feat(discv4): migrate DiscV4 UDP transport from Vert.x to Netty

[usmansaleem]

PR description

This PR ports the DiscV4 peer discovery UDP layer from Vert.x to Netty,
replacing VertxPeerDiscoveryAgent and VertxTimerUtil with a clean,
Vert.x-free implementation. It is a focused extraction from #10624 so
that the foundational transport change can be reviewed and merged
independently.

What changes

New files

• V4Transport — interface abstracting UDP send/receive from the agent
• transport/NettyV4Transport — Netty NIO UDP channel implementation (IPv4)
• NettyPeerDiscoveryAgent — concrete agent wiring ScheduledExecutorService
  threads for timers and crypto
• internal/ScheduledExecutorTimerUtil — replaces VertxTimerUtil
• internal/ScheduledExecutorAsyncExecutor — replaces the Vert.x worker pool

Deleted files

• VertxPeerDiscoveryAgent
• internal/VertxTimerUtil

Modified

• PeerDiscoveryAgentV4 — ported to V4Transport interface; added
  dispatchExecutor ordering guarantee (timer callbacks and inbound packet
  dispatch share a single thread, preserving the Vert.x event-loop ordering);
  a dedicated single-thread decode executor was added afterward (see "Fixes
  from review")
• PeerDiscoveryAgentFactoryV4 — wires NettyPeerDiscoveryAgent
• DefaultPeerDiscoveryAgentFactory — updated to match
• PeerDiscoveryController — adds a dispatchExecutor used to run outbound
  packet-creation callbacks on the same thread as inbound packet handling
  (see "Fixes from review")
• ethereum/p2p/build.gradle — adds netty-transport and netty-handler
• NodeRecordManager — fixes two ENR equality bugs (compressed pubkey
  comparison; fork-id wrapper list shape) that caused seq to increment on
  every restart even when nothing changed
• PingPacketData.getTo() — returns Optional<Endpoint> for EIP-8
  compliance (malformed to field must not prevent packet processing)
• Test classes updated throughout for the above API changes

Fixes from review

Since the initial migration, this PR picked up several concurrency/
correctness fixes from Copilot's automated review, a full manual code
review, and a live mainnet dry-run used to validate startup/shutdown
behavior:

• Outbound/inbound packet handling race closed: PeerDiscoveryController .createPacket()'s post-signing continuation now runs on the same
  single dispatch executor used for inbound packet matching, instead of
  whichever crypto-pool thread finished signing — this was a real race on
  PeerInteractionState's response-matching filter (a fast-arriving PONG
  could be matched before the filter update was visible).
• Inbound packet decode ordering restored: PeerDiscoveryAgentV4 now
  uses a dedicated single-thread decode executor
  (createDecodeExecutor()), separate from the 2-thread signing pool,
  restoring the packet arrival-order guarantee the removed Vert.x
  implementation provided via an ordered executeBlocking.
• Shutdown race closed: NettyPeerDiscoveryAgent.stop() now runs
  PeerDiscoveryController.stop() on timerScheduler itself rather than
  whatever Netty thread completes transport.stop(), closing a race with
  in-flight timer/dispatch work during shutdown.
• PING expiry validation restored: PingPacketDataRlpReader was
  rewritten to bypass PingPacketDataFactory (to tolerate a malformed to
  field per EIP-8), which also silently dropped the factory's expiry check.
  Expiry is now validated directly in the reader; malformed-to tolerance
  is unaffected.
• NettyV4Transport hardening:
  • UDP bind failures are wrapped in PeerDiscoveryServiceException with a
    descriptive host:port message again, matching the old Vert.x behavior.
  • The DEBUG/ERROR severity split in the inbound channel exception handler
    is restored (previously collapsed to unconditional DEBUG).
  • The event-loop group (and NettyPeerDiscoveryAgent's timer/crypto/decode
    executors) are now created lazily in start() instead of eagerly in the
    constructor, so a node running with discovery disabled carries no idle
    discv4 threads.
  • Shutdown uses an explicit short quiet period instead of Netty's 2s
    default — confirmed via a live mainnet run that this was adding ~2s to
    every node shutdown; it now completes in ~10-15ms.
• Endpoint EIP-8 decoding hardened: maybeDecodeStandalone()'s catch
  was broadened from IllegalPortException to any RuntimeException, so
  any malformed to field is tolerated, not just an out-of-range port.
  decodeStandalone() was also fixed to skip to the end of the malformed
  RLP list before leaving it, keeping the cursor in sync with the enclosing
  list regardless of where decoding failed.
• Executor edge cases: ScheduledExecutorAsyncExecutor now completes
  its future exceptionally instead of throwing synchronously when the
  underlying executor rejects a task (e.g. during shutdown);
  ScheduledExecutorTimerUtil now catches exceptions from periodic
  handlers so one failure doesn't permanently cancel the scheduled task.
• Test hardening: MockPeerDiscoveryAgent's mock transport no longer
  risks matching a stopped/replaced agent at a reused address, and its
  constructor-chain/mutable-array back-reference hack was replaced with a
  post-construction setter mirroring the production setInboundHandler
  pattern.

