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RRC: align SRB and PDCP re-establishment timing with TS 38.331 specifications

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This commit fixes the timing of SRB and DRB PDCP re-establishment
during RRC connection re-establishment to align with 3GPP TS 38.331
specifications.

Key Changes:

1. SRB1 activation and re-establishment (TS 38.331 5.3.7.4):
   - Move SRB1 activation to rrc_gNB_generate_RRCReestablishment()
   - Use SRB1 constant instead of magic number 1 for clarity
   - Remove redundant security configuration loop (handled by
     nr_pdcp_reestablishment internally)

2. SRB2 re-establishment (TS 38.331 5.3.5.6.3 SRB addition/modification):
   - Move SRB2 PDCP re-establishment from rrc_gNB_process_RRCReestablishmentComplete()
   to rrc_gNB_generate_dedicatedRRCReconfiguration(): per spec: SRB2
   should be re-established in the first RRCReconfiguration after
   re-establishment (with reestablishPDCP=true flag)

3. DRB re-establishment (TS 38.331 5.3.5.6.5 DRB addition/modification):
   - Move cuup_notify_reestablishment() from rrc_gNB_process_RRCReestablishmentComplete()
   to rrc_gNB_generate_dedicatedRRCReconfiguration(). e.g at the first
   reconfiguration after reestablishment
   - Ensures CU-UP is notified at the correct time
This commit is contained in:
Guido Casati
2026-01-29 10:17:42 +01:00
parent c5787aa9a9
commit fc8e537f20
1 changed files with 27 additions and 28 deletions
Download Patch File Download Diff File Expand all files Collapse all files
openair2/RRC/NR/rrc_gNB.c
+27 -28
View File
@@ -918,6 +918,9 @@ byte_array_t rrc_gNB_encode_RRCReconfiguration(gNB_RRC_INST *rrc, gNB_RRC_UE_t *
return msg;
}
/* Forward declaration */
static void cuup_notify_reestablishment(gNB_RRC_INST *rrc, gNB_RRC_UE_t *ue_p);
/** @brief Generate and send RRC Reconfiguration message.
* Handles both normal reconfiguration and first reconfiguration after re-establishment.
* @param rrc RRC instance
@@ -960,6 +963,22 @@ static void rrc_gNB_generate_dedicatedRRCReconfiguration(gNB_RRC_INST *rrc, gNB_
return;
}
/* Per TS 38.331 5.3.5.6.3, re-establish SRB2 PDCP when sending the first
* RRCReconfiguration after reestablishment */
if (is_reestablishment) {
if (ue_p->Srb[SRB2].Active) {
nr_pdcp_entity_security_keys_and_algos_t security_parameters = {0};
security_parameters.ciphering_algorithm = ue_p->ciphering_algorithm;
security_parameters.integrity_algorithm = ue_p->integrity_algorithm;
nr_derive_key(RRC_ENC_ALG, ue_p->ciphering_algorithm, ue_p->kgnb, security_parameters.ciphering_key);
nr_derive_key(RRC_INT_ALG, ue_p->integrity_algorithm, ue_p->kgnb, security_parameters.integrity_key);
nr_pdcp_reestablishment(ue_p->rrc_ue_id, SRB2, true, &security_parameters);
}
/* Per TS 38.331 5.3.5.6.5, re-establish PDCP for all DRBs when sending the first
* RRCReconfiguration after RRC connection re-establishment (over E1 to CU-UP) */
cuup_notify_reestablishment(rrc, ue_p);
}
LOG_UE_DL_EVENT(ue_p,
"Generate RRCReconfiguration%s (bytes %ld, xid %d)\n",
is_reestablishment ? " after re-establishment" : "",
@@ -1215,16 +1234,14 @@ static void rrc_gNB_generate_RRCReestablishment(rrc_gNB_ue_context_t *ue_context
security_parameters.integrity_algorithm = ue_p->integrity_algorithm;
security_parameters.ciphering_algorithm = 0;
/* SRBs */
for (int srb_id = 1; srb_id < NR_NUM_SRB; srb_id++) {
if (ue_p->Srb[srb_id].Active)
nr_pdcp_config_set_security(ue_p->rrc_ue_id, srb_id, true, &security_parameters);
}
/* Re-establish PDCP for SRB1, according to 5.3.7.4 of 3GPP TS 38.331 */
nr_pdcp_reestablishment(ue_p->rrc_ue_id,
1,
true,
&security_parameters);
/* Re-establish PDCP for SRB1, according to 5.3.7.4 of 3GPP TS 38.331,
* and configure security via set_security internally.
* Note: SRB2 is NOT re-established here. Per TS 38.331 5.3.5.6.3, SRB2
* should be re-established in the first RRCReconfiguration after
* RRCReestablishmentComplete */
ue_p->Srb[SRB1].Active = 1;
nr_pdcp_reestablishment(ue_p->rrc_ue_id, SRB1, true, &security_parameters);
/* F1AP DL RRC Message Transfer */
f1_ue_data_t ue_data = cu_get_f1_ue_data(ue_p->rrc_ue_id);
RETURN_IF_INVALID_ASSOC_ID(ue_data.du_assoc_id);
@@ -1259,24 +1276,6 @@ static void rrc_gNB_process_RRCReestablishmentComplete(gNB_RRC_INST *rrc,
ue_p->xids[xid] = RRC_ACTION_NONE;
ue_p->Srb[1].Active = 1;
/* Re-establish SRB2 according to clause 5.3.5.6.3 of 3GPP TS 38.331
* (SRB1 is re-established with RRCReestablishment message)
*/
int srb_id = 2;
if (ue_p->Srb[srb_id].Active) {
nr_pdcp_entity_security_keys_and_algos_t security_parameters;
security_parameters.ciphering_algorithm = ue_p->ciphering_algorithm;
security_parameters.integrity_algorithm = ue_p->integrity_algorithm;
nr_derive_key(RRC_ENC_ALG, ue_p->ciphering_algorithm, ue_p->kgnb, security_parameters.ciphering_key);
nr_derive_key(RRC_INT_ALG, ue_p->integrity_algorithm, ue_p->kgnb, security_parameters.integrity_key);
nr_pdcp_reestablishment(ue_p->rrc_ue_id, srb_id, true, &security_parameters);
}
/* PDCP Reestablishment of DRBs according to 5.3.5.6.5 of 3GPP TS 38.331 (over E1) */
cuup_notify_reestablishment(rrc, ue_p);
f1_ue_data_t ue_data = cu_get_f1_ue_data(ue_p->rrc_ue_id);
RETURN_IF_INVALID_ASSOC_ID(ue_data.du_assoc_id);