Multiple DUs host cells, whose cell ID cannot match (to identify them
uniquely). Hence, don't check for equality with CU, because otherwise,
we can never connect multiple DUs.
This is a workaround for a problem described in #706. In short, we
cannot reuse the cu_add/remove_f1_ue_data() functions if we are in an
integrated CU-UP/CP ("CU"), but then we can also not reliably use
different UE IDs in CU-UP and CU-CP (except if using even more hacks).
An assoc_id of 0 is used to mark UEs whose DU is "offline" (not
connected). In this patch, if a DU disconnects, we go through all UEs
and set their assoc_id to 0 if they belong to a UE that just went
offline.
This code printed BW masks (what is this) and number of MIMO layers. It
was dependent on the current DU, and only showed the information for the
current DU config (SCS, band). On DU disconnect, it leads to segfaults
to this dependency, and IMO is not useful in itself (it could rather be
printed when receiving the UE capabilities, for all bands etc.).
To allow to send F1 messages to multiple DUs from the CU, we need to
send these messages via different assoc_id (SCTP association ID,
basically akin to a file descriptor). Currently, the assoc_id is stored
in a context at the F1 module and retrieved in
f1ap_itti_send_sctp_data_req().
To facilitate a later change towards indicating (from the RRC) to which
assoc_id (hence, DU) to send a message, we refactor all
CU_send_*()/DU_send_*() functions to take the assoc_id as a parameter to
which to send messages. In this commit, we then pass the assoc_id from
the context. A later commit changes this (at the CU) to pass the
assoc_id from the message to be sent.
Previous to this commit, the CU creates an F1 instance and initializes
GTP after a successful connection establishment, and tears the F1
instance down after the DU disconnects. This does not work when trying
to connect multiple DUs, or have them reconnect, as e.g., GTP
re-initialization fails (socket already bound).
This commit makes the CU F1 instance creation and GTP init at CU task
init (only once), and also frees the F1 instance only after the CU task
exits, which is at termination of the application, typically.
Remove dead code, result of 2136ceec0d: we
cannot connect() in GTP on multiple remotes (as then only packets of one
host might be received), but might need to send to multiple remote
sockets.
The DU UE capability printing depends on data on SCS and band, which
currently is only stored with the DU. To avoid any assert, we check
that the DU is present. A follow-up commit will rework this.
Before this commit, as visible in the handler of an F1 UE release, it
can happen that we forward the RRC Release message to a UE and start the
release timer, while also removing the F1 UE data (containing e.g., the
CU UE ID). This can lead to asserts, since there might still be
subsequent traffic for such UE during a short time, while the DU does
not have the secondary UE ID stored anymore.
This commit changes the logic. It introduces function
nr_mac_release_ue() that removes the UE at MAC and RLC, frees the F1 UE
data (if applicable), and sends the complete, after timing expiry. If
the UE is out of sync, this function is used to free the UE immediately.
This fixes#685 and #698.
Robert Schmidt