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Reply-To: nicolas.dichtel@6wind.com
Subject: Re: [PATCH 1/5] rtnetlink: allow RTM_SETLINK to reference other
 namespaces
To:     Jonas Bonn <jonas@norrbonn.se>, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org
Cc:     davem@davemloft.net
References: <20191105081112.16656-1-jonas@norrbonn.se>
 <20191105081112.16656-2-jonas@norrbonn.se>
From:   Nicolas Dichtel <nicolas.dichtel@6wind.com>
Organization: 6WIND
Message-ID: <4c57e4b2-13d2-63e0-c513-62cd786497eb@6wind.com>
Date:   Tue, 5 Nov 2019 16:41:14 +0100
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Le 05/11/2019 à 09:11, Jonas Bonn a écrit :
> Netlink currently has partial support for acting on interfaces outside
> the current namespace.  This patch extends RTM_SETLINK with this
> functionality.
> 
> The current implementation has an unfortunate semantic ambiguity in the
> IFLA_TARGET_NETNSID attribute.  For setting the interface namespace, one
> may pass the IFLA_TARGET_NETNSID attribute with the namespace to move the
> interface to.  This conflicts with the meaning of this attribute for all
> other methods where IFLA_TARGET_NETNSID identifies the namespace in
> which to search for the interface to act upon:  the pair (namespace,
> ifindex) is generally given by (IFLA_TARGET_NETNSID, ifi->ifi_index).
> 
> In order to change the namespace of an interface outside the current
> namespace, we would need to specify both an IFLA_TARGET_NETNSID
> attribute and a namespace to move to using IFLA_NET_NS_[PID|FD].  This is
> currently now allowed as only one of these three flags may be specified.
> 
> This patch loosens the restrictions a bit but tries to maintain
> compatibility with the previous behaviour:
> i)  IFLA_TARGET_NETNSID may be passed together with one of
> IFLA_NET_NS_[PID|FD]
> ii)  IFLA_TARGET_NETNSID is primarily defined to be the namespace in
> which to find the interface to act upon
> iii)  In order to maintain backwards compatibility, if the device is not
> found in the specified namespace, we also look for it in the current
> namespace
> iv)  If only IFLA_TARGET_NETNSID is given, the device is still moved to
> that namespace, as before; and, as before, IFLA_NET_NS_[PID|FD] take
> precedence as namespace selectors
> 
> Ideally, IFLA_TARGET_NETNSID would only ever have been used to select the
> namespace of the device to act upon.  A separate flag, IFLA_NET_NS_ID
> would have been made available for changing namespaces
> 
> Signed-off-by: Jonas Bonn <jonas@norrbonn.se>
Acked-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>