nfs: add nodeserver within cephcsi

This commit adds nfs nodeserver capable of
mounting nfs volumes, even with pod networking
using NSenter design similar to rbd and cephfs.
NodePublish, NodeUnpublish, NodeGetVolumeStats
and NodeGetCapabilities have been implemented.

The nodeserver implementation has been inspired
from https://github.com/kubernetes-csi/csi-driver-nfs,
which was previously used for mounted cephcsi exported
nfs volumes. The current implementation is also
backward compatible for the previously created
PVCs.

Signed-off-by: Rakshith R <rar@redhat.com>

internal/util/csiconfig_test.go

@@ -291,3 +291,77 @@ func TestGetCephFSNetNamespaceFilePath(t *testing.T) {
 		})
 	}
 }
+
+func TestGetNFSNetNamespaceFilePath(t *testing.T) {
+	t.Parallel()
+	tests := []struct {
+		name      string
+		clusterID string
+		want      string
+	}{
+		{
+			name:      "get NFS specific NetNamespaceFilePath for cluster-1",
+			clusterID: "cluster-1",
+			want:      "/var/lib/kubelet/plugins/nfs.ceph.csi.com/cluster1-net",
+		},
+		{
+			name:      "get NFS specific NetNamespaceFilePath for cluster-2",
+			clusterID: "cluster-2",
+			want:      "/var/lib/kubelet/plugins/nfs.ceph.csi.com/cluster2-net",
+		},
+		{
+			name:      "when NFS specific NetNamespaceFilePath is empty",
+			clusterID: "cluster-3",
+			want:      "",
+		},
+	}
+
+	csiConfig := []ClusterInfo{
+		{
+			ClusterID: "cluster-1",
+			Monitors:  []string{"ip-1", "ip-2"},
+			NFS: struct {
+				NetNamespaceFilePath string `json:"netNamespaceFilePath"`
+			}{
+				NetNamespaceFilePath: "/var/lib/kubelet/plugins/nfs.ceph.csi.com/cluster1-net",
+			},
+		},
+		{
+			ClusterID: "cluster-2",
+			Monitors:  []string{"ip-3", "ip-4"},
+			NFS: struct {
+				NetNamespaceFilePath string `json:"netNamespaceFilePath"`
+			}{
+				NetNamespaceFilePath: "/var/lib/kubelet/plugins/nfs.ceph.csi.com/cluster2-net",
+			},
+		},
+		{
+			ClusterID: "cluster-3",
+			Monitors:  []string{"ip-5", "ip-6"},
+		},
+	}
+	csiConfigFileContent, err := json.Marshal(csiConfig)
+	if err != nil {
+		t.Errorf("failed to marshal csi config info %v", err)
+	}
+	tmpConfPath := t.TempDir() + "/ceph-csi.json"
+	err = os.WriteFile(tmpConfPath, csiConfigFileContent, 0o600)
+	if err != nil {
+		t.Errorf("failed to write %s file content: %v", CsiConfigFile, err)
+	}
+	for _, tt := range tests {
+		ts := tt
+		t.Run(ts.name, func(t *testing.T) {
+			t.Parallel()
+			got, err := GetNFSNetNamespaceFilePath(tmpConfPath, ts.clusterID)
+			if err != nil {
+				t.Errorf("GetNFSNetNamespaceFilePath() error = %v", err)
+
+				return
+			}
+			if got != ts.want {
+				t.Errorf("GetNFSNetNamespaceFilePath() = %v, want %v", got, ts.want)
+			}
+		})
+	}
+}