kubelet: add GetHostIDsForPod()

In future commits we will need this to set the user/group of supported
volumes of KEP 127 - Phase 1.

Signed-off-by: Rodrigo Campos <rodrigoca@microsoft.com>

pkg/kubelet/userns_manager_test.go

@@ -25,6 +25,7 @@ import (
 	"k8s.io/apimachinery/pkg/types"
 	utilfeature "k8s.io/apiserver/pkg/util/feature"
 	featuregatetesting "k8s.io/component-base/featuregate/testing"
+	runtimeapi "k8s.io/cri-api/pkg/apis/runtime/v1"
 	pkgfeatures "k8s.io/kubernetes/pkg/features"
 )
 
@@ -176,6 +177,136 @@ func TestUserNsManagerParseUserNsFile(t *testing.T) {
 	}
 }
 
+func TestUserNsManagerHostIDFromMapping(t *testing.T) {
+	// mapping []*runtimeapi.IDMapping, containerId *int64
+
+	cases := []struct {
+		name        string
+		success     bool
+		containerId int64 // -1 means a nil ptr will be used.
+		expHostId   int64
+		m           []*runtimeapi.IDMapping
+	}{
+		{
+			name:        "one basic mapping",
+			success:     true,
+			containerId: -1,
+			expHostId:   0,
+			m: []*runtimeapi.IDMapping{
+				{
+					HostId:      0,
+					ContainerId: 0,
+					Length:      userNsLength,
+				},
+			},
+		},
+		{
+			name:        "one unprivileged mapping",
+			success:     true,
+			containerId: -1,
+			expHostId:   userNsLength * 2,
+			m: []*runtimeapi.IDMapping{
+				{
+					HostId:      userNsLength * 2,
+					ContainerId: 0,
+					Length:      userNsLength,
+				},
+			},
+		},
+		{
+			name:        "one unprivileged mapping random id",
+			success:     true,
+			containerId: 3,
+			expHostId:   userNsLength*2 + 3,
+			m: []*runtimeapi.IDMapping{
+				{
+					HostId:      userNsLength * 2,
+					ContainerId: 0,
+					Length:      userNsLength,
+				},
+			},
+		},
+		{
+			name:        "two unprivileged mapping",
+			success:     true,
+			containerId: 0,
+			expHostId:   userNsLength*2 + 0,
+			m: []*runtimeapi.IDMapping{
+				{
+					HostId:      userNsLength * 2,
+					ContainerId: 0,
+					Length:      1,
+				},
+				{
+					HostId:      userNsLength*2 + 10,
+					ContainerId: 1,
+					Length:      1,
+				},
+			},
+		},
+		{
+			name:        "two unprivileged mapping - random id",
+			success:     true,
+			containerId: 1,
+			expHostId:   userNsLength*2 + 10,
+			m: []*runtimeapi.IDMapping{
+				{
+					HostId:      userNsLength * 2,
+					ContainerId: 0,
+					Length:      1,
+				},
+				{
+					HostId:      userNsLength*2 + 10,
+					ContainerId: 1,
+					Length:      1,
+				},
+			},
+		},
+		{
+			name:        "two unprivileged mapping - not mapped user",
+			success:     false,
+			containerId: 3,
+			m: []*runtimeapi.IDMapping{
+				{
+					HostId:      userNsLength * 2,
+					ContainerId: 0,
+					Length:      1,
+				},
+				{
+					HostId:      userNsLength*2 + 1,
+					ContainerId: 1,
+					Length:      1,
+				},
+			},
+		},
+		{
+			name:    "no mappings",
+			success: false,
+		},
+	}
+
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			var containerId *int64
+			if tc.containerId != -1 {
+				containerId = &tc.containerId
+			}
+
+			id, err := hostIDFromMapping(tc.m, containerId)
+			if (tc.success && err != nil) || (!tc.success && err == nil) {
+				t.Fatalf("%v: expected success: %v - got error: %v", tc.name, tc.success, err)
+			}
+			if !tc.success && err != nil {
+				return
+			}
+
+			if id != tc.expHostId {
+				t.Errorf("expected: %v - got: %v", tc.expHostId, id)
+			}
+		})
+	}
+}
+
 func BenchmarkBitmaskFindAndSetFirstZero(t *testing.B) {
 	b := makeBitArray(userNsLength)
 	for i := 0; i < userNsLength; i++ {