rootless: support `podman network create` (CNI-in-slirp4netns)

Usage:
```
$ podman network create foo
$ podman run -d --name web --hostname web --network foo nginx:alpine
$ podman run --rm --network foo alpine wget -O - http://web.dns.podman
Connecting to web.dns.podman (10.88.4.6:80)
...
<h1>Welcome to nginx!</h1>
...
```

See contrib/rootless-cni-infra for the design.

Signed-off-by: Akihiro Suda <akihiro.suda.cz@hco.ntt.co.jp>

1 files changed, 320 insertions, 0 deletions

diff --git a/libpod/rootless_cni_linux.go b/libpod/rootless_cni_linux.go
new file mode 100644
index 000000000..76dbfdcae
--- /dev/null
+++ b/libpod/rootless_cni_linux.go
@@ -0,0 +1,320 @@
+// +build linux
+
+package libpod
+
+import (
+	"bytes"
+	"context"
+	"io"
+	"path/filepath"
+	"runtime"
+
+	cnitypes "github.com/containernetworking/cni/pkg/types/current"
+	"github.com/containernetworking/plugins/pkg/ns"
+	"github.com/containers/podman/v2/libpod/define"
+	"github.com/containers/podman/v2/libpod/image"
+	"github.com/containers/podman/v2/pkg/util"
+	"github.com/containers/storage/pkg/lockfile"
+	"github.com/hashicorp/go-multierror"
+	spec "github.com/opencontainers/runtime-spec/specs-go"
+	"github.com/opencontainers/runtime-tools/generate"
+	"github.com/pkg/errors"
+	"github.com/sirupsen/logrus"
+)
+
+var rootlessCNIInfraImage = map[string]string{
+	// Built from ../contrib/rootless-cni-infra
+	// TODO: move to Podman's official quay
+	"amd64": "ghcr.io/akihirosuda/podman-rootless-cni-infra:gd34868a13-amd64",
+}
+
+const (
+	rootlessCNIInfraContainerNamespace = "podman-system"
+	rootlessCNIInfraContainerName      = "rootless-cni-infra"
+)
+
+// AllocRootlessCNI allocates a CNI netns inside the rootless CNI infra container.
+// Locks "rootless-cni-infra.lck".
+//
+// When the infra container is not running, it is created.
+//
+// AllocRootlessCNI does not lock c. c should be already locked.
+func AllocRootlessCNI(ctx context.Context, c *Container) (ns.NetNS, []*cnitypes.Result, error) {
+	if len(c.config.Networks) == 0 {
+		return nil, nil, errors.New("allocRootlessCNI shall not be called when len(c.config.Networks) == 0")
+	}
+	l, err := getRootlessCNIInfraLock(c.runtime)
+	if err != nil {
+		return nil, nil, err
+	}
+	l.Lock()
+	defer l.Unlock()
+	infra, err := ensureRootlessCNIInfraContainerRunning(ctx, c.runtime)
+	if err != nil {
+		return nil, nil, err
+	}
+	k8sPodName := getPodOrContainerName(c) // passed to CNI as K8S_POD_NAME
+	cniResults := make([]*cnitypes.Result, len(c.config.Networks))
+	for i, nw := range c.config.Networks {
+		cniRes, err := rootlessCNIInfraCallAlloc(infra, c.ID(), nw, k8sPodName)
+		if err != nil {
+			return nil, nil, err
+		}
+		cniResults[i] = cniRes
+	}
+	nsObj, err := rootlessCNIInfraGetNS(infra, c.ID())
+	if err != nil {
+		return nil, nil, err
+	}
+	logrus.Debugf("rootless CNI: container %q will join %q", c.ID(), nsObj.Path())
+	return nsObj, cniResults, nil
+}
+
+// DeallocRootlessCNI deallocates a CNI netns inside the rootless CNI infra container.
+// Locks "rootless-cni-infra.lck".
+//
+// When the infra container is no longer needed, it is removed.
+//
+// DeallocRootlessCNI does not lock c. c should be already locked.
+func DeallocRootlessCNI(ctx context.Context, c *Container) error {
+	if len(c.config.Networks) == 0 {
+		return errors.New("deallocRootlessCNI shall not be called when len(c.config.Networks) == 0")
+	}
+	l, err := getRootlessCNIInfraLock(c.runtime)
+	if err != nil {
+		return err
+	}
+	l.Lock()
+	defer l.Unlock()
+	infra, _ := getRootlessCNIInfraContainer(c.runtime)
+	if infra == nil {
+		return nil
+	}
+	var errs *multierror.Error
