Add query proc and use this for recurrent queries

This query proc is similar to the original (faulty) lookup proc.
But as we don't need to look for specific targets, it can be
used still as it gives a quicker and broader search resulting
in more nodes.

eth/p2p/discoveryv5/protocol.nim

@@ -116,7 +116,7 @@ type
     routingTable: RoutingTable
     codec*: Codec
     awaitedMessages: Table[(NodeId, RequestId), Future[Option[Message]]]
-    lookupLoop: Future[void]
+    queryLoop: Future[void]
     revalidateLoop: Future[void]
     bootstrapRecords*: seq[Record]
     rng*: ref BrHmacDrbgContext
@@ -710,16 +710,63 @@ proc lookup*(d: Protocol, target: NodeId): Future[seq[Node]]
 
   return closestNodes
 
-proc lookupRandom*(d: Protocol): Future[seq[Node]]
+proc query*(d: Protocol, target: NodeId, k = BUCKET_SIZE): Future[seq[Node]]
+    {.async, raises: [Exception, Defect].} =
+  ## Query k nodes for the given target, returns all nodes found, including the
+  ## nodes queried.
+  ##
+  ## This will take k nodes from the routing table closest to target and
+  ## query them for nodes closest to target. If there are less than k nodes in
+  ## the routing table, nodes returned by the first queries will be used.
+  var queryBuffer = d.routingTable.neighbours(target, k, seenOnly = false)
+
+  var asked, seen = initHashSet[NodeId]()
+  asked.incl(d.localNode.id) # No need to ask our own node
+  seen.incl(d.localNode.id) # No need to discover our own node
+  for node in queryBuffer:
+    seen.incl(node.id)
+
+  var pendingQueries = newSeqOfCap[Future[seq[Node]]](alpha)
+
+  while true:
+    var i = 0
+    while i < min(queryBuffer.len, k) and pendingQueries.len < alpha:
+      let n = queryBuffer[i]
+      if not asked.containsOrIncl(n.id):
+        pendingQueries.add(d.lookupWorker(n, target))
+      inc i
+
+    trace "discv5 pending queries", total = pendingQueries.len
+
+    if pendingQueries.len == 0:
+      break
+
+    let query = await one(pendingQueries)
+    trace "Got discv5 lookup query response"
+
+    let index = pendingQueries.find(query)
+    if index != -1:
+      pendingQueries.del(index)
+    else:
+      error "Resulting query should have been in the pending queries"
+
+    let nodes = query.read
+    # TODO: Remove node on timed-out query?
+    for n in nodes:
+      if not seen.containsOrIncl(n.id):
+        queryBuffer.add(n)
+
+  return queryBuffer
+
+proc queryRandom*(d: Protocol): Future[seq[Node]]
     {.async, raises:[Exception, Defect].} =
-  ## Perform a lookup for a random target, return the closest n nodes to the
-  ## target. Maximum value for n is `BUCKET_SIZE`.
+  ## Perform a query for a random target, return all nodes discovered.
   var id: NodeId
   var buf: array[sizeof(id), byte]
   brHmacDrbgGenerate(d.rng[], buf)
   copyMem(addr id, addr buf[0], sizeof(id))
 
-  return await d.lookup(id)
+  return await d.query(id)
 
 proc resolve*(d: Protocol, id: NodeId): Future[Option[Node]]
     {.async, raises: [Exception, Defect].} =
@@ -770,19 +817,19 @@ proc revalidateLoop(d: Protocol) {.async, raises: [Exception, Defect].} =
   except CancelledError:
     trace "revalidateLoop canceled"
 
-proc lookupLoop(d: Protocol) {.async, raises: [Exception, Defect].} =
+proc queryLoop(d: Protocol) {.async, raises: [Exception, Defect].} =
   # TODO: General Exception raised.
   try:
-    # lookup self (neighbour nodes)
-    let selfLookup = await d.lookup(d.localNode.id)
-    trace "Discovered nodes in self lookup", nodes = selfLookup
+    # query target self (neighbour nodes)
+    let selfQuery = await d.query(d.localNode.id)
+    trace "Discovered nodes in self target query", nodes = selfQuery.len
     while true:
-      let randomLookup = await d.lookupRandom()
-      trace "Discovered nodes in random lookup", nodes = randomLookup
+      let randomQuery = await d.queryRandom()
+      trace "Discovered nodes in random target query", nodes = randomQuery.len
       debug "Total nodes in discv5 routing table", total = d.routingTable.len()
       await sleepAsync(lookupInterval)
   except CancelledError:
-    trace "lookupLoop canceled"
+    trace "queryLoop canceled"
 
 proc newProtocol*(privKey: PrivateKey,
                   externalIp: Option[ValidIpAddress], tcpPort, udpPort: Port,
@@ -845,7 +892,7 @@ proc open*(d: Protocol) {.raises: [Exception, Defect].} =
       debug "Bootstrap node could not be added", uri = toURI(record)
 
 proc start*(d: Protocol) {.raises: [Exception, Defect].} =
-  d.lookupLoop = lookupLoop(d)
+  d.queryLoop = queryLoop(d)
   d.revalidateLoop = revalidateLoop(d)
 
 proc close*(d: Protocol) {.raises: [Exception, Defect].} =
@@ -854,8 +901,8 @@ proc close*(d: Protocol) {.raises: [Exception, Defect].} =
   debug "Closing discovery node", node = d.localNode
   if not d.revalidateLoop.isNil:
     d.revalidateLoop.cancel()
-  if not d.lookupLoop.isNil:
-    d.lookupLoop.cancel()
+  if not d.queryLoop.isNil:
+    d.queryLoop.cancel()
 
   d.transp.close()
 
@@ -865,7 +912,7 @@ proc closeWait*(d: Protocol) {.async, raises: [Exception, Defect].} =
   debug "Closing discovery node", node = d.localNode
   if not d.revalidateLoop.isNil:
     await d.revalidateLoop.cancelAndWait()
-  if not d.lookupLoop.isNil:
-    await d.lookupLoop.cancelAndWait()
+  if not d.queryLoop.isNil:
+    await d.queryLoop.cancelAndWait()
 
   await d.transp.closeWait()