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

pespin gerrit-no-reply at lists.osmocom.org
Tue Apr 13 18:06:48 UTC 2021


pespin has uploaded this change for review. ( https://gerrit.osmocom.org/c/osmo-sgsn/+/23743 )


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 times
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
Fixes: 3bad31bcb42c3449e6847ea7495578817029a2e1
Change-Id: I7279102ad51b0c39eb6d04c129986984112d15cc
---
M src/sgsn/gprs_mm_state_iu_fsm.c
1 file changed, 0 insertions(+), 1 deletion(-)



  git pull ssh://gerrit.osmocom.org:29418/osmo-sgsn refs/changes/43/23743/1

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 @@
 		break;
 	case E_PMM_USER_INACTIVITY:
 		sgsn_ranap_iu_release_free(ctx, &user_inactive_cause);
-		mm_state_iu_fsm_state_chg(fi, ST_PMM_DETACHED);
 		break;
 	case E_PMM_RA_UPDATE:
 		break;

-- 
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Gerrit-Project: osmo-sgsn
Gerrit-Branch: master
Gerrit-Change-Id: I7279102ad51b0c39eb6d04c129986984112d15cc
Gerrit-Change-Number: 23743
Gerrit-PatchSet: 1
Gerrit-Owner: pespin <pespin at sysmocom.de>
Gerrit-MessageType: newchange
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