XSKNF - Speed up development of AF_XDP-based NFs

The XSKNF library speeds up the development of AF_XDP based network functions taking care of all aspects related to AF_XDP buffers and rings management and threading aspects. The programmer just has to write a packet processing function that receives a single packet in input, processes it and provides a verdict.

Building

The library relies on libbpf and libxdp that are included as submodules and automatically updated when building.

The libelf, libz, and libmnl libraries are required and can be installed in Ubuntu with the following command:

sudo apt install libelf-dev zlib1g-dev libmnl-dev

Run make in the main project folder to build the library under ./src and the examples under ./examples.

Application setup

To process packets in user space through AF_XDP sockets you just need to include the XSKNF library in yout program and implement the xsknf_packet_processor() function. This function receives as parameters a pointer to the packet buffer, the length of the packet and the index of the ingress interface and must return the index of the output interface or -1 to drop the packet. Interface indexes reflect the order in which interfaces are passed on the command line (starting from 0).

A typical application based on XSKNF can be called with a set of XSKNF-specific arguments, followed by a double hypen (--), followed by a set of application-specific arguments (in a similar way to how DPDK applications are invoked). The following arguments are currently supported by the library:

-i, --iface=n[:m]   Interface to operate on (a copy mode between copy (c) or zero-copy (z)
                    can optionally be specified). Can be repeated multiple times
-p, --poll          Use poll syscall
-S, --xdp-skb=n     Use XDP skb-mode
-f, --frame-size=n  Set the frame size (must be a power of two in aligned mode, default is 4096)
-u, --unaligned     Enable unaligned chunk placement
-b, --batch-size=n  Batch size for sending or receiving packets. Default is 64
-B, --busy-poll     Busy poll
-M  --mode          Working mode (AF_XDP, XDP, COMBINED)
-w  --workers=n     Number of packet processing workers

The macswap example provides a very basic example of how to use the library. For example it can be run in the follwing way:

sudo ./macswap -i ens1f0 -i ens1f1 -- -q

This command tells XSKNF to use interfaces ens1f0 and ens1f1 (-i) and the application not to print periodic statistics (-q).

Architecture

TODO

Paper

For the tests of the paper Comparing User Space and In-Kernel Packet Processing for Edge Data Centers please refer to the tests folder.