From: Denys Fedoryshchenko <denys@visp.net.lb>
To: Stephen Hemminger <stephen@networkplumber.org>
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: Thu, 21 Feb 2013 01:24:02 +0200 [thread overview]
Message-ID: <3598cf904e2e235bc9060aa712dcce53@visp.net.lb> (raw)
In-Reply-To: <20130220152130.72df1258@samsung-9>
On 2013-02-21 01:21, Stephen Hemminger wrote:
> 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.
Thank you for clarification!
---
Denys Fedoryshchenko, Network Engineer, Virtual ISP S.A.L.
prev parent reply other threads:[~2013-02-20 23:24 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
2013-02-20 23:24 ` Denys Fedoryshchenko [this message]
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