Error when OpenAirInterface nr-softmodem reads messages from proxy

[nplrkn]

Hi there,

I am seeing an apparent interop problem when OpenAirInterface parses messages from the proxy.

When following your setup instructions and running the following two commands in different terminals:

sudo -E ./ran_build/build/nr-softmodem -O ../ci-scripts/conf_files/gnb.sa.band78.106prb.l2sim.conf --nfapi VNF --sa --emulate-l1
sudo -E ./build/proxy $number_of_ues --nr

I see the following output from the Proxy:

Read NR message unpack:  00  00  01  00  00  08  00  00  e8  2a  9b  75  ce  7f  00  00
Read NR message unpack:  00  00  01  00  00  08  00  00  e8  2a  9b  75  ce  7f  00  00

I see the following error output from OAI.

24745054618 [E]  645613312: nfapi_vnf_pnf_list_find: nfapi_vnf_pnf_list_find : curr->p5_idx:0 p5_idx:0
24745055077 [W]  645613312: vnf_nr_read_dispatch_message: sctp_recvmsg: unhandled mode with flags 0x0
24745055098 [W]  645613312: vnf_nr_read_dispatch_message: Disconnected socket

From code read of vnf.c it appears that the header message_length received from the proxy did not cover the complete packet and so the MSG_EOR 0x80 flag is not set.

According to tcpdump, the message sent by the proxy is a 78 byte message with value:
0000010100460000000010000021000000000000000000000000000000000000000000000000000000000000000000000000100100150

The message length is the 6th byte with value 0x46 = decimal 70. Since this is 8 bytes short of the actual SCTP payload length, this appears to explain the behaviour of OAI.

Are you familiar with this problem? Is it possible I have set up something wrong or am using incompatible code versions?

[Z4ZI3]

Hello,
I am trying to bring up the L2 oai simulator and facing the same issue.
Did you find any solution for this issue?

[nplrkn]

Hi @Z4ZI3, I'm afraid not. At the time back in 2023, I gave up. I would still be interested if we could get this working.