Each VLR requesting auth tuples should use a distinct IND pool for 3G auth. So
far we tied the IND to the GSUP peer connection; MSC and SGSN were always
distinct GSUP peers, they ended up using distinct INDs.
However, we have implemented a GSUP proxy, so that, in a distributed setup, a
remotely roaming subscriber has only one direct GSUP peer proxying for both
remote MSC and SGSN. That means as soon as a subscriber roams to a different
site, the site's MSC and SGSN compete for the same IND bucket, waste SQNs
rapidly and cause auth tuple generation load.
So instead of using the local client as IND, persistently keep a list of VLR
names and assign a different IND to each. Use the GSUP source_name as
indicator, which reflects the actual remote VLR's name.
Furthermore, make 100% sure that CS and PS pools can never collide, by keeping
all CS pools odd numbered and all PS pools even numbered.
Persist the site <-> IND assignments in the database.
Add an IND test to db_test.c
Related: OS#4319
Change-Id: I6f0a6bbef3a27507605c3b4a0e1a89bdfd468374
191f4b6eb3