xdp-loader - Man Page

XDP-loader - an XDP program loader

XDP-loader is a simple loader for XDP programs with support for attaching multiple programs to the same interface. To achieve this it exposes the same load and unload semantics exposed by the libxdp library.

Running xdp-loader

The syntax for running xdp-loader is:

xdp-loader COMMAND [options]

Where COMMAND can be one of:
       load        - load an XDP program on an interface
       unload      - unload an XDP program from an interface
       status      - show current XDP program status
       help        - show the list of available commands

Each command, and its options are explained below. Or use xdp-loader COMMAND --help to see the options for each command.

The LOAD command

The load command loads one or more XDP programs onto an interface.

The syntax for the load command is:

xdp-loader load [options] <ifname> <programs>

Where <ifname> is the name of the interface to load the programs onto, and the <programs> is one or more file names containing XDP programs. The programs will be loaded onto the interface in the order of their preference, as specified by the program metadata (see libxdp(3)).

The supported options are:

-m, --mode <mode>

Specifies which mode to load the XDP program to be loaded in. The valid values are 'native', which is the default in-driver XDP mode, 'skb', which causes the so-called skb mode (also known as generic XDP) to be used, 'hw' which causes the program to be offloaded to the hardware, or 'unspecified' which leaves it up to the kernel to pick a mode (which it will do by picking native mode if the driver supports it, or generic mode otherwise). Note that using 'unspecified' can make it difficult to predict what mode a program will end up being loaded in. For this reason, the default is 'native'.

-p, --pin-path <path>

This specifies a root path under which to pin any maps that define the 'pinning' attribute in their definitions. This path must be located on a bpffs file system. If not set, maps will not be pinned, even if they specify pinning in their definitions. When pinning maps, if the pinned location for a map already exist, the map pinned there will be reused if it is compatible with the type of the map being loaded.

-s, --section <section>

Specify which ELF section to load the XDP program(s) from in each file. The default is to use the first program in each file. If this option is set, it applies to all programs being loaded.

-v, --verbose

Enable debug logging. Specify twice for even more verbosity.

-h, --help

Display a summary of the available options

The UNLOAD command

The unload command is used for unloading programs from an interface.

The syntax for the unload command is:

xdp-loader unload [options] <ifname>

Where <ifname> is the name of the interface to load the programs onto. Either the --all or --id options must be used to specify which program(s) to unload.

The supported options are:

-i, --id <id>

Unload a single program from the interface by ID. Use xdp-loader status to obtain the ID of the program being unloaded. If this program is the last program loaded on the interface, the dispatcher program will also be removed, which makes the operation equivalent to specifying --all.

-a, --all

Unload all XDP programs on the interface, as well as the multi-program dispatcher.

-v, --verbose

Enable debug logging. Specify twice for even more verbosity.

-h, --help

Display a summary of the available options

The STATUS command

The status command displays a list of interfaces in the system, and the XDP program(s) loaded on each interface. For each interface, a list of programs are shown, with the run priority and "chain actions" for each program. See the section on program metadata for the meaning of this metadata.

-v, --verbose

Enable debug logging. Specify twice for even more verbosity.

-h, --help

Display a summary of the available options

Examples

To load an XDP program on the eth0 interface simply do:

# xdp-loader load eth0 xdp_drop.o
# xdp-loader status

CURRENT XDP PROGRAM STATUS:

Interface        Prio  Program name     Mode     ID   Tag               Chain actions
-------------------------------------------------------------------------------------
lo               <no XDP program>
eth0                   xdp_dispatcher   native   50   d51e469e988d81da
 =>              50    xdp_drop                  55   57cd311f2e27366b  XDP_PASS

Which shows that a dispatcher program was loaded on the interface, and the xdp_drop program was installed as the first (and only) component program after it. In this instance, the program does not specify any of the metadata above, so the defaults (priority 50 and XDP_PASS as its chain call action) was used.

To use the automatic map pinning, include the pinning attribute into the map definition in the program, something like:

struct {
	__uint(type, BPF_MAP_TYPE_ARRAY);
	__uint(max_entries, 10);
	__type(key, __u32);
	__type(value, __u64);
	__uint(pinning, LIBBPF_PIN_BY_NAME);
} my_map SEC(".maps");

And load it with the --pin-path attribute:

# xdp-loader load eth0 my_prog.o --pin-path /sys/fs/bpf/my-prog

This will pin the map at /sys/fs/bpf/my-prog/my_map. If this already exists, the pinned map will be reused instead of creating a new one, which allows different BPF programs to share the map.

Bugs

Please report any bugs on Github: https://github.com/xdp-project/xdp-tools/issues

Author

xdp-loader and this man page were written by Toke Høiland-Jørgensen.

Info

FEBRUARY 8, 2021 V1.1.1 XDP program loader