Hello Jenkins Builder,

I'd like you to reexamine a change. Please visit

https://gerrit.osmocom.org/c/osmo-hnbgw/+/35153?usp=email

to look at the new patch set (#2).

The following approvals got outdated and were removed: Verified+1 by Jenkins Builder

Change subject: mgw_fsm: Assume IuUP HNB IP addr = Iuh during MGCP CRCX on RAN side ......................................................................

mgw_fsm: Assume IuUP HNB IP addr = Iuh during MGCP CRCX on RAN side

In general, the HNBs end up binding its IuUP/RTP streams to the same IP address used for Iuh signalling.

When receiving a RAB-Ass-Req from CN, osmo-hnbgw creates an endpoint in its co-located MGW and creates 2 MGCP conns on it, one facing the RAN side and one facing the CN side. At that point, the remote CN IuUP IP address is known (was include din the received RAB-Ass-Req), but the RAN one is not yet known. Hence, the CRCX on the RAN-side conn contained no remote IP address, which means MGW has to blindly guess a good local IP address if "ip probing" is enabled. As a result, when RAB-Ass-Resp comes back from the hNodeB containing the allocated remote IuUP IP address and MGW is updated through MGCP MDCX, it may happen that MGW rebinds to a better fitting local IP address and returns it in MDCX. This has several downfalls: 1- We don't yet support updating the hNodeB about the changed IP address (see mgw_fsm_mdcx_hnb). For that, we'd need to send a RAB-Modify-Req+Resp. 2- Even if we supported it, in the general case we'd be delaying call establishment because an extra roundtrip is needed to update RAB-Modify-Req+Resp.

In general, the HNBs end up binding its IuUP/RTP streams to the same IP address used for the Iuh signalling. Hence, use this assumption to announce the Iuh IP address as a remote IuUP IP address when transmitting the MGCP CRCX at the RAN-side conn to the MGW. This way the MGW can potentially select a proper local IuUP IP address from the start, so no RAB-Modify-Req is required later on.

The logic to transmit RAB-Modify-Req is left unimplemented in this commit and is left as a later improvement.

Related: SYS#6657 Change-Id: Icf43e3a1cde809d844f17ef2d0600efe64bc3dfe --- M src/osmo-hnbgw/mgw_fsm.c 1 file changed, 56 insertions(+), 0 deletions(-)

git pull ssh://gerrit.osmocom.org:29418/osmo-hnbgw refs/changes/53/35153/2