Improve podCIDR detection

In K8s, each node is typically assigned a unique PodCIDR range for the pods that run on that node. Each node's PodCIDR is used to allocate IP addresses to the pods scheduled on that node. Only if the cluster is a single node deployment, we should rely on the node.Spec.PodCIDR as podCIDR of the cluster. Related to: submariner-io/submariner#2128 Signed-off-by: Sridhar Gaddam <[email protected]>
submariner-io · Sep 5, 2023 · ddeccee · ddeccee
1 parent d42f9c1
commit ddeccee
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Showing 2 changed files with 22 additions and 7 deletions.
diff --git a/pkg/discovery/network/generic.go b/pkg/discovery/network/generic.go
@@ -191,10 +191,11 @@ func findPodIPRangeFromNodeSpec(ctx context.Context, client controllerClient.Cli
 }
 
 func parseToPodCidr(nodes []corev1.Node) (string, error) {
-	for i := range nodes {
-		if nodes[i].Spec.PodCIDR != "" {
-			return nodes[i].Spec.PodCIDR, nil
-		}
+	// In K8s, each node is typically assigned a unique PodCIDR range for the pods that run on that node.
+	// Each node's PodCIDR is used to allocate IP addresses to the pods scheduled on that node. Only if
+	// the cluster is a single node deployment, we should rely on the node.Spec.PodCIDR as podCIDR of the cluster.
+	if len(nodes) == 1 {
+		return nodes[0].Spec.PodCIDR, nil
 	}
 
 	return "", nil

diff --git a/pkg/discovery/network/generic_test.go b/pkg/discovery/network/generic_test.go
@@ -222,13 +222,12 @@ var _ = Describe("Generic Network", func() {
 		})
 	})
 
-	When("Pod CIDR information exists on a node", func() {
+	When("Pod CIDR information exists on a single node cluster", func() {
 		var clusterNet *network.ClusterNetwork
 
 		BeforeEach(func() {
 			clusterNet = testDiscoverGenericWith(
-				fakeNode("node1", ""),
-				fakeNode("node2", testPodCIDR),
+				fakeNode("node1", testPodCIDR),
 			)
 		})
 
@@ -245,6 +244,21 @@ var _ = Describe("Generic Network", func() {
 		})
 	})
 
+	When("Pod CIDR information exists on a multi node cluster", func() {
+		var clusterNet *network.ClusterNetwork
+
+		BeforeEach(func() {
+			clusterNet = testDiscoverGenericWith(
+				fakeNode("node1", testPodCIDR),
+				fakeNode("node2", testPodCIDR),
+			)
+		})
+
+		It("Should return an empty ClusterNetwork structure with the pod CIDR", func() {
+			Expect(clusterNet.PodCIDRs).To(BeEmpty())
+		})
+	})
+
 	When("Both pod and service CIDR information exists", func() {
 		var clusterNet *network.ClusterNetwork