related state
machines and use them for both SUA and SCCP. If used with real SCCP
wire format, all messages are translated from SCCP to SUA on ingress and
translated from SUA to SCCP on egress. As SUA is a super-set of SCCP,
this can be done "lossless".
Change-Id: I916e895d9a4914b05483fe12ab5251f206d10dee
