Can't create an XDP link on eth0 but lo works fine

[viktordoronin]

Hello, I'm trying to run an example from the getting started guide. I'm running it on Debian Linux under WSL, eBPF and XDP and everything else that's required are enabled in the kernel. When I tried to run the compiled program however, this is what I got:

2025/01/23 21:33:01 Attaching XDP:failed to attach link: create link: operation not supported

I assumed it's some sort of configuration problem on my end, until I changed the interface in main.go(line 27) to loopback("lo"): then it worked! So there's something about eth0 that doesn't allow to create a link. Here's my ip link output:

1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP mode DEFAULT group default qlen 1000
    link/ether 00:15:5d:15:f7:81 brd ff:ff:ff:ff:ff:ff

Any ideas? Google turned up nothing but a possible MTU issue which is clearly not the case here.

[viktordoronin]

Digged some more and turns out WSL can have this problem because its network interfaces are in fact vlans. Apparently it's supported now but I couldn't find a straightforward fix. My kernel version is 5.15.150.1 if anybody needs that.

[viktordoronin]

Found it!
According to kernel.org article on Hyper-V network driver, Hyper-V's virtual adapters do support XDP, but have to have LRO disabled. Run the command as written in the article:

ethtool -K eth0 lro off

...and the example starts working on eth0!

Hope this can stay up here so it can be googled by somebody else, even though it's not strictly an ebpf-go thing. Thank you.

[ti-mo]

Awesome, thanks for following up with the solution! This is indeed necessary with some drivers. As usual, EINVAL and ENOTSUP keep us guessing. 😉