add support for `ResourceUnavailable` p2p error (#3476)

The `p2p-interface.md` spec defines a `ResourceUnavailable` error to
return in situations where data that exists on the network is locally
unavailable, e.g., when a block within `MIN_EPOCHS_FOR_BLOCK_REQUESTS`
is requested by `BeaconBlocksByRange` but cannot be provided. This patch
adds support for that additional error code.

beacon_chain/networking/eth2_network.nim

@@ -158,6 +158,7 @@ type
     Success
     InvalidRequest
     ServerError
+    ResourceUnavailable
 
   PeerStateInitializer* = proc(peer: Peer): RootRef {.gcsafe, raises: [Defect].}
   NetworkStateInitializer* = proc(network: EthereumNode): RootRef {.gcsafe, raises: [Defect].}
@@ -206,6 +207,8 @@ type
 
   InvalidInputsError* = object of CatchableError
 
+  ResourceUnavailableError* = object of CatchableError
+
   NetRes*[T] = Result[T, Eth2NetworkingError]
     ## This is type returned from all network requests
 
@@ -720,6 +723,13 @@ proc handleIncomingStream(network: Eth2Node,
     template returnInvalidRequest(msg: string) =
       returnInvalidRequest(ErrorMsg msg.toBytes)
 
+    template returnResourceUnavailable(msg: ErrorMsg) =
+      await sendErrorResponse(peer, conn, ResourceUnavailable, msg)
+      return
+
+    template returnResourceUnavailable(msg: string) =
+      returnResourceUnavailable(ErrorMsg msg.toBytes)
+
     let s = when useNativeSnappy:
       let fs = libp2pInput(conn)
 
@@ -794,8 +804,8 @@ proc handleIncomingStream(network: Eth2Node,
       await callUserHandler(MsgType, peer, conn, msg.get)
     except InvalidInputsError as err:
       returnInvalidRequest err.msg
-      await sendErrorResponse(peer, conn, ServerError,
-                              ErrorMsg err.msg.toBytes)
+    except ResourceUnavailableError as err:
+      returnResourceUnavailable err.msg
     except CatchableError as err:
       await sendErrorResponse(peer, conn, ServerError,
                               ErrorMsg err.msg.toBytes)

beacon_chain/networking/faststreams_backend.nim

@@ -1,5 +1,5 @@
 # beacon_chain
-# Copyright (c) 2018-2021 Status Research & Development GmbH
+# Copyright (c) 2018-2022 Status Research & Development GmbH
 # Licensed and distributed under either of
 #   * MIT license (license terms in the root directory or at https://opensource.org/licenses/MIT).
 #   * Apache v2 license (license terms in the root directory or at https://www.apache.org/licenses/LICENSE-2.0).
@@ -112,7 +112,7 @@ proc readResponseChunk(s: AsyncInputStream,
 
   let responseCode = ResponseCode responseCodeByte
   case responseCode:
-  of InvalidRequest, ServerError:
+  of InvalidRequest, ServerError, ResourceUnavailable:
     let errorMsgChunk = await readChunkPayload(s, noSnappy, string)
     let errorMsg = if errorMsgChunk.isOk: errorMsgChunk.value
                    else: return err(errorMsgChunk.error)

beacon_chain/networking/libp2p_streams_backend.nim

@@ -1,5 +1,5 @@
 # beacon_chain
-# Copyright (c) 2018-2021 Status Research & Development GmbH
+# Copyright (c) 2018-2022 Status Research & Development GmbH
 # Licensed and distributed under either of
 #   * MIT license (license terms in the root directory or at https://opensource.org/licenses/MIT).
 #   * Apache v2 license (license terms in the root directory or at https://www.apache.org/licenses/LICENSE-2.0).
@@ -148,7 +148,7 @@ proc readResponseChunk(conn: Connection, peer: Peer,
 
     let responseCode = ResponseCode responseCodeByte
     case responseCode:
-    of InvalidRequest, ServerError:
+    of InvalidRequest, ServerError, ResourceUnavailable:
       let
         errorMsgChunk = await readChunkPayload(conn, peer, ErrorMsg)
         errorMsg = if errorMsgChunk.isOk: errorMsgChunk.value