Unable to set MTU size = 9000 bytes for NIC interface in the Ethernet transmitter

[wei-lou]

Hi there, I compiled the latest 23.10.1 load on ubuntu 22.04 server VM. The NIC was passed through to the VM. However every time i am trying to run the code, it give me such error.

"labuser@srsran23101r:~$ sudo srsRAN_Project/build/apps/gnb/gnb -c srsRAN_Project/configs/gnb_ru_fuji_tdd_n48_40mhz_2x2_23101R.yml

The PRACH detector will not meet the performance requirements with the configuration {Format 0, ZCZ 0, SCS 1.25kHz, Rx ports 1}.

--== srsRAN gNB (commit 55c984b55) ==--

Connecting to AMF on 192.168.70.210:38412
Initializing Open Fronthaul Interface sector=0: ul_comp=[BFP,9], dl_comp=[BFP,9], prach_comp=[BFP,9] prach_cp_enabled=false, downlink_broadcast=false.
srsGNB ERROR: Unable to set MTU size = 9000 bytes for NIC interface in the Ethernet transmitter, current MTU = -1 bytes
Aborted (core dumped)

"
I have another VM running 23.10.1.Test load and I don't have such problem. Please find attached gnb.log.
MTU_Check_Failed_gnb.log

Thanks,

[andrepuschmann]

Hey @wei-lou - I don't think you can set the MTU in the VM, at least not for VFs. The code tries that but fails. You could try to comment the section in ethernet_transmitter_impl.cc to see if that works. Or there is an option to allow setting the MTU from within the VM.

[andrepuschmann]

But this is the bare metal config, not the VM's network config. You said bare metal it's working.

Please also check if you can get the formatting right using markdown. It's hard to read otherwise.

[wei-lou]

Hi @andrepuschmann. this is the VM installation. There two interfaces for the VM, ens16 which is 25G passthrough interface and ens18 is the VM virtual interface.

[andrepuschmann]

I don't understand why this isn't working if it's full PCI passthrough. Those ioctl syscalls are nothing special. We'll see if we can replicate it with Proxmox ourselves.

[wei-lou]

Thanks for checking. With 23.5 load, I didn't encounter this issue with VM installation. I skipped 23.10, so I didn't with that load there is issue or not.