linux-kernel - Re: [PATCH net-next 1/1] rtnetlink: request RTM

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Message-ID: <20180118205552.jm7shzcojbumax2k@gmail.com>
Date:   Thu, 18 Jan 2018 21:55:53 +0100
From:   Christian Brauner <christian.brauner@...onical.com>
To:     Jiri Benc <jbenc@...hat.com>
Cc:     Christian Brauner <christian.brauner@...ntu.com>,
        davem@...emloft.net, dsahern@...il.com, fw@...len.de,
        daniel@...earbox.net, lucien.xin@...il.com,
        mschiffer@...verse-factory.net, jakub.kicinski@...ronome.com,
        vyasevich@...il.com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, stephen@...workplumber.org
Subject: Re: [PATCH net-next 1/1] rtnetlink: request RTM_GETLINK by pid or fd

On Thu, Jan 18, 2018 at 09:29:14PM +0100, Jiri Benc wrote:
> On Thu, 18 Jan 2018 21:21:24 +0100, Christian Brauner wrote:
> > In such scenarios setting a netns id property is
> > not really wanted
> 
> Why? I think that's what you should do if you want to avoid setns. Just
> use netnsid. I don't see any problem with that and you didn't provide
> any explanation.

Ah, sorry, maybe I was to brief. When creating and destroying a lot of
short-lived network namespaces it seems unnecessary to give them all
label/netns id. Using a netns id makes much more sense when you want a
persistent, long-living network namespace. For example, iproute2 where
you want to create a persistent network namespace that sticks around via
ip netns add bla && ip netns set bla 5.

A more concrete scenario is creating a network namespace, moving a
device into it via RTM_SETLINK which also supports IFLA_NET_NS_{FD,PID}
and then wanting to query the device. This would be very easy to do if
one could reuse the IFLA_NET_NS_{FD,PID} without having to set a
netnsid.

Christian