Fixes to enable vxlan testing in cmd-forwarder-vpp. (#120)

Add NextNode  ethernet-input for vxlan:

  This allows assignment of an IP address to vxlan in a way
  that responds to arp.  It is used for testing.

Set route to IsMultipath == false:
  Fixes a bug in adding an deleting the same route repeatedly
  for vxlan interfaces

Signed-off-by: Ed Warnicke <hagbard@gmail.com>

pkg/networkservice/connectioncontext/ipcontext/routes/common.go

@@ -69,7 +69,7 @@ func routeAddDel(ctx context.Context, vppConn api.Connection, swIfIndex interfac
 	now := time.Now()
 	if _, err := ip.NewServiceClient(vppConn).IPRouteAddDel(ctx, &ip.IPRouteAddDel{
 		IsAdd:       isAdd,
-		IsMultipath: true,
+		IsMultipath: false,
 		Route:       route,
 	}); err != nil {
 		return errors.WithStack(err)

pkg/networkservice/mechanisms/vxlan/common.go

@@ -21,6 +21,7 @@ import (
 	"time"
 
 	"git.fd.io/govpp.git/api"
+	"git.fd.io/govpp.git/binapi/vpe"
 	"github.com/edwarnicke/govpp/binapi/vxlan"
 	"github.com/pkg/errors"
 
@@ -49,12 +50,30 @@ func addDel(ctx context.Context, conn *networkservice.Connection, vppConn api.Co
 		}
 
 		now := time.Now()
+
+		addNextNode := &vpe.AddNodeNext{
+			NodeName: "vxlan4-input",
+			NextName: "ethernet-input",
+		}
+
+		addNextNodeRsp, err := vpe.NewServiceClient(vppConn).AddNodeNext(ctx, addNextNode)
+		if err != nil {
+			return errors.WithStack(err)
+		}
+		log.FromContext(ctx).
+			WithField("NextIndex", addNextNodeRsp.NextIndex).
+			WithField("NodeName", addNextNode.NodeName).
+			WithField("NextName", addNextNode.NextName).
+			WithField("duration", time.Since(now)).
+			WithField("vppapi", "AddNodeNext").Debug("completed")
+
+		now = time.Now()
 		vxlanAddDelTunnel := &vxlan.VxlanAddDelTunnel{
 			IsAdd:          isAdd,
 			Instance:       ^uint32(0),
 			SrcAddress:     types.ToVppAddress(mechanism.SrcIP()),
 			DstAddress:     types.ToVppAddress(mechanism.DstIP()),
-			DecapNextIndex: ^uint32(0),
+			DecapNextIndex: addNextNodeRsp.NextIndex,
 			Vni:            mechanism.VNI(),
 		}
 		if !isClient {