[PATCH v5 00/10] net/rtap: add io_uring based TAP driver

Stephen Hemminger
2026-02-09T18:40:52Z

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.

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

Known working distributions: Debian 12+, Ubuntu 24.04+,
Fedora 37+, SLES 15 SP6+ / openSUSE Tumbleweed.
RHEL 9 is not supported (io_uring is disabled by default).

v5 - revised, renamed and expanded from the v4 ioring PMD
- more complete testing and dependency handling

Stephen Hemminger (10):
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 link state change interrupt
net/rtap: add multi-process support
net/rtap: add Rx interrupt support
test: add unit tests for rtap PMD

MAINTAINERS | 7 +
app/test/meson.build | 1 +
app/test/test_pmd_rtap.c | 2044 ++++++++++++++++++++++++
doc/guides/nics/features/rtap.ini | 25 +
doc/guides/nics/index.rst | 1 +
doc/guides/nics/rtap.rst | 101 ++
doc/guides/rel_notes/release_26_03.rst | 6 +
drivers/net/meson.build | 1 +
drivers/net/rtap/meson.build | 28 +
drivers/net/rtap/rtap.h | 100 ++
drivers/net/rtap/rtap_ethdev.c | 908 +++++++++++
drivers/net/rtap/rtap_intr.c | 267 ++++
drivers/net/rtap/rtap_rxtx.c | 784 +++++++++
13 files changed, 4273 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_rxtx.c

--
2.51.0