Bound Gossipsub control-plane work

[flcl42]

Summary

• cap IHAVE intake and IWANT responses, including retransmission and byte limits
• honor bounded, expiring IDONTWANT state for v1.2 peers
• track a bounded random sample of IHAVE promises for behavioral penalties

Validation

• Pubsub protocol unit tests

[Copilot]

Pull request overview

This PR introduces bounded, per-peer control-plane limits for Gossipsub to reduce abuse potential and to align behavior with protocol expectations around IHAVE/IWANT/IDONTWANT handling, including tracking and penalizing unmet IWANT “promises”.

Changes:

• Adds configurable caps for IHAVE intake, IWANT retransmission, and IWANT response byte size, plus bounded IWANT promise sampling and IDONTWANT TTL behavior.
• Introduces per-peer control state (PeerControlState) and an IwantPromiseTracker to support bounded suppression/retransmission and behavioral penalties.
• Adds unit tests covering the new control-plane limits and validations.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/libp2p/Libp2p.Protocols.Pubsub/PubSubSettings.cs	Adds new Gossipsub control-plane limit settings (IHAVE/IWANT/IDONTWANT/promise tracking).
src/libp2p/Libp2p.Protocols.Pubsub/PubsubRouter.Rpc.cs	Enforces new per-peer limits when handling IHAVE/IWANT/IDONTWANT; fulfills IWANT promises on message arrival.
src/libp2p/Libp2p.Protocols.Pubsub/PubsubRouter.cs	Wires in control settings validation, IWANT promise penalty application, and per-heartbeat reset of peer control counters.
src/libp2p/Libp2p.Protocols.Pubsub/PeerControlState.cs	New bounded per-peer state for counting envelopes/IDs, suppressing unwanted IDs, and limiting IWANT retransmissions.
src/libp2p/Libp2p.Protocols.Pubsub/IwantPromiseTracker.cs	New bounded sampler for IHAVE→IWANT promise tracking and expiry-based penalty accounting.
src/libp2p/Libp2p.Protocols.Pubsub.Tests/GossipsubControlLimitsTests.cs	Adds unit tests validating the new control limits and promise tracking behavior.

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[Copilot]

Pull request overview

Copilot reviewed 6 out of 6 changed files in this pull request and generated 3 comments.

Suppressed comments (1)

src/libp2p/Libp2p.Protocols.Pubsub/PubsubRouter.Rpc.cs:130

• IWANT promises are fulfilled for Accepted/Rejected/Ignored outcomes, but the signature-verification failure path still doesn't fulfill the promise. This can cause broken-promise penalties even though the message arrived (it just failed signature validation).

            _seenMessages.Add(messageId);
            _messageCache.Put(messageId, message);
            _iwantPromises.Fulfill(messageId);

[Copilot]

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