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MME/S6a: Always set Initial-Attach-Indicator flag in ULR

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According to 3GPP TS 29.272 (5.2.1.1.2), when an Update Location Request
is sent due to an initial attach, the MME shall set the
"Initial-Attach-Indicator" flag in the ULR-Flags IE. This ensures that
the HSS updates the MME identity and prevents ULA rejection with
UNKNOWN_SERVING_NODE when UE moves between MMEs or when GUTI mismatch
occurs.

Commercial MME/HSS implementations (e.g., Cisco StarOS) also set the
Initial-Attach-Indicator flag by default to handle UEs that do not reset
their GUTI when changing networks.

This patch hardcodes the Initial-Attach-Indicator bit for all ULR
messages to align with expected practical behavior and resolve attach
failures caused by HSS identity mismatch.

Issues: #4165
This commit is contained in:
Sukchan Lee 2025-12-04 17:01:18 +09:00
parent 255a341fc3
commit 40e494ec30
1 changed files with 1 additions and 0 deletions
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1
src/mme/mme-fd-path.c
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@ -1368,6 +1368,7 @@ void mme_s6a_send_ulr(enb_ue_t *enb_ue, mme_ue_t *mme_ue)
ret = fd_msg_avp_new(ogs_diam_s6a_ulr_flags, 0, &avp);
ogs_assert(ret == 0);
val.u32 = OGS_DIAM_S6A_ULR_S6A_S6D_INDICATOR;
val.u32 |= OGS_DIAM_S6A_ULR_INITIAL_ATTACH_IND;
ret = fd_msg_avp_setvalue(avp, &val);
ogs_assert(ret == 0);
ret = fd_msg_avp_add(req, MSG_BRW_LAST_CHILD, avp);