fix(rendezvous): peer registration limit (#1656)

libp2p/protocols/rendezvous.nim

@@ -43,7 +43,7 @@ const
   MaximumMessageLen = 1 shl 22 # 4MB
   MinimumNamespaceLen = 1
   MaximumNamespaceLen = 255
-  RegistrationLimitPerPeer = 1000
+  RegistrationLimitPerPeer* = 1000
   DiscoverLimit = 1000'u64
   SemaphoreDefaultSize = 5
 
@@ -397,9 +397,8 @@ proc sendDiscoverResponseError(
   await conn.writeLp(msg.buffer)
 
 proc countRegister(rdv: RendezVous, peerId: PeerId): int =
-  let n = Moment.now()
   for data in rdv.registered:
-    if data.peerId == peerId and data.expiration > n:
+    if data.peerId == peerId:
       result.inc()
 
 proc save(

tests/discovery/testrendezvous.nim

@@ -424,6 +424,29 @@ suite "RendezVous":
     # Returns only one record
     check (await peerRdvs[0].request(Opt.some(namespace))).len == 1
 
+  asyncTest "Peer registration is ignored if limit of 1000 registrations is reached":
+    let (rendezvousNode, peerNodes, peerRdvs, rendezvousRdv) =
+      setupRendezvousNodeWithPeerNodes(1)
+    (rendezvousNode & peerNodes).startAndDeferStop()
+
+    await connectNodes(peerNodes[0], rendezvousNode)
+
+    const namespace = "foo"
+    let peerRdv = peerRdvs[0]
+
+    # Create 999 registrations
+    await populatePeerRegistrations(
+      peerRdv, rendezvousRdv, namespace, RegistrationLimitPerPeer - 1
+    )
+
+    # 1000th registration allowed
+    await peerRdv.advertise(namespace)
+    check rendezvousRdv.registered.s.len == RegistrationLimitPerPeer
+
+    # 1001st registration ignored, limit reached
+    await peerRdv.advertise(namespace)
+    check rendezvousRdv.registered.s.len == RegistrationLimitPerPeer
+
   asyncTest "Various local error":
     let rdv = RendezVous.new(minDuration = 1.minutes, maxDuration = 72.hours)
     expect AdvertiseError:

tests/discovery/utils.nim

@@ -65,3 +65,19 @@ proc injectCookieForPeer*(
     rdv: RendezVous, peerId: PeerId, namespace: string, cookie: seq[byte]
 ) =
   discard rdv.cookiesSaved.hasKeyOrPut(peerId, {namespace: cookie}.toTable())
+
+proc populatePeerRegistrations*(
+    peerRdv: RendezVous, targetRdv: RendezVous, namespace: string, count: int
+) {.async.} =
+  # Test helper: quickly populate many registrations for a peer.
+  # We first create a single real registration, then clone that record
+  # directly into the rendezvous registry to reach the desired count fast.
+  #
+  # Notes:
+  # - Calling advertise() concurrently results in bufferstream defect.
+  # - Calling advertise() sequentially is too slow for large counts.
+  await peerRdv.advertise(namespace)
+
+  let record = targetRdv.registered.s[0]
+  for i in 0 ..< count - 1:
+    targetRdv.registered.s.add(record)