Assigns default=true on a multiple interface return for first interface with a gateway

pkg/utils/net-attach-def.go

@@ -122,6 +122,16 @@ func GetNetworkStatus(pod *corev1.Pod) ([]v1.NetworkStatus, error) {
 	return netStatuses, err
 }
 
+// gatewayInterfaceIndex determines the index of the first interface that has a gateway
+func gatewayInterfaceIndex(ips []*cni100.IPConfig) int {
+	for _, ipConfig := range ips {
+		if ipConfig.Gateway != nil && ipConfig.Interface != nil {
+			return *ipConfig.Interface
+		}
+	}
+	return -1
+}
+
 // CreateNetworkStatuses creates an array of NetworkStatus from CNI result
 // Not to be confused with CreateNetworkStatus (singular)
 // This is the preferred method and picks up when CNI ADD results contain multiple container interfaces
@@ -152,14 +162,36 @@ func CreateNetworkStatuses(r cnitypes.Result, networkName string, defaultNetwork
 	// Same for DNS
 	v1dns := convertDNS(result.DNS)
 
+	// Check for a gateway-associated interface, we'll use this later if we did to mark as the default.
+	gwInterfaceIdx := -1
+	if defaultNetwork {
+		gwInterfaceIdx = gatewayInterfaceIndex(result.IPs)
+	}
+
 	// Initialize NetworkStatus for each container interface (e.g. with sandbox present)
 	indexOfFoundPodInterface := 0
 	foundFirstSandboxIface := false
+	didSetDefault := false
 	for i, iface := range result.Interfaces {
 		if iface.Sandbox != "" {
+			isDefault := false
+
+			// If there's a gateway listed for this interface index found in the ips, we mark that interface as default
+			// notably, we use the first one we find.
+			if defaultNetwork && i == gwInterfaceIdx && !didSetDefault {
+				isDefault = true
+				didSetDefault = true
+			}
+
+			// Otherwise, if we didn't find it, we use the first sandbox interface.
+			if defaultNetwork && gwInterfaceIdx == -1 && !foundFirstSandboxIface {
+				isDefault = true
+				foundFirstSandboxIface = true
+			}
+
 			ns := &v1.NetworkStatus{
 				Name:       networkName,
-				Default:    defaultNetwork && !foundFirstSandboxIface,
+				Default:    isDefault,
 				Interface:  iface.Name,
 				Mac:        iface.Mac,
 				Mtu:        iface.Mtu,
@@ -172,7 +204,6 @@ func CreateNetworkStatuses(r cnitypes.Result, networkName string, defaultNetwork
 			// Map original index to the new slice index
 			indexMap[i] = indexOfFoundPodInterface
 			indexOfFoundPodInterface++
-			foundFirstSandboxIface = true
 		}
 	}
 

pkg/utils/net-attach-def_test.go

@@ -101,6 +101,62 @@ var _ = Describe("Netwok Attachment Definition manipulations", func() {
 		Expect(fakeStatus).To(Equal(getStatuses))
 	})
 
+	It("matches default=true when gateway is present for an interface", func() {
+		// CNI result using cni100.Result format
+		ifone := 1
+		iftwo := 3
+		cniResult := &cni100.Result{
+			CNIVersion: "1.0.0",
+			Interfaces: []*cni100.Interface{
+				{
+					Name: "0xsomething",
+					Mac:  "be:ee:ee:ee:ee:ef",
+				},
+				{
+					Name:    "eth0",
+					Mac:     "b1:aa:aa:aa:a5:ee",
+					Sandbox: "/var/run/netns/cni-309e7579-1b15-f905-5150-2cd232b0dad9",
+				},
+				{
+					Name: "0xotherthing",
+					Mac:  "b0:00:00:00:00:0f",
+				},
+				{
+					Name:    "other-primary",
+					Mac:     "c0:00:00:00:00:01",
+					Sandbox: "/var/run/netns/cni-309e7579-1b15-f905-5150-2cd232b0dad9",
+				},
+			},
+			IPs: []*cni100.IPConfig{
+				{
+					Interface: &ifone,
+					Address:   *EnsureCIDR("10.244.1.6/24"),
+				},
+				{
+					Interface: &iftwo,
+					Address:   *EnsureCIDR("10.20.1.3/24"),
+					Gateway:   net.ParseIP("10.20.1.1"),
+				},
+			},
+		}
+
+		// Call CreateNetworkStatuses with this CNI result
+		networkName := "test-network"
+		defaultNetwork := true
+		deviceInfo := &v1.DeviceInfo{} // mock device info if needed
+
+		networkStatuses, err := CreateNetworkStatuses(cniResult, networkName, defaultNetwork, deviceInfo)
+		Expect(err).NotTo(HaveOccurred())
+		Expect(networkStatuses).To(HaveLen(2)) // expecting 2 statuses for sandboxed interfaces
+
+		// Check that the interface with the gateway is marked as default
+		Expect(networkStatuses[0].Interface).To(Equal("eth0"))
+		Expect(networkStatuses[0].Default).To(BeFalse())
+
+		Expect(networkStatuses[1].Interface).To(Equal("other-primary"))
+		Expect(networkStatuses[1].Default).To(BeTrue()) // other-primary should be default because it has a gateway
+	})
+
 	Context("create network status from cni result", func() {
 		var cniResult *cni100.Result
 		var networkStatus *v1.NetworkStatus