OsmoSGSN / libgtp don't support GGSN-initiated PDP Context Deactivation
The GGSN can at any time deactivate a PDP context. See 3GPP TS 29.060:
7.3.5 Delete PDP Context Request
A Delete PDP Context Request shall be sent from a SGSN node to a GGSN node as part of the GPRS Detach procedure or the GPRS PDP Context Deactivation procedure or from a GGSN node to a SGSN node as part of the PDP Context Deactivation Initiated by GGSN procedure.
However, if we do this with OsmoSGSN, OsmoSGSN will log:
Sun Feb 18 22:23:15 2018 DLGTP <0025> gtp.c:3026 Packet from 127.0.0.2:2123, length: 14 content: 32 14 00 06 00 00 00 01 00 17 00 00 14 05 : Unexpected GTPv1 Signalling Message
I have created
SGSN_Tests.TC_attach_pdp_act_user_deact_mt to provoke this situation.