Merge pull request #50 from steveeJ/gwfix

bridge: add isDefaultGateway field

Documentation/bridge.md

@@ -17,7 +17,7 @@ If the bridge is missing, the plugin will create one on first use and, if gatewa
 	"name": "mynet",
 	"type": "bridge",
 	"bridge": "mynet0",
-	"isGateway": true,
+	"isDefaultGateway": true,
 	"ipMasq": true,
 	"hairpinMode": true,
 	"ipam": {
@@ -33,6 +33,7 @@ If the bridge is missing, the plugin will create one on first use and, if gatewa
 * `type` (string, required): "bridge".
 * `bridge` (string, optional): name of the bridge to use/create. Defaults to "cni0".
 * `isGateway` (boolean, optional): assign an IP address to the bridge. Defaults to false.
+* `isDefaultGateway` (boolean, optional): Sets isGateway to true and makes the assigned IP the default route. Defaults to false.
 * `ipMasq` (boolean, optional): set up IP Masquerade on the host for traffic originating from this network and destined outside of it. Defaults to false.
 * `mtu` (integer, optional): explicitly set MTU to the specified value. Defaults to the value chosen by the kernel.
 * `hairpinMode` (boolean, optional): set hairpin mode for interfaces on the bridge. Defaults to false.

plugins/main/bridge/bridge.go

@@ -37,6 +37,7 @@ type NetConf struct {
 	types.NetConf
 	BrName      string `json:"bridge"`
 	IsGW        bool   `json:"isGateway"`
+	IsDefaultGW bool   `json:"isDefaultGateway"`
 	IPMasq      bool   `json:"ipMasq"`
 	MTU         int    `json:"mtu"`
 	HairpinMode bool   `json:"hairpinMode"`
@@ -185,6 +186,10 @@ func cmdAdd(args *skel.CmdArgs) error {
 		return err
 	}
 
+	if n.IsDefaultGW {
+		n.IsGW = true
+	}
+
 	br, err := setupBridge(n)
 	if err != nil {
 		return err
@@ -206,6 +211,7 @@ func cmdAdd(args *skel.CmdArgs) error {
 		return err
 	}
 
+	// TODO: make this optional when IPv6 is supported
 	if result.IP4 == nil {
 		return errors.New("IPAM plugin returned missing IPv4 config")
 	}
@@ -214,10 +220,35 @@ func cmdAdd(args *skel.CmdArgs) error {
 		result.IP4.Gateway = calcGatewayIP(&result.IP4.IP)
 	}
 
-	err = netns.Do(func(_ ns.NetNS) error {
+	if err := netns.Do(func(_ ns.NetNS) error {
+		// set the default gateway if requested
+		if n.IsDefaultGW {
+			_, defaultNet, err := net.ParseCIDR("0.0.0.0/0")
+			if err != nil {
+				return err
+			}
+
+			for _, route := range result.IP4.Routes {
+				if defaultNet.String() == route.Dst.String() {
+					if route.GW != nil && !route.GW.Equal(result.IP4.Gateway) {
+						return fmt.Errorf(
+							"isDefaultGateway ineffective because IPAM sets default route via %q",
+							route.GW,
+						)
+					}
+				}
+			}
+
+			result.IP4.Routes = append(
+				result.IP4.Routes,
+				types.Route{Dst: *defaultNet, GW: result.IP4.Gateway},
+			)
+
+			// TODO: IPV6
+		}
+
 		return ipam.ConfigureIface(args.IfName, result)
-	})
-	if err != nil {
+	}); err != nil {
 		return err
 	}
 

plugins/main/bridge/bridge_test.go

@@ -116,7 +116,7 @@ var _ = Describe("bridge Operations", func() {
 		Expect(err).NotTo(HaveOccurred())
 	})
 
-	It("configures and deconfigures a bridge and veth with ADD/DEL", func() {
+	It("configures and deconfigures a bridge and veth with default route with ADD/DEL", func() {
 		const BRNAME = "cni0"
 		const IFNAME = "eth0"
 
@@ -127,7 +127,7 @@ var _ = Describe("bridge Operations", func() {
     "name": "mynet",
     "type": "bridge",
     "bridge": "%s",
-    "isGateway": true,
+    "isDefaultGateway": true,
     "ipMasq": false,
     "ipam": {
         "type": "host-local",
@@ -189,13 +189,27 @@ var _ = Describe("bridge Operations", func() {
 		})
 		Expect(err).NotTo(HaveOccurred())
 
-		// Find the veth peer in the container namespace
+		// Find the veth peer in the container namespace and the default route
 		err = targetNs.Do(func(ns.NetNS) error {
 			defer GinkgoRecover()
 
 			link, err := netlink.LinkByName(IFNAME)
 			Expect(err).NotTo(HaveOccurred())
 			Expect(link.Attrs().Name).To(Equal(IFNAME))
+
+			// Ensure the default route
+			routes, err := netlink.RouteList(link, 0)
+			Expect(err).NotTo(HaveOccurred())
+
+			var defaultRouteFound bool
+			for _, route := range routes {
+				defaultRouteFound = (route.Dst == nil && route.Src == nil && route.Gw.Equal(gwaddr))
+				if defaultRouteFound {
+					break
+				}
+			}
+			Expect(defaultRouteFound).To(Equal(true))
+
 			return nil
 		})
 		Expect(err).NotTo(HaveOccurred())