move message encoding to separate file

Messages and message encoding has nothing
to do with the underlying authenticated
communications framework. Separate these
two.

eth/p2p/discoveryv5/encoding.nim

@@ -17,7 +17,7 @@ import
   std/[tables, options, hashes, net],
   nimcrypto, stint, chronicles, bearssl, stew/[results, byteutils], metrics,
   ".."/../[rlp, keys],
-  "."/[messages, node, enr, hkdf, sessions]
+  "."/[messages, messages_encoding, node, enr, hkdf, sessions]
 
 from stew/objects import checkedEnumAssign
 
@@ -367,50 +367,6 @@ proc decodeHeader*(id: NodeId, iv, maskedHeader: openArray[byte]):
   ok((StaticHeader(authdataSize: authdataSize, flag: flag, nonce: nonce),
     staticHeader & authdata))
 
-proc decodeMessage*(body: openArray[byte]): DecodeResult[Message] =
-  ## Decodes to the specific `Message` type.
-  if body.len < 1:
-    return err("No message data")
-
-  var kind: MessageKind
-  if not checkedEnumAssign(kind, body[0]):
-    return err("Invalid message type")
-
-  var message = Message(kind: kind)
-  var rlp = rlpFromBytes(body.toOpenArray(1, body.high))
-  if rlp.enterList:
-    try:
-      message.reqId = rlp.read(RequestId)
-    except RlpError, ValueError:
-      return err("Invalid request-id")
-
-    proc decode[T](rlp: var Rlp, v: var T)
-        {.nimcall, raises:[RlpError, ValueError, Defect].} =
-      for k, v in v.fieldPairs:
-        v = rlp.read(typeof(v))
-
-    try:
-      case kind
-      of unused: return err("Invalid message type")
-      of ping: rlp.decode(message.ping)
-      of pong: rlp.decode(message.pong)
-      of findNode: rlp.decode(message.findNode)
-      of nodes: rlp.decode(message.nodes)
-      of talkReq: rlp.decode(message.talkReq)
-      of talkResp: rlp.decode(message.talkResp)
-      of regTopic, ticket, regConfirmation, topicQuery:
-        # We just pass the empty type of this message without attempting to
-        # decode, so that the protocol knows what was received.
-        # But we ignore the message as per specification as "the content and
-        # semantics of this message are not final".
-        discard
-    except RlpError, ValueError:
-      return err("Invalid message encoding")
-
-    ok(message)
-  else:
-    err("Invalid message encoding: no rlp list")
-
 proc decodeMessagePacket(c: var Codec, fromAddr: Address, nonce: AESGCMNonce,
     iv, header, ct: openArray[byte]): DecodeResult[Packet] =
   # We now know the exact size that the header should be
@@ -607,17 +563,3 @@ proc init*(T: type RequestId, rng: var BrHmacDrbgContext): T =
   var reqId = RequestId(id: newSeq[byte](8)) # RequestId must be <= 8 bytes
   brHmacDrbgGenerate(rng, reqId.id)
   reqId
-
-proc numFields(T: typedesc): int =
-  for k, v in fieldPairs(default(T)): inc result
-
-proc encodeMessage*[T: SomeMessage](p: T, reqId: RequestId): seq[byte] =
-  result = newSeqOfCap[byte](64)
-  result.add(messageKind(T).ord)
-
-  const sz = numFields(T)
-  var writer = initRlpList(sz + 1)
-  writer.append(reqId)
-  for k, v in fieldPairs(p):
-    writer.append(v)
-  result.add(writer.finish())

eth/p2p/discoveryv5/messages_encoding.nim

@@ -0,0 +1,69 @@
+import
+  std/[net],
+  stint, bearssl, metrics,
+  ".."/../[rlp, keys],
+  "."/[messages, node, enr]
+
+from stew/objects import checkedEnumAssign
+
+type
+  DecodeResult*[T] = Result[T, cstring]
+
+proc numFields(T: typedesc): int =
+  for k, v in fieldPairs(default(T)): inc result
+
+proc encodeMessage*[T: SomeMessage](p: T, reqId: RequestId): seq[byte] =
+  result = newSeqOfCap[byte](64)
+  result.add(messageKind(T).ord)
+
+  const sz = numFields(T)
+  var writer = initRlpList(sz + 1)
+  writer.append(reqId)
+  for k, v in fieldPairs(p):
+    writer.append(v)
+  result.add(writer.finish())
+
+proc decodeMessage*(body: openArray[byte]): DecodeResult[Message] =
+  ## Decodes to the specific `Message` type.
+  if body.len < 1:
+    return err("No message data")
+
+  var kind: MessageKind
+  if not checkedEnumAssign(kind, body[0]):
+    return err("Invalid message type")
+
+  var message = Message(kind: kind)
+  var rlp = rlpFromBytes(body.toOpenArray(1, body.high))
+  if rlp.enterList:
+    try:
+      message.reqId = rlp.read(RequestId)
+    except RlpError, ValueError:
+      return err("Invalid request-id")
+
+    proc decode[T](rlp: var Rlp, v: var T)
+        {.nimcall, raises:[RlpError, ValueError, Defect].} =
+      for k, v in v.fieldPairs:
+        v = rlp.read(typeof(v))
+
+    try:
+      case kind
+      of unused: return err("Invalid message type")
+      of ping: rlp.decode(message.ping)
+      of pong: rlp.decode(message.pong)
+      of findNode: rlp.decode(message.findNode)
+      of nodes: rlp.decode(message.nodes)
+      of talkReq: rlp.decode(message.talkReq)
+      of talkResp: rlp.decode(message.talkResp)
+      of regTopic, ticket, regConfirmation, topicQuery:
+        # We just pass the empty type of this message without attempting to
+        # decode, so that the protocol knows what was received.
+        # But we ignore the message as per specification as "the content and
+        # semantics of this message are not final".
+        discard
+    except RlpError, ValueError:
+      return err("Invalid message encoding")
+
+    ok(message)
+  else:
+    err("Invalid message encoding: no rlp list")
+

eth/p2p/discoveryv5/protocol.nim

@@ -78,7 +78,7 @@ import
   stew/shims/net as stewNet, json_serialization/std/net,
   stew/[endians2, results], chronicles, chronos, stint, bearssl, metrics,
   ".."/../[rlp, keys, async_utils],
-  "."/[messages, encoding, node, routing_table, enr, random2, sessions, ip_vote, nodes_verification]
+  "."/[messages, messages_encoding, encoding, node, routing_table, enr, random2, sessions, ip_vote, nodes_verification]
 
 import nimcrypto except toHex