netdev - Re: [PATCH net-next] veth: report NEWLINK event when moving the peer device in a new namespace

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Date:   Fri, 31 Aug 2018 18:54:44 +0200
From:   Lorenzo Bianconi <lorenzo.bianconi@...hat.com>
To:     David Ahern <dsahern@...il.com>
Cc:     davem@...emloft.net, netdev@...r.kernel.org
Subject: Re: [PATCH net-next] veth: report NEWLINK event when moving the peer
 device in a new namespace

> On 8/31/18 10:19 AM, Lorenzo Bianconi wrote:
> >> On 8/31/18 5:43 AM, Lorenzo Bianconi wrote:
> >>> When moving a veth device to another namespace, userspace receives a
> >>> RTM_DELLINK message indicating the device has been removed from current
> >>> netns. However, the other peer does not receive a netlink event
> >>> containing new values for IFLA_LINK_NETNSID and IFLA_LINK veth
> >>> attributes.
> >>> Fix that behaviour sending to userspace a RTM_NEWLINK message in the peer
> >>> namespace to report new IFLA_LINK_NETNSID/IFLA_LINK values
> >>>
> >>
> >> A newlink message is generated in the new namespace. What information is
> >> missing from that message?
> >>
> > 
> > Hi David,
> > 
> > let's assume we have two veth paired devices (veth0 and veth1) on inet
> > namespace. When moving a veth1 to another namespace, userspace is notified
> > with RTM_DELLINK event on inet namespace to indicate that veth1 has been
> > moved to another namespace. However some userspace applications
> > (e.g. NetworkManager), listening for events on inet namespace, are interested
> > in veth1 ifindex in the new namespace. This patch sends a new RTM_NEWLINK event
> > in inet namespace to provide new values for IFLA_LINK_NETNSID/IFLA_LINK 
> 
> This is in init namespace
> $ ip li set veth2 netns foo
> 
> $ ip monitor
> Deleted 20: veth2@...h1: <BROADCAST,MULTICAST,M-DOWN> mtu 1500 qdisc
> noop state DOWN group default
>     link/ether c6:d0:d6:c5:23:7d brd ff:ff:ff:ff:ff:ff new-netns foo
> new-ifindex 20
> 
> It shows the new namespace in the delete message.

Ops, I have not noticed this info has been already introduced in
the commit 38e01b30563a ("dev: advertise the new ifindex when the netns
iface changes"). Thanks for the hint.

DaveM please drop this patch.

Regards,
Lorenzo