Source-Based Routing Plugin¶

The SBR plugin enables source based routing on an interface. It must be used as a chained plugin in conjunction with another interface-creating plugin.

The following options are used to configure the plugin:

name (string, optional): The name of the network.
type (string, required): sbr

Example

The following example creates a pod with an additional bridge interface which has SBR enabled. There is also a demonstration pod without SBR enabled and an iperf server pod. Note the chained nature of the plugins.

apiVersion: "k8s.cni.cncf.io/v1"
kind: NetworkAttachmentDefinition
metadata:
  name: sbrnet1
spec:
  config: '{
      "cniVersion": "0.3.1",
      "name": "sbrnet",
      "plugins": [
          {
              "type": "bridge",
              "bridge": "mybr0",
              "ipam": {
                  "type": "static",
                  "addresses" : [
                      {
                          "address": "10.10.10.98/24",
                          "gateway": "10.10.10.254"
                      }
                  ]
              }
          },
          {
              "name": "brsbr",
              "type": "sbr"
          }
      ]

    }'
---
apiVersion: "k8s.cni.cncf.io/v1"
kind: NetworkAttachmentDefinition
metadata:
  name: nosbrnet1
spec:
  config: '{
      "cniVersion": "0.3.1",
      "type": "bridge",
      "bridge": "mybr0",
      "ipam": {
          "type": "static",
          "addresses" : [
              {
                  "address": "10.10.10.99/24",
                  "gateway": "10.10.10.254"
              }
          ]
      }
    }'
---
apiVersion: "k8s.cni.cncf.io/v1"
kind: NetworkAttachmentDefinition
metadata:
  name: iperfservernet0
spec:
  config: '{
      "cniVersion": "0.3.1",
      "type": "bridge",
      "bridge": "mybr0",
      "ipam": {
          "type": "static",
          "addresses" : [
              {
                  "address": "10.10.10.254/24"
              }
          ]
      }
    }'
---
apiVersion: "k8s.cni.cncf.io/v1"
kind: NetworkAttachmentDefinition
metadata:
  name: iperfservernet1
spec:
  config: '{
      "cniVersion": "0.3.1",
      "type": "bridge",
      "bridge": "mybr1",
      "ipam": {
          "type": "static",
          "addresses" : [
              {
                  "address": "20.20.20.254/24"
              }
          ]
      }
    }'
---
apiVersion: v1
kind: Pod
metadata:
  name: sbrpod1
  annotations:
    k8s.v1.cni.cncf.io/networks: '[
            { "name": "sbrnet1" }
    ]'
spec:
  containers:
  - name: sbr1
    image: praqma/network-multitool:extra
    imagePullPolicy: IfNotPresent
    command: [ "/bin/bash", "-c", "--" ]
    args: [ "while true; do sleep 300000; done;" ]
---
apiVersion: v1
kind: Pod
metadata:
  name: nosbrpod1
  annotations:
    k8s.v1.cni.cncf.io/networks: '[
            { "name": "nosbrnet1" }
    ]'
spec:
  containers:
  - name: sbr2
    image: praqma/network-multitool:extra
    imagePullPolicy: IfNotPresent
    command: [ "/bin/bash", "-c", "--" ]
    args: [ "while true; do sleep 300000; done;" ]
---
apiVersion: v1
kind: Pod
metadata:
  name: iperfserverpod1
  annotations:
    k8s.v1.cni.cncf.io/networks: '[
            { "name": "iperfservernet0" },
            { "name": "iperfservernet1" }
    ]'
spec:
  containers:
  - name: iperfserver1
    image: praqma/network-multitool:extra
    imagePullPolicy: IfNotPresent
    command: [ "/bin/bash", "-c", "--" ]
    args: [ "while true; do sleep 300000; done;" ]

Note

The default table number will be 100. One can see the result of the SBR plugin below. For an application to use source-based routing, it would bind its socket to the source address, causing the routes in the corresponding table to be used (rather than the default routes).

Related commands

Show the default routing table.

kubectl exec -it sbrpod1 -- ip route show
   default via 169.254.1.1 dev eth0
   169.254.1.1 dev eth0 scope link

Show the table created by SBR.

kubectl exec -it sbrpod1 -- ip rule list

     from all lookup local
 from 10.10.10.98 lookup 100  <----------
 from all lookup main
 from all lookup default

Show the contents of table 100.

kubectl exec -it sbrpod1 -- ip route show table 100

   default via 10.10.10.254 dev net1
   10.10.10.0/24 dev net1 proto kernel scope link src 10.10.10.98

Start the iperf server.

kubectl exec -it iperfserverpod1 -- iperf3 -s -B 20.20.20.254

Example of failure to connect from a pod without source based routing.

kubectl exec -it nosbrpod1 -- iperf3 -c 20.20.20.254 -B 10.10.10.99 -k 1

Example of failure to connect without binding to the source address.
```
kubectl exec -it sbrpod1 -- iperf3 -c 20.20.20.254 -k 1
```
Example of connection success for application binding to the source address.
```
kubectl exec -it sbrpod1 -- iperf3 -c 20.20.20.254 -B 10.10.10.98 -k 1
```

Source-Based Routing Plugin

Source-Based Routing Plugin¶

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