Skip to content

Pad all sent TCP frames to the same size via ChunkedMessageQueue#4446

Open
tnull wants to merge 3 commits intolightningdevkit:mainfrom
tnull:2026-02-chunky
Open

Pad all sent TCP frames to the same size via ChunkedMessageQueue#4446
tnull wants to merge 3 commits intolightningdevkit:mainfrom
tnull:2026-02-chunky

Conversation

@tnull
Copy link
Contributor

@tnull tnull commented Feb 25, 2026

In this PR we implement padding all sent TCP frames to the same size by ensuring all writes happen in chunks of length CHUNK_SIZE and any remainders are filled by adequately sized Ping messages.

This approach operating on the network-layer was discussed in the spec call and seems to be preferred by everybody. Hence it supersedes the approach taken in #4248.

TODO

  • Measurement/evaluation of introduced overhead

@tnull tnull requested a review from TheBlueMatt February 25, 2026 14:33
@ldk-reviews-bot
Copy link

ldk-reviews-bot commented Feb 25, 2026

👋 Thanks for assigning @TheBlueMatt as a reviewer!
I'll wait for their review and will help manage the review process.
Once they submit their review, I'll check if a second reviewer would be helpful.

@tnull tnull self-assigned this Feb 25, 2026
@tnull tnull moved this to Goal: Merge in Weekly Goals Feb 25, 2026
@tnull tnull changed the title Add ChunkedMessageQueue for message padding Pad all sent TCP frames to the same size via ChunkedMessageQueue Feb 25, 2026
@tnull tnull force-pushed the 2026-02-chunky branch 2 times, most recently from 48bb745 to 64e28db Compare February 25, 2026 15:08
@tnull
Copy link
Contributor Author

tnull commented Feb 25, 2026

Validated via Wireshark and LDK Node tests:

2026-02-25-161017_hyprshot

@codecov
Copy link

codecov bot commented Feb 25, 2026

Codecov Report

❌ Patch coverage is 96.11307% with 11 lines in your changes missing coverage. Please review.
✅ Project coverage is 85.98%. Comparing base (eb3980d) to head (d8de722).
⚠️ Report is 39 commits behind head on main.

Files with missing lines Patch % Lines
lightning/src/ln/peer_handler.rs 95.63% 9 Missing and 2 partials ⚠️
Additional details and impacted files
@@            Coverage Diff             @@
##             main    #4446      +/-   ##
==========================================
+ Coverage   85.88%   85.98%   +0.10%     
==========================================
  Files         159      159              
  Lines      104302   104850     +548     
  Branches   104302   104850     +548     
==========================================
+ Hits        89578    90157     +579     
+ Misses      12222    12188      -34     
- Partials     2502     2505       +3     
Flag Coverage Δ
tests 85.98% <96.11%> (+0.10%) ⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:
  • ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

Add `BorrowedVecWriter`, `encrypt_with_header_0s_at`, `encrypt_message_into`,
and `encrypt_buffer_into` to `PeerChannelEncryptor` to support encrypting
messages directly into a shared buffer at arbitrary offsets.

Define `ChunkedMessageQueue` struct in `peer_handler` with a contiguous byte
buffer that will replace the current `pending_outbound_buffer` /
`gossip_broadcast_buffer` dual-queue system. The queue pads all outgoing
traffic into fixed-size `CHUNK_SIZE` chunks using Ping messages as filler,
so an observer sees only constant-size writes on the wire. Ping padding
uses `ponglen = 65533` to suppress Pong responses per BOLT-1.

Co-Authored-By: HAL 9000
Replace `pending_outbound_buffer`,
`pending_outbound_buffer_first_msg_offset`, and
`gossip_broadcast_buffer` fields in `Peer` with a single `message_queue:
ChunkedMessageQueue`.

Co-Authored-By: HAL 9000
Add five new tests:
- `test_chunked_message_queue_ping_padding`: verifies chunk alignment for
  various message sizes
- `test_chunked_message_queue_small_remainder_overflow`: verifies the
  two-Ping edge case when remainder < `MIN_ENCRYPTED_PING_SIZE`
- `test_chunked_message_queue_chunk_alignment`: verifies alignment after
  encrypting multiple real messages
- `test_chunked_message_queue_buffer_compaction`: verifies `maybe_compact`
  correctly drains sent bytes
- `test_chunked_message_queue_pending_msg_bytes_tracking`: verifies that
  `pending_msg_bytes` tracks real message bytes and is unaffected by padding

Also extract a `get_test_encryptor` helper to reduce boilerplate across
the new tests.

Co-Authored-By: HAL 9000
Signed-off-by: Elias Rohrer <dev@tnull.de>
@ldk-reviews-bot
Copy link

🔔 1st Reminder

Hey @TheBlueMatt! This PR has been waiting for your review.
Please take a look when you have a chance. If you're unable to review, please let us know so we can find another reviewer.

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment

Labels

None yet

Projects

Status: Goal: Merge

Development

Successfully merging this pull request may close these issues.

2 participants