Get the right traffic mode in e2e tests (#2019)

Fix e2e test framework to get the right Antrea ConfigMap for retrieving
the traffic encap mode, when there are multiple Antrea ConfigMaps
created in the test Cluster.
Add information about building Antrea Ubuntu image to CONTRIBUTING.md,
and generating Antrea manifest to test/e2e/README.md.

CONTRIBUTING.md

@@ -180,6 +180,7 @@ To develop locally, you can follow these steps:
  2. Checkout your feature branch and `cd` into it.
  3. To build all Go files and install them under `bin`, run `make bin`
  4. To run all Go unit tests, run `make test-unit`
+ 5. To build the Antrea Ubuntu Docker image separately with the binaries generated in step 2, run `make ubuntu`
 
 ### CI testing
 

test/e2e/README.md

@@ -179,6 +179,10 @@ manifest to the control-plane Docker container:
 go test -v github.com/vmware-tanzu/antrea/test/e2e -provider=kind
 ```
 
+`generate-manifest.sh` supports generating the Antrea manifest with different
+Antrea configurations. Run `./hack/generate-manifest.sh --help` to see the
+supported config options.
+
 As part of code development, if you want to run the tests with local changes,
 then make the code changes on the local repo and
 [build the image](../../CONTRIBUTING.md#building-and-testing-your-change).

test/e2e/framework.go

@@ -1536,28 +1536,19 @@ func (data *TestData) doesOVSPortExist(antreaPodName string, portName string) (b
 }
 
 func (data *TestData) GetEncapMode() (config.TrafficEncapModeType, error) {
-	mapList, err := data.clientset.CoreV1().ConfigMaps(antreaNamespace).List(context.TODO(), metav1.ListOptions{})
+	configMap, err := data.GetAntreaConfigMap(antreaNamespace)
 	if err != nil {
-		return config.TrafficEncapModeInvalid, err
+		return config.TrafficEncapModeInvalid, fmt.Errorf("failed to get Antrea ConfigMap: %v", err)
 	}
-	for _, m := range mapList.Items {
-		if strings.HasPrefix(m.Name, "antrea-config") {
-			configMap, err := data.clientset.CoreV1().ConfigMaps(antreaNamespace).Get(context.TODO(), m.Name, metav1.GetOptions{})
-			if err != nil {
-				return config.TrafficEncapModeInvalid, err
-			}
-			for _, antreaConfig := range configMap.Data {
-				for _, mode := range config.GetTrafficEncapModes() {
-					searchStr := fmt.Sprintf("trafficEncapMode: %s", mode)
-					if strings.Index(strings.ToLower(antreaConfig), strings.ToLower(searchStr)) != -1 {
-						return mode, nil
-					}
-				}
+	for _, antreaConfig := range configMap.Data {
+		for _, mode := range config.GetTrafficEncapModes() {
+			searchStr := fmt.Sprintf("trafficEncapMode: %s", mode)
+			if strings.Index(strings.ToLower(antreaConfig), strings.ToLower(searchStr)) != -1 {
+				return mode, nil
 			}
-			return config.TrafficEncapModeEncap, nil
 		}
 	}
-	return config.TrafficEncapModeInvalid, fmt.Errorf("antrea-conf config map is not found")
+	return config.TrafficEncapModeEncap, nil
 }
 
 func (data *TestData) getFeatures(confName string, antreaNamespace string) (featuregate.FeatureGate, error) {