Do not request media sections for transceivers that cannot send by SKaterinenko · Pull Request #4892 · livekit/livekit

SKaterinenko · 2026-09-22T06:36:59Z

Problem

In client-offered mode (single peer connection / publisher transport) the server asks the client for media sections through MediaSectionsRequirement whenever it has local transceivers without a mid. getNumUnmatchedTransceivers counts every mid-less transceiver, but the client satisfies the requirement with recvonly sections, which pion's satisfyTypeAndDirection only pairs with local sendonly/sendrecv transceivers.

A transceiver whose track was removed before its section was negotiated (subscribe → unsubscribe within one negotiation window: direction goes sendrecv → recvonly, sender is nil) or that was stopped can therefore never be matched and stays "outstanding" forever. Because createAndSendAnswer resets numRequestSent* on every answer, every answer re-requests the same sections, the client appends another batch of transceivers each round, and its offer grows by a fixed amount per negotiation until it exceeds limit.signal_message_size_limit (2 MiB). The signalling socket is then closed with signal message exceeds size limit, the client does a full reconnect and the cycle starts over.

Observed

Reproduced on v1.13.7 and master (e77173d, 8cc3630) with the JS SDK, rooms of 40+ publishers and subscription churn (grid paging):

webrtc-internals: MediaSectionsRequirement for the same 5–7 video sections every ~0.5 s; one browser client went from 6 to 507 m-sections / 1.85 MB offer with 100 publishers, then got disconnected, reconnected and started growing again.
Production room, v1.13.7, 2026-09-18: ~130 participants over the day, 14 signal message exceeds size limit closes in two hours, 378 starting RTC session for the room.
Earlier production room with 59 participants: 145 closes in 20 minutes, 38 users affected.

Does not reproduce with Go/pion clients (lk load-test): they do not add transceivers on MediaSectionsRequirement.

Fix

Count only transceivers that have something to send. A released transceiver that AddTrack reuses later becomes sendrecv again and is counted as before. The existing behaviour of re-requesting on every answer is intentionally kept, so a requirement the client never received is still recovered.

Tests

transport_media_sections_test.go drives an answerer PCTransport against a pion client that honours every requirement by adding that many recvonly transceivers before its next offer:

TestMediaSectionsRequirementNotRepeatedForUnmatchableTransceiver — fails on master (6 video sections requested over 5 answers), passes with the fix.
TestMediaSectionsRequirementAfterTransceiverReuse — a track added after a released transceiver still gets a section, even when the client offers before the server negotiates.
TestMediaSectionsRequirementReissuedWhenLost — a requirement the client never received is issued again.

🤖 Generated with Claude Code

CLAassistant · 2026-09-22T06:37:07Z

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✅ Devin Review: No Issues Found

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

boks1971

Thank you for this. A couple of small comments.

boks1971 · 2026-09-22T07:38:09Z

+		client.Close()
+	})
+	return h
+}


can you please an empty line between functions? There are more instances below of no space between functions.

Done in 27353fd.

boks1971 · 2026-09-22T08:05:30Z

+	require.NoError(t, h.server.RemoveTrack(sender))
+	h.negotiate(nil)
+	h.negotiate(nil)
+	_, transceiver := h.addVideoTrack("v2")


I think it might be worth checking that the transceiver here is the same one as the first one. It should be re-used.

Good call — added require.Same(released, transceiver), and it does hold: pion hands back the released one. Done in 27353fd.

getNumUnmatchedTransceivers counted every local transceiver without a mid. A transceiver whose track was removed before its section was negotiated (direction recvonly, no sender) or that was stopped (inactive) can never be matched to the recvonly section the remote adds in response to a MediaSectionsRequirement, so it stayed "outstanding" forever: every answer asked the remote for a section for it again, the remote appended another batch of transceivers each round, and its offer grew by a fixed amount per negotiation until it exceeded limit.signal_message_size_limit and the signalling connection was closed (full reconnect, then the cycle restarts). Count only transceivers that have something to send. A released transceiver that AddTrack reuses later becomes sendrecv and is counted again. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

