DataChannel: reject oversized data messages before they break the channel - #1031
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xianshijing-lk
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some questions / nits
…nnel Sending more than the negotiated SCTP max-message-size makes libwebrtc return success from `sendData` and then abruptly tear down the publisher data channel; every subsequent publish then fails until the next full reconnect. Mirrors the fix from livekit/rust-sdks#1137. Parse `a=max-message-size` (RFC 8841) from the publisher answer SDP in `Room+SignalClientDelegate.didReceiveAnswer`, clamp to a 64000-byte default, and enforce the cap in `DataChannelPair.makeRequest` after serialization — the encoded byte count is what actually goes on the wire. A value of 0 means "no limit". Also logs an error when the publisher channel transitions to `.closed` without an SDK-initiated reset, surfacing the remaining failure modes for diagnosis. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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@xianshijing-lk the questions refer to the contract defined in livekit/rust-sdks#1137 rather than implementation details, so I'm delaying this PR until the above is merged. |
pblazej
marked this pull request as draft
June 8, 2026 09:08
pblazej
marked this pull request as ready for review
June 9, 2026 08:08
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Confirmed parity with merged livekit/rust-sdks#1137 — 64000-byte default, clamped to that ceiling when the answer SDP advertises more (e.g. libwebrtc's 256 KiB), |
hiroshihorie
approved these changes
Jun 9, 2026
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Summary
Sending more than the negotiated SCTP max-message-size makes libwebrtc return success from
sendDataand then abruptly tear down the publisher data channel — every subsequent publish fails until a full reconnect.a=max-message-size(RFC 8841) from the publisher answer SDP, clamp to a 64000-byte default.DataChannelPair.makeRequestafter serialization (encoded byte count = what goes on the wire).0means "no limit"..closedwithout an SDK-initiated reset.Ports the fix from livekit/rust-sdks#1137. Android does the simpler hardcoded-constant variant at
LocalParticipant.kt:984-986.Test plan
oversizedSendRejectedWithInvalidParameter,zeroLimitDisablesTheSizeGuard)xcodebuild buildmacOS clean