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… GOAWAY frame session.goaway(code, lastStreamID, opaqueData) wrote the buffer behind a GOAWAY header whatever its size. Above 16376 bytes the frame exceeded the default MAX_FRAME_SIZE, and at 2^24 - 8 bytes the 24-bit length field wrapped to 0, so the peer read the 16 MiB that followed as new frames. nghttp2 refuses a GOAWAY whose payload exceeds NGHTTP2_MAX_PAYLOADLEN (16384) and node ignores that result, so node sends nothing and does not throw. The native goaway() now does the same for client and server sessions. FrameHeader::write asserts the 24-bit bound in debug builds. The re-entrant detach test sent 64 KiB of opaque data. It now sends 16376 bytes, the most a GOAWAY carries.
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Navigate logical layers of code changes, visualize relationships, and explore their blast radius. WalkthroughThe HTTP/2 GOAWAY implementation limits opaque data to 16,376 bytes, rejects oversized payloads, and asserts the 24-bit frame-length limit. Client- and server-side tests check accepted and rejected payloads on the wire. ChangesGOAWAY payload enforcement
Suggested reviewers: Priority: ⬇️ Low Merge Risk: ⚪ Minimal · up to The GOAWAY limit and wire tests have no identified merge-blocking issue. The remaining comments concern test organization and cleanup conventions. 🚥 Pre-merge checks | ✅ 4✅ Passed checks (4 passed)
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Updated 11:53 PM PT - Oct 1st, 2026
❌ @robobun, your commit 6ee1b0e has some failures in 🧪 To try this PR locally: bunx bun-pr 42461That installs a local version of the PR into your bun-42461 --bun |
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Status Reproduced on release 1.4.3-canary (6a92015) with a raw TCP peer that sends an empty SETTINGS frame and records what the client writes: const c = http2.connect("http://127.0.0.1:" + port);
c.on("connect", () => c.goaway(0, 0, Buffer.alloc(2 ** 24 - 8, 0x41)));
// bun: GOAWAY header with length 0, then 16 MiB that parse as frames of type 0x41
// node v26.3.0: no frame for this call
The other open member of the same audit is #42459 ( CI at 6ee1b0e (Buildkite build 122721, finished): 180 of 181 jobs passed, and no test is red.
The diff is ready for review. |
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LGTM — focused Node-compat fix with the constant and drop-silently behavior both cited to upstream source.
What was reviewed:
- The early return in
js_goawaymatches Node's observable contract (nghttp2 refuses → node ignores → returnsundefined, sends nothing); all paths already returnedundefined, so the JS wrapper sees no difference. - The
debug_assert!bound is0xFF_FFFF(u24 max), and the release-path guard is the separatelen > MAX_GOAWAY_OPAQUE_DATA_SIZEcheck, so untrusted-input validation survives release builds. - The adjusted detach-regression test still overflows the cork buffer (9 + 8 + 16376 = 16393 >
H2_CORK_BUFFER_SIZE= 16384), sofired: trueremains meaningful. - New test: port 0, error/close wired to reject/resolve, try/finally cleanup before assertions, frame scanner buffers to 9-byte headers with a
frames.length < 16bound so the pre-fix wrap fails on the assertion rather than hanging.
Extended reasoning...
Overview
This PR adds a single length check in H2FrameParser::js_goaway (src/runtime/api/bun/h2_frame_parser.rs) that returns undefined without writing when opaqueData.len() > 16384 - 8, plus a debug_assert! in FrameHeader::write catching any 24-bit length overflow. The test file gains an it.each(["client", "server"]) case that inspects the raw wire from a TCP peer for at-limit / one-past / 2**24 - 8 opaque payloads, and the existing re-entrant-detach regression test is retuned from 64 KiB to 16376 bytes so it isn't dropped by the new cap.
Security risks
None introduced. The bug being fixed is outbound-only: a local application passing >16 MiB of opaque data would have wrapped the 24-bit length field and put bytes on the wire that the peer parses as new frames — a protocol-integrity problem for the sender's own connection, not an attack surface on Bun. The fix strictly narrows what can be sent. No auth, crypto, or untrusted-input parsing is touched; the length is read from a local ArrayBuffer the caller supplied.
Level of scrutiny
Medium. Node-compat native code in the HTTP/2 frame writer warrants checking against upstream, and the PR does so with pinned permalinks to both nghttp2_session.c (the 16384-byte payload cap independent of advertised MAX_FRAME_SIZE) and node_http2.cc (result ignored, no throw). REVIEW.md's "size arithmetic on external data as adversarial" and "debug assertions compile out — validation must survive release" are both satisfied: the runtime guard is the explicit if len > MAX check, and the debug_assert! is a separate tripwire against any other writer hitting the same wrap. The change is ~10 native lines with no new allocation, no new re-entry point, and no signature change.
