[myleshorton]

Upgrades the Unbounded outbound to the latest pion, and adds a tuning option so the server can tune pion's ICE, DTLS and SCTP defaults per track instead of per release.

Depends on getlantern/unbounded#478, now merged. go.mod pins broflake to its merge commit (ae5d221).

Why

Our consumer makes the offer, so it's the DTLS server. About 27% of Unbounded attempts reach "ICE connected" and then stall in the handshake. In rtcprobe runs at 20% UDP loss, upgrading only the consumer's pion took connections from 16/26 to 27/30. That's because of the dtls fixes for lost server flights; details in unbounded#478. Browser volunteers run Chrome's DTLS, so this repo is where the fix reaches users.

Changes

• go.mod / go.sum:

  • broflake bumped to the pion upgrade: webrtc v4.2.25, ice v4.4.8, sctp v1.12.0, dtls v3.1.15.
  • pion moved to pion/transport/v5.

• protocol/unbounded/net.go: rtcNet now implements transport/v5.Net. The method set is unchanged; only the package path moved.

• option/unbounded.go: a new tuning option, a map of named overrides given as decimal strings.

• protocol/unbounded/tuning.go: parses the map into broflake's WebRTCTuning:

  Key	Overrides (pion default)
  ice_max_binding_requests	ICE checks per candidate pair (7)
  stun_gather_timeout_ms	per-STUN-server gather wait (5 s)
  ice_disconnected_timeout_ms / ice_failed_timeout_ms / ice_keepalive_interval_ms	ICE liveness timers (5 s / 25 s / 2 s)
  srflx_acceptance_min_wait_ms	wait before nominating a srflx pair (500 ms)
  dtls_retransmit_ms	initial DTLS handshake retransmit (1 s, doubling)
  sctp_rto_max_ms	SCTP retransmission timeout cap (60 s)
  sctp_max_receive_buffer_bytes	SCTP receive buffer (1 MiB)

  Each key has a floor and a cap, kept in one table with its setter. Durations are capped at 10 minutes; floors stop pion retransmitting in a tight loop (e.g. dtls_retransmit_ms ≥ 100, sctp_rto_max_ms ≥ 1000, since a cap below pion's 1 s RTO floor becomes the RTO). ice_max_binding_requests is capped at 100 and the buffer is limited to 64 KiB–64 MiB. An out-of-range or non-numeric value keeps pion's default.
  A keepalive at or above the disconnected timeout (explicit, or pion's 5 s default) would let idle connections flap, so that combination drops all three ICE liveness overrides.

• protocol/unbounded/outbound.go: applies the parsed tuning and logs any ignored keys.

Why a map. It's what makes tuning open-ended: unknown keys are ignored, not rejected, so the server can add knobs without breaking clients that have this option. Clients older than this PR reject the tuning field outright, though, because sing-box rejects unknown outbound fields. So the server must send it only to clients that advertise common.CapabilityUnboundedTuning (getlantern/common, companion PR), which radiance will advertise once it carries this version.

Testing

• make test, as CI runs it: passes with no failures.
• New protocol/unbounded/tuning_test.go:
  • every key parses to the right field and unit;
  • unknown keys, non-numbers, zero, negative, below-floor and over-limit values are ignored and the defaults kept;
  • a keepalive at or above the disconnected timeout drops the ICE liveness overrides;
  • an empty map is a no-op;
  • a guard test fails if any key is missing from the every-key test input.
• Not tested: a live tuned connection from this repo. broflake's TestTunedPeersConnect covers a real tuned handshake.

Risk

Medium: a pion upgrade across ICE, DTLS and SCTP. With no tuning set, the only behaviour change is the new pion itself. With no loss, connect times are unchanged in rtcprobe. The riskiest file is net.go, because rtcNet routes every pion socket through sing-box, and its overrides must still be the ones pion calls. They are, and the build would fail otherwise.

How to revert

Revert the merge commit. Revert it before any server sends tuning to clients built from it.

Pre-PR review (local Codex gate)

• Rounds: 1, at high reasoning effort — final: CODEX GATE: verdict=approve critical=0 important=0 minor=0 preexisting=0 reviewed=27
• Reviewed at: 5058bec. Coverage included broflake's tuning code at the pinned version, both pion transport versions, and pion's setters.
• Exit: approve
• Step back: not needed
• Fixed: none
• Dismissed: none
• Pre-existing (not introduced here, worth filing): none
• Proposed AGENTS.md additions: none

🤖 Generated with Claude Code

https://claude.ai/code/session_019DnqgLJf7p4sK87dDvktjx

Summary by CodeRabbit

• New Features
  • Added optional WebRTC tuning settings, allowing supported clients to customize connection limits and timeouts. Valid values are applied; unknown or invalid settings are ignored, preserving default behavior for those options.
  • This setting is compatible only with clients that advertise support for unbounded tuning, so older clients should not receive it.

