From: Stephen Hemminger <stephen@networkplumber.org>
To: Denys Fedoryshchenko <denys@visp.net.lb>
Cc: <netdev@vger.kernel.org>, <pablo@netfilter.org>,
<jhs@mojatatu.com>, <davem@davemloft.net>,
<linux-kernel@vger.kernel.org>
Subject: Re: netlink, RTM_NEWTCLASS, nested attributes
Date: Wed, 20 Feb 2013 15:21:30 -0800 [thread overview]
Message-ID: <20130220152130.72df1258@samsung-9> (raw)
In-Reply-To: <3a8fd12d117d2281ac90cce96c0d68f3@visp.net.lb>
On Tue, 19 Feb 2013 23:45:25 +0200
Denys Fedoryshchenko <denys@visp.net.lb> wrote:
> Hi
>
> I tried recently to write my own tool based on amazing libmnl (which
> makes understanding of netlink - easy), written
> by Pablo Neira Ayuso, to manage QoS in Linux and faced problem, which i
> think probably
> a bug in handling netlink messages in kernel.
>
> For example if i send message, RTM_NEWTCLASS, after attribute
> TCA_OPTIONS i have nested attributes,
> for example in HTB: TCA_HTB_PARMS, TCA_HTB_RTAB, TCA_HTB_CTAB.
> libmnl, if i use nested attribute, adding a bit to it, by OR -
> NLA_F_NESTED(1 << 15).
> If i remove this flag - everything works fine. And here is the case,
> iproute2 tools
> just update length of TCA_OPTIONS, without setting flag, and it works
> because of that fine too.
>
> So there is basically 3 solutions:
> 1)New function in libmnl to do nested attributes without setting by OR
> flag
> 2)AND-ing attribute type in kernel to ignore nested flag
> 3)Keeping as is, who cares?
>
Several legacy netlink interfaces don't use NESTED flag. These are by
now enshrined in ABI and can't change. In code, that uses libmnl, I just
manually clear the flag as needed and document why. This could
be added to libmnl.
next prev parent reply other threads:[~2013-02-20 23:21 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-02-19 21:45 netlink, RTM_NEWTCLASS, nested attributes Denys Fedoryshchenko
2013-02-20 23:21 ` Stephen Hemminger [this message]
2013-02-20 23:24 ` Denys Fedoryshchenko
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