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Date:   Mon, 23 Apr 2018 22:08:44 +0200
From:   Florian Westphal <fw@strlen.de>
To:     Ahmed Abdelsalam <amsalam20@gmail.com>
Cc:     Pablo Neira Ayuso <pablo@netfilter.org>, fw@strlen.de,
        davem@davemloft.net, dav.lebrun@gmail.com,
        linux-kernel@vger.kernel.org, netfilter-devel@vger.kernel.org,
        coreteam@netfilter.org, netdev@vger.kernel.org
Subject: Re: [nf-next] netfilter: extend SRH match to support matching
 previous, next and last SID
Message-ID: <20180423200844.bq3ksj262brrifnj@breakpoint.cc>
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Ahmed Abdelsalam <amsalam20@gmail.com> wrote:
> > > @@ -50,6 +62,12 @@ struct ip6t_srh {
> > >  	__u8                    segs_left;
> > >  	__u8                    last_entry;
> > >  	__u16                   tag;
> > > +	struct in6_addr		psid_addr;
> > > +	struct in6_addr		nsid_addr;
> > > +	struct in6_addr		lsid_addr;
> > > +	struct in6_addr		psid_msk;
> > > +	struct in6_addr		nsid_msk;
> > > +	struct in6_addr		lsid_msk;
> > 
> > This is changing something exposed through UAPI, so you will need a
> > new revision for this.
> 
> Could you please advice what should be done in this case? 

You need to add
struct ip6t_srh_v1 {
	/* copy of struct ip6t_srh here */

	/* new fields go here */
};


Look at xt_conntrack.c, conntrack_mt_reg[] for an example of
multi-revision match.

You can probably re-origanise code to avoid too much duplication.
See 5a786232eb69a1f870ddc0cfd69d5bdef241a2ea in nf.git for an example,
it makes v0 into a v1 struct at runtime and re-uses new v1 code
for old v0.