libct/cg/sd/v1: add freezeBeforeSet unit test

Add a test for freezeBeforeSet, checking various scenarios including
those that were failing before the fix in the previous commit.

[v2: add more cases, add a check before creating a unit.]

Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>

libcontainer/cgroups/systemd/v1_test.go

@@ -0,0 +1,217 @@
+package systemd
+
+import (
+	"os"
+	"os/exec"
+	"strings"
+	"testing"
+
+	"golang.org/x/sys/unix"
+
+	"github.com/opencontainers/runc/libcontainer/cgroups"
+	"github.com/opencontainers/runc/libcontainer/configs"
+)
+
+func TestFreezeBeforeSet(t *testing.T) {
+	requireV1(t)
+
+	testCases := []struct {
+		desc string
+		// Test input.
+		cg        *configs.Cgroup
+		preFreeze bool
+		// Expected values.
+		// Before unit creation (Apply).
+		freeze0, thaw0 bool
+		// After unit creation.
+		freeze1, thaw1 bool
+	}{
+		{
+			// A slice with SkipDevices.
+			desc: "slice,skip-devices",
+			cg: &configs.Cgroup{
+				Name:   "system-runc_test_freeze_1.slice",
+				Parent: "system.slice",
+				Resources: &configs.Resources{
+					SkipDevices: true,
+				},
+			},
+			// Expected.
+			freeze0: false,
+			thaw0:   false,
+			freeze1: false,
+			thaw1:   false,
+		},
+		{
+			// A scope with SkipDevices. Not a realistic scenario with runc
+			// (as container can't have SkipDevices == true), but possible
+			// for a standalone cgroup manager.
+			desc: "scope,skip-devices",
+			cg: &configs.Cgroup{
+				ScopePrefix: "test",
+				Name:        "testFreeze2",
+				Parent:      "system.slice",
+				Resources: &configs.Resources{
+					SkipDevices: true,
+				},
+			},
+			// Expected.
+			freeze0: false,
+			thaw0:   false,
+			freeze1: false,
+			thaw1:   false,
+		},
+		{
+			// A slice that is about to be frozen in Set.
+			desc: "slice,will-freeze",
+			cg: &configs.Cgroup{
+				Name:   "system-runc_test_freeze_3.slice",
+				Parent: "system.slice",
+				Resources: &configs.Resources{
+					Freezer: configs.Frozen,
+				},
+			},
+			// Expected.
+			freeze0: true,
+			thaw0:   false,
+			freeze1: true,
+			thaw1:   false,
+		},
+		{
+			// A pre-frozen slice that should stay frozen.
+			desc: "slice,pre-frozen,will-freeze",
+			cg: &configs.Cgroup{
+				Name:   "system-runc_test_freeze_4.slice",
+				Parent: "system.slice",
+				Resources: &configs.Resources{
+					Freezer: configs.Frozen,
+				},
+			},
+			preFreeze: true,
+			// Expected.
+			freeze0: true, // not actually frozen yet.
+			thaw0:   false,
+			freeze1: false,
+			thaw1:   false,
+		},
+		{
+			// A pre-frozen scope with skip devices set.
+			desc: "scope,pre-frozen,skip-devices",
+			cg: &configs.Cgroup{
+				ScopePrefix: "test",
+				Name:        "testFreeze5",
+				Parent:      "system.slice",
+				Resources: &configs.Resources{
+					SkipDevices: true,
+				},
+			},
+			preFreeze: true,
+			// Expected.
+			freeze0: false,
+			thaw0:   false,
+			freeze1: false,
+			thaw1:   false,
+		},
+		{
+			// A pre-frozen scope which will be thawed.
+			desc: "scope,pre-frozen",
+			cg: &configs.Cgroup{
+				ScopePrefix: "test",
+				Name:        "testFreeze6",
+				Parent:      "system.slice",
+				Resources:   &configs.Resources{},
+			},
+			preFreeze: true,
+			// Expected.
+			freeze0: true, // not actually frozen yet.
+			thaw0:   true,
+			freeze1: false,
+			thaw1:   false,
+		},
+	}
+
+	for _, tc := range testCases {
+		tc := tc
+		t.Run(tc.desc, func(t *testing.T) {
+			m := NewLegacyManager(tc.cg, nil)
+			defer m.Destroy() //nolint:errcheck
+			lm := m.(*legacyManager)
+
+			// Checks for a non-existent unit.
+			freeze, thaw, err := lm.freezeBeforeSet(getUnitName(tc.cg), tc.cg.Resources)
+			if err != nil {
+				t.Fatal(err)
+			}
+			if freeze != tc.freeze0 || thaw != tc.thaw0 {
+				t.Errorf("before Apply (non-existent unit): expected freeze: %v, thaw: %v, got freeze: %v, thaw: %v",
+					tc.freeze0, tc.thaw0, freeze, thaw)
+			}
+
+			// Create systemd unit.
+			pid := -1
+			if strings.HasSuffix(getUnitName(tc.cg), ".scope") {
+				// Scopes require a process inside.
+				cmd := exec.Command("bash", "-c", "sleep 1m")
+				if err := cmd.Start(); err != nil {
+					t.Fatal(err)
+				}
+				pid = cmd.Process.Pid
+				// Make sure to not leave a zombie.
+				defer func() {
+					// These may fail, we don't care.
+					_ = cmd.Process.Kill()
+					_ = cmd.Wait()
+				}()
+			}
+			if err := m.Apply(pid); err != nil {
+				t.Fatal(err)
+			}
+			if tc.preFreeze {
+				if err := m.Freeze(configs.Frozen); err != nil {
+					t.Error(err)
+					return // no more checks
+				}
+			}
+			freeze, thaw, err = lm.freezeBeforeSet(getUnitName(tc.cg), tc.cg.Resources)
+			if err != nil {
+				t.Error(err)
+				return // no more checks
+			}
+			if freeze != tc.freeze1 || thaw != tc.thaw1 {
+				t.Errorf("expected freeze: %v, thaw: %v, got freeze: %v, thaw: %v",
+					tc.freeze1, tc.thaw1, freeze, thaw)
+			}
+			// Destroy() timeouts on a frozen container, so we need to thaw it.
+			if tc.preFreeze {
+				if err := m.Freeze(configs.Thawed); err != nil {
+					t.Error(err)
+				}
+			}
+			// Destroy() does not kill processes in cgroup, so we should.
+			if pid != -1 {
+				if err = unix.Kill(pid, unix.SIGKILL); err != nil {
+					t.Errorf("unable to kill pid %d: %s", pid, err)
+				}
+			}
+			// Not really needed, but may help catch some bugs.
+			if err := m.Destroy(); err != nil {
+				t.Errorf("destroy: %s", err)
+			}
+		})
+	}
+}
+
+// requireV1 skips the test unless a set of requirements (cgroup v1,
+// systemd, root) is met.
+func requireV1(t *testing.T) {
+	t.Helper()
+	if cgroups.IsCgroup2UnifiedMode() {
+		t.Skip("Test requires cgroup v1.")
+	}
+	if !IsRunningSystemd() {
+		t.Skip("Test requires systemd.")
+	}
+	if os.Geteuid() != 0 {
+		t.Skip("Test requires root.")
+	}
+}