Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Subject: Re: [PATCH net-next 1/3] netlink: make nla_nest_start() add
 NLA_F_NESTED flag
To:     Michal Kubecek <mkubecek@suse.cz>,
        "David S. Miller" <davem@davemloft.net>
Cc:     netdev@vger.kernel.org, Johannes Berg <johannes.berg@intel.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, linux-kernel@vger.kernel.org
References: <cover.1556269635.git.mkubecek@suse.cz>
 <5278b013a953d4fb2e7944fc810f783d70ea52a5.1556269635.git.mkubecek@suse.cz>
From:   David Ahern <dsahern@gmail.com>
Message-ID: <33d772e5-a2f4-c9a1-11df-27fa7baf8625@gmail.com>
Date:   Fri, 26 Apr 2019 09:03:59 -0600
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:52.0)
 Gecko/20100101 Thunderbird/52.9.1
MIME-Version: 1.0
In-Reply-To: <5278b013a953d4fb2e7944fc810f783d70ea52a5.1556269635.git.mkubecek@suse.cz>
Content-Type: text/plain; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On 4/26/19 3:13 AM, Michal Kubecek wrote:
> Even if the NLA_F_NESTED flag was introduced more than 11 years ago, most
> netlink based interfaces (including recently added ones) are still not
> setting it in kernel generated messages. Without the flag, message parsers
> not aware of attribute semantics (e.g. wireshark dissector or libmnl's
> mnl_nlmsg_fprintf()) cannot recognize nested attributes and won't display
> the structure of their contents.
> 
> Unfortunately we cannot just add the flag everywhere as there may be
> userspace applications which check nlattr::nla_type directly rather than
> through a helper masking out the flags. Therefore the patch renames
> nla_nest_start() to nla_nest_start_noflag() and introduces nla_nest_start()
> as a wrapper adding NLA_F_NESTED. The calls which add NLA_F_NESTED manually
> are rewritten to use nla_nest_start().
> 
> Except for changes in include/net/netlink.h, the patch was generated using
> this semantic patch:
> 
> @@ expression E1, E2; @@
> -nla_nest_start(E1, E2)
> +nla_nest_start_noflag(E1, E2)
> 
> @@ expression E1, E2; @@
> -nla_nest_start_noflag(E1, E2 | NLA_F_NESTED)
> +nla_nest_start(E1, E2)
> 
> Signed-off-by: Michal Kubecek <mkubecek@suse.cz>
> ---


Acked-by: David Ahern <dsahern@gmail.com>