netdev - Re: [PATCH nf-next] netfilter: add support for matching IPv4 options

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Date:   Sat, 1 Jun 2019 11:04:29 -0400
From:   Stephen Suryaputra <ssuryaextr@...il.com>
To:     Pablo Neira Ayuso <pablo@...filter.org>
Cc:     netfilter-devel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH nf-next] netfilter: add support for matching IPv4 options

On Sat, Jun 01, 2019 at 02:22:30AM +0200, Pablo Neira Ayuso wrote:
> > It is the same as the IPv6 one. The offset returned is the offset to the
> > specific option (target) or the byte beyond the options if the target
> > isn't specified (< 0).
> 
> Thanks for explaining. So you are using ipv6_find_hdr() as reference,
> but not sure this offset parameter is useful for this patchset since
> this is always set to zero, do you have plans to use this in a follow
> up patchset?

I developed this patchset to suit my employer needs and there is no plan
for a follow up patchset, however I think non-zero offset might be useful
in the future for tunneled packets.

> I mean, you make this check upfront from the _eval() path, ie.
> 
> static void nft_exthdr_ipv4_eval(const struct nft_expr *expr,
>                                  ...
> {
>         ...
> 
>         if (skb->protocol != htons(ETH_P_IP))
>                 goto err;

Got it.

Thanks.