rootless: Rearrange setup of rootless containers

In order to run Podman with VM-based runtimes unprivileged, the
network must be set up prior to the container creation. Therefore
this commit modifies Podman to run rootless containers by:
  1. create a network namespace
  2. pass the netns persistent mount path to the slirp4netns
     to create the tap inferface
  3. pass the netns path to the OCI spec, so the runtime can
     enter the netns

Closes #2897

Signed-off-by: Gabi Beyer <gabrielle.n.beyer@intel.com>

libpod/container_internal_linux.go

@@ -66,7 +66,7 @@ func (c *Container) prepare() (err error) {
 		wg                                                sync.WaitGroup
 		netNS                                             ns.NetNS
 		networkStatus                                     []*cnitypes.Result
-		createNetNSErr, mountStorageErr error
+		createNetNSErr, mountStorageErr, rootlessSetupErr error
 		mountPoint                                        string
 		tmpStateLock                                      sync.Mutex
 	)
@@ -87,6 +87,11 @@ func (c *Container) prepare() (err error) {
 				c.state.NetNS = netNS
 				c.state.NetworkStatus = networkStatus
 			}
+
+			// Setup rootless networking, requires c.state.NetNS to be set
+			if rootless.IsRootless() {
+				rootlessSetupErr = c.runtime.setupRootlessNetNS(c)
+			}
 		}
 	}()
 	// Mount storage if not mounted
@@ -132,6 +137,10 @@ func (c *Container) prepare() (err error) {
 		return mountStorageErr
 	}
 
+	if rootlessSetupErr != nil {
+		return rootlessSetupErr
+	}
+
 	// Save the container
 	return c.save()
 }

libpod/networking_linux.go

@@ -103,9 +103,6 @@ func (r *Runtime) configureNetNS(ctr *Container, ctrNS ns.NetNS) ([]*cnitypes.Re
 
 // Create and configure a new network namespace for a container
 func (r *Runtime) createNetNS(ctr *Container) (n ns.NetNS, q []*cnitypes.Result, err error) {
-	if rootless.IsRootless() {
-		return nil, nil, errors.New("cannot configure a new network namespace in rootless mode, only --network=slirp4netns is supported")
-	}
 	ctrNS, err := netns.NewNS()
 	if err != nil {
 		return nil, nil, errors.Wrapf(err, "error creating network namespace for container %s", ctr.ID())
@@ -123,7 +120,10 @@ func (r *Runtime) createNetNS(ctr *Container) (n ns.NetNS, q []*cnitypes.Result,
 
 	logrus.Debugf("Made network namespace at %s for container %s", ctrNS.Path(), ctr.ID())
 
-	networkStatus, err := r.configureNetNS(ctr, ctrNS)
+	networkStatus := []*cnitypes.Result{}
+	if !rootless.IsRootless() {
+		networkStatus, err = r.configureNetNS(ctr, ctrNS)
+	}
 	return ctrNS, networkStatus, err
 }
 
@@ -151,9 +151,6 @@ func checkSlirpFlags(path string) (bool, bool, error) {
 
 // Configure the network namespace for a rootless container
 func (r *Runtime) setupRootlessNetNS(ctr *Container) (err error) {
-	defer errorhandling.CloseQuiet(ctr.rootlessSlirpSyncR)
-	defer errorhandling.CloseQuiet(ctr.rootlessSlirpSyncW)
-
 	path := r.config.NetworkCmdPath
 
 	if path == "" {
@@ -177,7 +174,7 @@ func (r *Runtime) setupRootlessNetNS(ctr *Container) (err error) {
 
