podman unshare: add --rootless-cni to join the ns

Add a new --rootless-cni option to podman unshare to also join the
rootless-cni network namespace. This is useful if you want to connect
to a rootless container via IP address. This is only possible from the
rootless-cni namespace and not from the host namespace. This option also
helps to debug problems in the rootless-cni namespace.

Signed-off-by: Paul Holzinger <paul.holzinger@web.de>

8 files changed, 90 insertions, 22 deletions

diff --git a/cmd/podman/system/unshare.go b/cmd/podman/system/unshare.go
index 5e6ff569b..c07751532 100644
--- a/cmd/podman/system/unshare.go
+++ b/cmd/podman/system/unshare.go
@@ -12,9 +12,10 @@ import (
 )
 
 var (
+	unshareOptions     = entities.SystemUnshareOptions{}
 	unshareDescription = "Runs a command in a modified user namespace."
 	unshareCommand     = &cobra.Command{
-		Use:                   "unshare [COMMAND [ARG...]]",
+		Use:                   "unshare [options] [COMMAND [ARG...]]",
 		DisableFlagsInUseLine: true,
 		Short:                 "Run a command in a modified user namespace",
 		Long:                  unshareDescription,
@@ -33,6 +34,7 @@ func init() {
 	})
 	flags := unshareCommand.Flags()
 	flags.SetInterspersed(false)
+	flags.BoolVar(&unshareOptions.RootlessCNI, "rootless-cni", false, "Join the rootless network namespace used for CNI networking")
 }
 
 func unshare(cmd *cobra.Command, args []string) error {
@@ -49,5 +51,5 @@ func unshare(cmd *cobra.Command, args []string) error {
 		args = []string{shell}
 	}
 
-	return registry.ContainerEngine().Unshare(registry.Context(), args)
+	return registry.ContainerEngine().Unshare(registry.Context(), args, unshareOptions)
 }
diff --git a/docs/source/markdown/podman-unshare.1.md b/docs/source/markdown/podman-unshare.1.md
index 239213981..4451ad79c 100644
--- a/docs/source/markdown/podman-unshare.1.md
+++ b/docs/source/markdown/podman-unshare.1.md
@@ -24,6 +24,19 @@ The unshare session defines two environment variables:
 - **CONTAINERS_GRAPHROOT**: the path to the persistent container's data.
 - **CONTAINERS_RUNROOT**: the path to the volatile container's data.
 
+## OPTIONS
+
+#### **\-\-help**, **-h**
+
+Print usage statement
+
+#### **\-\-rootless-cni**
+
+Join the rootless network namespace used for CNI networking. It can be used to
+connect to a rootless container via IP address (CNI networking). This is otherwise
+not possible from the host network namespace.
+_Note: Using this option with more than one unshare session can have unexpected results._
+
 ## EXAMPLE
 
 ```
@@ -35,6 +48,30 @@ $ podman unshare cat /proc/self/uid_map /proc/self/gid_map
          1      10000      65536
          0       1000          1
          1      10000      65536
+
+$ podman unshare --rootless-cni ip addr
+1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
+    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
+    inet 127.0.0.1/8 scope host lo
+       valid_lft forever preferred_lft forever
+    inet6 ::1/128 scope host
+       valid_lft forever preferred_lft forever
+2: tap0: <BROADCAST,UP,LOWER_UP> mtu 65520 qdisc fq_codel state UNKNOWN group default qlen 1000
+    link/ether 36:0e:4a:c7:45:7e brd ff:ff:ff:ff:ff:ff
+    inet 10.0.2.100/24 brd 10.0.2.255 scope global tap0
+       valid_lft forever preferred_lft forever
+    inet6 fe80::340e:4aff:fec7:457e/64 scope link
+       valid_lft forever preferred_lft forever
+3: cni-podman2: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
+    link/ether 5e:3a:71:d2:b4:3a brd ff:ff:ff:ff:ff:ff
+    inet 10.89.1.1/24 brd 10.89.1.255 scope global cni-podman2
+       valid_lft forever preferred_lft forever
+    inet6 fe80::5c3a:71ff:fed2:b43a/64 scope link
+       valid_lft forever preferred_lft forever
+4: vethd4ba3a2f@if3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master cni-podman2 state UP group default
+    link/ether 8a:c9:56:32:17:0c brd ff:ff:ff:ff:ff:ff link-netnsid 0
+    inet6 fe80::88c9:56ff:fe32:170c/64 scope link
+       valid_lft forever preferred_lft forever
 ```
 
 
diff --git a/libpod/networking_linux.go b/libpod/networking_linux.go
index 3c4014c73..6e2c2880f 100644
--- a/libpod/networking_linux.go
+++ b/libpod/networking_linux.go
@@ -105,13 +105,13 @@ func (r *Runtime) getPodNetwork(id, name, nsPath string, networks []string, port
 	return ctrNetwork
 }
 
