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Routing: full-message suppression for partial-message peers (step 6)#467

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Routing: full-message suppression for partial-message peers (step 6)#467
lucassaldanha wants to merge 10 commits into
libp2p:developfrom
lucassaldanha:partial-messages-step-6

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Summary

  • Adds peerRequestsPartialForMessage(peer, topics) helper in GossipRouter that returns true when: partial messages are locally enabled, the peer completed the ControlExtensions handshake (peerSupportsPartialMessages), and the peer sent SubOpts.requestsPartial=true for any of the message's topics.
  • broadcastInbound: filters out peers matching the above before queuing the full message, so inbound messages are not forwarded to partial-requesting peers.
  • broadcastOutbound: same filter on the selected peer list, so locally published messages are not sent to partial-requesting peers.
  • Extends ManyRoutersTest with enabledGossipExtensions / partialMessagesHandler params to support the inbound suppression test.
  • New test class PartialMessagesFullMsgSuppressionTest with 6 tests covering both broadcast paths and the guard cases (extension disabled, no topic flag, supports-but-didn't-request).

Part of the partial-messages tracking issue #435. Spec reference: §5.1 of docs/partial-messages.md.

Test plan

  • PartialMessagesFullMsgSuppressionTest — 6 unit tests (both broadcast directions, all guard conditions)
  • Full gossip test suite green (./gradlew :libp2p:test --tests "io.libp2p.pubsub.gossip.*")
  • Step 7 (IDONTWANT suppression) and Step 9 (IHAVE replacement) are not yet implemented; this PR only covers the direct full-message send paths.

Captures the MVP scope, jvm-libp2p/client responsibility boundary,
client-facing API, routing semantics, per-group lifecycle and DoS
caps, and the implementation plan for the gossipsub partial-messages
extension. Lands ahead of implementation so sub-issues of libp2p#435 can
reference a stable design anchor.
Step 1 of the partial-messages extension: plumb SubOpts.requestsPartial /
SubOpts.supportsSendingPartial through subscribe announcements in both
directions, and track the per-peer-per-topic receive state.

- AbstractRouter parses the flags with the spec-mandated coercion
  (supportsSendingPartial := requestsPartial || supportsSendingPartial)
  and zeroes them on subscribe=false.
- New enqueueSubscribe hook unifies outbound subscribe enqueueing so
  GossipRouter can attach per-topic flags in a single override.
- GossipRouter exposes setTopicPartialFlags(topic, ...) to configure
  flags advertised for a locally-subscribed topic, and stores inbound
  flags in a new PartialSubscriptionState (plain HashMap on the pubsub
  event loop). State is cleaned on peer disconnect, topic unsubscribe,
  and per-peer unsubscribe.
- Outbound unsubscribe MUST NOT carry partial flags; enforced at the
  SubscriptionPart wire-build site.

No routing behaviour changes yet. See docs/partial-messages.md §4.5,
§5, §6.1 for context.
…t addSubscription overload

- `PartialSubscriptionWireTest`: route reads of `partialSubscriptionState`
  through `submitOnEventThread { ... }.join()`. The state container is
  not thread-safe; direct access from the JUnit thread races the event
  loop and can surface as `ConcurrentModificationException` or stale
  reads. Two helpers (`peerFlagsOnEventLoop`, `snapshotPartialStateOnEventLoop`)
  establish the happens-before barrier.

- `RpcPartsQueue`: remove the 2-arg `addSubscription(topic, status)`
  default overload. The remaining 4-arg abstract method is the single
  source of truth; `addSubscribe` / `addUnsubscribe` remain the
  convenience entry points.
- `PartialSubFlags.coerce(requestsPartial, supportsSendingPartial)`:
  single source of truth for the spec coercion rule
  `supportsSendingPartial := requestsPartial || supportsSendingPartial`.
  Used from `GossipRouter.setTopicPartialFlags` for the outbound side.
  AbstractRouter keeps the inline expression for the receive side to
  avoid a reverse layering dependency (pubsub -> gossip); a comment
  notes the rule is applied on both sides.

- `PartialSubscriptionState.setPeerFlags`: document that passing
  `PartialSubFlags.NONE` (or any equivalent all-false flags) is
  treated as a removal. Makes the set-sometimes-deletes invariant
  explicit for readers.

- `AbstractRouter.handleMessageSubscriptions`: add Kdoc now that the
  method is `protected open`. Documents the "call super" contract
  for overrides (GossipRouter relies on this to keep peersTopics and
  partialSubscriptionState in sync) and the flag-normalisation
  precondition.
Introduces the public partial-messages API surface and the internal
state management layer required before any routing logic lands:

Public API (io.libp2p.pubsub.gossip.partialmessages):
- PartialMessagesHandler<PeerState> — onIncomingRpc + onEmitGossip;
  PartialMessagesPeerFeedback passed per-call (resolves open question
  from design doc §9)
- PublishAction<PeerState> / PublishActionsFn<PeerState>
- PartialMessagesPeerFeedback interface + FeedbackKind enum

Internal state management:
- GroupId — content-equality ByteArray wrapper for use as map key
- GroupState<PeerState> — per-(topic,groupId) container with mutable
  TTL and app-opaque peerStates
- PartialGroupStateStore<PeerState> — TTL countdown, GC on ttl≤0 or
  empty peerStates, DoS caps (255/topic, 8/topic/peer, matching
  go-libp2p defaults), onPeerDisconnected, onTopicUnsubscribed
- PartialMessagesAdapter (internal interface) /
  PartialMessagesAdapterImpl<PeerState> — erases PeerState at the
  GossipRouter boundary via a single @Suppress("UNCHECKED_CAST")
  in the builder

Wiring:
- GossipRouterBuilder: partialMessagesHandler field; build-time error
  if PARTIAL_MESSAGES extension enabled without a handler
- GossipRouter: internal var partialMessages: PartialMessagesAdapter?

No routing changes in this step.
Replaces the stub in GossipRouter.processPartialMessageExtension with
the full flow: drop RPCs missing topicID or groupID, then delegate to
PartialMessagesAdapterImpl which gets-or-creates the GroupState (with
DoS cap enforcement) and calls handler.onIncomingRpc with the live
peerStates map.
Adds the outbound path for the partial-messages extension:

- GossipRpcPartsQueue: addPartialMessage queues a PartialMessagePart;
  takeMerged caps at 1 per RPC (proto field is optional, not repeated).
- PartialMessagesAdapter: publishPartial invokes the client's
  PublishActionsFn, enforces the spec MUST (omit partialMessage when peer
  supports but did not request), updates nextPeerState atomically, and
  calls back via enqueueFn.
- GossipRouter: publishPartial looks up PeerHandler by PeerId, routes
  through GossipRpcPartsQueue (not a direct send), and flushes pending.
- Gossip facade: publishPartial submits to the event thread and returns
  CompletableFuture<Unit>.

Tests: PartialMessagesOutboundRpcTest (5 wire-level) and 6 new unit
tests in PartialMessagesAdapterImplTest.
Exercises the full stack built in steps 1-4 — SubOpts flag plumbing,
ControlExtensions handshake, inbound handler dispatch, group-state
tracking, and outbound publishPartial — over real TCP/Noise/Mplex
using a trivial ByteArray bitmap as PeerState.

Four tests:
- Unidirectional partial RPC (payload + metadata delivered to handler)
- Bidirectional round-trip between two hosts
- nextPeerState persisted and visible to subsequent decide() calls
- Spec MUST: partialMessage omitted when peer supports but did not request

Both hosts bind to port 0 to avoid conflicts with other tests.
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