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.go

@@ -59,6 +59,11 @@ type ClusterInfo struct {
 		// RadosNamespace is a rados namespace in the pool
 		RadosNamespace string `json:"radosNamespace"`
 	} `json:"rbd"`
+	// NFS contains NFS specific options
+	NFS struct {
+		// symlink filepath for the network namespace where we need to execute commands.
+		NetNamespaceFilePath string `json:"netNamespaceFilePath"`
+	} `json:"nfs"`
 }
 
 // Expected JSON structure in the passed in config file is,
@@ -194,3 +199,13 @@ func GetCephFSNetNamespaceFilePath(pathToConfig, clusterID string) (string, erro
 
 	return cluster.CephFS.NetNamespaceFilePath, nil
 }
+
+// GetNFSNetNamespaceFilePath returns the netNamespaceFilePath for NFS volumes.
+func GetNFSNetNamespaceFilePath(pathToConfig, clusterID string) (string, error) {
+	cluster, err := readClusterInfo(pathToConfig, clusterID)
+	if err != nil {
+		return "", err
+	}
+
+	return cluster.NFS.NetNamespaceFilePath, nil
+}

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)
+			}
+		})
+	}
+}