From: Daniel Borkmann <dborkman@redhat.com>
To: Vladimir Kondratiev <qca_vkondrat@qca.qualcomm.com>
Cc: netdev@vger.kernel.org, Jiri Pirko <jpirko@redhat.com>
Subject: Re: [patch net-next v2] nlmon: use standard rtnetlink link api for add/del devices
Date: Tue, 16 Jul 2013 18:10:03 +0200 [thread overview]
Message-ID: <51E5705B.9070206@redhat.com> (raw)
In-Reply-To: <1561418.Jq9drZzso6@lx-vladimir>
On 07/16/2013 05:59 PM, Vladimir Kondratiev wrote:
> On Tuesday, July 16, 2013 04:49:53 PM Daniel Borkmann wrote:
>> On 07/16/2013 04:08 PM, Vladimir Kondratiev wrote:
>>> Jiri Pirko <jiri <at> resnulli.us> writes:
>>>
>>>> It is not nice when netdev is created right after module load and with
>>>> some implicit name. So rather change nlmon to use standard rtnl link API.
>>>
>>> Could you please elaborate a bit - how to capture netlink skb's after your
>>> patch? Before, it was netdev that may be used with tcpdump. Now, there is
>>> no such netdev. How to create it?
>>
>> modprobe nlmon
>> ip link add type nlmon
>> ip link set nlmon0 up
>>
>> tcpdump -i nlmon0 ....
>>
>> ip link set nlmon0 down
>> ip link del dev nlmon0
>> rmmod nlmon
>
> Thanks a lot! I guess it is worth to have this mentioned somewhere.
> It will save lots of questions. For example, in Kconfig:
Ok, I don't have a strong opinion on the below patch, I'm fine either way.
But, given that for such devices it is *common* to use the standard rtnl
link API (Jiri is right that this is a better/cleaner approach), I'm not
sure if this needs to be documented then ...
> diff --git a/drivers/net/Kconfig b/drivers/net/Kconfig
> index b45b240..13acea2 100644
> --- a/drivers/net/Kconfig
> +++ b/drivers/net/Kconfig
> @@ -247,8 +247,18 @@ config NLMON
> purpose of this is to analyze netlink messages with packet sockets.
> Thus applications like tcpdump will be able to see local netlink
> messages if they tap into the netlink device, record pcaps for further
> - diagnostics, etc. This is mostly intended for developers or support
> - to debug netlink issues. If unsure, say N.
> + diagnostics, etc. Typical flow is:
> +
> + modprobe nlmon
> + ip link add type nlmon
> + ip link set nlmon0 up
> + tcpdump -i nlmon0 ....
> + ip link set nlmon0 down
> + ip link del dev nlmon0
> + rmmod nlmon
> +
> + This is mostly intended for developers or support to debug netlink
> + issues. If unsure, say N.
>
> endif # NET_CORE
>
next prev parent reply other threads:[~2013-07-16 16:10 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-07-02 8:55 [patch net-next v2] nlmon: use standard rtnetlink link api for add/del devices Jiri Pirko
2013-07-02 19:47 ` Daniel Borkmann
2013-07-02 19:53 ` David Miller
2013-07-16 14:08 ` Vladimir Kondratiev
2013-07-16 14:49 ` Daniel Borkmann
2013-07-16 15:59 ` Vladimir Kondratiev
2013-07-16 16:10 ` Daniel Borkmann [this message]
2013-07-16 16:41 ` Jiri Pirko
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