Implement socket.recvmsg_into on Unix by 1ndahous3 · Pull Request #9268 · RustPython/RustPython

1ndahous3 · 2026-10-20T22:02:38Z

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Found when importing Trio on Linux, which expects socket.recvmsg_into to be available.

Summary

Receive into an iterable of writable buffers and return the byte count, ancillary data, flags and sender address.
Preserve scatter ordering, buffer exports, timeouts and datagram/TCP MSG_TRUNC behavior, without holding Python buffer locks while waiting for socket data.
Materialize the iterable before exporting its buffers, allowing callbacks and generators to mutate the original collection.
Reuse the existing recvmsg path with aligned ancillary storage.

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Summary by CodeRabbit

New Features
- Added Unix support for receiving socket data directly into multiple writable buffers with recvmsg_into.
- The new method returns the number of bytes received, ancillary data, message flags, and the sender address.
- Supports iterable buffer inputs and preserves existing handling for truncated messages and discarded ancillary data.
Bug Fixes
- Improved ancillary-data handling and buffer validation for socket message reception.
- Added coverage for distributing received data across multiple buffers.

Assisted-by: Codex:GPT-6

chatgpt-codex-connector · 2026-10-20T22:02:47Z

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Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-10-20T22:09:10.696495Z	`43ac480`	PR opened

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coderabbitai · 2026-10-20T22:03:16Z

📝 Walkthrough

The Unix socket implementation adds vectored receiving to the host and Python layers. The Python API validates writable buffer iterables, receives data across buffers, and returns ancillary data, flags, and the address.

Changes: Unix socket receive

Layer / File(s)	Summary
Host vectored receive `crates/host_env/src/socket.rs`	Adds `RecvMsgIntoResult` and `recvmsg_into` for vectored uninitialized buffers. Ancillary storage is aligned, platform-width conversions are checked, and `recvmsg` delegates to the new receive path.
Python socket API `crates/stdlib/src/socket.rs`, `extra_tests/snippets/stdlib_socket.py`	Adds `PySocket.recvmsg_into` with buffer and ancillary-size validation, byte distribution, and discard-mode handling. Ancillary payloads move into Python bytes objects. A socket-pair test checks iterable exhaustion and data distribution across two buffers.

Priority: ➖ Normal

Estimated code review effort: 3 (Moderate) | ~25 minutes

Change: Feature

Sequence Diagram(s)

sequenceDiagram
  participant PythonCaller
  participant PySocket
  participant host_env_socket
  participant recvmsg
  PythonCaller->>PySocket: Call recvmsg_into with writable buffers
  PySocket->>host_env_socket: Receive into temporary buffers
  host_env_socket->>recvmsg: Submit iovecs and ancillary storage
  recvmsg-->>host_env_socket: Return bytes read, flags, address, and control data
  host_env_socket-->>PySocket: Return RecvMsgIntoResult
  PySocket->>PySocket: Distribute bytes and parse ancillary data
  PySocket-->>PythonCaller: Return count, ancillary data, flags, and address

Suggested reviewers: youknowone

Merge Risk: 🔵 Low · up to 43ac4

Receiving into buffers works through the existing timeout path, but an iterable that raises an exception reports a misleading TypeError instead. This is a bounded issue that can be fixed before merge or accepted for follow-up.

Pre-merge checks: 5

Check name	Status	Explanation
Description Check		Check skipped - CodeRabbit’s high-level summary is enabled.
Title check		The title clearly and concisely identifies the main change: implementing Unix socket.recvmsg_into.
Docstring Coverage		Docstring coverage is 83.33% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 6 functions across 3 files.
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.

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Inline comments:
Review comments at @crates/stdlib/src/socket.rs:
- Around line 2500-2502: Update the buffer extraction in recvmsg_into to replace
only TypeError with the “argument 1 must be an iterable” TypeError, while
propagating all other exceptions unchanged; follow the existing collect_iterable
logic used by sendmsg.

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📥 Commits

Reviewing files that changed from the base of the PR and between 657bab3 and 43ac480.

📒 Files selected for processing: 3

crates/host_env/src/socket.rs
crates/stdlib/src/socket.rs
extra_tests/snippets/stdlib_socket.py

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chatgpt-codex-connector

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youknowone

Thanks!

Implement socket.recvmsg_into on Unix

43ac480

Assisted-by: Codex:GPT-6

coderabbitai Bot reviewed Oct 20, 2026

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Comment thread crates/stdlib/src/socket.rs Resolved

chatgpt-codex-connector Bot reviewed Oct 20, 2026

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Comment thread crates/stdlib/src/socket.rs Resolved

youknowone approved these changes Oct 21, 2026

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youknowone merged commit b0142d0 into RustPython:main Oct 21, 2026
30 checks passed

1ndahous3 deleted the socket_recvmsg_into branch October 25, 2026 09:34

This was referenced Nov 5, 2026

Fix clippy warnings on main #9725

Merged

Use aligned control buffers and CMSG macros for ancillary data #9818

Merged

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Implement socket.recvmsg_into on Unix - #9268

Implement socket.recvmsg_into on Unix#9268
youknowone merged 1 commit into
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1ndahous3:socket_recvmsg_into

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