Fix test failure of ServiceExternalIP with LoadBalancerModeDSR (#6994)

Fixes: #6992

Signed-off-by: Xu Liu <[email protected]>

test/e2e/framework.go

@@ -494,6 +494,25 @@ func controlPlaneNoScheduleTolerations() []corev1.Toleration {
 	}
 }
 
+func (data *TestData) getDefaultLoadBalancerMode() (config.LoadBalancerMode, error) {
+	featureGate, err := GetAgentFeatures()
+	if err != nil {
+		return config.LoadBalancerModeInvalid, err
+	}
+	if !featureGate.Enabled(features.LoadBalancerModeDSR) {
+		return config.LoadBalancerModeNAT, nil
+	}
+	agentConf, err := data.GetAntreaAgentConf()
+	if err != nil {
+		return config.LoadBalancerModeInvalid, err
+	}
+	valid, mode := config.GetLoadBalancerModeFromStr(agentConf.AntreaProxy.DefaultLoadBalancerMode)
+	if !valid {
+		return config.LoadBalancerModeInvalid, fmt.Errorf("invalid LoadBalancer mode %s", agentConf.AntreaProxy.DefaultLoadBalancerMode)
+	}
+	return mode, nil
+}
+
 func (data *TestData) InitProvider(providerName, providerConfigPath string) error {
 	providerFactory := map[string]func(string) (providers.ProviderInterface, error){
 		"vagrant": providers.NewVagrantProvider,

test/e2e/service_externalip_test.go

@@ -35,6 +35,7 @@ import (
 	utilnet "k8s.io/utils/net"
 
 	"antrea.io/antrea/pkg/agent/apis"
+	"antrea.io/antrea/pkg/agent/config"
 	antreaagenttypes "antrea.io/antrea/pkg/agent/types"
 	"antrea.io/antrea/pkg/apis/crd/v1beta1"
 	"antrea.io/antrea/pkg/features"
@@ -779,6 +780,32 @@ func testExternalIPAccess(t *testing.T, data *TestData) {
 					externalIP, host, err := waitExternalIPConfigured(service)
 					require.NoError(t, err)
 
+					lbMode, err := data.getDefaultLoadBalancerMode()
+					require.NoError(t, err)
+					// A route to the client IP is required in DSR mode.
+					if lbMode == config.LoadBalancerModeDSR {
+						nodeInfo := getNodeByName(host)
+						workerNodeIP := clusterInfo.nodes[nodeInfo.idx].ip()
+						addRouteToClientIPCmd := []string{"ip", "route", "replace", tt.clientIP, "via", workerNodeIP}
+						delRouteToClientIPCmd := []string{"ip", "route", "del", tt.clientIP, "via", workerNodeIP}
+						// We run backend Pods for the Service on two Nodes,
+						// so we need the route to be installed on the Node
+						// where the client is not running.
+						for idx := range nodes {
+							node := nodes[idx]
+							if node == host {
+								continue
+							}
+							stdout, stderr, err := data.RunCommandFromAntreaPodOnNode(node, addRouteToClientIPCmd)
+							require.NoError(t, err, "Failed to add route to client IP on Node %s, stdout: %s, stderr: %s: cmd: %q", node, stdout, stderr, addRouteToClientIPCmd)
+
+							defer func() {
+								stdout, stderr, err := data.RunCommandFromAntreaPodOnNode(node, delRouteToClientIPCmd)
+								assert.NoError(t, err, "Failed to delete route to client IP on Node %s, stdout: %s, stderr: %s", node, stdout, stderr)
+							}()
+						}
+					}
+
 					// Create a pod in a different netns with the same subnet of the external IP to mock as another Node in the same subnet.
 					cmd, netns := getCommandInFakeExternalNetwork("sleep 3600", tt.clientIPMaskLen, tt.clientIP, tt.localIP)