Multiple DRBs - ASN1 & RRC

1. Added guard for exceeding DRB creation in ASN1 & RRC
2. Created function for finding the next available drb

Note: tested with 2 UEs in RFSIM mode

openair2/RRC/NR/MESSAGES/asn1_msg.c

@@ -1550,6 +1550,8 @@ void fill_mastercellGroupConfig(NR_CellGroupConfig_t *cellGroupConfig, NR_CellGr
 
   // DRB Configuration
   for (int i = bearer_id_start; i < bearer_id_start + nb_bearers_to_setup; i++ ){
+    if(i > MAX_DRBS_PER_PDUSESSION)
+        break;
     const NR_RLC_Config_PR rlc_conf = use_rlc_um_for_drb ? NR_RLC_Config_PR_um_Bi_Directional : NR_RLC_Config_PR_am;
     NR_RLC_BearerConfig_t *rlc_BearerConfig = get_DRB_RLC_BearerConfig(3 + i, i, rlc_conf, priority[i-bearer_id_start]);
     ASN_SEQUENCE_ADD(&cellGroupConfig->rlc_BearerToAddModList->list, rlc_BearerConfig);

openair2/RRC/NR/nr_rrc_defs.h

@@ -93,7 +93,9 @@
 
 #define NR_UE_MODULE_INVALID ((module_id_t) ~0) // FIXME attention! depends on type uint8_t!!!
 #define NR_UE_INDEX_INVALID  ((module_id_t) ~0) // FIXME attention! depends on type uint8_t!!! used to be -1
-
+#define MAX_DRBS_PER_PDUSESSION (4)             /* Maximum number of DRBs per PDU Session,
+                                                   this value is not standardized, so we can
+                                                   find another way to assign it more dynamically. */
 typedef enum {
   NR_RRC_OK=0,
   NR_RRC_ConnSetup_failed,

openair2/RRC/NR/rrc_gNB.c

@@ -823,8 +823,10 @@ rrc_gNB_generate_dedicatedRRCReconfiguration(
     }
 
     for(long drb_id_add = 1; drb_id_add <= nb_drb_to_setup; drb_id_add++){
-      NR_DRB_ToAddMod_t *DRB_config = generateDRB(&ue_context_pP->ue_context.pduSession[i],
-                                                  drb_id_add,
+      if(drb_id_add > MAX_DRBS_PER_PDUSESSION)
+        break;
+      NR_DRB_ToAddMod_t *DRB_config = generateDRB(ctxt_pP->rnti,
+                                                  &ue_context_pP->ue_context.pduSession[i],
                                                   rrc->configuration.enable_sdap,
                                                   rrc->security.do_drb_integrity,
                                                   rrc->security.do_drb_ciphering);

openair2/RRC/NR/rrc_gNB_drbs.c

@@ -21,11 +21,18 @@
 
 #include "rrc_gNB_drbs.h"
 
-NR_DRB_ToAddMod_t *generateDRB(const pdu_session_param_t *pduSession,
-                               long drb_id,
+typedef struct {
+  nr_ue_t *list; /* UE Linked List, every element is a UE*/
+} nr_ue_list_t;
+
+static nr_ue_list_t ues;
+
+NR_DRB_ToAddMod_t *generateDRB(rnti_t rnti,
+                               const pdu_session_param_t *pduSession,
                                bool enable_sdap,
                                int do_drb_integrity,
                                int do_drb_ciphering) {
+  uint8_t drb_id = next_available_drb(rnti, pduSession->param.pdusession_id);
   NR_DRB_ToAddMod_t *DRB_config  = NULL;
   NR_SDAP_Config_t  *SDAP_config = NULL;
 
