feat(mix): cover traffic with constant rate and spam protection toggle

apps/chat2mix/chat2mix.nim

@@ -576,7 +576,7 @@ proc processInput(rfd: AsyncFD, rng: ref HmacDrbgContext) {.async.} =
     if kadBootstrapPeers.len > 0:
       node.wakuKademlia = WakuKademlia.new(
         node.switch,
-        ExtendedKademliaDiscoveryParams(
+        ExtendedServiceDiscoveryParams(
           bootstrapNodes: kadBootstrapPeers,
           mixPubKey: some(mixPubKey),
           advertiseMix: false,

simulations/mixnet/README.md

@@ -24,6 +24,7 @@ The simulation includes:
 | `run_chat_mix.sh`  | Chat app instance 1                        |
 | `run_chat_mix1.sh` | Chat app instance 2                        |
 | `build_setup.sh`   | Build and generate RLN credentials         |
+| `check_cover_traffic.sh` | Monitor cover traffic metrics from all nodes |
 
 ## Prerequisites
 
@@ -130,3 +131,35 @@ To exit the chat apps, enter `/exit`:
 >> /exit
 quitting...
 ```
+
+## Running Without DoS Protection
+
+To test cover traffic without RLN spam protection (avoids heavy proof generation compute), the config files include two flags:
+
+```toml
+mix-user-message-limit=2        # slots per epoch (reduce for lighter testing)
+mix-disable-spam-protection=true # skip RLN proof generation/verification
+```
+
+These are already set in `config.toml` through `config4.toml`. To re-enable RLN, set `mix-disable-spam-protection=false` (or remove the line) and ensure credentials are generated via `./build_setup.sh`.
+
+When running without DoS protection, cover traffic uses an internal epoch timer and does not require RLN credentials or `rln_tree.db`.
+
+### Monitoring Cover Traffic
+
+Use the metrics script to verify cover traffic is working:
+
+```bash
+./check_cover_traffic.sh
+```
+
+Key metrics to look for:
+- `mix_cover_emitted_total` — cover messages generated per node (should increase each epoch)
+- `mix_cover_received_total` — cover messages received back at origin after 3-hop mix path
+- `mix_slots_exhausted_total` — expected when slots per epoch are low
+
+### Note on Rate Limit and Expected Errors
+
+The default `mix-user-message-limit=2` (R=2) with path length L=3 yields a fractional cover target of `R/(1+L) = 0.5` packets per epoch. Because this is not an integer, epoch boundary jitter can cause two cover emissions in one epoch, exhausting all slots and leaving none for forwarding. This produces `SLOT_EXHAUSTED` and `SPAM_PROOF_GEN_FAILED` errors at intermediate hops — these are expected with the default config.
+
+For a clean setup, R should be a multiple of `(1+L) = 4`. Setting `mix-user-message-limit=4` gives exactly 1 cover packet per epoch with 3 slots remaining for forwarding, eliminating these errors.

simulations/mixnet/check_cover_traffic.sh

@@ -0,0 +1,18 @@
+#!/bin/bash
+# Check cover traffic metrics from all mix nodes.
+# Ports: 8008 + ports-shift (1-5) = 8009-8013
+
+echo "=== Cover Traffic Metrics ==="
+echo ""
+
+for i in 1 2 3 4 5; do
+  port=$((8008 + i))
+  echo "--- Node $i (port $port) ---"
+  metrics=$(curl -s "http://127.0.0.1:$port/metrics" 2>/dev/null)
+  if [ -z "$metrics" ]; then
+    echo "  (unreachable)"
+  else
+    echo "$metrics" | grep -E "mix_cover_|mix_slot_" | grep -v "^#" || echo "  (no cover metrics yet)"
+  fi
+  echo ""
+done

simulations/mixnet/config.toml

@@ -7,6 +7,7 @@ lightpush = true
 max-connections = 150
 peer-exchange = false
