bsc/ussd: Send faked CM Service Accept before sending USSD

The MS do not show the USSD messages yet. This patch modifies the
implementation to insert a CM Service Accept before the ussdNotify
to finish the establishment of the MM connection according to
3GPP TS 04.10/3.2.1.

This fix has been tested with a Blackberry phone that has shown
an ussd_grace_txt after rf_locked has been set to '1'. Without this
patch, that message wasn't shown. The phone has sent a CC Setup
and other messages before processing the channel release message sent
by the BSC, but these messages have not been forwarded to the MSC (as
expected).

Ticket: OW#957
Sponsored-by: On-Waves ehf
4 files changed
tree: 1ce74c0b496a8d387a1ee1a8a374ae6317aea9bc
  1. debian/
  2. hlrsync/
  3. linux-kernel/
  4. openbsc/
  5. wireshark/
  6. README