datapath: Only make ETH_HLEN as static data if L3 dev exist

This should eliminate a datapath perf penalty introduced by the L2-less
changes when running on systems which all involved devices have L2
addrs.

Signed-off-by: Martynas Pumputis <m@lambda.lt>

daemon/cmd/kube_proxy_replacement.go

@@ -29,6 +29,7 @@ import (
 	"github.com/cilium/cilium/pkg/datapath/loader"
 	datapathOption "github.com/cilium/cilium/pkg/datapath/option"
 	"github.com/cilium/cilium/pkg/logging/logfields"
+	"github.com/cilium/cilium/pkg/mac"
 	"github.com/cilium/cilium/pkg/maglev"
 	"github.com/cilium/cilium/pkg/node"
 	"github.com/cilium/cilium/pkg/option"
@@ -434,7 +435,7 @@ func finishKubeProxyReplacementInit(isKubeProxyReplacementStrict bool) {
 		case (option.Config.EnableIPv4Masquerade || option.Config.EnableIPv6Masquerade) &&
 			!option.Config.EnableBPFMasquerade:
 			msg = fmt.Sprintf("BPF host routing requires %s.", option.EnableBPFMasquerade)
-		case !hasHardwareAddress():
+		case !mac.HaveMACAddr(option.Config.Devices):
 			msg = fmt.Sprintf("BPF host routing is currently not supported with devices without L2 addr.")
 		default:
 			probesManager := probes.NewProbeManager()
@@ -728,16 +729,3 @@ func hasFullHostReachableServices() bool {
 		option.Config.EnableHostServicesTCP &&
 		option.Config.EnableHostServicesUDP
 }
-
-func hasHardwareAddress() bool {
-	for _, iface := range option.Config.Devices {
-		iface, err := netlink.LinkByName(iface)
-		if err != nil {
-			return false
-		}
-		if len(iface.Attrs().HardwareAddr) == 0 {
-			return false
-		}
-	}
-	return true
-}

pkg/datapath/linux/config/config.go

@@ -598,8 +598,11 @@ func (h *HeaderfileWriter) writeStaticData(fw io.Writer, e datapath.EndpointConf
 		fmt.Fprint(fw, defineUint32("SECCTX_FROM_IPCACHE", 1))
 		fmt.Fprint(fw, defineUint32("HOST_EP_ID", uint32(e.GetID())))
 
-		// L2 hdr len (for L2-less devices it will be replaced with "0")
-		fmt.Fprint(fw, defineUint32("ETH_HLEN", mac.EthHdrLen))
+		// Use templating for ETH_HLEN only if there is any L2-less device
+		if !mac.HaveMACAddr(option.Config.Devices) {
+			// L2 hdr len (for L2-less devices it will be replaced with "0")
+			fmt.Fprint(fw, defineUint32("ETH_HLEN", mac.EthHdrLen))
+		}
 	} else {
 		// We want to ensure that the template BPF program always has "LXC_IP"
 		// defined and present as a symbol in the resulting object file after

pkg/mac/mac.go

@@ -20,6 +20,8 @@ import (
 	"encoding/hex"
 	"fmt"
 	"net"
+
+	"github.com/vishvananda/netlink"
 )
 
 // Untagged ethernet (IEEE 802.3) frame header len
@@ -109,3 +111,17 @@ func GenerateRandMAC() (MAC, error) {
 
 	return MAC(buf), nil
 }
+
+// HaveMACAddr return true if all given network interfaces have L2 addr.
+func HaveMACAddr(ifaces []string) bool {
+	for _, iface := range ifaces {
+		iface, err := netlink.LinkByName(iface)
+		if err != nil {
+			return false
+		}
+		if len(iface.Attrs().HardwareAddr) == 0 {
+			return false
+		}
+	}
+	return true
+}