-type rootlessCNI struct {
+type RootlessCNI struct {
 	ns   ns.NetNS
 	dir  string
 	lock lockfile.Locker
 }
 
-func (r *rootlessCNI) Do(toRun func() error) error {
+func (r *RootlessCNI) Do(toRun func() error) error {
 	err := r.ns.Do(func(_ ns.NetNS) error {
 		// before we can run the given function
 		// we have to setup all mounts correctly
@@ -174,9 +174,14 @@ func (r *rootlessCNI) Do(toRun func() error) error {
 	return err
 }
 
-// cleanup the rootless cni namespace if needed
+// Cleanup the rootless cni namespace if needed
 // check if we have running containers with the bridge network mode
-func (r *rootlessCNI) cleanup(runtime *Runtime) error {
+func (r *RootlessCNI) Cleanup(runtime *Runtime) error {
+	_, err := os.Stat(r.dir)
+	if os.IsNotExist(err) {
+		// the directory does not exists no need for cleanup
+		return nil
+	}
 	r.lock.Lock()
 	defer r.lock.Unlock()
 	running := func(c *Container) bool {
@@ -234,10 +239,10 @@ func (r *rootlessCNI) cleanup(runtime *Runtime) error {
 	return nil
 }
 
-// getRootlessCNINetNs returns the rootless cni object. If create is set to true
+// GetRootlessCNINetNs returns the rootless cni object. If create is set to true
 // the rootless cni namespace will be created if it does not exists already.
-func (r *Runtime) getRootlessCNINetNs(new bool) (*rootlessCNI, error) {
-	var rootlessCNINS *rootlessCNI
+func (r *Runtime) GetRootlessCNINetNs(new bool) (*RootlessCNI, error) {
+	var rootlessCNINS *RootlessCNI
 	if rootless.IsRootless() {
 		runDir, err := util.GetRuntimeDir()
 		if err != nil {
@@ -421,7 +426,7 @@ func (r *Runtime) getRootlessCNINetNs(new bool) (*rootlessCNI, error) {
 			os.Setenv("PATH", path)
 		}
 
-		rootlessCNINS = &rootlessCNI{
+		rootlessCNINS = &RootlessCNI{
 			ns:   ns,
 			dir:  cniDir,
 			lock: lock,
@@ -433,7 +438,7 @@ func (r *Runtime) getRootlessCNINetNs(new bool) (*rootlessCNI, error) {
 // setUpOCICNIPod will set up the cni networks, on error it will also tear down the cni
 // networks. If rootless it will join/create the rootless cni namespace.
 func (r *Runtime) setUpOCICNIPod(podNetwork ocicni.PodNetwork) ([]ocicni.NetResult, error) {
-	rootlessCNINS, err := r.getRootlessCNINetNs(true)
+	rootlessCNINS, err := r.GetRootlessCNINetNs(true)
 	if err != nil {
 		return nil, err
 	}
@@ -651,7 +656,7 @@ func (r *Runtime) closeNetNS(ctr *Container) error {
 // Tear down a container's CNI network configuration and joins the
 // rootless net ns as rootless user
 func (r *Runtime) teardownOCICNIPod(podNetwork ocicni.PodNetwork) error {
-	rootlessCNINS, err := r.getRootlessCNINetNs(false)
+	rootlessCNINS, err := r.GetRootlessCNINetNs(false)
 	if err != nil {
 		return err
 	}
@@ -665,7 +670,7 @@ func (r *Runtime) teardownOCICNIPod(podNetwork ocicni.PodNetwork) error {
 		// execute the cni setup in the rootless net ns
 		err = rootlessCNINS.Do(tearDownPod)
 		if err == nil {
-			err = rootlessCNINS.cleanup(r)
+			err = rootlessCNINS.Cleanup(r)
 		}
 	} else {
 		err = tearDownPod()
diff --git a/pkg/domain/entities/engine_container.go b/pkg/domain/entities/engine_container.go
index bcab617af..f695d32fd 100644
--- a/pkg/domain/entities/engine_container.go
+++ b/pkg/domain/entities/engine_container.go
@@ -88,7 +88,7 @@ type ContainerEngine interface {
 	SecretRm(ctx context.Context, nameOrID []string, opts SecretRmOptions) ([]*SecretRmReport, error)
 	Shutdown(ctx context.Context)
 	SystemDf(ctx context.Context, options SystemDfOptions) (*SystemDfReport, error)
-	Unshare(ctx context.Context, args []string) error
+	Unshare(ctx context.Context, args []string, options SystemUnshareOptions) error
 	Version(ctx context.Context) (*SystemVersionReport, error)
 	VolumeCreate(ctx context.Context, opts VolumeCreateOptions) (*IDOrNameResponse, error)
 	VolumeExists(ctx context.Context, namesOrID string) (*BoolReport, error)
diff --git a/pkg/domain/entities/system.go b/pkg/domain/entities/system.go
index 1a671d59e..31a6185dc 100644
--- a/pkg/domain/entities/system.go
+++ b/pkg/domain/entities/system.go
@@ -98,6 +98,11 @@ type SystemVersionReport struct {
 	Server *define.Version `json:",omitempty"`
 }
 
