Merge pull request #18108 from phemmer/no-mtu-discovery

don't try to use default route MTU as container MTU
Upstream-commit: b36b4920399cc95e1b357f60aa738e84bd970f47
Component: engine

components/engine/daemon/container_operations_windows.go

@@ -162,10 +162,6 @@ func detachMounted(path string) error {
 	return nil
 }
 
-func getDefaultRouteMtu() (int, error) {
-	return -1, errSystemNotSupported
-}
-
 func killProcessDirectly(container *container.Container) error {
 	return nil
 }

components/engine/daemon/daemon.go

@@ -1382,13 +1382,8 @@ func setDefaultMtu(config *Config) {
 		return
 	}
 	config.Mtu = defaultNetworkMtu
-	if routeMtu, err := getDefaultRouteMtu(); err == nil {
-		config.Mtu = routeMtu
-	}
 }
 
-var errNoDefaultRoute = errors.New("no default route was found")
-
 // verifyContainerSettings performs validation of the hostconfig and config
 // structures.
 func (daemon *Daemon) verifyContainerSettings(hostConfig *runconfig.HostConfig, config *runconfig.Config) ([]string, error) {

components/engine/daemon/daemon_unix.go

@@ -33,7 +33,6 @@ import (
 	"github.com/docker/libnetwork/types"
 	blkiodev "github.com/opencontainers/runc/libcontainer/configs"
 	"github.com/opencontainers/runc/libcontainer/label"
-	"github.com/vishvananda/netlink"
 )
 
 const (
@@ -670,25 +669,6 @@ func (daemon *Daemon) conditionalUnmountOnCleanup(container *container.Container
 	daemon.Unmount(container)
 }
 
-// getDefaultRouteMtu returns the MTU for the default route's interface.
-func getDefaultRouteMtu() (int, error) {
-	routes, err := netlink.RouteList(nil, 0)
-	if err != nil {
-		return 0, err
-	}
-	for _, r := range routes {
-		// a nil Dst means that this is the default route.
-		if r.Dst == nil {
-			i, err := net.InterfaceByIndex(r.LinkIndex)
-			if err != nil {
-				continue
-			}
-			return i.MTU, nil
-		}
-	}
-	return 0, errNoDefaultRoute
-}
-
 func restoreCustomImage(driver graphdriver.Driver, is image.Store, ls layer.Store, ts tag.Store) error {
 	// Unix has no custom images to register
 	return nil