Change in osmo-sgsn[master]: mm_state_iu_fsm: T3314 expiry must lead to PMM IDLE, not PMM DETACHED

pespin gerrit-no-reply at
Wed Apr 14 15:24:07 UTC 2021

pespin has submitted this change. ( )

Change subject: mm_state_iu_fsm: T3314 expiry must lead to PMM IDLE, not PMM DETACHED

mm_state_iu_fsm: T3314 expiry must lead to PMM IDLE, not PMM DETACHED

This Iu timer is Osmocom specific, but is made to resemble T3314 timer
from GERAN (also named READY timer). The READY timer mission is to make
the MM state transition from READY to STANDBY, which in PMM (UTRAN)
matches the transition from CONNECTED to IDLE.
Instead, the patch introducing the timer was making it transition to
DETACHED directly, but this was clearly not the intention:
* Detaching a UE after 44 seconds (default value for T3314) is overkill.
* The comment describing it says: "Iu User inactivity timer. On expiry
  release Iu connection". The release of Iu connection happens during
  the CONNECTED->IDLE transition (that's basically the difference between
  both states).

The transition CONNECTED->IDLE is done by means of calling
sgsn_ranap_iu_release_free(), which will eventually answer with a event
RANAP_IU_EVENT_IU_RELEASE from lower layers when the Release Complete is
received. At that point, osmo-sgsn code frees the connection and
transitions to IDLE state. This way we maintain the state according to
the connection existance.

Related: SYS#5389
Related: osmo-iuh.git Change-Id Iac822c74e56750dc40e94573eae0e20853ff68c0
Fixes: 3bad31bcb42c3449e6847ea7495578817029a2e1
Change-Id: I7279102ad51b0c39eb6d04c129986984112d15cc
M src/sgsn/gprs_mm_state_iu_fsm.c
1 file changed, 0 insertions(+), 1 deletion(-)

  lynxis lazus: Looks good to me, approved
  Jenkins Builder: Verified

diff --git a/src/sgsn/gprs_mm_state_iu_fsm.c b/src/sgsn/gprs_mm_state_iu_fsm.c
index 69b4ef0..7f2d3b4 100644
--- a/src/sgsn/gprs_mm_state_iu_fsm.c
+++ b/src/sgsn/gprs_mm_state_iu_fsm.c
@@ -64,7 +64,6 @@
 		sgsn_ranap_iu_release_free(ctx, &user_inactive_cause);
-		mm_state_iu_fsm_state_chg(fi, ST_PMM_DETACHED);

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Gerrit-Project: osmo-sgsn
Gerrit-Branch: master
Gerrit-Change-Id: I7279102ad51b0c39eb6d04c129986984112d15cc
Gerrit-Change-Number: 23743
Gerrit-PatchSet: 3
Gerrit-Owner: pespin <pespin at>
Gerrit-Reviewer: Jenkins Builder
Gerrit-Reviewer: daniel <dwillmann at>
Gerrit-Reviewer: laforge <laforge at>
Gerrit-Reviewer: lynxis lazus <lynxis at>
Gerrit-Reviewer: pespin <pespin at>
Gerrit-MessageType: merged
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