Limitations / known constraints

• IPv4-only transport: NettyV4Transport is pinned to
  SocketProtocolFamily.INET. Peers that advertise an IPv6-only address
  are silently skipped (TRACE log). Dual-stack IPv4+IPv6 peers work
  normally via their IPv4 address. This is an intentional temporary
  restriction; the follow-on feat(p2p): DiscV4 + DiscV5 on shared UDP socket with --discovery-mode selector #10624 introduces a shared dual-stack channel
  that lifts this limitation.
• DNS discovery still uses Vert.x: DNSDaemon / DNSResolver remain
  Vert.x-based. The ethereum/p2p module retains its vertx-core
  dependency for that subsystem.
• vertx_eventloop_pending_tasks metric dropped: That gauge was
  Vert.x-specific and has no direct equivalent. All other discovery metrics
  (besu_network_discovery_*) come from PeerDiscoveryController and are
  unaffected.

Fixed Issue(s)

Thanks for sending a pull request! Have you done the following?

• Checked out our contribution guidelines?
• Considered documentation and added the doc-change-required label to this PR if updates are required.
• Considered the changelog and included an update if required.
• For database changes (e.g. KeyValueSegmentIdentifier) considered compatibility and performed forwards and backwards compatibility tests

Locally, you can run these tests to catch failures early:

• spotless: ./gradlew spotlessApply
• unit tests: ./gradlew build
• acceptance tests: ./gradlew acceptanceTest
• integration tests: ./gradlew integrationTest
• reference tests: ./gradlew ethereum:referenceTests:referenceTests
• hive tests: Engine or other RPCs modified?

[Copilot]

Pull request overview

This PR migrates the DiscV4 UDP discovery transport from a Vert.x-based implementation to a Netty-based transport with a new V4Transport abstraction, aiming to preserve Vert.x event-loop ordering semantics while removing Vert.x from the DiscV4 UDP layer. It also hardens ENR reuse logic in NodeRecordManager and updates DiscV4 PING handling for EIP-8 tolerance around malformed to fields, with broad test updates.

Changes:

• Introduces V4Transport and a Netty UDP transport (NettyV4Transport), wiring a new NettyPeerDiscoveryAgent via the factory paths.
• Refactors PeerDiscoveryAgentV4 to use the transport abstraction and a single-thread dispatch executor for ordered controller mutations.
• Fixes ENR “reuse-if-unchanged” equality checks (compressed pubkey + fork-id wrapper shape) and updates PING packet to handling to be optional for EIP-8 compliance.