 	cmdArgs := []string{}
 	if havePortMapping {
-		cmdArgs = append(cmdArgs, "--api-socket", apiSocket, fmt.Sprintf("%d", ctr.state.PID))
+		cmdArgs = append(cmdArgs, "--api-socket", apiSocket)
 	}
 	dhp, mtu, err := checkSlirpFlags(path)
 	if err != nil {
@@ -189,13 +186,27 @@ func (r *Runtime) setupRootlessNetNS(ctr *Container) (err error) {
 	if mtu {
 		cmdArgs = append(cmdArgs, "--mtu", "65520")
 	}
-	cmdArgs = append(cmdArgs, "-c", "-e", "3", "-r", "4", fmt.Sprintf("%d", ctr.state.PID), "tap0")
+
+	cmdArgs = append(cmdArgs, "-c", "-e", "3", "-r", "4")
+	if !ctr.config.PostConfigureNetNS {
+		ctr.rootlessSlirpSyncR, ctr.rootlessSlirpSyncW, err = os.Pipe()
+		if err != nil {
+			return errors.Wrapf(err, "failed to create rootless network sync pipe")
+		}
+		cmdArgs = append(cmdArgs, "--netns-type=path", ctr.state.NetNS.Path(), "tap0")
+	} else {
+		defer errorhandling.CloseQuiet(ctr.rootlessSlirpSyncR)
+		defer errorhandling.CloseQuiet(ctr.rootlessSlirpSyncW)
+		cmdArgs = append(cmdArgs, fmt.Sprintf("%d", ctr.state.PID), "tap0")
+	}
 
 	cmd := exec.Command(path, cmdArgs...)
-
+	logrus.Debugf("slirp4netns command: %s", strings.Join(cmd.Args, " "))
 	cmd.SysProcAttr = &syscall.SysProcAttr{
 		Setpgid: true,
 	}
+
+	// Leak one end of the pipe in slirp4netns, the other will be sent to conmon
 	cmd.ExtraFiles = append(cmd.ExtraFiles, ctr.rootlessSlirpSyncR, syncW)
 
 	if err := cmd.Start(); err != nil {
@@ -410,8 +421,10 @@ func (r *Runtime) teardownNetNS(ctr *Container) error {
 		}
 	}
 
-	logrus.Debugf("Tearing down network namespace at %s for container %s", ctr.state.NetNS.Path(), ctr.ID())
+	logrus.Debugf("Tearing down network namespace for container %s", ctr.ID())
 
+	// rootless containers do not use the CNI plugin
+	if !rootless.IsRootless() {
 		var requestedIP net.IP
 		if ctr.requestedIP != nil {
 			requestedIP = ctr.requestedIP
@@ -427,6 +440,7 @@ func (r *Runtime) teardownNetNS(ctr *Container) error {
 		if err := r.netPlugin.TearDownPod(podNetwork); err != nil {
 			return errors.Wrapf(err, "error tearing down CNI namespace configuration for container %s", ctr.ID())
 		}
+	}
 
 	// First unmount the namespace
 	if err := netns.UnmountNS(ctr.state.NetNS); err != nil {

libpod/oci_internal_linux.go

@@ -130,10 +130,16 @@ func (r *OCIRuntime) createOCIContainer(ctr *Container, restoreOptions *Containe
 	}
 
 	if ctr.config.NetMode.IsSlirp4netns() {
+		if ctr.config.PostConfigureNetNS {
 			ctr.rootlessSlirpSyncR, ctr.rootlessSlirpSyncW, err = os.Pipe()
 			if err != nil {
 				return errors.Wrapf(err, "failed to create rootless network sync pipe")
 			}
+		} else {
+			defer errorhandling.CloseQuiet(ctr.rootlessSlirpSyncR)
+			defer errorhandling.CloseQuiet(ctr.rootlessSlirpSyncW)
+		}
+
 		// Leak one end in conmon, the other one will be leaked into slirp4netns
 		cmd.ExtraFiles = append(cmd.ExtraFiles, ctr.rootlessSlirpSyncW)
 	}

libpod/oci_linux.go

@@ -405,6 +405,14 @@ func (r *OCIRuntime) stopContainer(ctr *Container, timeout uint) error {
 		stopSignal = uint(syscall.SIGTERM)
 	}
 
+	defer func() {
+		// cleanup container networking
+		err = ctr.cleanupNetwork()
+		if err != nil {
+			logrus.Errorf("Error cleaning up container: %s network: %v", ctr.ID(), err)
+		}
+	}()
+
 	if timeout > 0 {
 		if err := r.killContainer(ctr, stopSignal); err != nil {
 			// Is the container gone?