+	for _, nw := range c.config.Networks {
+		err := rootlessCNIInfraCallDelloc(infra, c.ID(), nw)
+		if err != nil {
+			errs = multierror.Append(errs, err)
+		}
+	}
+	if isIdle, err := rootlessCNIInfraIsIdle(infra); isIdle || err != nil {
+		if err != nil {
+			logrus.Warn(err)
+		}
+		logrus.Debugf("rootless CNI: removing infra container %q", infra.ID())
+		if err := c.runtime.removeContainer(ctx, infra, true, false, true); err != nil {
+			return err
+		}
+		logrus.Debugf("rootless CNI: removed infra container %q", infra.ID())
+	}
+	return errs.ErrorOrNil()
+}
+
+func getRootlessCNIInfraLock(r *Runtime) (lockfile.Locker, error) {
+	fname := filepath.Join(r.config.Engine.TmpDir, "rootless-cni-infra.lck")
+	return lockfile.GetLockfile(fname)
+}
+
+func getPodOrContainerName(c *Container) string {
+	pod, err := c.runtime.GetPod(c.PodID())
+	if err != nil || pod.config.Name == "" {
+		return c.Name()
+	}
+	return pod.config.Name
+}
+
+func rootlessCNIInfraCallAlloc(infra *Container, id, nw, k8sPodName string) (*cnitypes.Result, error) {
+	logrus.Debugf("rootless CNI: alloc %q, %q, %q", id, nw, k8sPodName)
+	var err error
+
+	_, err = rootlessCNIInfraExec(infra, "alloc", id, nw, k8sPodName)
+	if err != nil {
+		return nil, err
+	}
+	cniResStr, err := rootlessCNIInfraExec(infra, "print-cni-result", id, nw)
+	if err != nil {
+		return nil, err
+	}
+	var cniRes cnitypes.Result
+	if err := json.Unmarshal([]byte(cniResStr), &cniRes); err != nil {
+		return nil, errors.Wrapf(err, "unmarshaling as cnitypes.Result: %q", cniResStr)
+	}
+	return &cniRes, nil
+}
+
+func rootlessCNIInfraCallDelloc(infra *Container, id, nw string) error {
+	logrus.Debugf("rootless CNI: dealloc %q, %q", id, nw)
+	_, err := rootlessCNIInfraExec(infra, "dealloc", id, nw)
+	return err
+}
+
+func rootlessCNIInfraIsIdle(infra *Container) (bool, error) {
+	type isIdle struct {
+		Idle bool `json:"idle"`
+	}
+	resStr, err := rootlessCNIInfraExec(infra, "is-idle")
+	if err != nil {
+		return false, err
+	}
+	var res isIdle
+	if err := json.Unmarshal([]byte(resStr), &res); err != nil {
+		return false, errors.Wrapf(err, "unmarshaling as isIdle: %q", resStr)
+	}
+	return res.Idle, nil
+}
+
+func rootlessCNIInfraGetNS(infra *Container, id string) (ns.NetNS, error) {
+	type printNetnsPath struct {
+		Path string `json:"path"`
+	}
+	resStr, err := rootlessCNIInfraExec(infra, "print-netns-path", id)
+	if err != nil {
+		return nil, err
+	}
+	var res printNetnsPath
+	if err := json.Unmarshal([]byte(resStr), &res); err != nil {
+		return nil, errors.Wrapf(err, "unmarshaling as printNetnsPath: %q", resStr)
+	}
+	nsObj, err := ns.GetNS(res.Path)
+	if err != nil {
+		return nil, err
+	}
+	return nsObj, nil
+}
+
+func getRootlessCNIInfraContainer(r *Runtime) (*Container, error) {
+	containers, err := r.GetContainersWithoutLock(func(c *Container) bool {
+		return c.Namespace() == rootlessCNIInfraContainerNamespace &&
+			c.Name() == rootlessCNIInfraContainerName
+	})
+	if err != nil {
+		return nil, err
+	}
+	if len(containers) == 0 {
+		return nil, nil
+	}
+	return containers[0], nil
+}
+
+func ensureRootlessCNIInfraContainerRunning(ctx context.Context, r *Runtime) (*Container, error) {
+	c, err := getRootlessCNIInfraContainer(r)
+	if err != nil {
+		return nil, err
+	}
+	if c == nil {
+		return startRootlessCNIInfraContainer(ctx, r)
+	}
+	st, err := c.ContainerState()
+	if err != nil {
+		return nil, err
+	}
+	if st.State == define.ContainerStateRunning {
+		logrus.Debugf("rootless CNI: infra container %q is already running", c.ID())
+		return c, nil
+	}
+	logrus.Debugf("rootless CNI: infra container %q is %q, being started", c.ID(), st.State)
