From d1f998b42137465b610667439527917a00030b4d Mon Sep 17 00:00:00 2001 From: Christophe Besson Date: Mon, 7 Sep 2026 16:02:10 +0200 Subject: fix(mnp): give a reply an id, so it stops being routed by luck MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit MNP carried no correlation id. A reply named its own type and nothing else, so a client with more than one request in flight worked out which one a message answered from the message itself — and for the replies that name nothing it could not. `_dispatch` fell through to matching by arrival order, which is a guess. `_sendAndWait` had the right value all along: it keys `_pending` by `this._seqId++` and never put it on the wire. The guess fails asymmetrically, which is why it hid. The victim is not the request that was answered wrongly — it is the unrelated one that now waits out its own 30s timeout for a reply already delivered elsewhere. Live on 2026-09-06: five `music_meta_req` sat pending for over 100 seconds behind a failing MusicBrainz, and a `device_list_result` was handed to one of them. The composer is disabled while a send is in flight, so a chat message whose reply went astray the same way left the Chat tab looking frozen for thirty seconds, then unfroze on its own. The `ack` half of this was fixed on 2026-08-30 by matching on request type. That closed the instance and left the class open: a refusal has no type to match on either, and `_dispatch_message`'s catch-all answers every unforeseen failure with `{"type": "error", "detail": "Request failed"}` — 238 of this module's 240 error sends name nothing at all. `req_id` now rides on the request and comes back on the reply. On the node it is published for the whole handler in a ContextVar and stamped by `_send`: a parameter would have meant threading an argument through all 240 send sites, and asyncio copies the context into a task, so a handler that `_spawn`s its real work still answers under the right id. It is never stamped on a broadcast — those answer nothing, and the owner check in `_send` is what keeps a chat broadcast or an index push from reaching another peer looking like a reply. On the client, `_dispatch` resolves on `req_id` first and the arrival-order fallback is gone the moment a node proves it stamps (`_correlates`, armed by the handshake's own reply). The fallback stays for an MNP 1.0 node, unchanged and no wider: there it is the only thing there is, and removing it would leave device_list_result, join_result and the handshake replies reaching nobody. Two things fall out. `sendChat` refuses an `error` reply like every other request in the file — it returned it as success, which did not matter while a refusal reached the wrong caller anyway and would now show a rejected message as sent. And `_group_ctx` uses `.get`: a reload pops a removed group while sessions connected to it are open, and every request they had left raised KeyError into that same catch-all. Sealed index messages are the one exception to the fast path. They cannot be handed over until they are opened, which is asynchronous while `_dispatch` is not — resolving on the id alone gave `fetchIndex` the envelope and skipped `onIndexSync` entirely. Caught by extending `index_seal_probe.mjs` to stamp a reply the way a current node does, after the hub suite passed over it: the probe built its own frames and had never seen one. Tests, all failing before and passing after: `test_chat_send.py` drives the real ChatPanel over the real transport for both shapes of reply with an older request pending (3 of its 6 are new, and the 3 for `ack` pass either way, so it discriminates); `test_reply_correlation.py` pins the node's half — the refusals that name nothing else, the broadcast that must not be stamped, and a late reply from a spawned task answering under its own id rather than the most recent request's. Full suite: 1897 passed, same 11 pre-existing failures as before. QUIC keeps its own dispatch and is not stamped. It is disabled by default and no browser request reaches it, but the asymmetry is real. Co-Authored-By: Claude Opus 5 Claude-Session: https://claude.ai/code/session_01Dn1xYx9uT69mCB6UDvyKAN --- CLAUDE.md | 27 ++++++++++++++++++++++----- 1 file changed, 22 insertions(+), 5 deletions(-) (limited to 'CLAUDE.md') diff --git a/CLAUDE.md b/CLAUDE.md index 4a4175f..04f6e61 100644 --- a/CLAUDE.md +++ b/CLAUDE.md @@ -471,11 +471,28 @@ anything that assumes one key per person. next visit to the tab, since the node had stored it and answered. Every line of `chat-app.js` is correct and every routed message in `transport.js` is routed correctly; the defect is in the seam, which is why - `tests/harness/chat_send_probe.py` drives the two together. `ack` is now - matched by request type (`chat_msg`, or the keypair-bundle store/delete that - name themselves in `detail`). Anything left to the "oldest pending" guess is - a latent version of this bug: a request type deserves a key, and a reply - deserves something to key it by + `tests/harness/chat_send_probe.py` drives the two together. `ack` was matched + by request type (`chat_msg`, or the keypair-bundle store/delete that name + themselves in `detail`), and that closed the instance — **but it left the + class open, and it came back on 2026-09-06 through the other door.** A + refusal has no type of its own to key on: `_dispatch_message`'s catch-all + answers every unforeseen failure with `{"type": "error", "detail": "Request + failed"}`, and 238 of `webrtc_server.py`'s 240 error sends name nothing + either. So a chat send the node refused was routed by luck all over again — + same frozen composer, same 30 s, and rare enough (it needs an older request + still waiting, which a `music_meta_req` behind a failing third-party lookup + supplies for over a hundred seconds) to look like once every couple of days. + The keys were never the fix, only a workaround for a protocol that carried no + correlation id at all: `_seqId` existed, indexed `_pending`, and was never put + on the wire. It is now (`req_id`, see `protocol.py`) — the node stamps it on + the reply from `_send`, via a ContextVar so a handler's spawned work still + answers under the right id, and never on a broadcast, which answers nothing. + With that, the arrival-order fallback is gone for any node that stamps. + The lesson is not "key the replies": it is that **matching by arrival order + is a guess that fails silently and asymmetrically** — the victim is never + the request that was answered wrongly, it is the unrelated one that now + waits for a reply already delivered elsewhere. A reply needs an identifier + the protocol guarantees, not a field it happens to have - **A refusal that never rejects.** Denying Chromium's `fullscreen` permission does not make `requestFullscreen()` throw — the promise never settles. The -- cgit v1.2.3