…r reuse Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

…7 ➔ v1.13.8) (#2275) This PR contains the following updates: | Package | Update | Change | |---|---|---| | [docker.io/livekit/livekit-server](https://github.com/livekit/livekit) | patch | `v1.13.7` → `v1.13.8` | --- ### Release Notes <details> <summary>livekit/livekit (docker.io/livekit/livekit-server)</summary> ### [`v1.13.8`](https://github.com/livekit/livekit/releases/tag/v1.13.8) [Compare Source](livekit/livekit@v1.13.7...v1.13.8) ##### Added - agent: HTTP endpoints data plane ([#4779](livekit/livekit#4779)) - use sender report pass through setting to forward abs-capture-time verbatim ([#4812](livekit/livekit#4812)) - Add sdk lable to session start time and participant join ([#4885](livekit/livekit#4885)) - Add a local participant method to get recently disconnected ([#4911](livekit/livekit#4911)) - service: start room composite egress configured in a room preset ([#4926](livekit/livekit#4926)) ##### Changed - Update github workflows ([#4446](livekit/livekit#4446)) - Reduce descriptor marshal allocations on Go 1.26.4/linux-amd64 ([#4681](livekit/livekit#4681)) - config: reject unknown send\_side\_bwe\_pacer, warn on unwired fallback ([#4804](livekit/livekit#4804)) - Update github.com/livekit/protocol digest to [`a879e94`](livekit/livekit@a879e94) ([#4864](livekit/livekit#4864)) - Update module github.com/gotesttools/gotestfmt/v2 to v2.5.0 ([#4865](livekit/livekit#4865)) - Update module github.com/urfave/cli/v3 to v3.11.0 ([#4867](livekit/livekit#4867)) - Update module golang.org/x/mod to v0.41.0 ([#4868](livekit/livekit#4868)) - sfu: return VP8 munged header by value to avoid per-packet allocation ([#4871](livekit/livekit#4871)) - sfu: patch pacer header extensions without per-packet allocation ([#4872](livekit/livekit#4872)) - Update pion/sdp to get lesser SDP retention ([#4873](livekit/livekit#4873)) - sfu: skip pacer allocation assertion under the race detector ([#4874](livekit/livekit#4874)) - sfu: broadcast RTP to down tracks without per-packet allocations ([#4875](livekit/livekit#4875)) - Track action versions and stop quarantining our own actions ([#4877](livekit/livekit#4877)) - test: fix two data races in the test suites ([#4878](livekit/livekit#4878)) - Bump go.opentelemetry.io/otel/sdk ([#4879](livekit/livekit#4879)) - deps: update psrpc to v0.8.0 ([#4882](livekit/livekit#4882)) - Update module github.com/moby/moby/client to v0.6.0 ([#4883](livekit/livekit#4883)) - Update module golang.org/x/sync to v0.23.0 ([#4884](livekit/livekit#4884)) - Propagate SIP\_TRUNK\_FAILURE ([#4890](livekit/livekit#4890)) - ccutils: use millisecond resolution for probe interval backoff ([#4891](livekit/livekit#4891)) - Increase receiver loadbalance threshold when batch io enabled ([#4899](livekit/livekit#4899)) - rtc: parse each remote offer once per negotiation ([#4904](livekit/livekit#4904)) - Bump protocol ([#4909](livekit/livekit#4909)) - rtc: split EndSession out of MoveToRoom ([#4917](livekit/livekit#4917)) - telemetry: drop the stats worker re-key path ([#4918](livekit/livekit#4918)) - sfu: report forwarding latency as p90 instead of the mean ([#4920](livekit/livekit#4920)) - rtc: accept ICE Completed in ICE-restart connect assertions ([#4921](livekit/livekit#4921)) - rtc: measure data blob keys by their content, not their text form ([#4923](livekit/livekit#4923)) - Remove deprecatred way of setting prometheus from the config file ([#4928](livekit/livekit#4928)) - test: give mock participants a connection quality, close test rooms ([#4933](livekit/livekit#4933)) - update warp dep ([#4943](livekit/livekit#4943)) ##### Fixed - Do not add down tracks after receiver close ([#4857](livekit/livekit#4857)) - Do not request media sections for transceivers that cannot send ([#4892](livekit/livekit#4892)) - Deregister