From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Borkmann 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 Message-ID: <51E5705B.9070206@redhat.com> References: <1372755331-1267-1-git-send-email-jiri@resnulli.us> <51E55D91.5050000@redhat.com> <1561418.Jq9drZzso6@lx-vladimir> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, Jiri Pirko To: Vladimir Kondratiev Return-path: Received: from mx1.redhat.com ([209.132.183.28]:23260 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932183Ab3GPQKP (ORCPT ); Tue, 16 Jul 2013 12:10:15 -0400 In-Reply-To: <1561418.Jq9drZzso6@lx-vladimir> Sender: netdev-owner@vger.kernel.org List-ID: 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 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 >