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Network Fencing

Terminology

Term Definition
CO Container Orchestration system that communicates with plugins using CSI service RPCs.
SP Storage Provider, the vendor of a CSI plugin implementation.
DR Disaster Recovery.
RPC Remote Procedure Call.

Objective

Define a standard that will enable storage providers (SP) to perform node level fencing using corresponding CIDR blocks.

Goals in MVP

The new extension will define a procedure that allows SP to block access to any client using corresponding CIDR blocks, and unblock as per the requirement.

If multiple COs are accessing a shared resource provided by the SP, and a node failure takes place, this procedure will allow the SP to block access from any node of CO, and thus preventing further access and corruption of data.

Non-Goals in MVP

  • Application level fencing, i.e blocklisting by maintaining a list of applications that are to be denied access.

Solution Overview

This specification defines an interface along with the minimum operational and packaging recommendations for a storage provider (SP) to implement fencing operation. The interface declares the RPCs that a plugin MUST expose.

Since the fencing is network based, the fencing mechanism will be most aptly implemented by the CSI Controller.

RPC Interface

  • FenceController Service: The Controller plugin MUST implement these sets of RPCs.
syntax = "proto3";
package fence;

import "github.com/container-storage-interface/spec/lib/go/csi/csi.proto";
import "google/protobuf/descriptor.proto";

option go_package = "github.com/csi-addons/spec/lib/go/fence";

// FenceController holds the RPC method for performing fencing operations.
service FenceController {
  // FenceClusterNetwork RPC call to perform a fencing operation.
  rpc FenceClusterNetwork (FenceClusterNetworkRequest)
  returns (FenceClusterNetworkResponse) {}

  // UnfenceClusterNetwork RPC call to remove a list of CIDR blocks from the
  // list of blocklisted/fenced clients.
  rpc UnfenceClusterNetwork (UnfenceClusterNetworkRequest)
  returns (UnfenceClusterNetworkResponse) {}

  // ListClusterFence RPC call to provide a list of blocklisted/fenced clients.
  rpc ListClusterFence(ListClusterFenceRequest)
  returns (ListClusterFenceResponse){}
}

FenceClusterNetwork

// FenceClusterNetworkRequest contains the information needed to identify
// the storage cluster so that the appropriate fencing operation can be
// performed.
message FenceClusterNetworkRequest {
  // Plugin specific parameters passed in as opaque key-value pairs.
  map<string, string> parameters = 1;
  // Secrets required by the plugin to complete the request.
  map<string, string> secrets = 2 [(csi.v1.csi_secret) = true];
  // list of CIDR blocks on which the fencing operation is expected to be
  // performed.
  repeated CIDR cidrs = 3;
}

// FenceClusterNetworkResponse is returned by the CSI-driver as a result of
// the FenceClusterNetworkRequest call.
message FenceClusterNetworkResponse {
  // Intentionally empty.
}

UnfenceClusterNetwork

// UnfenceClusterNetworkRequest contains the information needed to identify
// the cluster so that the appropriate fence operation can be
// disabled.
message UnfenceClusterNetworkRequest {
  // Plugin specific parameters passed in as opaque key-value pairs.
  map<string, string> parameters = 1;
  // Secrets required by the plugin to complete the request.
  map<string, string> secrets = 2 [(csi.v1.csi_secret) = true];
  // list of CIDR blocks on which the fencing operation is expected to be
  // performed.
  repeated CIDR cidrs = 3;
}

// UnfenceClusterNetworkResponse is returned by the CSI-driver as a result of
// the UnfenceClusterNetworkRequest call.
message UnfenceClusterNetworkResponse {
  // Intentionally empty.
}

ListClusterFence

// ListClusterFenceRequest contains the information needed to identify
// the cluster so that the appropriate fenced clients can be listed.
message ListClusterFenceRequest {
  // Plugin specific parameters passed in as opaque key-value pairs.
  map<string, string> parameters = 1;
  // Secrets required by the plugin to complete the request.
  map<string, string> secrets = 2 [(csi.v1.csi_secret) = true];
}

// ListClusterFenceResponse holds the information about the result of the
// ListClusterFenceResponse call.
message ListClusterFenceResponse {
  // list of IPs that are blocklisted by the SP.
  repeated CIDR cidrs = 1;
}

CIDR blocks

// CIDR holds a CIDR block.
message CIDR {
  // CIDR block
  string cidr = 1;
}

Error Scheme

Condition gRPC Code Description Recovery Behavior
Missing required field 3 INVALID_ARGUMENT Indicates that a required field is missing from the request. Caller MUST fix the request by adding the missing required field before retrying.
Invalid or unsupported field in the request 3 INVALID_ARGUMENT Indicates that the one or more fields in this field is either not allowed by the CSI-driver or has an invalid value. Caller MUST fix the field before retrying.
Call not implemented 12 UNIMPLEMENTED The invoked RPC is not implemented by the CSI-driver or disabled in the driver's current mode of operation. Caller MUST NOT retry.
Not authenticated 16 UNAUTHENTICATED The invoked RPC does not carry secrets that are valid for authentication. Caller SHALL either fix the secrets provided in the RPC, or otherwise regalvanize said secrets such that they will pass authentication by the CSI-driver for the attempted RPC, after which point the caller MAY retry the attempted RPC.
Error is Unknown 2 UNKNOWN Indicates that a unknown error is generated Caller MUST study the logs before retrying