SCTP bind failed: Cannot assign requested address - Unable to connecto to free5gc AMF

[lpfernandes]

Hi, I'm trying to set a basic enviroment where I have a VM with free5gc core running and another VM wieht ueransim, I have made the changes to the config files on both sides however I unable to connect to the AMF on free5gc VM.
The following is the error I get:

coreadmin@ueransim:~/UERANSIM/build$ ./nr-gnb -c ../config/free5gc-gnb.yaml
UERANSIM v3.2.5
[2024-08-07 11:22:22.794] [sctp] [info] Trying to establish SCTP connection... (192.168.176.135:38412)
[2024-08-07 11:22:22.795] [gtp] [error] GTP/UDP task could not be created. Socket bind failed: Cannot assign requested address
[2024-08-07 11:22:22.798] [sctp] [error] Binding to 192.168.176.135:0 failed. SCTP bind failed: Cannot assign requested address

If I run a manually test from the ueransim VM using ncat I can establish a connection:

UERANSIM VM:
coreadmin@ueransim:~/UERANSIM/build$ ncat 192.168.176.135 38412 --sctp

free5gc VM:
2024-08-07T11:24:55.219220642Z [INFO][AMF][Ngap] [AMF] SCTP Accept from: 192.168.176.137:52824
2024-08-07T11:28:02.253648226Z [INFO][AMF][Ngap] Handle SCTP Notification[addr: 192.168.176.137:52824]
2024-08-07T11:28:02.253880811Z [WARN][AMF][Ngap] RAN context has been removed[addr: 192.168.176.137:52824]
2024-08-07T11:28:02.254034277Z [INFO][AMF][Ngap] Handle SCTP Connection Error[addr: 192.168.176.137:52824] - remove RAN
2024-08-07T11:28:02.254081094Z [WARN][AMF][Ngap] RAN context has been removed[addr: 192.168.176.137:52824]
SCTPConn: SCTPWrite failed bad file descriptor

The following are my config files:

coreadmin@ueransim:~/UERANSIM/build$ cat ../config/free5gc-gnb.yaml
mcc: '208' # Mobile Country Code value
mnc: '93' # Mobile Network Code value (2 or 3 digits)

nci: '0x000000010' # NR Cell Identity (36-bit)
idLength: 32 # NR gNB ID length in bits [22...32]
tac: 1 # Tracking Area Code

linkIp: 127.0.0.1 # gNB's local IP address for Radio Link Simulation (Usually same with local IP)
ngapIp: 192.168.176.135 # gNB's local IP address for N2 Interface (Usually same with local IP)
gtpIp: 192.168.176.135 # gNB's local IP address for N3 Interface (Usually same with local IP)

List of AMF address information

amfConfigs:

• address: 192.168.176.135
  port: 38412

List of supported S-NSSAIs by this gNB

slices:

• sst: 0x1
  sd: 0x010203

Indicates whether or not SCTP stream number errors should be ignored.

ignoreStreamIds: true

---

coreadmin@free5gc:~/free5gc/config$ less ~/free5gc/config/amfcfg.yaml

info:
version: 1.0.9
description: AMF initial local configuration

configuration:
amfName: AMF # the name of this AMF
ngapIpList: # the IP list of N2 interfaces on this AMF
- 192.168.176.135 # ip of free5gc VM

---

less ~/free5gc/config/smfcfg.yaml

interfaces: # Interface list for this UPF
- interfaceType: N3 # the type of the interface (N3 or N9)
endpoints: # the IP address of this N3/N9 interface on this UPF
- 192.168.176.135

less ~/free5gc/config/upfcfg.yaml

version: 1.0.3
description: UPF initial local configuration

The listen IP and nodeID of the N4 interface on this UPF (Can't set to 0.0.0.0)

pfcp:
addr: 127.0.0.8 # IP addr for listening
nodeID: 127.0.0.8 # External IP or FQDN can be reached
retransTimeout: 1s # retransmission timeout
maxRetrans: 3 # the max number of retransmission

gtpu:
forwarder: gtp5g

The IP list of the N3/N9 interfaces on this UPF

If there are multiple connection, set addr to 0.0.0.0 or list all the addresses

ifList:
- addr: 192.168.176.135
type: N3
# name: upf.5gc.nctu.me
# ifname: gtpif
# mtu: 1400

Using UERANSIM v3.2.6 and free5gc v3.4.2

Any help would be appreciated, thanks.

[laf0rge]

I would start with an strace on the ueransim to check the details of the SCTP socket bind call it is issuing.