Add client mode in findNode

codexdht/private/eth/p2p/discoveryv5/protocol.nim

@@ -180,6 +180,7 @@ type
     talkProtocols*: Table[seq[byte], TalkProtocol] # TODO: Table is a bit of
     rng*: ref HmacDrbgContext
     providers: ProvidersManager
+    clientMode*: bool
 
   TalkProtocolHandler* = proc(p: TalkProtocol, request: seq[byte], fromId: NodeId, fromUdpAddress: Address): seq[byte]
     {.gcsafe, raises: [Defect].}
@@ -340,10 +341,13 @@ proc handleFindNode(d: Protocol, fromId: NodeId, fromAddr: Address,
   if fn.distances.len == 0:
     d.sendNodes(fromId, fromAddr, reqId, [])
   elif fn.distances.contains(0):
-    # A request for our own record.
-    # It would be a weird request if there are more distances next to 0
-    # requested, so in this case lets just pass only our own. TODO: OK?
-    d.sendNodes(fromId, fromAddr, reqId, [d.localNode])
+    if d.clientMode:
+      d.sendNodes(fromId, fromAddr, reqId, [])
+    else:
+      # A request for our own record.
+      # It would be a weird request if there are more distances next to 0
+      # requested, so in this case lets just pass only our own. TODO: OK?
+      d.sendNodes(fromId, fromAddr, reqId, [d.localNode])
   else:
     # TODO: Still deduplicate also?
     if fn.distances.all(proc (x: uint16): bool = return x <= 256):
@@ -731,7 +735,7 @@ proc addProvider*(
 
   var res = await d.lookup(cId)
   # TODO: lookup is specified as not returning local, even if that is the closest. Is this OK?
-  if res.len == 0:
+  if res.len == 0 and not d.clientMode:
       res.add(d.localNode)
   for toNode in res:
     if toNode != d.localNode:

tests/discv5/test_discoveryv5.nim

@@ -777,3 +777,36 @@ suite "Discovery v5 Tests":
 
     await node1.closeWait()
     await node2.closeWait()
+
+  test "Client mode: findNode(distance=0) returns empty":
+    # In client mode, the node should not advertise itself when asked for its
+    # own record (distance=0), so it does not appear in other nodes' routing tables.
+    let
+      clientNode = initDiscoveryNode(rng, PrivateKey.example(rng), localAddress(20310))
+      serverNode = initDiscoveryNode(rng, PrivateKey.example(rng), localAddress(20311))
+
+    clientNode.clientMode = true
+
+    let response = await discv5_protocol.findNode(serverNode, clientNode.localNode, @[0'u16])
+
+    check:
+      response.isOk()
+      response[].len == 0
+
+    await clientNode.closeWait()
+    await serverNode.closeWait()
+
+  test "Server mode: findNode(distance=0) returns own record":
+    let
+      node1 = initDiscoveryNode(rng, PrivateKey.example(rng), localAddress(20312))
+      node2 = initDiscoveryNode(rng, PrivateKey.example(rng), localAddress(20313))
+
+    let response = await discv5_protocol.findNode(node1, node2.localNode, @[0'u16])
+
+    check:
+      response.isOk()
+      response[].len == 1
+      response[][0].id == node2.localNode.id
+
+    await node1.closeWait()
+    await node2.closeWait()