picoquic — Encoder instruction naming a static index that does not exist

Inconclusive

The client completed its request and closed without objecting, but the anomaly was written to the control stream — a unidirectional stream nothing obliges it to read on any schedule. A one-shot request can finish before that stream is picked up, so this is equally consistent with accepting the violation and with never having seen it, and neither can be told from here.

The run did not establish what this client does here — either it was never put in the situation, or its answer admits more than one reading. Not a failure, and never counted as one.

What was measured

Client

picoquic — picoquic + picotls, 8162550

Test

Encoder instruction naming a static index that does not exist — h-qpack-encoder-bad-name-index

Clause

RFC 9204 §3.1, §4.3.2 (MUST)

Class

correctness — Rejected something invalid, with the code the RFC names.

Required behaviour

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.

Measured

2026-09-18

Reproduce it

The suite is the judge, so the reproduction is to point the same client at the same test and let the server report what it saw.

SESSION=$(curl -sX POST https://conformance.pqcrypta.com/session | jq -r .id)
# then drive picoquic at the test URL and read the verdict:
curl -s https://conformance.pqcrypta.com/report/$SESSION.json | jq '.results["h-qpack-encoder-bad-name-index"]'