Reviewed changes

Copilot reviewed 37 out of 37 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
ethereum/p2p/src/test/java/org/hyperledger/besu/ethereum/p2p/network/DefaultP2PNetworkTestBuilder.java	Removes Vert.x wiring from discovery factory usage in tests.
ethereum/p2p/src/test/java/org/hyperledger/besu/ethereum/p2p/discovery/discv4/transport/NettyV4TransportTest.java	Adds transport-level UDP bind/send/stop tests for Netty transport.
ethereum/p2p/src/test/java/org/hyperledger/besu/ethereum/p2p/discovery/discv4/PeerDiscoveryBootstrappingTest.java	Updates assertions for PingPacketData.getTo() becoming optional.
ethereum/p2p/src/test/java/org/hyperledger/besu/ethereum/p2p/discovery/discv4/PeerDiscoveryAgentV4Test.java	Updates ENR reuse assertions and packet serializer API change (Bytes.size()).
ethereum/p2p/src/test/java/org/hyperledger/besu/ethereum/p2p/discovery/discv4/NettyPeerDiscoveryAgentTest.java	Adds focused tests for new Netty agent send/error-stop gating behavior.
ethereum/p2p/src/test/java/org/hyperledger/besu/ethereum/p2p/discovery/discv4/internal/ScheduledExecutorTimerUtilTest.java	Adds tests for JDK scheduled-executor-backed timer util.
ethereum/p2p/src/test/java/org/hyperledger/besu/ethereum/p2p/discovery/discv4/internal/PeerDiscoveryControllerTest.java	Updates mocks/matchers for optional PING to.
ethereum/p2p/src/test/java/org/hyperledger/besu/ethereum/p2p/discovery/discv4/internal/packet/ping/PingPacketDataRlpWriterTest.java	Updates construction for optional to.
ethereum/p2p/src/test/java/org/hyperledger/besu/ethereum/p2p/discovery/discv4/internal/packet/ping/PingPacketDataRlpReaderTest.java	Updates reader construction and assertions for optional to.
ethereum/p2p/src/test/java/org/hyperledger/besu/ethereum/p2p/discovery/discv4/internal/packet/ping/PingPacketDataFactoryTest.java	Updates factory expectations for optional to.
ethereum/p2p/src/test/java/org/hyperledger/besu/ethereum/p2p/discovery/discv4/internal/packet/PacketSerializerTest.java	Updates serializer return type from Vert.x Buffer to Bytes.
ethereum/p2p/src/test/java/org/hyperledger/besu/ethereum/p2p/discovery/discv4/internal/packet/PacketDeserializerTest.java	Updates deserializer input type from Vert.x Buffer to Bytes.
ethereum/p2p/src/test/java/org/hyperledger/besu/ethereum/p2p/discovery/discv4/internal/MockPeerDiscoveryAgent.java	Refactors mock agent to route through V4Transport and new dispatch executor model.
ethereum/p2p/src/main/java/org/hyperledger/besu/ethereum/p2p/discovery/PeerDiscoveryAgent.java	Adds prepareHandlers() hook for pre-bind handler registration.
ethereum/p2p/src/main/java/org/hyperledger/besu/ethereum/p2p/discovery/NodeRecordManager.java	Fixes ENR reuse equality checks (compressed pubkey + wrapped fork-id field).
ethereum/p2p/src/main/java/org/hyperledger/besu/ethereum/p2p/discovery/discv4/VertxPeerDiscoveryAgent.java	Removes Vert.x-based DiscV4 UDP implementation (deleted).
ethereum/p2p/src/main/java/org/hyperledger/besu/ethereum/p2p/discovery/discv4/V4Transport.java	Introduces transport abstraction interface for DiscV4 UDP send/receive.
ethereum/p2p/src/main/java/org/hyperledger/besu/ethereum/p2p/discovery/discv4/transport/NettyV4Transport.java	Adds Netty NIO UDP channel transport implementation (IPv4-only).
