Fix H3 quiche traffic handling

[bneradt]

Overview

This patch extends the HTTP/3 autest coverage, using curl, golang, and
Proxy Verifier HTTP/3 clients to generate their implementations of h3
traffic. It also adds request and response bodies of various sizes,
including "large" 300k bodies to exercise multiple packet, buffer, and
flow control ATS HTTP/3 implementations. It also exercises some
interesting requests, such as HEAD and 204 responses. This patch also
includes the various production fixes needed for these tests.

Issues Found and their Fixes

UDP batches could stall large H3 transfers

Large request and response bodies exposed a UDP receive starvation bug
in the UDP read path. On systems using recvmmsg() with
edge-triggered readiness, ATS could read one full batch of datagrams
and then leave the rest queued in the kernel without another readable
event to wake the QUIC stack.

This changes
UDPNetProcessorInternal::read_multiple_messages_from_net() in
src/iocore/net/UnixUDPNet.cc to return whether the kernel supplied a
full batch. udp_read_from_net() now loops while full batches are
returned, draining the socket before handing packets to QUIC and
avoiding large-transfer stalls caused by unread UDP bursts.

QUIC stream writes consumed data before quiche accepted it

The stream write path consumed the QUICStreamVCAdapter write reader
inside _read(), before QUICStream::send_data() knew whether
quiche_conn_stream_send() had accepted the bytes. When quiche accepted
only a partial write or returned a flow-control error, ATS could lose
stream data and report write progress too early.

This makes QUICStream::send_data() keep a pending
IOBufferBlock/FIN pair until quiche reports successful consumption,
and only then calls the new QUICStreamAdapter::consume() hook. The
concrete reader accounting lives in QUICStreamVCAdapter::_consume(),
while QUICStream::has_data_to_send(), QUICStream::on_write(), and
QUICNetVConnection::on_stream_updated() make newly writable stream
data schedule packet writes again. This also treats completed finite
writes with only FIN left as writable stream state, so empty bodies and
fully consumed bodies still close the H3 stream cleanly.

H3 transaction cleanup raced with stream closure

The timeout and stream lifetime tests exposed cases where an
HQTransaction could be deleted while an event handler was still
active, or while the QUIC stream adapter still had read/write cleanup to
finish. That left later stream-close and timeout paths touching state
that had already been torn down.

This adds explicit transaction lifetime state in HQTransaction:
_closed, _stream_closed, _event_handler_active, and
_is_write_buffer_flushed(). Http3App::on_stream_close() now calls
HQTransaction::stream_closed(), and
HQTransaction::_delete_if_possible() waits until the transaction is
done, the stream is closed or no longer readable, and pending writes
have flushed before deleting the transaction.

H3 read completion could run before headers and DATA were settled

The H3 request read path could signal completion before asynchronous
QPACK header decode and buffered DATA delivery had finished updating the
sink VIO. That showed up around HEAD, 204, and stream-close timing
because the HTTP state machine needed a stable view of whether headers
were decoded and whether a request body existed.

This updates Http3HeaderVIOAdaptor::_on_qpack_decode_complete() to add
the printed header length to the sink VIO and notify
Http3Transaction::on_header_decode_complete(), which schedules the
appropriate read event. Http3StreamDataVIOAdaptor::finalize() now uses
a persistent reader, writes buffered DATA into the sink VIO exactly
once, and updates ndone/nbytes consistently before the transaction
is signaled.

The QPACK static table had drifted from the standard table

The HEAD, 204, and quic-go coverage exposed that ATS's static QPACK
table was not the table used by external HTTP/3 implementations. The
extra zstd entry and modified accept-encoding value in
src/proxy/http3/QPACK.cc shifted later static indexes, so an
externally encoded :status 204 could decode as a different status.

This restores the standard static table entries by using
accept-encoding: gzip, deflate, br and removing the non-standard
content-encoding: zstd entry. The new 204 cases in
tests/gold_tests/h3/replays/h3_proxy_verifier.replay.yaml and
tests/gold_tests/h3/replays/h3_server_for_go_client.replay.yaml cover
this interoperability point with Proxy Verifier and quic-go.

[Copilot]

Pull request overview

This PR improves HTTP/3 over QUIC handling for larger bodies and stream lifecycle edge cases, and adds H3 interoperability/timeout coverage around curl, Proxy Verifier, SNI, session tickets, and stream cleanup.

Changes:

• Keeps QUIC stream write data pending until accepted, schedules packet writes on stream updates, and adjusts H3 transaction cleanup.
• Drains UDP recvmmsg batches for edge-triggered sockets.
• Adds/updates HTTP/3 gold tests and replay support for QUIC ports.

Reviewed changes

Copilot reviewed 32 out of 32 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
src/iocore/net/quic/QUICStream.cc	Adds pending send-block handling and delayed consumption.
src/iocore/net/quic/QUICStreamVCAdapter.cc	Defers write consumption and schedules stream write updates.
src/iocore/net/quic/QUICStreamAdapter.cc	Adds explicit consume path.
src/iocore/net/QUICNetVConnection.cc	Schedules packet writes when streams update.
src/iocore/net/UnixUDPNet.cc	Drains full recvmmsg batches.
src/proxy/http3/Http3Transaction.cc	Updates H3 transaction read/write/close lifecycle.
src/proxy/http3/Http3StreamDataVIOAdaptor.cc	Buffers and finalizes DATA delivery via persistent reader.
src/proxy/http3/Http3HeaderVIOAdaptor.cc	Tracks decoded header bytes and signals decode completion.
src/proxy/http3/Http3App.cc	Notifies transactions when streams close.
include/** QUIC/H3 headers	Adds APIs and state needed by the implementation changes.
include/iocore/net/quic/Mock.h	Updates QUIC mocks for new interfaces.
src/iocore/net/P_UDPNet.h	Updates UDP batch-read return type.
src/iocore/net/P_QUICNetVConnection.h	Declares stream update callback.
tests/gold_tests/autest-site/ats_replay.test.ext	Adds HTTP/3 port wiring for replay tests.
tests/gold_tests/h3/*	Adds H3 curl, Proxy Verifier, stream lifetime, timeout, SNI, and session ticket tests/replays.
tests/gold_tests/timeout/*	Updates QUIC feature gating for timeout tests.

[zwoop]

[approve ci autest 2]

[Copilot]

Pull request overview

Copilot reviewed 39 out of 40 changed files in this pull request and generated 2 comments.