+	if err := c.initAndStart(ctx); err != nil {
+		return nil, err
+	}
+	logrus.Debugf("rootless CNI: infra container %q is running", c.ID())
+	return c, nil
+}
+
+func startRootlessCNIInfraContainer(ctx context.Context, r *Runtime) (*Container, error) {
+	imageName, ok := rootlessCNIInfraImage[runtime.GOARCH]
+	if !ok {
+		return nil, errors.Errorf("cannot find rootless-podman-network-sandbox image for %s", runtime.GOARCH)
+	}
+	logrus.Debugf("rootless CNI: ensuring image %q to exist", imageName)
+	newImage, err := r.ImageRuntime().New(ctx, imageName, "", "", nil, nil,
+		image.SigningOptions{}, nil, util.PullImageMissing)
+	if err != nil {
+		return nil, err
+	}
+	logrus.Debugf("rootless CNI: image %q is ready", imageName)
+
+	g, err := generate.New("linux")
+	if err != nil {
+		return nil, err
+	}
+	g.SetupPrivileged(true)
+	// Set --pid=host for ease of propagating "/proc/PID/ns/net" string
+	if err := g.RemoveLinuxNamespace(string(spec.PIDNamespace)); err != nil {
+		return nil, err
+	}
+	g.RemoveMount("/proc")
+	procMount := spec.Mount{
+		Destination: "/proc",
+		Type:        "bind",
+		Source:      "/proc",
+		Options:     []string{"rbind", "nosuid", "noexec", "nodev"},
+	}
+	g.AddMount(procMount)
+	// Mount CNI networks
+	etcCNINetD := spec.Mount{
+		Destination: "/etc/cni/net.d",
+		Type:        "bind",
+		Source:      r.config.Network.NetworkConfigDir,
+		Options:     []string{"ro"},
+	}
+	g.AddMount(etcCNINetD)
+	// FIXME: how to propagate ProcessArgs and Envs from Dockerfile?
+	g.SetProcessArgs([]string{"sleep", "infinity"})
+	g.AddProcessEnv("CNI_PATH", "/opt/cni/bin")
+	var options []CtrCreateOption
+	options = append(options, WithRootFSFromImage(newImage.ID(), imageName, imageName))
+	options = append(options, WithCtrNamespace(rootlessCNIInfraContainerNamespace))
+	options = append(options, WithName(rootlessCNIInfraContainerName))
+	options = append(options, WithPrivileged(true))
+	options = append(options, WithSecLabels([]string{"disable"}))
+	options = append(options, WithRestartPolicy("always"))
+	options = append(options, WithNetNS(nil, false, "slirp4netns", nil))
+	c, err := r.NewContainer(ctx, g.Config, options...)
+	if err != nil {
+		return nil, err
+	}
+	logrus.Debugf("rootless CNI infra container %q is created, now being started", c.ID())
+	if err := c.initAndStart(ctx); err != nil {
+		return nil, err
+	}
+	logrus.Debugf("rootless CNI: infra container %q is running", c.ID())
+
+	return c, nil
+}
+
+func rootlessCNIInfraExec(c *Container, args ...string) (string, error) {
+	cmd := "rootless-cni-infra"
+	var (
+		outB    bytes.Buffer
+		errB    bytes.Buffer
+		streams define.AttachStreams
+		config  ExecConfig
+	)
+	streams.OutputStream = &nopWriteCloser{Writer: &outB}
+	streams.ErrorStream = &nopWriteCloser{Writer: &errB}
+	streams.AttachOutput = true
+	streams.AttachError = true
+	config.Command = append([]string{cmd}, args...)
+	config.Privileged = true
+	logrus.Debugf("rootlessCNIInfraExec: c.ID()=%s, config=%+v, streams=%v, begin",
+		c.ID(), config, streams)
+	code, err := c.Exec(&config, &streams, nil)
+	logrus.Debugf("rootlessCNIInfraExec: c.ID()=%s, config=%+v, streams=%v, end (code=%d, err=%v)",
+		c.ID(), config, streams, code, err)
+	if err != nil {
+		return "", err
+	}
+	if code != 0 {
+		return "", errors.Errorf("command %s %v in container %s failed with status %d, stdout=%q, stderr=%q",
+			cmd, args, c.ID(), code, outB.String(), errB.String())
+	}
+	return outB.String(), nil
+}
+
+type nopWriteCloser struct {
+	io.Writer
+}
+
+func (nwc *nopWriteCloser) Close() error {
+	return nil
+}