Other factors
The new test follows the repo's harness conventions closely: port: 0, Promise.withResolvers(), error/sessionError/close wired to reject/resolve, Buffer.alloc(n, 0x41), a single combined .toEqual assertion, try/finally cleanup registered before the assertion, and both session kinds via it.each. The frame scanner buffers to the 9-byte header boundary and skips payloads, and the frames.length < 16 cap plus close→resolve mean the pre-fix behavior fails on the frame-list assertion instead of hanging. I confirmed H2_CORK_BUFFER_SIZE = 16384, so the retuned detach test (16393-byte frame) still forces the cork flush it was written to exercise. CODEOWNERS does not cover these paths, and the timeline shows no prior reviews or outstanding objections.
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A note on the red Measured today with a debug (ASAN) build of this diff on top of main 5d5f03f. The diff applies there with no conflict.
Buildkite build 114706 ran the file on every platform and passed. On the release binary the two new tests fail without the fix and pass with it. The diff is ready for review. |
…2-goaway-opaque-data-limit
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Actionable comments posted: 2
- 🪄 Fix CodeRabbit comments on this PR
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Inline comments:
Review comments at @test/js/node/http2/node-http2.test.js:
- Line 2038: Replace the `it.each(["client", "server"])` parameterization with a
`describe.each(["client", "server"])` block, placing the shared test inside it
so each case is grouped under its client or server description.
- Around line 2125-2128: Update the test containing the client?.destroy() and
server?.close() cleanup to register created clients and servers in the suite’s
resource-tracking arrays, then clean them up through afterEach() instead of the
local finally block.
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This push (6ee1b0e) changes no behavior. It merges main (faac63e) and moves two things so that this PR no longer touches lines that #37558 changes:
Checked:
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Problem
session.goaway(code, lastStreamID, opaqueData)writesopaqueDatabehind a GOAWAY header whatever its size. Above 16376 bytes the frame exceeds the defaultMAX_FRAME_SIZE.2**24 - 8bytesu32::try_from(8 + len)fits, thenFrameHeader::writekeeps 24 bits (h2_frame_parser.rs:400). The length goes out as 0 and the peer reads the 16 MiB behind it as new frames.Fix
goaway()returns before it writes whenopaqueData.length + 8 > 16384. Client and server sessions share that function.nghttp2_session_add_goawayreturnsNGHTTP2_ERR_INVALID_ARGUMENTaboveNGHTTP2_MAX_PAYLOADLEN, whateverMAX_FRAME_SIZEthe peer advertises.Http2Session::Goawayin node ignores the result. 16384 is also the smallest legalMAX_FRAME_SIZE, so the frame always fits the peer.FrameHeader::writeasserts the 24-bit bound in debug builds.test/js/node/http2/node-http2.test.js. The new test covers both session kinds. It fails on 1.4.3-canary and passes unchanged under Node v26.3.0. Also ran the other files intest/js/node/http2/.Background
MAX_FRAME_SIZEit advertised (default 16384).h2_frame_parser.rs.Notes
Origin. An integer cast audit of main found the length wrap. No user reported it.
Frames on the wire. A raw TCP peer records
[type, payload length]of what a session sends after threegoaway(0, 0, Buffer.alloc(n))calls (n = 16376, 16377,2**24 - 8) and a 3-byte marker GOAWAY.[7, 16384],[7, 11][7, 16384],[7, 16385],[7, 0], then[0, 0],[65, 4276545], ... (the opaque bytes read as frames)[7, 16384],[7, 11]The limit does not move when the peer advertises
MAX_FRAME_SIZE = 2**20: Node still sends nothing for 16377 bytes.Sources:
nghttp2_session.c#L7227-L7229,node_http2.cc#L2979-L2980.Why no throw. Node returns
undefinedand sends nothing. A throw here would be stricter than Node, and code that runs on Node would fail on bun.Other writers. All other callers of
send_go_awaypass short static strings. ALTSVC and ORIGIN already have a 16384-byte rule. DATA and HEADERS are split by the peer's frame size.Existing test changed. "opaqueData survives re-entrant buffer detach over a JS Duplex" (#36905) sent 64 KiB of opaque data. It now sends 16376 bytes, the most a GOAWAY carries. The frame is 16393 bytes, so it still overflows the 16 KiB cork buffer, and the fixture still reports
fired: true.Related. #37558 changes how the same function reads the error code. #37554 shares the JS argument validation between client and server sessions and has no size rule. This branch merges with both without a textual conflict: trial merges of the three heads in three orders give the same tree. nghttp2 also refuses a
lastStreamIDof the sender's own parity. That rule is not in this PR.[human-review] gate passed · iteration 1 · 2 files touched
fails on main (without fix)
passes on PR (with fix)
diff hotspot
gate history · 1 passed · 1 rejected · iteration 1
evidence per changed file