Re: [RFC] xdp: add device context to bpf_xdp_link_attach_failed tracepoint

[Leon Hwang]

On 2026/7/5 10:11, Masashi Honma wrote:
> 2026年7月4日(土) 22:28 Leon Hwang <leon.hwang@xxxxxxxxx>:
>> Probably, you can get the 'extack->_msg' by tracing dev_xdp_attach using
>> kprobe+kretprobe or kprobe.session, if the extack is not NULL.
> 
> Thanks, that's a nice pointer -- dev_xdp_attach() has both the net_device
> (so the ifindex, which lets us correlate a failure to a specific attach)
> and the extack, and it avoids depending on the tracepoint you want to
> retire.
> 
> The tradeoff is that dev_xdp_attach() is a static internal function, so a
> probe on it can break across kernels (inlining/signature changes). For a
> best-effort error message that's tolerable with a graceful fallback, but
> it's a maintenance cost on our side.
> 
> Since this is ultimately just an error-message improvement, and your
> in-band BPF_LINK_CREATE work would solve it cleanly for all link types, I
> think we'd lean toward waiting for that rather than adding an internal
> kprobe to Cilium. Do you have a rough timeline for the BPF_LINK_CREATE
> series? That would help us decide whether a stopgap is worth it.


I will post the RFC around October.

Thanks,
Leon