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From include/ci/tools/platform/*: include <linux/stdargs.h> or <stdargs.h>.
From ci/tools/sysdep.h: do not include log.h, because it needs stdargs.
From include/cplane/mib.h and include/onload/dshm.h: explicitly include
debug.h and log.h

This all is necessary to avoid redefinition of va_copy on linux-5.15,
because this kernel provides its own version of va_copy in linux/stdargs.h.

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Onload®️ is a high performance user-level network stack, which accelerates TCP and UDP network I/O for applications using the BSD sockets on Linux.


  • Low Application-to-application latency.
  • Binary compatible with existing applications.
  • Open Source (GPLv2.0 and BSD-2-Clause).

OpenOnload comprises a user-level shared library that intercepts network- related system calls and implements the protocol stack, and supporting kernel modules. It is compatible with the full system call API, including those aspects that are usually problematic for user-level networking, such as fork(), exec(), passing sockets through Unix domain sockets, and advancing the protocol when the application is not scheduled.

Installation and Quick Start Guide

OpenOnload is distributed as source code. Instructions for building, packaging and installing may be found in

For each interface on which Onload is to use AF_XDP, execute the following:

echo ens2f0 > /sys/module/sfc_resource/afxdp/register

The application to be Onloaded should be launched by prefixing the command line with onload.


Please see

Compatible network adapters, drivers and operating systems

OpenOnload can accelerate applications on operating systems with AF_XDP support. AF_XDP support needs Linux kernel version 5.3 or later. To support zero-copy, Onload needs AF_XDP network adapter drivers to implement the necessary AF_XDP primitives. Typically the latest drivers from the network adapter vendors will support these primitives.

The AF_XDP support is currently under development and is not yet at final release quality.

The following operating system distributions are known to provide an adequate level of AF_XDP support for Onload:

  • Ubuntu LTS 20.04
  • Ubuntu 21.04
  • Debian 10 with Linux kernel 5.10
  • Debian 11
  • Redhat Enterprise Linux 8.3, 8.4
  • Linux kernel in the range 5.3 - 5.13

Onload also works with the native ef_vi hardware interface, supported by Xilinx network adapters. In this mode of operation, AF_XDP kernel and driver support is not required. This allows Onload to be used on older operating systems and take advantage of additional features. A version of the 'sfc' net driver for Xilinx network adapters is included.

Compatible Xilinx network adapters

The following adapters at least are able to support OpenOnload without AF_XDP:

  • X2541
  • X2522, X2522-25G
  • SFN8042
  • SFN8522, SFN8542

Compatible Linux kernels and distributions for Xilinx network adapters

This source tree is known to work with Xilinx network adapters on following Linux distributions:

  • Ubuntu LTS 18.04, LTS 20.04, 21.04
  • Debian 10, 11
  • Redhat Enterprise Linux 7.9, 8.3, 8.4
  • Linux kernel in the range 4.15 - 5.13


The publicly-hosted repository is a community-supported project.

Supported releases of OpenOnload are available from


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