Bug #4629
closedstatically configured Gb interface not recovering after SGSN restart
100%
Description
In a situation when OsmoSGSN is interworking via Gb with a third-party BSS, we have a problem recovering after a SGSN restart.
The BSS continues to send uplink BSSGP PDUs like nothing happened, and OsmoSGSN responds with BSSGP STATUS (Cause = BVCI unknown). Normally, we would expect the BSS to understand that and follow up with a BVC-RESET in order to re-create the BVC for that BVCI. However, nothing of that sort happens.
In theory, the SGSN could also do a BVC-RESET. But it's a bit of a chicken-and-egg situation: If the BVC does not exist, as the SGSN has just restarted and lost all state, how would it know which BSSes exist out there, and send BVC-RESET to all of them?
So we'd have to cheat a bit and wait until any BSSGP PDU for a non-existant BVC is received, and then use the BVCI from that to send a SGSN-originated BSSGP RESET.