RE: [PATCH v6 00/11] net/rtap: add io_uring based TAP driver

[Konstantin Ananyev <konstantin.ananyev@huawei.com>]

> 
> This series adds net_rtap, an experimental poll mode driver that uses
> Linux io_uring for asynchronous packet I/O with kernel TAP interfaces.
> 
> Like net_tap, net_rtap creates a kernel network interface visible to
> standard tools (ip, ethtool) and the Linux TCP/IP stack.  From DPDK
> it is an ordinary ethdev.
> 
> Motivation
> ----------
> 
> This driver started as an experiment to determine whether Linux
> io_uring could deliver better packet I/O performance than the
> traditional read()/write() system calls used by net_tap.  By posting
> batches of I/O requests asynchronously, io_uring amortizes system
> call overhead across multiple packets.
 
Sounds interesting...
Curious did you make any perf comparisons vs our traditional tap?
 
> The project also served as a testbed for using AI tooling to help
> build a comprehensive test suite, refactor code, and improve
> documentation.  The result is intended as an example for other PMD
> authors: the driver has thorough unit tests covering data path,
> offloads, multi-queue, fd lifecycle, and more, along with detailed
> code comments explaining design choices.
>
>
> 
> Why not extend net_tap?
> -----------------------
> 
> The existing net_tap driver was designed to provide feature parity
> with mlx5 when used behind the failsafe PMD.  That goal led to
> significant complexity: rte_flow support emulated via eBPF programs,
> software GSO implementation, and other features that duplicate in
> user space what the kernel already does.
> 
> net_rtap takes the opposite approach -- use the kernel efficiently
> and let it do what it does well.  There is no rte_flow support;
> receive queue selection is left to the kernel's native RSS/steering.
> There is no software GSO; the driver passes segmentation requests
> to the kernel via the virtio-net header and lets the kernel handle
> it.  The result is a much simpler driver that is easier to maintain
> and reason about.
> 
> Given these fundamentally different design goals, a clean
> implementation was more practical than refactoring net_tap.
> 
> Acknowledgement
> ---------------
> 
> Parts of the test suite, code review, and refactoring were done
> with the assistance of Anthropic Claude (AI).  All generated code
> was reviewed and tested by the author.
> 
> Requirements:
>   - Kernel headers with IORING_ASYNC_CANCEL_ALL (upstream since 5.19)
>   - liburing >= 2.0
> 
> Should work on distributions: Debian 12+, Ubuntu 24.04+,
> Fedora 37+, SLES 15 SP6+ / openSUSE Tumbleweed.
> RHEL 9 is not supported (io_uring is disabled by default).
> 
> v6:
>   - fix lots of bugs found doing automated review
>   - convert to use ifindex and netlink to avoid rename issues
>   - implement xstats
> 
> Stephen Hemminger (11):
>   net/rtap: add driver skeleton and documentation
>   net/rtap: add TAP device creation and queue management
>   net/rtap: add Rx/Tx with scatter/gather support
>   net/rtap: add statistics and device info
>   net/rtap: add link and device management operations
>   net/rtap: add checksum and TSO offload support
>   net/rtap: add multi-process support
>   net/rtap: add link state change interrupt
>   net/rtap: add Rx interrupt support
>   net/rtap: add extended statistics support
>   test: add unit tests for rtap PMD
> 
>  MAINTAINERS                            |    7 +
>  app/test/meson.build                   |    1 +
>  app/test/test_pmd_rtap.c               | 2620 ++++++++++++++++++++++++
>  doc/guides/nics/features/rtap.ini      |   26 +
>  doc/guides/nics/index.rst              |    1 +
>  doc/guides/nics/rtap.rst               |  101 +
>  doc/guides/rel_notes/release_26_03.rst |    7 +
>  drivers/net/meson.build                |    1 +
>  drivers/net/rtap/meson.build           |   30 +
>  drivers/net/rtap/rtap.h                |  152 ++
>  drivers/net/rtap/rtap_ethdev.c         |  864 ++++++++
>  drivers/net/rtap/rtap_intr.c           |  207 ++
>  drivers/net/rtap/rtap_netlink.c        |  445 ++++
>  drivers/net/rtap/rtap_rxtx.c           |  803 ++++++++
>  drivers/net/rtap/rtap_xstats.c         |  293 +++
>  15 files changed, 5558 insertions(+)
>  create mode 100644 app/test/test_pmd_rtap.c
>  create mode 100644 doc/guides/nics/features/rtap.ini
>  create mode 100644 doc/guides/nics/rtap.rst
>  create mode 100644 drivers/net/rtap/meson.build
>  create mode 100644 drivers/net/rtap/rtap.h
>  create mode 100644 drivers/net/rtap/rtap_ethdev.c
>  create mode 100644 drivers/net/rtap/rtap_intr.c
>  create mode 100644 drivers/net/rtap/rtap_netlink.c
>  create mode 100644 drivers/net/rtap/rtap_rxtx.c
>  create mode 100644 drivers/net/rtap/rtap_xstats.c
> 
> --
> 2.51.0