netdev - Re: [PATCH net-next v11 20/23] ovpn: kill key and notify userspace in case of IV exhaustion

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Message-ID: <ZzS3jgNQoDH_0TvK@hog>
Date: Wed, 13 Nov 2024 15:28:30 +0100
From: Sabrina Dubroca <sd@...asysnail.net>
To: Antonio Quartulli <antonio@...nvpn.net>
Cc: Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	Donald Hunter <donald.hunter@...il.com>,
	Shuah Khan <shuah@...nel.org>, ryazanov.s.a@...il.com,
	Andrew Lunn <andrew@...n.ch>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH net-next v11 20/23] ovpn: kill key and notify userspace
 in case of IV exhaustion

2024-11-12, 16:44:09 +0100, Antonio Quartulli wrote:
> On 05/11/2024 11:33, Sabrina Dubroca wrote:
> > 2024-10-29, 11:47:33 +0100, Antonio Quartulli wrote:
> > > +int ovpn_nl_key_swap_notify(struct ovpn_peer *peer, u8 key_id)
> > > +{
> > [...]
> > > +
> > > +	nla_nest_end(msg, k_attr);
> > > +	genlmsg_end(msg, hdr);
> > > +
> > > +	genlmsg_multicast_netns(&ovpn_nl_family, dev_net(peer->ovpn->dev), msg,
> > > +				0, OVPN_NLGRP_PEERS, GFP_ATOMIC);
> > > +
> > 
> > Is openvpn meant to support moving the device to a different netns? In
> > that case I'm not sure the netns the ovpn netdevice is in is the right
> > one, the userspace client will be in the encap socket's netns instead
> > of the netdevice's?
> > 
> > (same thing in the next patch)
> 
> Well, moving between netns's may not be among the most common use cases, but
> I can see people doing all kind of weird things, if not forbidden.

The idea would be that only the ovpn device is in one particular
netns, so that no packets can make it out of that netns unencrypted. I
don't know if anybody actually does that.

> Hence, I would not assume the netdevice to always stay in the same netns all
> time long.
> 
> This said, what you say assumes that the userspace process won't change
> netns after having added the peer.

That shouldn't matter as long as it's still listening to multicast
messages in the original netns.

Around that same "which netns" question, ovpn_udp{4,6}_output uses the
socket's, but ovpn_nexthop_from_rt{4,6} uses the netdev's.

-- 
Sabrina