queue messages during handshake and send later

If a handshake was already in progress, messages were dropped.
Instead of this, it is better to queue these and send as soon
as the handshake is finished and thus the encryption key is known.

Signed-off-by: Csaba Kiraly <csaba.kiraly@gmail.com>

libp2pdht/private/eth/p2p/discoveryv5/transport.nim

@@ -6,7 +6,7 @@
 
 # Everything below the handling of ordinary messages
 import
-  std/[tables, options],
+  std/[tables, options, sets],
   bearssl/rand,
   chronos,
   chronicles,
@@ -26,6 +26,8 @@ type
     bindAddress: Address ## UDP binding address
     transp: DatagramTransport
     pendingRequests: Table[AESGCMNonce, PendingRequest]
+    handshakeInProgress: HashSet[NodeId]
+    pendingRequestsByNode: Table[NodeId, seq[seq[byte]]]
     codec*: Codec
     rng: ref HmacDrbgContext
 
@@ -77,8 +79,23 @@ proc sendMessage*(t: Transport, toNode: Node, message: seq[byte]) =
   let (data, nonce, haskey) = encodeMessagePacket(t.rng[], t.codec,
     toNode.id, address, message)
 
-  t.registerRequest(toNode, message, nonce)
-  t.send(toNode, data)
+  if haskey:
+    trace "Send message: has key", myport = t.bindAddress.port , dstId = toNode
+    t.registerRequest(toNode, message, nonce)
+    t.send(toNode, data)
+  else:
+    if not (toNode.id in t.handshakeInProgress):
+      trace "Send message: send random", myport = t.bindAddress.port , dstId = toNode
+      t.registerRequest(toNode, message, nonce)
+      t.send(toNode, data)
+      t.handshakeInProgress.incl(toNode.id)
+      sleepAsync(responseTimeout).addCallback() do(data: pointer):
+        t.handshakeInProgress.excl(toNode.id)
+    else:
+      # delay sending this message until handshake, have to reencode once keys are clear
+      t.pendingRequestsByNode.mgetOrPut(toNode.id, newSeq[seq[byte]]()).add(message)
+      trace "Send message: Node with this id already has ongoing handshake, delaying packet",
+            myport = t.bindAddress.port , dstId = toNode, qlen=t.pendingRequestsByNode[toNode.id].len
 
 proc sendWhoareyou(t: Transport, toId: NodeId, a: Address,
     requestNonce: AESGCMNonce, node: Option[Node]) =
@@ -103,8 +120,20 @@ proc sendWhoareyou(t: Transport, toId: NodeId, a: Address,
     t.sendToA(a, data)
   else:
     # TODO: is this reasonable to drop it? Should we allow a mini-queue here?
-    debug "Node with this id already has ongoing handshake, ignoring packet", myport = t.bindAddress.port , dstId = toId, address = a
+    # Queue should be on sender side, as this is random encoded!
+    debug "Node with this id already has ongoing handshake, queuing packet", myport = t.bindAddress.port , dstId = toId, address = a
 
+proc sendPending(t:Transport, toNode: Node):
+      Future[void] {.async.} =
+  if t.pendingRequestsByNode.hasKey(toNode.id):
+    trace "Found pending request", myport = t.bindAddress.port, src = toNode, len = t.pendingRequestsByNode[toNode.id].len
+    for message in t.pendingRequestsByNode[toNode.id]:
+      trace "Sending pending packet", myport = t.bindAddress.port, dstId = toNode.id
+      let address = toNode.address.get()
+      let (data, nonce, haskey) = encodeMessagePacket(t.rng[], t.codec, toNode.id, address, message)
+      t.registerRequest(toNode, message, nonce)
+      t.send(toNode, data)
+    t.pendingRequestsByNode.del(toNode.id)
 proc receive*(t: Transport, a: Address, packet: openArray[byte]) =
   let decoded = t.codec.decodePacket(a, packet)
   if decoded.isOk:
@@ -142,6 +171,10 @@ proc receive*(t: Transport, a: Address, packet: openArray[byte]) =
 
         trace "Send handshake message packet", dstId = toNode.id, address
         t.send(toNode, data)
+        # handshake ready, we can send queued packets
+        t.handshakeInProgress.excl(toNode.id)
+        discard t.sendPending(toNode)
+
       else:
         debug "Timed out or unrequested whoareyou packet", address = a
     of HandshakeMessage:
@@ -162,6 +195,9 @@ proc receive*(t: Transport, a: Address, packet: openArray[byte]) =
           node.seen = true
           if t.client.addNode(node):
             trace "Added new node to routing table after handshake", node, tablesize=t.client.nodesDiscovered()
+          # handshake finished, TODO: should this be inside the if above?
+          t.handshakeInProgress.excl(node.id)
+          discard t.sendPending(node)
   else:
     trace "Packet decoding error", myport = t.bindAddress.port, error = decoded.error, address = a