fix(gossipsub): cap prune backoff and process all prune entries (#3682)

Clamp the backoff accepted from a peer in a PRUNE message to one hour,
matching rust-libp2p, and skip PRUNE entries for topics we are not
meshed in instead of dropping the rest of the control message, matching
go-libp2p and rust-libp2p.

🤖 Generated with AI assistance

Co-authored-by: lodekeeper <lodekeeper@users.noreply.github.com>

Author: lodekeeper

packages/gossipsub/src/constants.ts

@@ -198,6 +198,12 @@ export const GossipsubPrunePeers = 16
  */
 export const GossipsubPruneBackoff = minute
 
+/**
+ * GossipsubMaxPruneBackoff is the maximum backoff time we accept from a peer in a PRUNE message.
+ * Larger values are clamped to this.
+ */
+export const GossipsubMaxPruneBackoff = 60 * minute
+
 /**
  * Backoff to use when unsubscribing from a topic. Should not resubscribe to this topic before it expired.
  */

packages/gossipsub/src/gossipsub.ts

@@ -1619,7 +1619,7 @@ export class GossipSub extends TypedEventEmitter<GossipSubEvents> implements Typ
 
       const peersInMesh = this.mesh.get(topicID)
       if (peersInMesh == null) {
-        return
+        continue
       }
 
       this.log('PRUNE: Remove mesh link to %s in %s', id, topicID)
@@ -1631,7 +1631,7 @@ export class GossipSub extends TypedEventEmitter<GossipSubEvents> implements Typ
 
       // is there a backoff specified by the peer? if so obey it
       if (typeof backoff === 'number' && backoff > 0) {
-        this.doAddBackoff(id, topicID, backoff * 1000)
+        this.doAddBackoff(id, topicID, Math.min(backoff * 1000, constants.GossipsubMaxPruneBackoff))
       } else {
         this.addBackoff(id, topicID)
       }

packages/gossipsub/test/prune.spec.ts

@@ -0,0 +1,48 @@
+import { stop } from '@libp2p/interface'
+import { expect } from 'aegir/chai'
+import { GossipsubMaxPruneBackoff } from '../src/constants.ts'
+import { createComponents } from './utils/create-pubsub.ts'
+import { createPeerId } from './utils/index.ts'
+import type { GossipSubAndComponents } from './utils/create-pubsub.ts'
+
+const TOPIC = 'prune-topic'
+
+describe('handlePrune', () => {
+  let node: GossipSubAndComponents
+  let peer: string
+
+  beforeEach(async () => {
+    node = await createComponents({ init: {} })
+    peer = (await createPeerId()).toString()
+  })
+
+  afterEach(async () => {
+    await stop(node.pubsub, ...Object.values(node.components))
+  })
+
+  it('caps the backoff accepted from a peer at GossipsubMaxPruneBackoff', async () => {
+    const gs = node.pubsub as any
+    gs.mesh.set(TOPIC, new Set([peer]))
+
+    const before = Date.now()
+    await gs.handlePrune(peer, [{ topicID: TOPIC, peers: [], backoff: Number.MAX_SAFE_INTEGER }])
+    const after = Date.now()
+
+    const expire = gs.backoff.get(TOPIC)?.get(peer)
+    expect(expire).to.be.at.least(before + GossipsubMaxPruneBackoff)
+    expect(expire).to.be.at.most(after + GossipsubMaxPruneBackoff)
+  })
+
+  it('processes remaining entries after a topic that is not in the mesh', async () => {
+    const gs = node.pubsub as any
+    gs.mesh.set(TOPIC, new Set([peer]))
+
+    await gs.handlePrune(peer, [
+      { topicID: 'not-joined-topic', peers: [] },
+      { topicID: TOPIC, peers: [] }
+    ])
+
+    expect(node.pubsub.mesh.get(TOPIC)?.has(peer)).to.equal(false)
+    expect(gs.backoff.get(TOPIC)?.has(peer)).to.equal(true)
+  })
+})