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Subject: Re: [PATCH net-next 0/3] make nla_nest_start() add NLA_F_NESTED flag
From:   Johannes Berg <johannes@sipsolutions.net>
To:     Michal Kubecek <mkubecek@suse.cz>,
        "David S. Miller" <davem@davemloft.net>
Cc:     "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
        David Ahern <dsahern@gmail.com>,
        Jiri Pirko <jiri@mellanox.com>,
        Pablo Neira Ayuso <pablo@netfilter.org>,
        Jozsef Kadlecsik <kadlec@blackhole.kfki.hu>,
        Florian Westphal <fw@strlen.de>,
        "netfilter-devel@vger.kernel.org" <netfilter-devel@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Date:   Fri, 26 Apr 2019 11:24:15 +0200
In-Reply-To: <cover.1556269635.git.mkubecek@suse.cz>
References: <cover.1556269635.git.mkubecek@suse.cz>
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On Fri, 2019-04-26 at 09:13 +0000, Michal Kubecek wrote:

> Another observation was that even if NLA_F_NESTED flag was introduced in
> 2007, only few netlink based interfaces set it in kernel generated messages
> and even many recently added APIs omit it. That is unfortunate as without
> the flag, message parsers not familiar with attribute semantics cannot
> recognize nested attributes and do not see message structure; this affects
> e.g. wireshark dissector or mnl_nlmsg_fprintf() from libmnl.

Indeed.

I wonder if we should also (start) enforcing that the userspace sender
side sets this, if the policy is strict?

johannes