 metrics-logging = false
+metrics-server = true
 cluster-id = 2
 discv5-discovery = false
 discv5-udp-port = 9000
@@ -26,3 +27,5 @@ nat = "extip:127.0.0.1"
 ext-multiaddr = ["/ip4/127.0.0.1/tcp/60001"]
 ext-multiaddr-only = true
 ip-colocation-limit=0
+mix-user-message-limit=4
+mix-disable-spam-protection=false

simulations/mixnet/config1.toml

@@ -7,6 +7,7 @@ lightpush = true
 max-connections = 150
 peer-exchange = false
 metrics-logging = false
+metrics-server = true
 cluster-id = 2
 discv5-discovery = false
 discv5-udp-port = 9001
@@ -27,4 +28,6 @@ nat = "extip:127.0.0.1"
 ext-multiaddr = ["/ip4/127.0.0.1/tcp/60002"]
 ext-multiaddr-only = true
 ip-colocation-limit=0
+mix-user-message-limit=4
+mix-disable-spam-protection=false
 #staticnode = ["/ip4/127.0.0.1/tcp/60001/p2p/16Uiu2HAmPiEs2ozjjJF2iN2Pe2FYeMC9w4caRHKYdLdAfjgbWM6o", "/ip4/127.0.0.1/tcp/60003/p2p/16Uiu2HAmTEDHwAziWUSz6ZE23h5vxG2o4Nn7GazhMor4bVuMXTrA","/ip4/127.0.0.1/tcp/60004/p2p/16Uiu2HAmPwRKZajXtfb1Qsv45VVfRZgK3ENdfmnqzSrVm3BczF6f","/ip4/127.0.0.1/tcp/60005/p2p/16Uiu2HAmRhxmCHBYdXt1RibXrjAUNJbduAhzaTHwFCZT4qWnqZAu"]

simulations/mixnet/config2.toml

@@ -7,6 +7,7 @@ lightpush = true
 max-connections = 150
 peer-exchange = false
 metrics-logging = false
+metrics-server = true
 cluster-id = 2
 discv5-discovery = false
 discv5-udp-port = 9002
@@ -27,4 +28,6 @@ nat = "extip:127.0.0.1"
 ext-multiaddr = ["/ip4/127.0.0.1/tcp/60003"]
 ext-multiaddr-only = true
 ip-colocation-limit=0
+mix-user-message-limit=4
+mix-disable-spam-protection=false
 #staticnode = ["/ip4/127.0.0.1/tcp/60001/p2p/16Uiu2HAmPiEs2ozjjJF2iN2Pe2FYeMC9w4caRHKYdLdAfjgbWM6o", "/ip4/127.0.0.1/tcp/60002/p2p/16Uiu2HAmLtKaFaSWDohToWhWUZFLtqzYZGPFuXwKrojFVF6az5UF","/ip4/127.0.0.1/tcp/60004/p2p/16Uiu2HAmPwRKZajXtfb1Qsv45VVfRZgK3ENdfmnqzSrVm3BczF6f","/ip4/127.0.0.1/tcp/60005/p2p/16Uiu2HAmRhxmCHBYdXt1RibXrjAUNJbduAhzaTHwFCZT4qWnqZAu"]

simulations/mixnet/config3.toml

@@ -7,6 +7,7 @@ lightpush = true
 max-connections = 150
 peer-exchange = false
 metrics-logging = false
+metrics-server = true
 cluster-id = 2
 discv5-discovery = false
 discv5-udp-port = 9003
@@ -27,4 +28,6 @@ nat = "extip:127.0.0.1"
 ext-multiaddr = ["/ip4/127.0.0.1/tcp/60004"]
 ext-multiaddr-only = true
 ip-colocation-limit=0
+mix-user-message-limit=4
+mix-disable-spam-protection=false
 #staticnode = ["/ip4/127.0.0.1/tcp/60002/p2p/16Uiu2HAmLtKaFaSWDohToWhWUZFLtqzYZGPFuXwKrojFVF6az5UF", "/ip4/127.0.0.1/tcp/60003/p2p/16Uiu2HAmTEDHwAziWUSz6ZE23h5vxG2o4Nn7GazhMor4bVuMXTrA","/ip4/127.0.0.1/tcp/60001/p2p/16Uiu2HAmPiEs2ozjjJF2iN2Pe2FYeMC9w4caRHKYdLdAfjgbWM6o","/ip4/127.0.0.1/tcp/60005/p2p/16Uiu2HAmRhxmCHBYdXt1RibXrjAUNJbduAhzaTHwFCZT4qWnqZAu"]

simulations/mixnet/config4.toml

@@ -7,6 +7,7 @@ lightpush = true
 max-connections = 150
 peer-exchange = false
 metrics-logging = false
+metrics-server = true
 cluster-id = 2
 discv5-discovery = false
 discv5-udp-port = 9004
@@ -27,4 +28,6 @@ nat = "extip:127.0.0.1"
 ext-multiaddr = ["/ip4/127.0.0.1/tcp/60005"]
 ext-multiaddr-only = true
 ip-colocation-limit=0
+mix-user-message-limit=4
+mix-disable-spam-protection=false
 #staticnode = ["/ip4/127.0.0.1/tcp/60001/p2p/16Uiu2HAmPiEs2ozjjJF2iN2Pe2FYeMC9w4caRHKYdLdAfjgbWM6o", "/ip4/127.0.0.1/tcp/60003/p2p/16Uiu2HAmTEDHwAziWUSz6ZE23h5vxG2o4Nn7GazhMor4bVuMXTrA","/ip4/127.0.0.1/tcp/60004/p2p/16Uiu2HAmPwRKZajXtfb1Qsv45VVfRZgK3ENdfmnqzSrVm3BczF6f","/ip4/127.0.0.1/tcp/60002/p2p/16Uiu2HAmLtKaFaSWDohToWhWUZFLtqzYZGPFuXwKrojFVF6az5UF"]

