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Encoder instruction naming a static index that does not exist

Close the connection with QPACK_ENCODER_STREAM_ERROR (0x201). The same bad index means different things depending on where it arrives, and §3.1 says both: on a field line it is QPACK_DECOMPRESSION_FAILED, and "if this index is received on the encoder stream, this MUST be treated as a connection error of type QPACK_ENCODER_STREAM_ERROR". Paired deliberately with the field-line version on the neighbouring port: a client that answers both with the same code has collapsed a distinction the specification draws twice in one paragraph.

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Every one of these is a page: what the server emits, the clause it is judged against, and how each client answered. The full list carries the verdict tallies too.

h-qpack-encoder-bad-name-index · RFC 9204 §3.1, §4.3.2 · correctness · layer http3 · udp/4507 · MUST

Passing this means: Rejected something invalid, with the code the RFC names.

Anomaly type: other_uni_stream

How each client answered

ClientVersionVerdictWhat happened
curl libcurl/8.23.0 ngtcp2/1.25.0 Fail Objected at the QUIC layer (rejected at the QUIC layer with INTERNAL_ERROR) instead of signalling the HTTP/3 error. The violation was detected and rejected, which is the right instinct; §8.1 requires an HTTP/3 connection error to be carried in an application close, and this test names 0x201. A transport close carries no HTTP/3 code at all, so a peer has no way to learn what was wrong.
quinn noq fork (189b0ed) Pass Rejected with the required error code 0x201.
aioquic 1.3.0 (PyPI wheel) Pass Rejected with the required error code 0x201.
chromium build 1248 Pass Rejected with the required error code 0x201.
quic-go quic-go v0.61.0 (h1:9So2anK4Tp22) Unsupported does not read the QPACK encoder stream, so the invalid instruction on it never reached its decoder. This endpoint filled the flow-control window the client granted on that stream and no credit came back while the client stayed connected -- a client that had consumed the stream would have had to grant more.
quiche 0.30.0 (1c8e976) Fail Accepted a protocol violation and carried on. The anomaly was on the QPACK encoder stream, and this client extended flow-control credit on it -- a receiver extends credit on a stream only once its application has consumed what was already there, so the bytes were read rather than merely delivered. This should have been rejected.
neqo 0.31.1 (cac2b74) Pass Rejected with the required error code 0x201.
picoquic 8162550 Fail Accepted a protocol violation and carried on. The anomaly was on the QPACK encoder stream, and this client extended flow-control credit on it -- a receiver extends credit on a stream only once its application has consumed what was already there, so the bytes were read rather than merely delivered. This should have been rejected.
ngtcp2 3c23148 Pass Rejected with the required error code 0x201.
lsquic 4.9.4 (2b30189) Pass Rejected with the required error code 0x201.
xquic 2060a44 Fail Rejected, but with error 0x106 where the specification requires 0x201. The violation was detected; the code reported is wrong.
msquic 2.7.0 (7e6525d) Fail Accepted a protocol violation and carried on. The anomaly was on the QPACK encoder stream, and this client extended flow-control credit on it -- a receiver extends credit on a stream only once its application has consumed what was already there, so the bytes were read rather than merely delivered. This should have been rejected.
quico 0.7.0 (npm) Pass Rejected with the required error code 0x201.

What the clause requires

Close the connection with QPACK_ENCODER_STREAM_ERROR (0x201). The same bad index means different things depending on where it arrives, and §3.1 says both: on a field line it is QPACK_DECOMPRESSION_FAILED, and "if this index is received on the encoder stream, this MUST be treated as a connection error of type QPACK_ENCODER_STREAM_ERROR". Paired deliberately with the field-line version on the neighbouring port: a client that answers both with the same code has collapsed a distinction the specification draws twice in one paragraph.

Judged against RFC 9204.

Run this one yourself

Every test is reachable from your own client. Nothing here needs an account.

curl -s https://conformance.pqcrypta.com/catalog.json \
  | jq '.tests[] | select(.id == "h-qpack-encoder-bad-name-index")'