Added --ignore-iface option to netcheck and use it to ignore weave bridge route

net/route.go

@@ -9,13 +9,17 @@ import (
 
 // A network is considered free if it does not overlap any existing
 // routes on this host. This is the same approach taken by Docker.
-func CheckNetworkFree(subnet *net.IPNet) error {
+func CheckNetworkFree(subnet *net.IPNet, ignoreIfName string) error {
 	routes, err := netlink.RouteList(nil, netlink.FAMILY_V4)
 	if err != nil {
 		return err
 	}
 	for _, route := range routes {
 		if route.Dst != nil && overlaps(route.Dst, subnet) {
+			if link, err := netlink.LinkByIndex(route.LinkIndex); err == nil && link.Attrs().Name == ignoreIfName {
+				continue
+			}
+
 			return fmt.Errorf("Network %s overlaps with existing route %s on host.", subnet, route.Dst)
 		}
 	}
@@ -29,13 +33,16 @@ func overlaps(n1, n2 *net.IPNet) bool {
 
 // For a specific address, we only care if it is actually *inside* an
 // existing route, because weave-local traffic never hits IP routing.
-func CheckAddressOverlap(addr net.IP) error {
+func CheckAddressOverlap(addr net.IP, ignoreIfName string) error {
 	routes, err := netlink.RouteList(nil, netlink.FAMILY_V4)
 	if err != nil {
 		return err
 	}
 	for _, route := range routes {
 		if route.Dst != nil && route.Dst.Contains(addr) {
+			if link, err := netlink.LinkByIndex(route.LinkIndex); err == nil && link.Attrs().Name == ignoreIfName {
+				continue
+			}
 			return fmt.Errorf("Address %s overlaps with existing route %s on host.", addr, route.Dst)
 		}
 	}

prog/netcheck/netcheck.go

@@ -6,6 +6,7 @@ import (
 	"net"
 	"os"
 
+	"github.com/docker/docker/pkg/mflag"
 	weavenet "github.com/weaveworks/weave/net"
 )
 
@@ -15,19 +16,25 @@ func fatal(err error) {
 }
 
 func main() {
-	if len(os.Args) <= 1 {
-		os.Exit(0)
+	var ignoreIfaceName string
+
+	mflag.StringVar(&ignoreIfaceName, []string{"-ignore-iface"}, "", "name of interface to ignore)")
+	mflag.Parse()
+
+	if len(mflag.Args()) < 1 {
+		fmt.Fprintln(os.Stderr, "usage: netcheck [--ignore-iface <iface-name>] network-cidr")
+		os.Exit(1)
 	}
 
-	cidrStr := os.Args[1]
+	cidrStr := mflag.Args()[0]
 	addr, ipnet, err := net.ParseCIDR(cidrStr)
 	if err != nil {
 		fatal(err)
 	}
 	if ipnet.IP.Equal(addr) {
-		err = weavenet.CheckNetworkFree(ipnet)
+		err = weavenet.CheckNetworkFree(ipnet, ignoreIfaceName)
 	} else {
-		err = weavenet.CheckAddressOverlap(addr)
+		err = weavenet.CheckAddressOverlap(addr, ignoreIfaceName)
 	}
 	if err != nil {
 		fatal(err)

weave

@@ -860,7 +860,7 @@ ipam_cidrs() {
             ALL_CIDRS="$ALL_CIDRS $CIDR"
         else
             # This is a plain IP address; warn if it clashes but carry on
-            command_exists netcheck && netcheck $1 || true
+            command_exists netcheck && netcheck --ignore-iface=$BRIDGE $1 || true
             ALL_CIDRS="$ALL_CIDRS $1"
         fi
         shift 1
@@ -998,7 +998,7 @@ launch_router() {
     eval "set -- $ARGS"
     if [ -z "$IPRANGE_SPECIFIED" ] ; then
         IPRANGE="10.32.0.0/12"
-        if command_exists netcheck && ! netcheck $IPRANGE ; then
+        if command_exists netcheck && ! netcheck --ignore-iface=$BRIDGE $IPRANGE ; then
             echo "Default --ipalloc-range $IPRANGE overlaps with existing route on host." >&2
             echo "Please pick another range and set it on all hosts." >&2
             exit 1