simulations/mixnet/setup_credentials.nim

@@ -20,8 +20,8 @@ import
 
 const
   KeystorePassword = "mix-rln-password" # Must match protocol.nim
-  DefaultUserMessageLimit = 100'u64 # Network-wide default rate limit
-  SpammerUserMessageLimit = 3'u64 # Lower limit for spammer testing
+  DefaultUserMessageLimit = 4'u64 # R=4 slots per 10s epoch
+  SpammerUserMessageLimit = 3'u64 # Higher limit for spammer testing
 
   # Peer IDs derived from nodekeys in config files
   # config.toml:   nodekey = "f98e3fba96c32e8d1967d460f1b79457380e1a895f7971cecc8528abe733781a"

tests/test_wakunode.nim

@@ -1,7 +1,7 @@
 {.used.}
 
 import
-  std/[sequtils, strutils, net],
+  std/[options, sequtils, strutils, net],
   stew/byteutils,
   testutils/unittests,
   chronicles,

tests/waku_relay/test_wakunode_relay.nim

@@ -1,7 +1,7 @@
 {.used.}
 
 import
-  std/[os, strutils, sequtils, sysrand, math],
+  std/[options, os, strutils, sequtils, sysrand, math],
   stew/byteutils,
   testutils/unittests,
   chronos,

tests/waku_store/test_wakunode_store.nim

@@ -1,7 +1,7 @@
 {.used.}
 
 import
-  std/sequtils,
+  std/[options, sequtils],
   testutils/unittests,
   chronicles,
   chronos,

tests/waku_store_legacy/test_wakunode_store.nim

@@ -1,7 +1,7 @@
 {.used.}
 
 import
-  std/net,
+  std/[net, options],
   testutils/unittests,
   chronos,
   libp2p/crypto/crypto,

tools/confutils/cli_args.nim

@@ -643,6 +643,17 @@ with the drawback of consuming some more bandwidth.""",
       name: "mixnode"
     .}: seq[MixNodePubInfo]
 
+    mixUserMessageLimit* {.
+      desc: "Maximum messages per RLN epoch for mix cover traffic. If not set, uses plugin default.",
+      name: "mix-user-message-limit"
+    .}: Option[int]
+
+    mixDisableSpamProtection* {.
+      desc: "Disable RLN spam protection for mix protocol (for testing only).",
+      defaultValue: false,
+      name: "mix-disable-spam-protection"
+    .}: bool
+
     # Kademlia Discovery config
     enableKadDiscovery* {.
       desc:
@@ -1073,6 +1084,9 @@ proc toWakuConf*(n: WakuNodeConf): ConfResult[WakuConf] =
   b.withMix(n.mix)
   if n.mixkey.isSome():
     b.mixConf.withMixKey(n.mixkey.get())
+  if n.mixUserMessageLimit.isSome():
+    b.mixConf.withUserMessageLimit(n.mixUserMessageLimit.get())
+  b.mixConf.withDisableSpamProtection(n.mixDisableSpamProtection)
 
   b.filterServiceConf.withEnabled(n.filter)
   b.filterServiceConf.withSubscriptionTimeout(n.filterSubscriptionTimeout)

waku.nimble

@@ -159,9 +159,13 @@ task chat2mix, "Build example Waku chat mix usage":
   #buildBinary name, "examples/", "-d:chronicles_log_level=WARN"
 
   let name = "chat2mix"
+  # Sink uses textlines (stdout) instead of textlines[file]: the latter
+  # currently triggers a chronicles compile-time macro-eval bug with Nim 2.2.4.
+  # Callers can redirect stdout to a file (the existing run_chat_mix*.sh
+  # scripts already do this).
   buildBinary name,
     "apps/chat2mix/",
-    "-d:chronicles_sinks=textlines[file] -d:chronicles_log_level='TRACE' "
+    "-d:chronicles_sinks=textlines -d:chronicles_log_level='TRACE' "
   #  -d:ssl - cause unlisted exception error in libp2p/utility...
 
 task chat2bridge, "Build chat2bridge":

waku/common/option_shims.nim

@@ -0,0 +1,28 @@
+# Compatibility shims for std/options
+# The results library removed valueOr/withValue support for Option[T].
+# These templates restore that functionality.
