RLC: add per-UE RLF callback

If the RLC cannot retransmit a package, 3GPP specs say that we should
declare radio link failure (RLF). Up to this commit, the code did
nothing though. In this commit, add a per-UE RLF callback; the RLC will
call into this function to signal that RLF has been detected through
maximum retransmissions on a particular RLC bearer.

openair2/LAYER2/nr_rlc/nr_rlc_oai_api.c

@@ -619,10 +619,6 @@ static void max_retx_reached(void *_ue, nr_rlc_entity_t *entity)
   int i;
   int is_srb;
   int rb_id;
-#if 0
-  MessageDef *msg;
-#endif
-  int is_enb;
 
   /* is it SRB? */
   for (i = 0; i < 2; i++) {
@@ -650,23 +646,18 @@ rb_found:
         is_srb ? "SRB" : "DRB",
         rb_id);
 
-  /* TODO: do something for DRBs? */
+  if (ue->rlf_handler)
-  if (is_srb == 0)
+    ue->rlf_handler(ue->ue_id);
-    return;
+  else
+    LOG_W(RLC, "UE %04x: RLF detected, but no callable RLF handler registered\n", ue->ue_id);
+}
 
-  is_enb = nr_rlc_manager_get_enb_flag(nr_rlc_ue_manager);
+void nr_rlc_set_rlf_handler(int ue_id, rlf_handler_t rlf_h)
-  if (!is_enb)
+{
-    return;
+  nr_rlc_manager_lock(nr_rlc_ue_manager);
-
+  nr_rlc_ue_t *ue = nr_rlc_manager_get_ue(nr_rlc_ue_manager, ue_id);
-#if 0
+  ue->rlf_handler = rlf_h;
-  msg = itti_alloc_new_message(TASK_RLC_ENB, RLC_SDU_INDICATION);
+  nr_rlc_manager_unlock(nr_rlc_ue_manager);
-  RLC_SDU_INDICATION(msg).rnti          = ue->rnti;
-  RLC_SDU_INDICATION(msg).is_successful = 0;
-  RLC_SDU_INDICATION(msg).srb_id        = rb_id;
-  RLC_SDU_INDICATION(msg).message_id    = -1;
-  /* TODO: accept more than 1 instance? here we send to instance id 0 */
-  itti_send_msg_to_task(TASK_RRC_ENB, 0, msg);
-#endif
 }
 
 void nr_rlc_reestablish_entity(int ue_id, int lc_id)

openair2/LAYER2/nr_rlc/nr_rlc_oai_api.h

@@ -44,6 +44,8 @@ struct NR_LogicalChannelConfig;
 void nr_rlc_add_srb(int ue_id, int srb_id, const NR_RLC_BearerConfig_t *rlc_BearerConfig);
 void nr_rlc_add_drb(int ue_id, int drb_id, const NR_RLC_BearerConfig_t *rlc_BearerConfig);
 
+void nr_rlc_set_rlf_handler(int ue_id, rlf_handler_t rlf_h);
+
 logical_chan_id_t nr_rlc_get_lcid_from_rb(int ue_id, bool is_srb, int rb_id);
 void nr_rlc_reestablish_entity(int ue_id, int lc_id);
 void nr_rlc_remove_ue(int ue_id);

openair2/LAYER2/nr_rlc/nr_rlc_ue_manager.h

@@ -37,12 +37,15 @@ typedef struct nr_rlc_rb_t {
   } choice;
 } nr_rlc_rb_t;
 
+typedef void (*rlf_handler_t)(int rnti);
+
 typedef struct nr_rlc_ue_t {
   int ue_id;
   nr_rlc_entity_t *srb0;
   nr_rlc_entity_t *srb[3];
   nr_rlc_entity_t *drb[MAX_DRBS_PER_UE];
   nr_rlc_rb_t lcid2rb[32];
+  rlf_handler_t rlf_handler;
 } nr_rlc_ue_t;
 
 /***********************************************************************/