fix: skip reserved IPs (#2060)

Co-authored-by: Jaeryn <[email protected]>

Author: jaer-tsun

cns/kubecontroller/nodenetworkconfig/conversion_windows.go

@@ -9,16 +9,16 @@ import (
 )
 
 // createNCRequestFromStaticNCHelper generates a CreateNetworkContainerRequest from a static NetworkContainer.
-// If the NC's DefaultGateway is empty, it will set the 0th IP as the gateway IP and all remaining IPs as
-// secondary IPs. If the gateway is not empty, it will not reserve the 0th IP and add it as a secondary IP.
+// If the NC's DefaultGateway is empty and nc type is overlay, it will set the 2nd IP (*.1) as the gateway IP and all remaining IPs as
+// secondary IPs. If the gateway is not empty, it will not reserve the 2nd IP and add it as a secondary IP.
 //
 //nolint:gocritic //ignore hugeparam
 func createNCRequestFromStaticNCHelper(nc v1alpha.NetworkContainer, primaryIPPrefix netip.Prefix, subnet cns.IPSubnet) *cns.CreateNetworkContainerRequest {
 	secondaryIPConfigs := map[string]cns.SecondaryIPConfig{}
-
-	// if NC DefaultGateway is empty, set the 0th IP to the gateway and add the rest of the IPs
-	// as secondary IPs
-	startingAddr := primaryIPPrefix.Masked().Addr() // the masked address is the 0th IP in the subnet
+	// the masked address is the 0th IP in the subnet and startingAddr is the 2nd IP (*.1)
+	startingAddr := primaryIPPrefix.Masked().Addr().Next()
+	lastAddr := startingAddr
+	// if NC DefaultGateway is empty, set the 2nd IP (*.1) to the gateway and add the rest of the IPs as secondary IPs
 	if nc.DefaultGateway == "" {
 		nc.DefaultGateway = startingAddr.String()
 		startingAddr = startingAddr.Next()
@@ -31,7 +31,10 @@ func createNCRequestFromStaticNCHelper(nc v1alpha.NetworkContainer, primaryIPPre
 			IPAddress: addr.String(),
 			NCVersion: int(nc.Version),
 		}
+		lastAddr = addr
 	}
+	delete(secondaryIPConfigs, lastAddr.String())
+
 	return &cns.CreateNetworkContainerRequest{
 		SecondaryIPConfigs:   secondaryIPConfigs,
 		NetworkContainerid:   nc.ID,

cns/kubecontroller/nodenetworkconfig/conversion_windows_test.go

@@ -13,22 +13,14 @@ var validOverlayRequest = &cns.CreateNetworkContainerRequest{
 			PrefixLength: uint8(subnetPrefixLen),
 			IPAddress:    primaryIP,
 		},
-		GatewayIPAddress: "10.0.0.0",
+		GatewayIPAddress: "10.0.0.1",
 	},
 	NetworkContainerid:   ncID,
 	NetworkContainerType: cns.Docker,
 	SecondaryIPConfigs: map[string]cns.SecondaryIPConfig{
-		"10.0.0.1": {
-			IPAddress: "10.0.0.1",
-			NCVersion: version,
-		},
 		"10.0.0.2": {
 			IPAddress: "10.0.0.2",
-			NCVersion: version,
-		},
-		"10.0.0.3": {
-			IPAddress: "10.0.0.3",
-			NCVersion: version,
+			NCVersion: 0,
 		},
 	},
 }