rename handshakeInProgress to keyexchangeInProgress

Handshake is also a name of a message, which makes previous
name less clear.

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

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

@@ -26,7 +26,7 @@ type
     bindAddress*: Address ## UDP binding address
     transp: DatagramTransport
     pendingRequests: Table[AESGCMNonce, PendingRequest]
-    handshakeInProgress: HashSet[NodeId]
+    keyexchangeInProgress: HashSet[NodeId]
     pendingRequestsByNode: Table[NodeId, seq[seq[byte]]]
     codec*: Codec
     rng: ref HmacDrbgContext
@@ -84,17 +84,21 @@ proc sendMessage*(t: Transport, toNode: Node, message: seq[byte]) =
     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
+    # we don't have an encryption key for this target, so we should initiate keyexchange
+    if not (toNode.id in t.keyexchangeInProgress):
+      trace "Send message: send random to trigger Whoareyou", myport = t.bindAddress.port , dstId = toNode
       t.registerRequest(toNode, message, nonce)
       t.send(toNode, data)
-      t.handshakeInProgress.incl(toNode.id)
+      t.keyexchangeInProgress.incl(toNode.id)
+      trace "keyexchangeInProgress added", myport = t.bindAddress.port , dstId = toNode
       sleepAsync(responseTimeout).addCallback() do(data: pointer):
-        t.handshakeInProgress.excl(toNode.id)
+        t.keyexchangeInProgress.excl(toNode.id)
+        trace "keyexchangeInProgress removed (timeout)", myport = t.bindAddress.port , dstId = toNode
     else:
-      # delay sending this message until handshake, have to reencode once keys are clear
+      # delay sending this message until whoareyou is received and handshake is sent
+      # 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",
+      trace "Send message: Node with this id already has ongoing keyexchage, delaying packet",
             myport = t.bindAddress.port , dstId = toNode, qlen=t.pendingRequestsByNode[toNode.id].len
 
 proc sendWhoareyou(t: Transport, toId: NodeId, a: Address,
@@ -149,6 +153,12 @@ proc receive*(t: Transport, a: Address, packet: openArray[byte]) =
       else:
         trace "Not decryptable message packet received", myport = t.bindAddress.port,
           srcId = packet.srcId, address = a
+        # If we already have a keyexchange in progress, we have a case of simultaneous cross-connect.
+        # We could try to decide here which should go on, but since we are on top of UDP, a more robust
+        # choice is to answer here and resolve conflicts in the next stage (reception of Whoareyou), or
+        # even later (reception of Handshake).
+        if packet.srcId in t.keyexchangeInProgress:
+          trace "cross-connect detected, still sending Whoareyou"
         t.sendWhoareyou(packet.srcId, a, packet.requestNonce,
           t.client.getNode(packet.srcId))
 
@@ -170,10 +180,11 @@ proc receive*(t: Transport, a: Address, packet: openArray[byte]) =
                     toNode.pubkey
                   ).expect("Valid handshake packet to encode")
 
-        trace "Send handshake message packet", dstId = toNode.id, address
+        trace "Send handshake message packet", myport = t.bindAddress.port, dstId = toNode.id, address
         t.send(toNode, data)
-        # handshake ready, we can send queued packets
-        t.handshakeInProgress.excl(toNode.id)
+        # keyexchange ready, we can send queued packets
+        t.keyexchangeInProgress.excl(toNode.id)
+        trace "keyexchangeInProgress removed (finished)", myport = t.bindAddress.port, dstId = toNode.id, address
         discard t.sendPending(toNode)
 
       else:
@@ -197,7 +208,7 @@ proc receive*(t: Transport, a: Address, packet: openArray[byte]) =
           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)
+          t.keyexchangeInProgress.excl(node.id)
           discard t.sendPending(node)
   else:
     trace "Packet decoding error", myport = t.bindAddress.port, error = decoded.error, address = a