netdev - Re: [PATCH iproute2-next 0/2] tc: add NLM_F_ECHO support for actions and filters

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Date: Thu, 25 Jan 2024 10:37:46 +0800
From: Hangbin Liu <liuhangbin@...il.com>
To: Victor Nogueira <victor@...atatu.com>
Cc: stephen@...workplumber.org, dsahern@...nel.org, netdev@...r.kernel.org,
	jhs@...atatu.com, kernel@...atatu.com
Subject: Re: [PATCH iproute2-next 0/2] tc: add NLM_F_ECHO support for actions
 and filters

On Wed, Jan 24, 2024 at 12:34:54PM -0300, Victor Nogueira wrote:
> Continuing on what Hangbin Liu started [1], this patch set adds support for
> the NLM_F_ECHO flag for tc actions and filters. For qdiscs it will require
> some kernel surgery, and we'll send it soon after this surgery is merged.
> 
> When user space configures the kernel with netlink messages, it can set
> NLM_F_ECHO flag to request the kernel to send the applied configuration
> back to the caller. This allows user space to receive back configuration
> information that is populated by the kernel. Often because there are
> parameters that can only be set by the kernel which become visible with the
> echo, or because user space lets the kernel choose a default value.
> 
> To illustrate a use case where the kernel will give us a default value,
> the example below shows the user not specifying the action index:
> 
>     tc -echo actions add action mirred egress mirror dev lo
>   
>     total acts 0
>     Added action
>           action order 1: mirred (Egress Mirror to device lo) pipe
>           index 1 ref 1 bind 0
>           not_in_hw
> 
> Note that the echoed response indicates that the kernel gave us a value
> of index 1
> 

Looks good to me.

Reviewed-by: Hangbin Liu <liuhangbin@...il.com>