libnetwork: avoid restarting rootless helper during teardown

common/libnetwork/internal/rootlessnetns/netns_linux.go

@@ -105,10 +105,17 @@ func (n *Netns) getPath(path string) string {
 
 // getOrCreateNetns returns the rootless netns, if it created a new one the
 // returned bool is set to true.
-func (n *Netns) getOrCreateNetns() (netns.NetNS, bool, error) {
+func (n *Netns) getOrCreateNetns(create bool) (netns.NetNS, bool, error) {
 	nsPath := n.getPath(rootlessNetnsDir)
 	nsRef, err := netns.GetNS(nsPath)
 	if err == nil {
+		if !create {
+			if err := n.deserializeInfo(); err != nil {
+				return nil, false, wrapError("deserialize info", err)
+			}
+			return nsRef, false, nil
+		}
+
 		pidPath := n.getPath(rootlessNetNsConnPidFile)
 		pid, err := readPidFile(pidPath)
 		if err == nil {
@@ -133,6 +140,10 @@ func (n *Netns) getOrCreateNetns() (netns.NetNS, bool, error) {
 		}
 		// In case of errors continue and setup the network cmd again.
 	} else {
+		if !create {
+			return nil, false, err
+		}
+
 		// Special case, the file might exist already but is not a valid netns.
 		// One reason could be that a previous setup was killed between creating
 		// the file and mounting it. Or if the file is not on tmpfs (deleted on boot)
@@ -539,8 +550,8 @@ func (n *Netns) setupMounts() error {
 	return nil
 }
 
-func (n *Netns) runInner(toRun func() error, cleanup bool) (err error) {
-	nsRef, newNs, err := n.getOrCreateNetns()
+func (n *Netns) runInner(toRun func() error, cleanup bool, create bool) (err error) {
+	nsRef, newNs, err := n.getOrCreateNetns(create)
 	if err != nil {
 		return err
 	}
@@ -568,7 +579,7 @@ func (n *Netns) runInner(toRun func() error, cleanup bool) (err error) {
 }
 
 func (n *Netns) Setup(nets int, toRun func() error) error {
-	err := n.runInner(toRun, true)
+	err := n.runInner(toRun, true, true)
 	if err != nil {
 		return err
 	}
@@ -577,7 +588,7 @@ func (n *Netns) Setup(nets int, toRun func() error) error {
 }
 
 func (n *Netns) Teardown(nets int, toRun func() error) error {
-	err := n.runInner(toRun, true)
+	err := n.runInner(toRun, true, false)
 	if err != nil {
 		return err
 	}
@@ -614,7 +625,7 @@ func (n *Netns) Run(lock *lockfile.LockFile, toRun func() error) error {
 		return err
 	}
 
-	inErr := n.runInner(inner, false)
+	inErr := n.runInner(inner, false, true)
 	// make sure to always reset the ref counter afterwards
 	count, err := refCount(n.dir, -1)
 	if err != nil {

common/libnetwork/internal/rootlessnetns/netns_linux_test.go

@@ -7,6 +7,7 @@ import (
 	"testing"
 
 	"github.com/stretchr/testify/assert"
+	"go.podman.io/common/pkg/config"
 )
 
 func Test_refCount(t *testing.T) {
@@ -75,3 +76,32 @@ func Test_refCount(t *testing.T) {
 		})
 	}
 }
+
+func Test_getOrCreateNetnsNoCreateDoesNotRestartHelper(t *testing.T) {
+	dir := t.TempDir()
+
+	conf, err := config.Default()
+	assert.NoError(t, err)
+
+	n, err := New(dir, conf)
+	assert.NoError(t, err)
+
+	nsPath := n.getPath(rootlessNetnsDir)
+	err = os.Symlink("/proc/self/ns/net", nsPath)
+	assert.NoError(t, err)
+
+	err = os.WriteFile(
+		n.getPath(rootlessNetNsConnPidFile),
+		[]byte("99999999"),
+		0o600,
+	)
+	assert.NoError(t, err)
+
+	ns, created, err := n.getOrCreateNetns(false)
+	assert.NoError(t, err)
+	assert.False(t, created)
+
+	if ns != nil {
+		assert.NoError(t, ns.Close())
+	}
+}