netdev - Re: [PATCH net] ipv6: addrconf: fix Juniper SSL VPN client regression

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Date:	Sun, 10 Jul 2016 01:23:55 +0200
From:	Bjørn Mork <bjorn@...k.no>
To:	Hannes Frederic Sowa <hannes@...essinduktion.org>
Cc:	netdev@...r.kernel.org, Valdis Kletnieks <Valdis.Kletnieks@...edu>,
	Jonas Lippuner <jonas@...puner.ca>,
	吉藤英明 <hideaki.yoshifuji@...aclelinux.com>
Subject: Re: [PATCH net] ipv6: addrconf: fix Juniper SSL VPN client regression

Hannes Frederic Sowa <hannes@...essinduktion.org> writes:
> On Sat, Jul 9, 2016, at 23:13, Bjørn Mork wrote:
>> The Juniper SSL VPN client use a "tun" interface and seems to
>> be picky about visible changes.to it. Commit cc9da6cc4f56
>> ("ipv6: addrconf: use stable address generator for ARPHRD_NONE")
>> made such interfaces get an auto-generated IPv6 link local address
>> by default, similar to most other interface types. This made the
>> Juniper SSL VPN client fail for unknown reasons.
>> 
>> Fixing this regression by effectively reverting the behaviour to
>> what we had before, while keeping the new "addrgenmode random"
>> feature.
>
> I wonder if we can simply add a flag, something like
> IFF_SUPPRESS_AUTO_IPV6_LL, to net_device->priv_flags and use that. So we
> can keep behavior for qmi, vxlan-gpe and gre. tun is the only device
> that is really user space facing, so maybe we just limit it to this?

Sounds good to me, but I don't know if the use case really qualifies as

 "* You should have a pretty good reason to be extending these flags."


The automatic address is certainly nice to have, but "good reason"?  I
don't know...  We can always just configure those devices for automatic
LL addresses using "ip link set foo addrgen random" or similar.


Bjørn