@@ -99,3 +106,74 @@ NR_DRB_ToAddMod_t *generateDRB(const pdu_session_param_t *pduSession,
   }
   return DRB_config;
 }
+
+uint8_t next_available_drb(rnti_t rnti, uint8_t pdusession_id) {
+  nr_ue_t *ue;
+  if(nr_ue_get(rnti))
+    ue = nr_ue_get(rnti);
+  else
+    ue = nr_ue_new(rnti);
+
+  uint8_t drb_id;
+  for (drb_id = 0; drb_id < MAX_DRBS_PER_UE; drb_id++) {
+    if(ue->used_drbs[drb_id] == NULL_DRB && ue->pdus->drbs_established < MAX_DRBS_PER_PDUSESSION) {
+      ue->pdus->pdu_drbs[ue->pdus->drbs_established] = drb_id;  /* Store drb_id to pdusession */
+      ue->used_drbs[drb_id] = pdusession_id;                    /* Store the pdusession id that is using that drb */
+      ue->pdus->drbs_established++;                             /* Increment the index for drbs */
+      return ++drb_id;
+    }
+  }
+  return NULL_DRB;
+}
+
+nr_ue_t *nr_ue_new(rnti_t rnti) {
+  if(nr_ue_get(rnti)) {
+    LOG_D(RRC, "UE already exists with rnti: %u\n", rnti);
+    return nr_ue_get(rnti);
+  }
+
+  nr_ue_t *ue;
+  ue = calloc(1, sizeof(nr_ue_t));
+  ue->ue_id = rnti;
+  ue->next_ue = ues.list;
+  ues.list = ue;
+  return ues.list;
+}
+
+nr_ue_t *nr_ue_get(rnti_t rnti) {
+  nr_ue_t *ue;
+  ue = ues.list;
+
+  if(ue == NULL)
+    return NULL;
+
+  while(ue->ue_id != rnti && ue->next_ue != NULL)
+    ue = ue->next_ue;
+
+  if(ue->ue_id == rnti)
+    return ue;
+
+  return NULL;
+}
+
+void nr_ue_delete(rnti_t rnti) {
+  nr_ue_t *ue;
+  ue = ues.list;
+
+  if(ue->ue_id == rnti) {
+    ues.list = ues.list->next_ue;
+    free(ue);
+  } else {
+    nr_ue_t *uePrev = NULL;
+
+    while(ue->ue_id != rnti && ue->next_ue != NULL) {
+      uePrev = ue;
+      ue = ue->next_ue;
+    }
+
+    if(ue->ue_id != rnti) {
+      uePrev->next_ue = ue->next_ue;
+      free(ue);
+    }
+  }
+}
\ No newline at end of file

openair2/RRC/NR/rrc_gNB_drbs.h

@@ -26,10 +26,32 @@
 #include "NR_SDAP-Config.h"
 #include "NR_DRB-ToAddMod.h"
 
-NR_DRB_ToAddMod_t *generateDRB(const pdu_session_param_t *pduSession,
-                               long drb_id,
+#define MAX_DRBS_PER_UE         (32)  /* Maximum number of Data Radio Bearers per UE */
+#define MAX_PDUS_PER_UE         (8)   /* Maximum number of PDU Sessions per UE */
+#define NULL_DRB                (0)   /* Non existing DRB */
+typedef struct nr_pdus_s {
+  uint8_t pdu_drbs[MAX_DRBS_PER_PDUSESSION];  /* Data Radio Bearers of PDU Session */
+  uint8_t pdusession_id;
+  uint8_t drbs_established;                   /* Max value -> MAX_DRBS_PER_PDUSESSION*/
+} nr_pdus_t;
+
+typedef struct nr_ue_s {
+  nr_pdus_t pdus[MAX_PDUS_PER_UE];      /* PDU Sessions */
+  uint8_t   used_drbs[MAX_DRBS_PER_UE]; /* Data Radio Bearers of UE, the value is not the drb_id but the pdusession_id */
+  rnti_t    ue_id;
+
+  struct nr_ue_s *next_ue;
+} nr_ue_t;
+
+NR_DRB_ToAddMod_t *generateDRB(rnti_t rnti,
+                               const pdu_session_param_t *pduSession,
                                bool enable_sdap,
                                int do_drb_integrity,
                                int do_drb_ciphering);
 
+nr_ue_t *nr_ue_get(rnti_t rnti);
+nr_ue_t *nr_ue_new(rnti_t rnti);
+void nr_ue_delete(rnti_t rnti);
+uint8_t next_available_drb(rnti_t rnti, uint8_t pdusession_id);
+
 #endif
\ No newline at end of file