Subject: Re: [PATCH net-next 1/2] net/sched: sch_fq_pie: add per-flow statistics via class ops

From: Stephen Hemminger <[email-masked]>
Date: Sun, 31 May 2026 15:41:49 -0700

On Sun, 31 May 2026 18:23:13 +0530
"Hemendra M. Naik" <[email-masked]> wrote:

> +struct tc_fq_pie_xstats {
> +	__u32	type;
> +	union {
> +		struct tc_fq_pie_qd_stats qdisc_stats;
> +		struct tc_fq_pie_cl_stats class_stats;
> +	};
> +};

Sorry, you can't change the kernel/userspace ABI like this.
How will old iproute2 hand new kernel and vice/versa.

The better safer way to do this is to either extend the
existing structure and have iproute2 know how how to handle
short (missing) class data; or use another netlink
type for class data.