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

common/utils.go

@@ -2,12 +2,14 @@ package common
 
 import (
 	"fmt"
-	"github.com/vishvananda/netlink"
-	"github.com/vishvananda/netns"
 	"net"
 	"os"
-	"runtime"
 	"strings"
+
+	"github.com/vishvananda/netlink"
+	"github.com/vishvananda/netns"
+
+	weavenet "github.com/weaveworks/weave/net"
 )
 
 // Assert test is true, panic otherwise
@@ -25,25 +27,6 @@ func ErrorMessages(errors []error) string {
 	return strings.Join(result, "\n")
 }
 
-func WithNetNS(ns netns.NsHandle, work func() error) error {
-	runtime.LockOSThread()
-	defer runtime.UnlockOSThread()
-
-	oldNs, err := netns.Get()
-	if err == nil {
-		defer oldNs.Close()
-
-		err = netns.Set(ns)
-		if err == nil {
-			defer netns.Set(oldNs)
-
-			err = work()
-		}
-	}
-
-	return err
-}
-
 type NetDev struct {
 	Name  string
 	MAC   net.HardwareAddr
@@ -63,7 +46,7 @@ func FindNetDevs(processID int, match func(link netlink.Link) bool) ([]NetDev, e
 	}
 	defer ns.Close()
 
-	err = WithNetNS(ns, func() error {
+	err = weavenet.WithNetNS(ns, func() error {
 		return forEachLink(func(link netlink.Link) error {
 			if match(link) {
 				netDev, err := linkToNetDev(link)

net/arp.go

@@ -1,4 +1,4 @@
-package common
+package net
 
 import "fmt"
 import "io"

net/netns.go

@@ -0,0 +1,37 @@
+package net
+
+import (
+	"runtime"
+
+	"github.com/vishvananda/netlink"
+	"github.com/vishvananda/netns"
+)
+
+func WithNetNS(ns netns.NsHandle, work func() error) error {
+	runtime.LockOSThread()
+	defer runtime.UnlockOSThread()
+
+	oldNs, err := netns.Get()
+	if err == nil {
+		defer oldNs.Close()
+
+		err = netns.Set(ns)
+		if err == nil {
+			defer netns.Set(oldNs)
+
+			err = work()
+		}
+	}
+
+	return err
+}
+
+func WithNetNSLink(ns netns.NsHandle, ifName string, work func(link netlink.Link) error) error {
+	return WithNetNS(ns, func() error {
+		link, err := netlink.LinkByName(ifName)
+		if err != nil {
+			return err
+		}
+		return work(link)
+	})
+}

net/veth.go

@@ -4,9 +4,10 @@ import (
 	"fmt"
 	"net"
 
+	"github.com/j-keck/arping"
 	"github.com/vishvananda/netlink"
+	"github.com/vishvananda/netns"
 
-	"github.com/weaveworks/weave/common"
 	"github.com/weaveworks/weave/common/odp"
 )
 
@@ -73,22 +74,65 @@ func CreateAndAttachVeth(localName, peerName, bridgeName string, mtu int, init f
 	return local, nil
 }
 
-func SetupGuest(guest netlink.Link, name string, cidrs []net.IPNet) error {
+func SetupGuest(guest netlink.Link, name string) error {
 	var err error
 	if err = netlink.LinkSetName(guest, name); err != nil {
 		return err
 	}
-	if err = netlink.LinkSetUp(guest); err != nil {
+	if err = ConfigureARPCache(name); err != nil {
 		return err
 	}
-	if err = common.ConfigureARPCache(name); err != nil {
+	return nil
+}
+
+func AddAddresses(guest netlink.Link, cidrs []*net.IPNet) error {
+	for _, ipnet := range cidrs {
+		if err := netlink.AddrAdd(guest, &netlink.Addr{IPNet: ipnet}); err != nil {
+			return fmt.Errorf("failed to add IP address to %q: %v", guest.Attrs().Name, err)
+		}
+		arping.GratuitousArpOverIfaceByName(ipnet.IP, guest.Attrs().Name)
+	}
+	return nil
+}
+
+func interfaceExistsInNamespace(ns netns.NsHandle, ifName string) bool {
+	err := WithNetNS(ns, func() error {
+		_, err := netlink.LinkByName(ifName)
 		return err
+	})
+	return err == nil
+}
+
+func AttachContainer(ns netns.NsHandle, id, ifName, bridgeName string, mtu int, cidrs []*net.IPNet) error {
+	if !interfaceExistsInNamespace(ns, ifName) {
+		if len(id) > 5 {
+			id = id[:5]
+		}
+		name, peerName := "vethwepl"+id, "vethwg"+id
+		_, err := CreateAndAttachVeth(name, peerName, bridgeName, 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 := WithNetNS(ns, func() error {
+				return SetupGuest(guest, ifName)
+			}); err != nil {
+				return fmt.Errorf("error setting up interface: %s", err)
+			}
+			return nil
+		})
+		if err != nil {
+			return err
+		}
 	}
-	for _, ipnet := range cidrs {
-		if err = netlink.AddrAdd(guest, &netlink.Addr{IPNet: &ipnet}); err != nil {
-			return fmt.Errorf("failed to add IP address to %q: %v", name, err)
+
+	if err := WithNetNSLink(ns, ifName, func(guest netlink.Link) error {
+		if err := AddAddresses(guest, cidrs); err != nil {
+			return err
 		}
-		arping.GratuitousArpOverIfaceByName(ipnet.IP, name)
+		return netlink.LinkSetUp(guest)
+	}); err != nil {
+		return err
 	}
+
 	return nil
 }

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