Unknown error 524

[NirGeller18]

Hi there,

I'm trying to run a basic xdp drop program I found on

https://developers.redhat.com/blog/2021/04/01/get-started-with-xdp#task_1__write_and_run_a_simple_program_with_xdp

And I'm running into the following error:

# xdp-loader load -vv -m skb -s xdp_drop veth1 xdp_drop.o
...
...
libxdp: Loaded XDP program xdp_dispatcher, got fd 11
libxdp: Failed to attach test program to dispatcher: Unknown error 524
libxdp: Compatibility check for dispatcher program failed: Unknown error 524
libxdp: Falling back to loading single prog without dispatcher
libxdp: Loaded XDP program xdp_drop_prog, got fd 5
libxdp: Replacing XDP fd -1 with 6 on ifindex 6

I'm running kernel 5.10.109 on a imx8m+ based board.
I added all the required kernel configs I thought were missing.
I cloned xdp-tools, built libbpf 0.8.0, then configured and built xdp-tools:

root@r3pa-8cb4:~/xdp/xdp-tools# ./configure
Found clang binary 'clang' with version 12 (from 'clang version 12.0.0 (https://github.com/llvm/llvm-project d28af7c654d8db0b68c175db5ce212d74fb5e9bc)')
libbpf support: submodule v0.8.0
perf_buffer__consume support: yes (submodule)
btf__load_from_kernel_by_id support: yes (submodule)
btf__type_cnt support: yes (submodule)
bpf_object__next_map support: yes (submodule)
bpf_object__next_program support: yes (submodule)
bpf_program__insn_cnt support: yes (submodule)
bpf_map_create support: yes (submodule)
perf_buffer__new_raw support: yes (submodule)
bpf_xdp_attach support: yes (submodule)
zlib support: yes
ELF support: yes
pcap support: yes
secure_getenv support: yes

Can you give me a hint how to solve this error?

Thanks a lot,

Nir.

[Toke Høiland-Jørgensen]

The compatibility check fails because the needed kernel functionality is not available on ARM architectures (see the libxdp man page). However, AFAICT the fallback mechanism is working as it should, so you should be able to attach programs just fine, you just can't attach multiple programs to the same interface...

[NirGeller18]

According to the example at
https://developers.redhat.com/blog/2021/04/01/get-started-with-xdp#task_1__write_and_run_a_simple_program_with_xdp
I was expecting to see xdp_dispatcher running, but I see only one program loaded:

root@r3pa-8cb4:~/xdp# xdp-tools/xdp-loader/xdp-loader status
CURRENT XDP PROGRAM STATUS:

Interface Prio Program name Mode ID Tag Chain actions

lo <No XDP program loaded!>
eth0 <No XDP program loaded!>
eth1 <No XDP program loaded!>
can0 <No XDP program loaded!>
can1 <No XDP program loaded!>
veth1 xdp_drop_prog skb 47 57cd311f2e27366b_

Does this mean I can still run a XDP program directly on a nic? (assuming it is supporting xdp of course...)

[Toke Høiland-Jørgensen]

NirGeller18 ***@***.***> writes:

According to the example at https://developers.redhat.com/blog/2021/04/01/get-started-with-xdp#task_1__write_and_run_a_simple_program_with_xdp I was expecting to see xdp_dispatcher running, but I see only one program loaded: ***@***.***:~/xdp# xdp-tools/xdp-loader/xdp-loader status CURRENT XDP PROGRAM STATUS: Interface Prio Program name Mode ID Tag Chain actions -------------------------------------------------------------------------------------- lo <No XDP program loaded!> eth0 <No XDP program loaded!> eth1 <No XDP program loaded!> can0 <No XDP program loaded!> can1 <No XDP program loaded!> veth1 xdp_drop_prog skb 47 57cd311f2e27366b_ Does this mean I can still run a XDP program directly on a nic? (assuming it is supporting xdp of course...)

Yeah, the dispatcher is what's used for running multiple programs, but it relies on kernel features that are not supported on ARM. libxdp will detect this and fall back to just loading the single XDP program, which is what you're seeing in the list. This will work just fine as long as you only need to run a single program, and should also work on physical NICs...

[NirGeller18]

Thank you.