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Date: Mon, 14 Apr 2025 14:24:16 -0700
From: Jakub Kicinski <kuba@kernel.org>
To: Cong Wang <xiyou.wangcong@gmail.com>
Cc: Toke =?UTF-8?B?SMO4aWxhbmQtSsO4cmdlbnNlbg==?= <toke@redhat.com>, Jamal
 Hadi Salim <jhs@mojatatu.com>, Jiri Pirko <jiri@resnulli.us>, "David S.
 Miller" <davem@davemloft.net>, Eric Dumazet <edumazet@google.com>, Paolo
 Abeni <pabeni@redhat.com>, Simon Horman <horms@kernel.org>,
 netdev@vger.kernel.org
Subject: Re: [PATCH net-next] tc: Return an error if filters try to attach
 too many actions
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On Mon, 14 Apr 2025 14:03:31 -0700 Cong Wang wrote:
> > > I wonder ENOSPC is a better errno than EINVAL here?  
> > 
> > I think EINVAL is fine, it's the generic "netlink says no" error code. 
> > The string error should be clear enough.  
> 
> IMHO, EINVAL is abused (which is probably why we introduced extack). I
> prefer to find a better errno than EINVAL whenever possible.
>  
> Extack is available but it is mostly for human to read, not technically
> an API for programs to interpret.

How is user space going to interpret the error code here?
Seems to me that'd mean the user space is both aware of the limit 
and yet trying to send more actions.