Introduce UnsetGateway(IPv6) methods

Sandbox needs unset gateway methods to cleanup
gateway settings to enable smooth transition
of the sandbox between endpoints.

Signed-off-by: Jana Radhakrishnan <mrjana@docker.com>

libnetwork/sandbox/configure_linux.go

@@ -30,7 +30,7 @@ func configureInterface(iface netlink.Link, settings *Interface) error {
 	return nil
 }
 
-func programGateway(path string, gw net.IP) error {
+func programGateway(path string, gw net.IP, isAdd bool) error {
 	runtime.LockOSThread()
 	defer runtime.UnlockOSThread()
 
@@ -57,7 +57,15 @@ func programGateway(path string, gw net.IP) error {
 		return fmt.Errorf("route for the gateway could not be found: %v", err)
 	}
 
-	return netlink.RouteAdd(&netlink.Route{
+	if isAdd {
+		return netlink.RouteAdd(&netlink.Route{
+			Scope:     netlink.SCOPE_UNIVERSE,
+			LinkIndex: gwRoutes[0].LinkIndex,
+			Gw:        gw,
+		})
+	}
+
+	return netlink.RouteDel(&netlink.Route{
 		Scope:     netlink.SCOPE_UNIVERSE,
 		LinkIndex: gwRoutes[0].LinkIndex,
 		Gw:        gw,

libnetwork/sandbox/namespace_linux.go

@@ -308,26 +308,72 @@ func (n *networkNamespace) AddInterface(i *Interface) error {
 }
 
 func (n *networkNamespace) SetGateway(gw net.IP) error {
+	// Silently return if the gateway is empty
 	if len(gw) == 0 {
 		return nil
 	}
 
-	err := programGateway(n.path, gw)
+	err := programGateway(n.path, gw, true)
 	if err == nil {
+		n.Lock()
 		n.sinfo.Gateway = gw
+		n.Unlock()
+	}
+
+	return err
+}
+
+func (n *networkNamespace) UnsetGateway() error {
+	n.Lock()
+	gw := n.sinfo.Gateway
+	n.Unlock()
+
+	// Silently return if the gateway is empty
+	if len(gw) == 0 {
+		return nil
+	}
+
+	err := programGateway(n.path, gw, false)
+	if err == nil {
+		n.Lock()
+		n.sinfo.Gateway = net.IP{}
+		n.Unlock()
 	}
 
 	return err
 }
 
 func (n *networkNamespace) SetGatewayIPv6(gw net.IP) error {
+	// Silently return if the gateway is empty
 	if len(gw) == 0 {
 		return nil
 	}
 
-	err := programGateway(n.path, gw)
+	err := programGateway(n.path, gw, true)
 	if err == nil {
+		n.Lock()
 		n.sinfo.GatewayIPv6 = gw
+		n.Unlock()
+	}
+
+	return err
+}
+
+func (n *networkNamespace) UnsetGatewayIPv6() error {
+	n.Lock()
+	gw := n.sinfo.GatewayIPv6
+	n.Unlock()
+
+	// Silently return if the gateway is empty
+	if len(gw) == 0 {
+		return nil
+	}
+
+	err := programGateway(n.path, gw, false)
+	if err == nil {
+		n.Lock()
+		n.sinfo.GatewayIPv6 = net.IP{}
+		n.Unlock()
 	}
 
 	return err

libnetwork/sandbox/sandbox.go

@@ -35,6 +35,12 @@ type Sandbox interface {
 	// Set default IPv6 gateway for the sandbox
 	SetGatewayIPv6(gw net.IP) error
 
+	// Unset the previously set default IPv4 gateway in the sandbox
+	UnsetGateway() error
+
+	// Unset the previously set default IPv6 gateway in the sandbox
+	UnsetGatewayIPv6() error
+
 	// Add a static route to the sandbox.
 	AddStaticRoute(*types.StaticRoute) error