agent job when the server terminates it ([#4893](livekit/livekit#4893)) - sfu: don't hold bindLock across the blank-frame flush in CloseWithFlush ([#4895](livekit/livekit#4895)) - dynacast: re-send subscribed qualities after every publisher answer ([#4907](livekit/livekit#4907)) - agent: release JobTerminate handler when job ends before registration ([#4908](livekit/livekit#4908)) - Report disconnected for older disconnected participants. ([#4910](livekit/livekit#4910)) - rtc: record a room's departure when the participant leaves it ([#4913](livekit/livekit#4913)) - update deps to fix warp issue ([#4916](livekit/livekit#4916)) - sfu: fix data stats active window bitrate and duration units ([#4922](livekit/livekit#4922)) - fix: reject instead of drop for no dispatch rule ([#4927](livekit/livekit#4927)) - fix: skip RTX/FEC when picking a fallback video codec ([#4930](livekit/livekit#4930)) - fix: do not read invalid delta ([#4935](livekit/livekit#4935)) - fix: use the fast debounce for the first negotiation ([#4936](livekit/livekit#4936)) - fix: skip DTLS HelloVerifyRequest ([#4937](livekit/livekit#4937)) - config: parse generated duration flags as durations ([#4939](livekit/livekit#4939)) - fix: use the most common recent packet rate in connection quality ([#4940](livekit/livekit#4940)) - fix: copy RED history packets instead of keeping pointers ([#4941](livekit/livekit#4941)) - fix: keep one subscription when first subscribes race ([#4944](livekit/livekit#4944)) - bump protocol to get unlock on no key fix ([#4945](livekit/livekit#4945)) - fix: count leftover upstream loss after RTX repairs ([#4946](livekit/livekit#4946)) - fix: switch VP8 temporal layer up only at a layer sync frame ([#4947](livekit/livekit#4947)) - fix: reconcile everything when the reconcile queue overflows ([#4948](livekit/livekit#4948)) - fix: enable H.264 publish for desktop Linux Firefox ([#4949](livekit/livekit#4949)) </details> --- ### Configuration 📅 **Schedule**: (UTC) - Branch creation - At any time (no schedule defined) - Automerge - At any time (no schedule defined) 🚦 **Automerge**: Disabled by config. Please merge this manually once you are satisfied. ♻ **Rebasing**: Whenever PR becomes conflicted, or you tick the rebase/retry checkbox. 🔕 **Ignore**: Close this PR and you won't be reminded about these updates again. --- - [ ] If you want to rebase/retry this PR, check this box --- This PR has been generated by [Mend Renovate CLI](https://github.com/renovatebot/renovate).  Reviewed-on: https://git.erwanleboucher.dev/eleboucher/homelab/pulls/2275

SKaterinenko requested a review from a team as a code owner September 22, 2026 06:37

devin-ai-integration Bot reviewed Sep 22, 2026

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boks1971 reviewed Sep 22, 2026

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SKaterinenko and others added 2 commits September 22, 2026 14:12

Address review: blank lines between test functions, assert transceive…

27353fd

…r reuse Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

SKaterinenko force-pushed the fix/media-sections-requirement-convergence branch from c704d24 to 27353fd Compare September 22, 2026 09:12

boks1971 approved these changes Sep 22, 2026

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boks1971 merged commit abf98e5 into livekit:master Sep 22, 2026
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Do not request media sections for transceivers that cannot send - #4892

Do not request media sections for transceivers that cannot send#4892
boks1971 merged 2 commits into
livekit:masterfrom
SKaterinenko:fix/media-sections-requirement-convergence

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SKaterinenko commented Sep 22, 2026

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