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

Konstantin Ananyev
2026-02-15T08:58:19Z

>
> 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