linux-kernel - Re: [PATCH net-next 3/6] tools: ynl-gen: use uapi mask definition in NLA_POLICY

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <20251014123201.6ecfd146@kernel.org>
Date: Tue, 14 Oct 2025 12:32:01 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Asbjørn Sloth Tønnesen
 <ast@...erby.net>
Cc: "David S. Miller" <davem@...emloft.net>, Eric Dumazet
 <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>, Alexei Starovoitov
 <ast@...nel.org>, Andrew Lunn <andrew+netdev@...n.ch>, Arkadiusz Kubalewski
 <arkadiusz.kubalewski@...el.com>, Daniel Borkmann <daniel@...earbox.net>,
 Daniel Zahka <daniel.zahka@...il.com>, Donald Hunter
 <donald.hunter@...il.com>, Jacob Keller <jacob.e.keller@...el.com>, Jesper
 Dangaard Brouer <hawk@...nel.org>, Jiri Pirko <jiri@...nulli.us>, Joe
 Damato <jdamato@...tly.com>, John Fastabend <john.fastabend@...il.com>,
 Jonathan Corbet <corbet@....net>, Simon Horman <horms@...nel.org>,
 Stanislav Fomichev <sdf@...ichev.me>, Toke Høiland-Jørgensen <toke@...hat.com>, Vadim Fedorenko
 <vadim.fedorenko@...ux.dev>, Willem de Bruijn <willemb@...gle.com>,
 bpf@...r.kernel.org, netdev@...r.kernel.org, linux-doc@...r.kernel.org,
 linux-kernel@...r.kernel.org, "Jason A. Donenfeld" <Jason@...c4.com>
Subject: Re: [PATCH net-next 3/6] tools: ynl-gen: use uapi mask definition
 in NLA_POLICY_MASK

On Tue, 14 Oct 2025 17:29:30 +0000 Asbjørn Sloth Tønnesen wrote:
> On 10/14/25 12:59 AM, Jakub Kicinski wrote:
> > On Mon, 13 Oct 2025 16:50:00 +0000 Asbjørn Sloth Tønnesen wrote:  
> >> Currently when generating policies using NLA_POLICY_MASK(), then
> >> we emit a pre-computed decimal mask.
> >>
> >> When render-max is set, then we can re-use the mask definition,
> >> that has been generated in the uapi header.  
> > 
> > This will encourage people to render masks in uAPI which just pollutes
> > the uAPI files.  
> 
> It might, but is that a problem, given that most flag-sets are rather small?

Problem is a strong word. But if the choice is having a constant in
auto-generated code, or pointless, cargo-cult'ed mask values in the 
uAPI headers - I choose the former.

> Example from include/uapi/linux/wireguard.h:
>  > enum wgpeer_flag {
>  >     WGPEER_F_REMOVE_ME = 1U << 0,
>  >     WGPEER_F_REPLACE_ALLOWEDIPS = 1U << 1,
>  >     WGPEER_F_UPDATE_ONLY = 1U << 2,
>  >     __WGPEER_F_ALL = WGPEER_F_REMOVE_ME | WGPEER_F_REPLACE_ALLOWEDIPS |
>  >                      WGPEER_F_UPDATE_ONLY
>  > };  
> 
> I agree that a private "WGPEER_F_ALL" would be pollution, but "__WGPEER_F_ALL"
> is less likely to accidentally be used by user-space.
> 
> I get why Jason likes having the __WGPEER_F_ALL in a place where it is easy
> to review that it has contains all flags, and why he don't like a policy like
> NLA_POLICY_MASK(.., 0x7).
> 
> We could do the mask definition in the kernel code, like many handwritten
> netlink families does, but we still need to keep NETDEV_XDP_ACT_MASK in
> netdev.h or remove it's YNL-GEN header for some time.

It's a transitional problem. People coming from hand-crafted code feel
like they need a human-readable mask. 6mo later once they are
comfortable with YNL codegen they won't care. But, sadly, at that point
it is too late to delete stuff from the uAPI header.