netdev - Re: [PATCH v3] netfilter: nft_meta: Add NFT_META

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Date:   Fri, 18 Jan 2019 15:32:08 +0100
From:   Florian Westphal <fw@...len.de>
To:     Pablo Neira Ayuso <pablo@...filter.org>
Cc:     wenxu@...oud.cn, fw@...len.de, netdev@...r.kernel.org,
        netfilter-devel@...r.kernel.org, David Ahern <dsahern@...il.com>
Subject: Re: [PATCH v3] netfilter: nft_meta: Add NFT_META_I/OIFKIND meta type

Pablo Neira Ayuso <pablo@...filter.org> wrote:
> > +	case NFT_META_IIFKIND:
> > +		if (in == NULL || in->rtnl_link_ops == NULL)
> > +			goto err;
> > +		strncpy((char *)dest, in->rtnl_link_ops->kind, IFNAMSIZ);
> 
> It seems kind can be arbitrarily large, no limitation in its length.

Its limited to 60 or 56 bytes it seems:
char kind[MODULE_NAME_LEN];

nla_strlcpy(kind, linfo[IFLA_INFO_KIND], sizeof(kind));

(linkinfo_to_kind_ops in rtnetlink.c).

> Thinking...
> 
> There is no other way to identify a vft device rather than this
> string? The only l3mdev that exists if vrf, right?

There is, I suggested this more generic approach, as it would allow
to create rules that match on the kind of device used (vrf, ppp, etc.).

If you think its too generic, ok.