libpod/runtime_pod_infra_linux.go

@@ -95,7 +95,9 @@ func (r *Runtime) makeInfraContainer(ctx context.Context, p *Pod, imgName, imgID
 	if isRootless {
 		netmode = "slirp4netns"
 	}
-	options = append(options, WithNetNS(p.config.InfraContainer.PortBindings, isRootless, netmode, networks))
+	// PostConfigureNetNS should not be set since user namespace sharing is not implemented
+	// and rootless networking no longer supports post configuration setup
+	options = append(options, WithNetNS(p.config.InfraContainer.PortBindings, false, netmode, networks))
 
 	return r.newContainer(ctx, g.Config, options...)
 }

pkg/netns/netns_linux.go

@@ -23,23 +23,42 @@ import (
 	"fmt"
 	"os"
 	"path"
+	"path/filepath"
 	"runtime"
 	"strings"
 	"sync"
 
 	"github.com/containernetworking/plugins/pkg/ns"
+	"github.com/containers/libpod/pkg/rootless"
+	"github.com/containers/libpod/pkg/util"
 	"github.com/sirupsen/logrus"
 	"golang.org/x/sys/unix"
 )
 
-const nsRunDir = "/var/run/netns"
+// get NSRunDir returns the dir of where to create the netNS. When running
+// rootless, it needs to be at a location writable by user.
+func getNSRunDir() (string, error) {
+	if rootless.IsRootless() {
+		rootlessDir, err := util.GetRootlessRuntimeDir()
+		if err != nil {
+			return "", err
+		}
+		return filepath.Join(rootlessDir, "netns"), nil
+	}
+	return "/var/run/netns", nil
+}
 
 // NewNS creates a new persistent (bind-mounted) network namespace and returns
 // an object representing that namespace, without switching to it.
 func NewNS() (ns.NetNS, error) {
 
+	nsRunDir, err := getNSRunDir()
+	if err != nil {
+		return nil, err
+	}
+
 	b := make([]byte, 16)
-	_, err := rand.Reader.Read(b)
+	_, err = rand.Reader.Read(b)
 	if err != nil {
 		return nil, fmt.Errorf("failed to generate random netns name: %v", err)
 	}
@@ -127,7 +146,7 @@ func NewNS() (ns.NetNS, error) {
 		// Put this thread back to the orig ns, since it might get reused (pre go1.10)
 		defer func() {
 			if err := origNS.Set(); err != nil {
-				logrus.Errorf("unable to set namespace: %q", err)
+				logrus.Warnf("unable to set namespace: %q", err)
 			}
 		}()
 
@@ -150,6 +169,11 @@ func NewNS() (ns.NetNS, error) {
 
 // UnmountNS unmounts the NS held by the netns object
 func UnmountNS(ns ns.NetNS) error {
+	nsRunDir, err := getNSRunDir()
+	if err != nil {
+		return err
+	}
+
 	nsPath := ns.Path()
 	// Only unmount if it's been bind-mounted (don't touch namespaces in /proc...)
 	if strings.HasPrefix(nsPath, nsRunDir) {

pkg/spec/createconfig.go

@@ -267,7 +267,7 @@ func (c *CreateConfig) getContainerCreateOptions(runtime *libpod.Runtime, pod *l
 		options = append(options, libpod.WithNetNSFrom(connectedCtr))
 	} else if !c.NetMode.IsHost() && !c.NetMode.IsNone() {
 		hasUserns := c.UsernsMode.IsContainer() || c.UsernsMode.IsNS() || len(c.IDMappings.UIDMap) > 0 || len(c.IDMappings.GIDMap) > 0
-		postConfigureNetNS := c.NetMode.IsSlirp4netns() || (hasUserns && !c.UsernsMode.IsHost())
+		postConfigureNetNS := hasUserns && !c.UsernsMode.IsHost()
 		options = append(options, libpod.WithNetNS(portBindings, postConfigureNetNS, string(c.NetMode), networks))
 	}