apiVersion: v1
kind: Pod
metadata:
namespace: project1
name: example-pod
spec:
containers:
- name: example-pod
...
ports:
- containerPort: 30100
name: sctpserver
protocol: SCTP
As a cluster administrator, you can use the Stream Control Transmission Protocol (SCTP) on a cluster.
As a cluster administrator, you can enable SCTP on the hosts in the cluster. On Red Hat Enterprise Linux CoreOS (RHCOS), the SCTP module is disabled by default.
SCTP is a reliable message based protocol that runs on top of an IP network.
When enabled, you can use SCTP as a protocol with pods, services, and network policy.
A Service
object must be defined with the type
parameter set to either the ClusterIP
or NodePort
value.
You can configure a pod or service to use SCTP by setting the protocol
parameter to the SCTP
value in the pod or service object.
In the following example, a pod is configured to use SCTP:
apiVersion: v1
kind: Pod
metadata:
namespace: project1
name: example-pod
spec:
containers:
- name: example-pod
...
ports:
- containerPort: 30100
name: sctpserver
protocol: SCTP
In the following example, a service is configured to use SCTP:
apiVersion: v1
kind: Service
metadata:
namespace: project1
name: sctpserver
spec:
...
ports:
- name: sctpserver
protocol: SCTP
port: 30100
targetPort: 30100
type: ClusterIP
In the following example, a NetworkPolicy
object is configured to apply to SCTP network traffic on port 80
from any pods with a specific label:
kind: NetworkPolicy
apiVersion: networking.k8s.io/v1
metadata:
name: allow-sctp-on-http
spec:
podSelector:
matchLabels:
role: web
ingress:
- ports:
- protocol: SCTP
port: 80
As a cluster administrator, you can load and enable the blacklisted SCTP kernel module on worker nodes in your cluster.
Install the OpenShift CLI (oc
).
Access to the cluster as a user with the cluster-admin
role.
Create a file named load-sctp-module.yaml
that contains the following YAML definition:
apiVersion: machineconfiguration.openshift.io/v1
kind: MachineConfig
metadata:
name: load-sctp-module
labels:
machineconfiguration.openshift.io/role: worker
spec:
config:
ignition:
version: 3.2.0
storage:
files:
- path: /etc/modprobe.d/sctp-blacklist.conf
mode: 0644
overwrite: true
contents:
source: data:,
- path: /etc/modules-load.d/sctp-load.conf
mode: 0644
overwrite: true
contents:
source: data:,sctp
To create the MachineConfig
object, enter the following command:
$ oc create -f load-sctp-module.yaml
Optional: To watch the status of the nodes while the MachineConfig Operator applies the configuration change, enter the following command. When the status of a node transitions to Ready
, the configuration update is applied.
$ oc get nodes
You can verify that SCTP is working on a cluster by creating a pod with an application that listens for SCTP traffic, associating it with a service, and then connecting to the exposed service.
Access to the internet from the cluster to install the nc
package.
Install the OpenShift CLI (oc
).
Access to the cluster as a user with the cluster-admin
role.
Create a pod starts an SCTP listener:
Create a file named sctp-server.yaml
that defines a pod with the following YAML:
apiVersion: v1
kind: Pod
metadata:
name: sctpserver
labels:
app: sctpserver
spec:
containers:
- name: sctpserver
image: registry.access.redhat.com/ubi9/ubi
command: ["/bin/sh", "-c"]
args:
["dnf install -y nc && sleep inf"]
ports:
- containerPort: 30102
name: sctpserver
protocol: SCTP
Create the pod by entering the following command:
$ oc create -f sctp-server.yaml
Create a service for the SCTP listener pod.
Create a file named sctp-service.yaml
that defines a service with the following YAML:
apiVersion: v1
kind: Service
metadata:
name: sctpservice
labels:
app: sctpserver
spec:
type: NodePort
selector:
app: sctpserver
ports:
- name: sctpserver
protocol: SCTP
port: 30102
targetPort: 30102
To create the service, enter the following command:
$ oc create -f sctp-service.yaml
Create a pod for the SCTP client.
Create a file named sctp-client.yaml
with the following YAML:
apiVersion: v1
kind: Pod
metadata:
name: sctpclient
labels:
app: sctpclient
spec:
containers:
- name: sctpclient
image: registry.access.redhat.com/ubi9/ubi
command: ["/bin/sh", "-c"]
args:
["dnf install -y nc && sleep inf"]
To create the Pod
object, enter the following command:
$ oc apply -f sctp-client.yaml
Run an SCTP listener on the server.
To connect to the server pod, enter the following command:
$ oc rsh sctpserver
To start the SCTP listener, enter the following command:
$ nc -l 30102 --sctp
Connect to the SCTP listener on the server.
Open a new terminal window or tab in your terminal program.
Obtain the IP address of the sctpservice
service. Enter the following command:
$ oc get services sctpservice -o go-template='{{.spec.clusterIP}}{{"\n"}}'
To connect to the client pod, enter the following command:
$ oc rsh sctpclient
To start the SCTP client, enter the following command. Replace <cluster_IP>
with the cluster IP address of the sctpservice
service.
# nc <cluster_IP> 30102 --sctp