tree 5eabc8bd4caf6fec8d39896b36c933e4c46104ef
parent 26f6ced05c8311a93eb4b9c6228ceeb2559c57d0
author Holger Hans Peter Freyther <holger@moiji-mobile.com> 1468338806 +0200
committer Holger Freyther <holger@freyther.de> 1479495877 +0000

ussd: Add band-aid for interrogationSS

This is a speculative change for interrogateSS and by not answering
the request the radio connection would remain open long.

The SS/USSD code is from a time where none of knew much about GSM. We
do not support SS but should reject it. We have checked for an empty
string in the text field to guess if it is a result/release to not send
more information. The right way forward is to decode the ASN1 into the
fields REQUEST/RESULT(last).

Fix an issue and make the code worse. Assume ss_code > 0 to see if this
is a interrogate invoke. The issue is that code 0 is a well defined
value but unlikely to be used.

MAP ASN1 definition:

SS-Code ::= OCTET STRING (SIZE (1))
        -- This type is used to represent the code identifying a single
        -- supplementary service, a group of supplementary services, or
        -- all supplementary services. The services and abbreviations
        -- used are defined in TS 3GPP TS 22.004 [5]. The internal structure is
        -- defined as follows:
        --
        -- bits 87654321: group (bits 8765), and specific service
        -- (bits 4321)

allSS                   SS-Code ::= '00000000'B

Change-Id: Ib0dc4485388f030eb172fe21f5327b7ab94751f5