Re: [PATCH libnftnl] set: Add support for NFTA_SET_SUBKEY attributes

From: Stefano Brivio <sbrivio@redhat.com>
To: Phil Sutter <phil@nwl.cc>
Cc: "Pablo Neira Ayuso" <pablo@netfilter.org>,
	netfilter-devel@vger.kernel.org,
	"Florian Westphal" <fw@strlen.de>,
	"Kadlecsik József" <kadlec@blackhole.kfki.hu>,
	"Eric Garver" <eric@garver.life>
Subject: Re: [PATCH libnftnl] set: Add support for NFTA_SET_SUBKEY attributes
Date: Wed, 20 Nov 2019 13:12:56 +0100	[thread overview]
Message-ID: <20191120131256.4f17cdf1@redhat.com> (raw)
In-Reply-To: <20191120130152.7d4d3ca8@redhat.com>

On Wed, 20 Nov 2019 13:01:52 +0100
Stefano Brivio <sbrivio@redhat.com> wrote:

> On Wed, 20 Nov 2019 12:24:48 +0100
> Phil Sutter <phil@nwl.cc> wrote:
>
> [...]
>
> > > +		if (!*l)
> > > +			break;
> > > +		v = *l;
> > > +		mnl_attr_put_u32(nlh, NFTA_SET_SUBKEY_LEN, htonl(v));    
> > 
> > I guess you're copying the value here because how htonl() is declared,
> > but may it change the input value non-temporarily? I mean, libnftnl is
> > in control over the array so from my point of view it should be OK to
> > directly pass it to htonl().  
> 
> It won't change the input value at all, but that's not the point: I'm
> reading from an array of 8-bit values and attributes are 32 bits. If I
> htonl() directly on the input array, it's going to use 24 bits around
> those 8 bits.

Err, wait, never mind :) I'm just passing the value, not the reference
there -- no need to copy anything of course. I'll drop this copy in v2.

-- 
Stefano