@@ -327,25 +327,23 @@ successful_delivery() and max_retx_reached(): in ??? trigger, the RLC sends a it
The PDCP implementation is also protected through a general mutex.
The design is very similar to rlc layer. The pdcp data is isolated and encapsulated.
pdcp_layer_init(): same as rlc init
nr_pdcp_layer_init(): same as rlc init
we have to call a second init function: pdcp_module_init()
At Tx side (DL in gNB), pdcp_data_req() is the entry function that the upper layer calls.
At Tx side (DL in gNB), `pdcp_data_req_drb()` and `pdcp_data_req_srb()` are the entry functions that the upper layer calls.
The upper layer can be GTP or a PDCP internal thread enb_tun_read_thread() that read directly from Linux socket in case we skip 3GPP core implementation.
PDCP internals for pdcp_data_req() is thread safe: inside pdcp_data_req_drb(), the pdcp manager protects with the mutex the access to the SDU receiving function of PDCP (recv_sdu() callback, corresponding to nr_pdcp_entity_drb_am_recv_sdu() for DRBs). When it needs, the pdcp layer push this data to rlc by calling : rlc_data_req()
Also, incoming downlink sdu can comme from internal RRC: in this case, pdcp_run() reads a itti queue, for message RRC_DCCH_DATA_REQ, to0 only call 'pdcp_data_req()'
PDCP internals for nr_pdcp_data_req_srb()/nr_pdcp_data_req_drb() are thread safe: inside them, the pdcp manager protects with the mutex the access to the SDU receiving function of PDCP (recv_sdu() callback, corresponding to nr_pdcp_entity_drb_am_recv_sdu() for DRBs). When it needs, the pdcp layer push this data to rlc by calling : rlc_data_req()
At Rx side, pdcp_data_ind() is the entry point that receives the data from RLC.
- Inside pdcp_data_ind(), the pdcp manager mutex protects the access to the PDU receiving function of PDCP (recv_pdu() callback corresponding to nr_pdcp_entity_drb_am_recv_pdu() for DRBs)
- Then deliver_sdu_drb() function sends the received data to GTP thread through an ITTI message (GTPV1U_TUNNEL_DATA_REQ).
pdcp_config_set_security(): not yet developped
nr_pdcp_config_set_security(): sets the keys for AS security of a UE
nr_DRB_preconfiguration(): the mac layer calls this for ???
nr_DRB_preconfiguration(): the mac layer calls this for configuration in phy-test/do-ra mode
nr_pdcp_add_srbs() adds UE SRBs in pdcp, pdcp_remove_UE() removes it
nr_pdcp_add_drbs() adds UE DRBs in pdcp, pdcp_remove_UE() removes it
nr_pdcp_add_srbs() adds UE SRBs in pdcp, nr_pdcp_remove_UE() removes it
nr_pdcp_add_drbs() adds UE DRBs in pdcp, nr_pdcp_remove_UE() removes it
# GTP
Gtp + UDP are two twin threads performing the data plane interface to the core network
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@@ -357,7 +355,7 @@ PDCP layer push to the GTP queue (outside UDP thread that do almost nothing and
## GTP thread running code from other layers
gtp thread calls directly pdcp_data_req(), so it runs inside it's context internal pdcp structures updates
gtp thread calls directly nr_pdcp_data_req_drb(), so it runs inside it's context internal pdcp structures updates
## inside other threads
gtpv1u_create_s1u_tunnel(), delete tunnel, ... functions are called inside the other threads, without mutex.