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([2601:282:800:fd80:c824:60cf:2bea:8fbc]) by smtp.googlemail.com with ESMTPSA id x66sm61093803pfb.78.2019.04.26.08.04.00 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 26 Apr 2019 08:04:01 -0700 (PDT) Subject: Re: [PATCH net-next 1/3] netlink: make nla_nest_start() add NLA_F_NESTED flag To: Michal Kubecek , "David S. Miller" Cc: netdev@vger.kernel.org, Johannes Berg , Jiri Pirko , Pablo Neira Ayuso , Jozsef Kadlecsik , Florian Westphal , netfilter-devel@vger.kernel.org, linux-kernel@vger.kernel.org References: <5278b013a953d4fb2e7944fc810f783d70ea52a5.1556269635.git.mkubecek@suse.cz> From: David Ahern 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: netfilter-devel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netfilter-devel@vger.kernel.org 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 > --- Acked-by: David Ahern