Merge pull request #211 from mkalinin/invalid-payload-attributes

Engine API: respond with error if payload attributes are invalid

src/engine/specification.md

@@ -109,6 +109,7 @@ The list of error codes introduced by this specification can be found below.
 | -32603 | Internal error | Internal JSON-RPC error. |
 | -32000 | Server error | Generic client error while processing request. |
 | -32001 | Unknown payload | Payload does not exist / is not available. |
+| -31002 | Invalid payload attributes | Payload attributes are invalid / inconsistent. |
 
 Each error returns a `null` `data` value, except `-32000` which returns the `data` object with a `err` member that explains the error encountered.
 
@@ -301,16 +302,19 @@ The payload build process is specified as follows:
   * The values `(forkchoiceState.headBlockHash, forkchoiceState.finalizedBlockHash)` of this method call map on the `POS_FORKCHOICE_UPDATED` event of [EIP-3675](https://eips.ethereum.org/EIPS/eip-3675#block-validity) and **MUST** be processed according to the specification defined in the EIP
   * All updates to the forkchoice state resulting from this call **MUST** be made atomically.
 
-6. Client software **MUST** begin a payload build process building on top of `forkchoiceState.headBlockHash` and identified via `buildProcessId` value if `payloadAttributes` is not `null` and the forkchoice state has been updated successfully. The build process is specified in the [Payload building](#payload-building) section.
+6. Client software **MUST** ensure that `payloadAttributes.timestamp` is greater than `timestamp` of a block referenced by `forkchoiceState.headBlockHash`. If this condition isn't held client software **MUST** respond with `-31002: Invalid payload attributes` and **MUST NOT** begin a payload build process. In such an event, the `forkchoiceState` update **MUST NOT** be rolled back.
 
-7. Client software **MUST** respond to this method call in the following way:
+7. Client software **MUST** begin a payload build process building on top of `forkchoiceState.headBlockHash` and identified via `buildProcessId` value if `payloadAttributes` is not `null` and the forkchoice state has been updated successfully. The build process is specified in the [Payload building](#payload-building) section.
+
+8. Client software **MUST** respond to this method call in the following way:
   * `{payloadStatus: {status: SYNCING, latestValidHash: null, validationError: null}, payloadId: null}` if `forkchoiceState.headBlockHash` references an unknown payload or a payload that can't be validated because requisite data for the validation is missing
   * `{payloadStatus: {status: INVALID, latestValidHash: validHash, validationError: errorMessage | null}, payloadId: null}` obtained from the [Payload validation](#payload-validation) process if the payload is deemed `INVALID`
   * `{payloadStatus: {status: INVALID_TERMINAL_BLOCK, latestValidHash: null, validationError: errorMessage | null}, payloadId: null}` obtained either from the [Payload validation](#payload-validation) process or as a result of validating a PoW block referenced by `forkchoiceState.headBlockHash`
   * `{payloadStatus: {status: VALID, latestValidHash: forkchoiceState.headBlockHash, validationError: null}, payloadId: null}` if the payload is deemed `VALID` and a build process hasn't been started
-  * `{payloadStatus: {status: VALID, latestValidHash: forkchoiceState.headBlockHash, validationError: null}, payloadId: buildProcessId}` if the payload is deemed `VALID` and the build process has begun.
+  * `{payloadStatus: {status: VALID, latestValidHash: forkchoiceState.headBlockHash, validationError: null}, payloadId: buildProcessId}` if the payload is deemed `VALID` and the build process has begun
+  * `{error: {code: -31002, message: "Invalid payload attributes"}}` if the payload is deemed `VALID` and `forkchoiceState` has been applied successfully, but no build process has been started due to invalid `payloadAttributes`.
 
-8. If any of the above fails due to errors unrelated to the normal processing flow of the method, client software **MUST** respond with an error object.
+9. If any of the above fails due to errors unrelated to the normal processing flow of the method, client software **MUST** respond with an error object.
 
 ### engine_getPayloadV1