All additional release fields are considered optional, and the
CSN_DESCR for Content_t already marks almost all as such, except
DownlinkDualCarrierCapability_r7.
It has been found that some MS transmits a MS RA Capability with a Length=61 bits
where the last bit in the buffer is setting the Exist bit for
DownlinkDualCarrierCapability_r7 as 1. Hence, the CSN1 decoder failed to
decode the whole message because it expected to keep reading there
despite there's no more bytes to read.
While this is could actually be considered an MS bug, let's relax our
expectancies and simply consider the case { 1 <end> } as it was { 0 },
and mark skip decoding DownlinkDualCarrierCapability_r7. That waht
wireshark (packet-gsm_a_gsm.c) or pycrate do for instance.
This patch itself doesn't fix the problem where actually the Exist bit
is stored as 1 in the output decoded structure, but simply allows keep
ongoing with decoding until the end. This issue will be fixed in a
follow-up patch.
Related: SYS#5552
Related: OS#4955
Related: OS#5020
Change-Id: I9a2541bd3544802a646890f32725201836abb0da
Pau Espin
ebdc0d8c17