+
+{.push raises: [].}
+
+import std/options
+
+template valueOr*[T](self: Option[T], def: untyped): T =
+  let tmp = self
+  if tmp.isSome():
+    tmp.get()
+  else:
+    def
+
+template withValue*[T](self: Option[T], value, body: untyped): untyped =
+  let tmp = self
+  if tmp.isSome():
+    let value {.inject.} = tmp.get()
+    body
+
+template withValue*[T](self: Option[T], value, body, elseBody: untyped): untyped =
+  let tmp = self
+  if tmp.isSome():
+    let value {.inject.} = tmp.get()
+    body
+  else:
+    elseBody

waku/common/rate_limit/request_limiter.nim

@@ -24,6 +24,7 @@ import
 
 import std/times except TimeInterval, Duration, seconds, minutes
 
+import ../option_shims
 import ./[single_token_limiter, service_metrics, timed_map]
 
 export token_bucket, setting, service_metrics

waku/discovery/waku_discv5.nim

@@ -10,7 +10,7 @@ import
   eth/keys as eth_keys,
   eth/p2p/discoveryv5/node,
   eth/p2p/discoveryv5/protocol
-import ../node/peer_manager/peer_manager, ../waku_core, ../waku_enr
+import ../common/option_shims, ../node/peer_manager/peer_manager, ../waku_core, ../waku_enr
 
 export protocol, waku_enr
 

waku/discovery/waku_kademlia.nim

@@ -9,8 +9,8 @@ import
   libp2p/[peerid, multiaddress, switch],
   libp2p/extended_peer_record,
   libp2p/crypto/curve25519,
-  libp2p/protocols/[kademlia, kad_disco],
-  libp2p/protocols/kademlia_discovery/types as kad_types,
+  libp2p/protocols/[kademlia, service_discovery],
+  libp2p/protocols/service_discovery/types as kad_types,
   libp2p/protocols/mix/mix_protocol
 
 import waku/waku_core, waku/node/peer_manager
@@ -19,20 +19,20 @@ logScope:
   topics = "waku extended kademlia discovery"
 
 const
-  DefaultExtendedKademliaDiscoveryInterval* = chronos.seconds(5)
-  ExtendedKademliaDiscoveryStartupDelay* = chronos.seconds(5)
+  DefaultExtendedServiceDiscoveryInterval* = chronos.seconds(5)
+  ExtendedServiceDiscoveryStartupDelay* = chronos.seconds(5)
 
 type
   MixNodePoolSizeProvider* = proc(): int {.gcsafe, raises: [].}
   NodeStartedProvider* = proc(): bool {.gcsafe, raises: [].}
 
-  ExtendedKademliaDiscoveryParams* = object
+  ExtendedServiceDiscoveryParams* = object
     bootstrapNodes*: seq[(PeerId, seq[MultiAddress])]
     mixPubKey*: Option[Curve25519Key]
     advertiseMix*: bool = false
 
   WakuKademlia* = ref object
-    protocol*: KademliaDiscovery
+    protocol*: ServiceDiscovery
     peerManager: PeerManager
     discoveryLoop: Future[void]
     running*: bool
@@ -42,21 +42,21 @@ type
 proc new*(
     T: type WakuKademlia,
     switch: Switch,
-    params: ExtendedKademliaDiscoveryParams,
+    params: ExtendedServiceDiscoveryParams,
     peerManager: PeerManager,
     getMixNodePoolSize: MixNodePoolSizeProvider = nil,
     isNodeStarted: NodeStartedProvider = nil,
 ): Result[T, string] =
   if params.bootstrapNodes.len == 0:
     info "creating kademlia discovery as seed node (no bootstrap nodes)"
 
-  let kademlia = KademliaDiscovery.new(
+  let kademlia = ServiceDiscovery.new(
     switch,
     bootstrapNodes = params.bootstrapNodes,
     config = KadDHTConfig.new(
       validator = kad_types.ExtEntryValidator(), selector = kad_types.ExtEntrySelector()
     ),
-    codec = ExtendedKademliaDiscoveryCodec,
+    codec = ExtendedServiceDiscoveryCodec,
   )
 
   try:
@@ -197,7 +197,7 @@ proc runDiscoveryLoop(
     while wk.running:
       # Wait for node to be started
       if not wk.isNodeStarted.isNil() and not wk.isNodeStarted():
-        await sleepAsync(ExtendedKademliaDiscoveryStartupDelay)
+        await sleepAsync(ExtendedServiceDiscoveryStartupDelay)
         continue
 
       var records: seq[ExtendedPeerRecord]
@@ -247,7 +247,7 @@ proc runDiscoveryLoop(
 
 proc start*(
     wk: WakuKademlia,
-    interval: Duration = DefaultExtendedKademliaDiscoveryInterval,
+    interval: Duration = DefaultExtendedServiceDiscoveryInterval,
     minMixPeers: int = 0,
 ): Future[Result[void, string]] {.async: (raises: []).} =
   if wk.running: