Extract AttachContainer() function

Also move netlink and netns code from common to net

Creates interface if not already there
Adds addresses
Move the set link 'up' to after addresses are added

plugin/net/cni.go

@@ -10,7 +10,6 @@ import (
 	"github.com/appc/cni/pkg/ipam"
 	"github.com/appc/cni/pkg/skel"
 	"github.com/appc/cni/pkg/types"
-	"github.com/j-keck/arping"
 	"github.com/vishvananda/netlink"
 	"github.com/vishvananda/netns"
 	weaveapi "github.com/weaveworks/weave/api"
@@ -94,24 +93,14 @@ func (c *CNIPlugin) CmdAdd(args *skel.CmdArgs) error {
 		id = fmt.Sprintf("%x", data)
 	}
 
-	name, peerName := vethPair(id)
-	_, err = weavenet.CreateAndAttachVeth(name, peerName, conf.BrName, conf.MTU, func(local, guest netlink.Link) error {
-		if err = netlink.LinkSetNsFd(guest, int(ns)); err != nil {
-			return fmt.Errorf("failed to move veth to container netns: %s", err)
-		}
-		if err = common.WithNetNS(ns, func() error {
-			if err := weavenet.SetupGuest(guest, args.IfName, []net.IPNet{result.IP4.IP}); err != nil {
-				return err
-			}
-			return setupRoutes(guest, args.IfName, result.IP4.IP, result.IP4.Gateway, result.IP4.Routes)
-		}); err != nil {
-			return fmt.Errorf("error setting up interface: %s", err)
-		}
-		return nil
-	})
-	if err != nil {
+	if err := weavenet.AttachContainer(ns, id, args.IfName, conf.BrName, conf.MTU, []*net.IPNet{&result.IP4.IP}); err != nil {
 		return err
 	}
+	if err := weavenet.WithNetNSLink(ns, args.IfName, func(guest netlink.Link) error {
+		return setupRoutes(guest, args.IfName, result.IP4.IP, result.IP4.Gateway, result.IP4.Routes)
+	}); err != nil {
+		return fmt.Errorf("error setting up routes: %s", err)
+	}
 
 	result.DNS = conf.DNS
 	return result.Print()
@@ -186,7 +175,7 @@ func (c *CNIPlugin) CmdDel(args *skel.CmdArgs) error {
 		return err
 	}
 	defer ns.Close()
-	err = common.WithNetNS(ns, func() error {
+	err = weavenet.WithNetNS(ns, func() error {
 		link, err := netlink.LinkByName(args.IfName)
 		if err != nil {
 			return err