+// SystemUnshareOptions describes the options for the unshare command
+type SystemUnshareOptions struct {
+	RootlessCNI bool
+}
+
 type ComponentVersion struct {
 	types.Version
 }
diff --git a/pkg/domain/infra/abi/system.go b/pkg/domain/infra/abi/system.go
index a3e753384..f87f9e370 100644
--- a/pkg/domain/infra/abi/system.go
+++ b/pkg/domain/infra/abi/system.go
@@ -390,13 +390,25 @@ func unshareEnv(graphroot, runroot string) []string {
 		fmt.Sprintf("CONTAINERS_RUNROOT=%s", runroot))
 }
 
-func (ic *ContainerEngine) Unshare(ctx context.Context, args []string) error {
-	cmd := exec.Command(args[0], args[1:]...)
-	cmd.Env = unshareEnv(ic.Libpod.StorageConfig().GraphRoot, ic.Libpod.StorageConfig().RunRoot)
-	cmd.Stdin = os.Stdin
-	cmd.Stdout = os.Stdout
-	cmd.Stderr = os.Stderr
-	return cmd.Run()
+func (ic *ContainerEngine) Unshare(ctx context.Context, args []string, options entities.SystemUnshareOptions) error {
+	unshare := func() error {
+		cmd := exec.Command(args[0], args[1:]...)
+		cmd.Env = unshareEnv(ic.Libpod.StorageConfig().GraphRoot, ic.Libpod.StorageConfig().RunRoot)
+		cmd.Stdin = os.Stdin
+		cmd.Stdout = os.Stdout
+		cmd.Stderr = os.Stderr
+		return cmd.Run()
+	}
+
+	if options.RootlessCNI {
+		rootlesscni, err := ic.Libpod.GetRootlessCNINetNs(true)
+		if err != nil {
+			return err
+		}
+		defer rootlesscni.Cleanup(ic.Libpod)
+		return rootlesscni.Do(unshare)
+	}
+	return unshare()
 }
 
 func (ic ContainerEngine) Version(ctx context.Context) (*entities.SystemVersionReport, error) {
diff --git a/pkg/domain/infra/tunnel/system.go b/pkg/domain/infra/tunnel/system.go
index d2c5063c9..7400d3771 100644
--- a/pkg/domain/infra/tunnel/system.go
+++ b/pkg/domain/infra/tunnel/system.go
@@ -28,7 +28,7 @@ func (ic *ContainerEngine) SystemDf(ctx context.Context, options entities.System
 	return system.DiskUsage(ic.ClientCtx, nil)
 }
 
-func (ic *ContainerEngine) Unshare(ctx context.Context, args []string) error {
+func (ic *ContainerEngine) Unshare(ctx context.Context, args []string, options entities.SystemUnshareOptions) error {
 	return errors.New("unshare is not supported on remote clients")
 }
 
diff --git a/test/e2e/unshare_test.go b/test/e2e/unshare_test.go
index 515b3a42e..24ab98916 100644
--- a/test/e2e/unshare_test.go
+++ b/test/e2e/unshare_test.go
@@ -49,4 +49,11 @@ var _ = Describe("Podman unshare", func() {
 		ok, _ := session.GrepString(userNS)
 		Expect(ok).To(BeFalse())
 	})
+
+	It("podman unshare --rootles-cni", func() {
+		session := podmanTest.Podman([]string{"unshare", "--rootless-cni", "ip", "addr"})
+		session.WaitWithDefaultTimeout()
+		Expect(session.ExitCode()).To(Equal(0))
+		Expect(session.OutputToString()).To(ContainSubstring("tap0"))
+	})
 })