netdev - Re: [PATCH ipsec-next] xfrm: delete not-used XFRM_OFFLOAD

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Date:   Tue, 1 Feb 2022 09:22:17 +0200
From:   Leon Romanovsky <leon@...nel.org>
To:     Steffen Klassert <steffen.klassert@...unet.com>
Cc:     "David S . Miller" <davem@...emloft.net>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        netdev@...r.kernel.org
Subject: Re: [PATCH ipsec-next] xfrm: delete not-used XFRM_OFFLOAD_IPV6 define

On Tue, Feb 01, 2022 at 07:58:36AM +0100, Steffen Klassert wrote:
> On Thu, Jan 27, 2022 at 08:24:58PM +0200, Leon Romanovsky wrote:
> > From: Leon Romanovsky <leonro@...dia.com>
> > 
> > XFRM_OFFLOAD_IPV6 define was exposed in the commit mentioned in the
> > fixes line, but it is never been used both in the kernel and in the
> > user space. So delete it.
> 
> How can you be sure that is is not used in userspace? At least some
> versions of strongswan set that flag. So even if it is meaningless
> in the kernel, we can't remove it.

I looked over all net/* and include/uapi/* code with "git log -p" and didn't
see any use of this flag ever. 

Looking in strongsswan, I see that they bring kernel header files [1] for the build
and removal won't break build of old strongsswan versions.

We just can't use this bit anymore, because of this commit [2]. I have
no clue why it was used there.

So yes, we can remove, but worth to add a comment about old strongsswan.

And if we are talking about xfrm_user_offload flags, there is a
well-known API mistake in xfrm_dev_state_add() of not checking validity
of flags. So *theoretically* we can find some software in the wild that
uses other bits too.

I would like to see it is fixed.

[1] 5bfae68670f2 ("include: Update xfrm.h to include hardware offloading extensions")
[2] d42948fc057e ("kernel-netlink: Enable hardware offloading if configured for an SA")

Thanks

> 
> > 
> > Fixes: d77e38e612a0 ("xfrm: Add an IPsec hardware offloading API")
> > Signed-off-by: Leon Romanovsky <leonro@...dia.com>
> > ---
> >  include/uapi/linux/xfrm.h | 1 -
> >  1 file changed, 1 deletion(-)
> > 
> > diff --git a/include/uapi/linux/xfrm.h b/include/uapi/linux/xfrm.h
> > index 4e29d7851890..2c822671cc32 100644
> > --- a/include/uapi/linux/xfrm.h
> > +++ b/include/uapi/linux/xfrm.h
> > @@ -511,7 +511,6 @@ struct xfrm_user_offload {
> >  	int				ifindex;
> >  	__u8				flags;
> >  };
> > -#define XFRM_OFFLOAD_IPV6	1
> >  #define XFRM_OFFLOAD_INBOUND	2
> >  
> >  struct xfrm_userpolicy_default {
> > -- 
> > 2.34.1