fix: Using Node IP as the primary IP allowing the use of all the IPs in the subnet for pods in Vnet Scale Mode and added the fix for Vnet Scale Cillium (#2660)

* Testing with NodeIP as the PrimaryIP

* Updated the secondary IP configs to not delete the first IP from Primary IP field as we will now use the Node IP for all functions related to Primary IP

* Fixed the invalid UT to test out and validate the use of Node IP for SNAT and including the primary IP for use in secondary IP blocks

* Combined the common code for Prefix Length

* Updated to set the Host Primary IP for both Overlay and Vnet Scale as it is primarily only being used to setup IMDS SNAT Rules

* Fixing the valid overlay UT to include the Host Primary IP

Author: nairashu

cns/kubecontroller/nodenetworkconfig/conversion.go

@@ -87,14 +87,20 @@ func CreateNCRequestFromStaticNC(nc v1alpha.NetworkContainer) (*cns.CreateNetwor
 	if err != nil {
 		return nil, errors.Wrapf(err, "invalid SubnetAddressSpace %s", nc.SubnetAddressSpace)
 	}
+
 	subnet := cns.IPSubnet{
-		IPAddress:    primaryPrefix.Addr().String(),
 		PrefixLength: uint8(subnetPrefix.Bits()),
 	}
+	if nc.Type == v1alpha.VNETBlock {
+		subnet.IPAddress = nc.NodeIP
+	} else {
+		subnet.IPAddress = primaryPrefix.Addr().String()
+	}
 
 	req, err := createNCRequestFromStaticNCHelper(nc, primaryPrefix, subnet)
 	if err != nil {
 		return nil, errors.Wrapf(err, "error while creating NC request from static NC")
 	}
+
 	return req, err
 }

cns/kubecontroller/nodenetworkconfig/conversion_linux.go

@@ -27,8 +27,6 @@ func createNCRequestFromStaticNCHelper(nc v1alpha.NetworkContainer, primaryIPPre
 
 	// Add IPs from CIDR block to the secondary IPConfigs
 	if nc.Type == v1alpha.VNETBlock {
-		// Delete primary IP reserved for Primary IP for NC
-		delete(secondaryIPConfigs, primaryIPPrefix.Addr().String())
 
 		for _, ipAssignment := range nc.IPAssignments {
 			cidrPrefix, err := netip.ParsePrefix(ipAssignment.IP)
@@ -48,6 +46,7 @@ func createNCRequestFromStaticNCHelper(nc v1alpha.NetworkContainer, primaryIPPre
 	}
 
 	return &cns.CreateNetworkContainerRequest{
+		HostPrimaryIP:        nc.NodeIP,
 		SecondaryIPConfigs:   secondaryIPConfigs,
 		NetworkContainerid:   nc.ID,
 		NetworkContainerType: cns.Docker,

cns/kubecontroller/nodenetworkconfig/conversion_linux_test.go

@@ -7,7 +7,8 @@ import (
 )
 
 var validOverlayRequest = &cns.CreateNetworkContainerRequest{
-	Version: strconv.FormatInt(0, 10),
+	HostPrimaryIP: validOverlayNC.NodeIP,
+	Version:       strconv.FormatInt(0, 10),
 	IPConfiguration: cns.IPConfiguration{
 		IPSubnet: cns.IPSubnet{
 			PrefixLength: uint8(subnetPrefixLen),
@@ -37,18 +38,23 @@ var validOverlayRequest = &cns.CreateNetworkContainerRequest{
 }
 
 var validVNETBlockRequest = &cns.CreateNetworkContainerRequest{
-	Version: strconv.FormatInt(version, 10),
+	Version:       strconv.FormatInt(version, 10),
+	HostPrimaryIP: vnetBlockNodeIP,
 	IPConfiguration: cns.IPConfiguration{
 		GatewayIPAddress: vnetBlockDefaultGateway,
 		IPSubnet: cns.IPSubnet{
 			PrefixLength: uint8(vnetBlockSubnetPrefixLen),
-			IPAddress:    vnetBlockPrimaryIP,
+			IPAddress:    vnetBlockNodeIP,
 		},
 	},
 	NetworkContainerid:   ncID,
 	NetworkContainerType: cns.Docker,
 	// Ignore first IP in first CIDR Block, i.e. 10.224.0.4
 	SecondaryIPConfigs: map[string]cns.SecondaryIPConfig{
+		"10.224.0.4": {
+			IPAddress: "10.224.0.4",
+			NCVersion: version,
+		},
 		"10.224.0.5": {
 			IPAddress: "10.224.0.5",
 			NCVersion: version,