In some rare cases the modem might send a xid indication that does
not contain anything except the version number field. The sgsn
ignors such SNDCP-XID indications by stripping the entire field
from the response. We found a modem in the wild that started to
act problematic when the empty SNDCP-XID was missing in the
response. This patch changes the XID negotiation behaviour in
a way that if a modem should send empty SNDCP-XID indications,
the reply will also contain an empty SNDCP-XID indication. Apart
from that the SNDCP-XID version number is now parsed and echoed
in the response. This ensures that we always reply with the version
number that the modem expects. (The version was 0 in all cases we
observed so far)
Change-Id: I097a770cb4907418f53e620a051ebb8cd110c5f2
Related: OS#1794
Philipp Maier
db142dc59d