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• protocol/unbounded/tuning.go
• protocol/unbounded/tuning_test.go

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Reviewing files that changed from the base of the PR and between d01ea47 and 5058bec.

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Files selected for processing: 6

• go.mod
• option/unbounded.go
• protocol/unbounded/net.go
• protocol/unbounded/outbound.go
• protocol/unbounded/tuning.go
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Walkthrough

The changes upgrade Pion dependencies and add optional tuning overrides to Unbounded outbound options. The outbound setup parses and validates the overrides, applies valid values to WebRTC options, and logs ignored entries.

Changes: Unbounded tuning

Layer / File(s)	Summary
Upgrade Pion transport dependencies go.mod, protocol/unbounded/net.go	The project updates Pion Transport and related WebRTC dependencies. The Unbounded network imports now use Transport v5.
Parse and apply tuning overrides option/unbounded.go, protocol/unbounded/tuning.go, protocol/unbounded/outbound.go, protocol/unbounded/tuning_test.go	UnboundedOutboundOptions adds an optional tuning map. parseTuning validates recognized decimal-string values, applies valid values, and returns unknown or invalid entries. NewOutbound assigns the parsed tuning and logs ignored entries. Tests cover all nine keys, invalid values, unknown keys, and nil input.

Priority: Normal

Estimated code review effort: 3 (Moderate) | ~20 minutes

Change: Bug fix

Sequence Diagram(s)

sequenceDiagram
  participant UnboundedOutboundOptions
  participant NewOutbound
  participant parseTuning
  participant WebRTCOptions
  UnboundedOutboundOptions->>NewOutbound: provide tuning map
  NewOutbound->>parseTuning: parse tuning values
  parseTuning-->>NewOutbound: return tuning and ignored entries
  NewOutbound->>WebRTCOptions: assign parsed tuning

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Possibly related issues

• Issue 2374: The PR adds a tuning field and defines how unknown and invalid tuning values are handled. It does not include the issue’s general serialization cleanup.
• Issue 2470: The PR adds a signaling field that older clients reject and documents capability gating for sending it. It does not implement the proposed hard fork.

Merge Risk: Minimal · up to 5058b

No concrete merge-blocking issue is established. Complete normal testing and the planned dependency repin before merging.

Pre-merge checks: 4 · 1

Failed checks: 1 warning

Check name	Status	Explanation	Resolution
Docstring Coverage		Docstring coverage is 28.57% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 7 functions across 5 files. (1 skipped: 1…	Write docstrings for the functions missing them to satisfy the coverage threshold.

Passed checks: 4 passed

Check name	Status	Explanation
Description Check		Check skipped - CodeRabbit’s high-level summary is enabled.
Title check		The title names the two changes in the PR: upgrading Unbounded's Pion dependencies (go.mod, net.go, and the WebRTC/transport module bumps) and accepting server-provided tuning (the new Tuning option, …
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.

Full details: Title check

Explanation

The title names the two changes in the PR: upgrading Unbounded's Pion dependencies (go.mod, net.go, and the WebRTC/transport module bumps) and accepting server-provided tuning (the new Tuning option, outbound.go parsing, and tuning.go/tuning_test.go). Both match the changeset, so the title is fully related to the main change. It uses 7 words and no file lists or vague terms.

Full details: Docstring Coverage

Explanation

Docstring coverage is 28.57% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 7 functions across 5 files. (1 skipped: 1 unsupported.)

Resolution

Write docstrings for the functions missing them to satisfy the coverage threshold.

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[Copilot]

🔵 Needs a closer look

The coordinated networking-stack upgrade needs final human review after the upstream dependency merges and broflake is re-pinned and revalidated.

No open issues 🎉

What changed in this PR

Upgrades Unbounded’s Pion networking stack to improve handshake reliability under packet loss and adds server-provided tuning without requiring a client release for each adjustment.

Changes:

• Updates broflake and Pion dependencies and migrates rtcNet to transport/v5.
• Adds bounded tuning overrides that preserve defaults for unknown or invalid values.
• Tests key mappings, invalid inputs, and empty configuration.

File	Description
protocol/​unbounded/​tuning.go	Parses and validates named tuning overrides.
protocol/​unbounded/​tuning_test.go	Tests parsing, ignored values, and key coverage.
protocol/​unbounded/​outbound.go	Applies tuning and logs ignored options.
protocol/​unbounded/​net.go	Switches transport imports to v5.
option/​unbounded.go	Exposes the tuning map and documents capability gating.
go.sum	Updates dependency checksums.
go.mod	Pins upgraded broflake and Pion dependencies.

_{Review effort: Balanced}

[Copilot]

🔵 Needs a closer look

The coordinated transport upgrade warrants final human validation after broflake is re-pinned to the upstream merge commit.

No open issues 🎉

_{Review effort: Balanced}