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WebTransport and HTTP Datagram Support#629

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dtikhonov wants to merge 216 commits intomasterfrom
202601241123-web-transport-suport
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WebTransport and HTTP Datagram Support#629
dtikhonov wants to merge 216 commits intomasterfrom
202601241123-web-transport-suport

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@dtikhonov dtikhonov commented Mar 16, 2026 •
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This PR adds first-class WebTransport over HTTP/3 support to lsquic, including
transport pieces needed to run real applications (devious baton), plus
HTTP Datagram integration and RESET_STREAM_AT plumbing.

What this delivers

1) WebTransport support (major feature)

  • New public API in include/lsquic_wt.h for:
    • session establishment/acceptance
    • WT stream lifecycle (bidi + uni)
    • WT datagram send/receive
    • app callback interface (lsquic_webtransport_if)
  • CONNECT-based WT session handoff in server flow (via handler dispatch), with
    baton wired as the first concrete application.
  • Support for concurrent WT sessions and stream/session bookkeeping in connection code.
  • Stream-core/WT decoupling improvements so WT logic lives in WT layer, not stream internals.

2) HTTP Datagram integration

  • End-to-end HTTP Datagram read/write path integrated with WT.
  • WT datagram API supports immediate send + internal buffering.
  • Configurable queue behavior (policy/limits), with fallback behavior for large payloads.
  • Non-WT datagrams continue to route to default engine-level handler when configured.

3) RESET_STREAM_AT plumbing

  • WT-related deferred reset plumbing integrated with RESET_STREAM_AT support path.
  • Related stream/reset handling paths were tightened to avoid reentrancy and lifecycle hazards.

Protocol / draft alignment

  • Updated implementation toward current WebTransport draft behavior (including settings/TP handling),
    while retaining compatibility needed for interop with draft-14 style peers where practical.

Tooling and application support

  • Devious baton implementation under bin/ and integration with http_server baton mode.
  • Client/server behavior and logs improved for protocol observability and debugging.

Validation

  • Build coverage includes core lib + WT-facing tools/tests.
  • test_wt and baton flows exercised.
  • Interop exercised against external servers (including draft skew scenarios).

Why this is a single PR

This is intentionally a feature PR, not a refactor-only PR:
WebTransport requires coordinated changes across public API, stream/conn internals,
HTTP Datagram handling, settings negotiation, and application wiring.

Issue references

dtikhonov and others added 30 commits January 17, 2026 12:15
@dtikhonov
Add BAT protocol IETF draft
13db9d1 
BAT (Bidirectional Attestation Test) is a simple echo protocol for
testing HTTP Datagrams (RFC 9297) implementations. Modeled after
SiDUCK (draft-pardue-quic-siduck), BAT provides:

- Simple echo service over HTTP CONNECT
- Support for QUIC DATAGRAM frames (HTTP/3)
- Support for DATAGRAM Capsules (all HTTP versions)
- Protocol identifier: bat-00
- Testing tool for HTTP Datagram interoperability
@dtikhonov
Clarify BAT for HTTP/3 datagrams
c847b74
@dtikhonov
Define failure when H3 datagrams not negotiated
a216f08
@dtikhonov
Add support for HTTP Datagrams (RFC 9297)
f109b13 
Add first-class HTTP Datagram support for HTTP/3, aligned with RFC
9297.  The implementation handles QUIC DATAGRAM transport as well as
Capsule Protocol encapsulation when datagrams cannot fit the QUIC path,
providing a complete end-to-end feature for this new extension.

Core stream and connection logic now parses and emits HTTP Datagram frames
and capsules per RFC 9297 rules, including Quarter Stream ID handling
and strict error signaling.
@dtikhonov
Cover http dg error handling in stream tests
9413553
@dtikhonov
Addressed PR review comments
d2f0f59
@dtikhonov
Guard HTTP datagram memcpy bounds
69bea6d
@dtikhonov
Simplify HTTP datagram payload sizing
9a8b763
@dtikhonov
Update src/liblsquic/lsquic_full_conn_ietf.c
54c27f4 
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
@dtikhonov
Annotate HTTP/3 datagram stream ID check
11e166d
@dtikhonov
Add HTTP datagram history wrappers
912c8ce
@dtikhonov
Devious Baton!
27b692c
@dtikhonov
docs: add reliable stream reset draft
f816000
@dtikhonov
Add RESET_STREAM_AT parsing and TP plumbing
885859f
@dtikhonov
Add RESET_STREAM_AT frame unit tests
47403b5
@dtikhonov
Implement RESET_STREAM_AT receive handling
753b051
@dtikhonov
Gate RESET_STREAM_AT behind engine setting
fa22960
@dtikhonov
Rename RESET_STREAM_AT flag and split reset handlers
ec3cfb8
@dtikhonov
Small stylistic changes
dc39f43
@dtikhonov
Drop IETF checks from gQUIC reset path
271301f
@dtikhonov
Reduce number of forward declarations
7e68beb
@dtikhonov
Remove IETF checks from IETF reset path
d0e16f4
@dtikhonov
Cleanup
5d8eee6
@dtikhonov
Add webtransport draft to docs for easy reference
480b22b
@dtikhonov
Add public WebTransport API header
689c514
@dtikhonov
Whitespace changes
f17a8c4
@dtikhonov
tests: cover reset frame edge cases
e867d5f
@dtikhonov
tests: include IETF error codes for reset checks
960c1fe
@dtikhonov
tests: cover maybe_reset and qpack reset branches
0121925
@dtikhonov
tests: cover STOP_SENDING cleanup branches
3294abf
dtikhonov added 22 commits April 11, 2026 13:25
@dtikhonov
Validate WT response header counts
8115550
@dtikhonov
Rollback WT datagram write interest on failure
7c44707
@dtikhonov
Recover from WT uni stream init failure
bd01cf7
@dtikhonov
Fix WT uni allocation test plumbing
e6762f7
@dtikhonov
Close WT streams on read errors
eced683
@dtikhonov
Add WebTransport fuzz harness
bbc26bd
@dtikhonov
Harden WT fuzz close-capsule helper
47eec96
@dtikhonov
Reject truncated WT uni session IDs
febd714
@dtikhonov
Reject truncated HTTP datagram capsule types
fc95288
@dtikhonov
Make WT fuzz harness scenario-driven
79c1e1a
@dtikhonov
Add WT datagram-write fuzz hook
bac7919
@dtikhonov
Reject impossible WT session counts
cec2f39
@dtikhonov
Require 2xx WT accept responses
4d3104b
@dtikhonov
Reject 2xx WT reject statuses
c167137
@dtikhonov
Guard WT APIs against null sessions
a5358bf
@dtikhonov
Close WT streams on write errors
1995b27
@dtikhonov
Reject control stream WT reset operations
245cc57
@dtikhonov
Reject client-side WT accept streams
0b571ee
@dtikhonov
Guard WT datagram wrapper null sessions
47f497c
@dtikhonov
Reject late WT accept handoff
a2d0527
@dtikhonov
Revert WT null-session API hardening
92e82ec
@dtikhonov
Restore WT client accept handoff
5abf9a4
@litespeedtech litespeedtech deleted the 202601241123-web-transport-suport branch April 22, 2026 20:22
@litespeedtech litespeedtech restored the 202601241123-web-transport-suport branch April 22, 2026 20:36
@dtikhonov dtikhonov reopened this Apr 24, 2026
@dtikhonov dtikhonov mentioned this pull request Apr 24, 2026
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Add support for HTTP Datagrams (RFC 9297) Add support for WebTransport

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@dtikhonov @litespeedtech