RRCSetup in response to RRCReestablishment request not working

[sgarg00]

Originally reported by Luis Pereira on 2026-05-28 — GitLab #1100

RRCSetup in response to RRCReestablishment request not working with OAI UE
Steps to reproduce:

1. Apply diff.diff and build OAI:

cd ~/openairinterface5g/cmake_targets/
./build_oai --gNB --nrUE --ninja -w USRP -C

2. Start CN
3. Start gNB with:

cd ~/openairinterface5g/cmake_targets/ran_build/build
sudo ./nr-softmodem -O ../../../targets/PROJECTS/GENERIC-NR-5GC/CONF/gnb.sa.band78.fr1.106PRB.usrpb210.conf --gNBs.[0].min_rxtxtime 4 --rfsim

4. Start UE with:

cd ~/openairinterface5g/cmake_targets/ran_build/build
sudo ./nr-uesoftmodem --band 78 -C 3619200000 -r 106 --numerology 1 --ssb 516 --rfsim -O ../../../targets/PROJECTS/GENERIC-NR-5GC/CONF/ue.conf

5. Wait for a RRCReestablishment procedure
6. There is no LCID 4 anymore and at the UE:
   [RLC] Radio Bearer (channel ID 1) is NULL for UE 0

Note: Ensure that UE gets PDUSession and LCID4 before the RRCReestablishment, if not, check CN configurations.

Note 2: This issue was found with USRPs, so it is not exclusive to RFsim

Note 3: The patch and the way the issue is triggered is just a way to reproduce it, in real scenario the issue happens, for example, because of real time issues (a.k.a. LLLLLLLLLLLLLLLLLLLLLs).

Logs for reference:

gNB.txt

ue.txt