Unable to expose SCTP server running in a kubernetes pod using NodePort

I have a single node kubernetes cluster running in a VM in azure. I have a service running SCTP server in port 38412. I need to expose that port externally. I have tried by changing the port type to NodePort. But no success. I am using flannel as a overlay network. using Kubernetes version 1.23.3.

This is my service.yaml file

apiVersion: v1
kind: Service
metadata:
  annotations:
    meta.helm.sh/release-name: fivegcore
    meta.helm.sh/release-namespace: open5gs
  creationTimestamp: "2022-02-11T09:24:09Z"
  labels:
    app.kubernetes.io/managed-by: Helm
    epc-mode: amf
  name: fivegcore-amf
  namespace: open5gs
  resourceVersion: "33072"
  uid: 4392dd8d-2561-49ab-9d57-47426b5d951b
spec:
  clusterIP: 10.111.94.85
  clusterIPs:
  - 10.111.94.85
  externalTrafficPolicy: Cluster
  internalTrafficPolicy: Cluster
  ipFamilies:
  - IPv4
  ipFamilyPolicy: SingleStack
  ports:
  - name: tcp
    nodePort: 30314
    port: 80
    protocol: TCP
    targetPort: 80
  - name: ngap
    nodePort: 30090
    port: 38412
    protocol: SCTP
    targetPort: 38412
  selector:
    epc-mode: amf
  sessionAffinity: None
  type: NodePort
status:
  loadBalancer: {}

As you can see I changed the port type to NodePort.

open5gs fivegcore-amf NodePort 10.111.94.85  <none>  80:30314/TCP,38412:30090/SCTP

This is my Configmap.yaml. In this configmap that ngap dev is the server I want to connect which is using default eth0 interface in the container.

apiVersion: v1
data:
  amf.yaml: |
    logger:
        file: /var/log/open5gs/amf.log
        #level: debug
        #domain: sbi

    amf:
        sbi:
        - addr: 0.0.0.0
          advertise: fivegcore-amf
        ngap:
          dev: eth0
        guami:
          - plmn_id:
              mcc: 208
              mnc: 93
            amf_id:
              region: 2
              set: 1
        tai:
          - plmn_id:
              mcc: 208
              mnc: 93
            tac: 7
        plmn_support:
        - plmn_id:
            mcc: 208
            mnc: 93
          s_nssai:
          - sst: 1
            sd: 1
        security:
            integrity_order : [ NIA2, NIA1, NIA0 ]
            ciphering_order : [ NEA0, NEA1, NEA2 ]
        network_name:
            full: Open5GS
        amf_name: open5gs-amf0
    nrf:
     sbi:
       name: fivegcore-nrf
kind: ConfigMap
metadata:
  annotations:
    meta.helm.sh/release-name: fivegcore
    meta.helm.sh/release-namespace: open5gs
  creationTimestamp: "2022-02-11T09:24:09Z"
  labels:
    app.kubernetes.io/managed-by: Helm
    epc-mode: amf

I exec in to the container and check whether the server is running or not. This is the netstat of the container.

Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name
tcp        0      0 10.244.0.31:37742       10.105.167.186:80       ESTABLISHED 1/open5gs-amfd
sctp                10.244.0.31:38412                               LISTEN      1/open5gs-amfd

sctp module is also loaded in the host.

$lsmod | grep sctp
sctp                  356352  8
xt_sctp                20480  0
libcrc32c              16384  5 nf_conntrack,nf_nat,nf_tables,ip_vs,sctp
x_tables               49152  18 ip6table_filter,xt_conntrack,xt_statistic,iptable_filter,iptable_security,xt_tcpudp,xt_addrtype,xt_nat,xt_comment,xt_owner,ip6_tables,xt_sctp,ipt_REJECT,ip_tables,ip6table_mangle,xt_MASQUERADE,iptable_mangle,xt_mark

Is it possible to expose this server externally?

Solution

Neither AKS nor Flannel supports SCTP at this point of writing. Here's some details about it.