[xianshijing-lk]

Port of livekit/client-sdk-js#2114.

The bug

PeerConnectionTransport.setRemoteDescription already rejected answers carrying an older offer id:

if (sd.type == ANSWER && currentOfferId > 0 && offerId > 0 && currentOfferId > offerId) {
    return Either.Right("Old offer, ignoring. ...")
}

But a second copy of the answer for the current offer satisfies currentOfferId == offerId, so it fell straight through to peerConnection.setRemoteDescription. A proxy duplicating the signal message, or a server retry, therefore applied the same answer twice. The second apply happens with no local offer left to answer — an invalid transition — so a renegotiation that had actually succeeded came back reporting an error.

Repro

Added duplicateAnswerForTheSameOfferIsIgnored to RTCEngineMockE2ETest: complete one publisher renegotiation, then deliver a second answer carrying the same offer id. The payload differs only so the test can tell whether it reached the peer connection.

Against the unfixed code:

RTCEngineMockE2ETest > duplicateAnswerForTheSameOfferIsIgnored FAILED
  org.junit.ComparisonFailure: duplicate answer was applied to the peer connection
    expected:<remote_answer[]> but was:<remote_answer[_duplicate]>

The fix

Track two things, mirroring upstream:

• answeredOfferId — the offer whose answer was applied. Set only after a successful apply, so a retry after a genuine failure still goes through.
• answerInFlight — the offer whose answer is being applied right now. Claimed before the apply suspends, so a copy arriving mid-apply is caught too, and released in a finally however the apply ends.

The decision itself is a pure isDuplicateAnswer function, matching the JS SDK's exported helper, with the legacy unnumbered-answer path falling back to the signaling state (in STABLE there is no local offer pending).

Verification

:livekit-android-test:testReleaseUnitTest green. The new behavioural test fails before the change and passes after; IsDuplicateAnswerTest covers the eight edge cases (in-flight, already-applied, retry-after-failure, new offer, and the two unnumbered-answer paths). The pre-existing offerIdMismatchIsIgnored and offerIdMismatchButZeroIsAccepted tests still pass, so the stale-offer and legacy behaviour are unchanged.

Note

This SDK has no deferred-initial-offer (offer-with-join), so the upstream helper's hasPendingInitialOffer parameter has no analogue here and is omitted — the local offer is always set immediately after it is created.

🤖 Generated with Claude Code

[changeset-bot]

🦋 Changeset detected

Latest commit: f31dff8

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
client-sdk-android	Patch

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[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no bugs or issues to report.

[github-actions]

Diffuse output:

OLD: diffuse-source-file
NEW: livekit-android-sdk-release.aar

 AAR      │ old      │ new      │ diff     
──────────┼──────────┼──────────┼──────────
      jar │    3 MiB │    3 MiB │ +1.3 KiB 
 manifest │  1.5 KiB │  1.5 KiB │      0 B 
 lint-jar │ 12.7 KiB │ 12.7 KiB │      0 B 
    other │  2.4 KiB │  2.4 KiB │      0 B 
──────────┼──────────┼──────────┼──────────
    total │    3 MiB │    3 MiB │ +1.3 KiB 

 JAR     │ old   │ new   │ diff       
─────────┼───────┼───────┼────────────
 classes │  1707 │  1707 │  0 (+0 -0) 
 methods │ 21992 │ 21997 │ +5 (+5 -0) 
  fields │  5708 │  5711 │ +3 (+3 -0)

AAR

 size  │ diff     │ path          
───────┼──────────┼───────────────
 3 MiB │ +1.3 KiB │ ∆ classes.jar 
───────┼──────────┼───────────────
 3 MiB │ +1.3 KiB │ (total)

JAR

METHODS:

   old   │ new   │ diff       
  ───────┼───────┼────────────
   21992 │ 21997 │ +5 (+5 -0) 
  
  + io.livekit.android.room.PeerConnectionTransport access_getAnswerInFlight_p(PeerConnectionTransport) → Integer
  + io.livekit.android.room.PeerConnectionTransport access_getAnsweredOfferId_p(PeerConnectionTransport) → AtomicInteger
  + io.livekit.android.room.PeerConnectionTransport access_setAnswerInFlight_p(PeerConnectionTransport, Integer)
  + io.livekit.android.room.PeerConnectionTransportKt isDuplicateAnswer(int, Integer, int, PeerConnection_SignalingState) → boolean
  + java.util.concurrent.atomic.AtomicInteger set(int)
  

FIELDS:

   old  │ new  │ diff       
  ──────┼──────┼────────────
   5708 │ 5711 │ +3 (+3 -0) 
  
  + io.livekit.android.room.PeerConnectionTransport answerInFlight: Integer
  + io.livekit.android.room.PeerConnectionTransport answeredOfferId: AtomicInteger
  + livekit.org.webrtc.PeerConnection_SignalingState STABLE: PeerConnection_SignalingState