ethereum/p2p/src/main/java/org/hyperledger/besu/ethereum/p2p/discovery/discv4/PeerDiscoveryAgentV4.java	Ports agent to V4Transport, adds ordered dispatch executor and raw inbound decode path.
ethereum/p2p/src/main/java/org/hyperledger/besu/ethereum/p2p/discovery/discv4/PeerDiscoveryAgentFactoryV4.java	Switches factory wiring from Vert.x agent to Netty agent + Netty transport.
ethereum/p2p/src/main/java/org/hyperledger/besu/ethereum/p2p/discovery/discv4/NettyPeerDiscoveryAgent.java	Adds Netty-backed DiscV4 agent with scheduled-executor timer + worker pool.
ethereum/p2p/src/main/java/org/hyperledger/besu/ethereum/p2p/discovery/discv4/internal/VertxTimerUtil.java	Removes Vert.x timer util (deleted).
ethereum/p2p/src/main/java/org/hyperledger/besu/ethereum/p2p/discovery/discv4/internal/ScheduledExecutorTimerUtil.java	Adds scheduled-executor-based timer util implementation.
ethereum/p2p/src/main/java/org/hyperledger/besu/ethereum/p2p/discovery/discv4/internal/ScheduledExecutorAsyncExecutor.java	Adds executor-service-based async worker wrapper for controller packet creation.
ethereum/p2p/src/main/java/org/hyperledger/besu/ethereum/p2p/discovery/discv4/internal/packet/ping/PingPacketDataRlpWriter.java	Updates writer to encode optional to (currently assumes present for outbound).
ethereum/p2p/src/main/java/org/hyperledger/besu/ethereum/p2p/discovery/discv4/internal/packet/ping/PingPacketDataRlpReader.java	Updates reader to produce PingPacketData with optional to for malformed tolerance.
ethereum/p2p/src/main/java/org/hyperledger/besu/ethereum/p2p/discovery/discv4/internal/packet/ping/PingPacketDataFactory.java	Updates factory to wrap to in Optional.
ethereum/p2p/src/main/java/org/hyperledger/besu/ethereum/p2p/discovery/discv4/internal/packet/ping/PingPacketData.java	Makes to optional and updates string representation accordingly.
ethereum/p2p/src/main/java/org/hyperledger/besu/ethereum/p2p/discovery/discv4/internal/packet/PacketSerializer.java	Switches serializer output from Vert.x Buffer to Bytes.
ethereum/p2p/src/main/java/org/hyperledger/besu/ethereum/p2p/discovery/discv4/internal/packet/PacketDeserializer.java	Switches deserializer input from Vert.x Buffer to Bytes.
ethereum/p2p/src/main/java/org/hyperledger/besu/ethereum/p2p/discovery/discv4/Endpoint.java	Improves standalone endpoint decode list-leave behavior on decode errors.
ethereum/p2p/src/main/java/org/hyperledger/besu/ethereum/p2p/discovery/DefaultPeerDiscoveryAgentFactory.java	Removes Vert.x from default factory builder/wiring.
ethereum/p2p/build.gradle	Adds Netty handler/transport dependencies for new UDP transport/agent.
ethereum/eth/src/test/java/org/hyperledger/besu/ethereum/eth/transactions/TestNode.java	Removes Vert.x dependency from discovery factory usage in tests.
ethereum/api/src/test/java/org/hyperledger/besu/ethereum/api/jsonrpc/JsonRpcHttpServiceRpcApisTest.java	Removes Vert.x dependency from discovery factory usage in tests.
app/src/test/java/org/hyperledger/besu/RunnerBuilderTest.java	Updates test setup for ENR reuse behavior by configuring fork blocks.
app/src/main/java/org/hyperledger/besu/RunnerBuilder.java	Removes Vert.x dependency from discovery agent factory wiring.

[Copilot]

Pull request overview

Copilot reviewed 41 out of 41 changed files in this pull request and generated 3 comments.

[Copilot]

Pull request overview

Copilot reviewed 41 out of 41 changed files in this pull request and generated no new comments.