netdev - Re: [PATCH net] tun: fix premature POLLOUT notification on tun devices

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Message-Id: <20170313.220122.1218068190297475298.davem@davemloft.net>
Date:   Mon, 13 Mar 2017 22:01:22 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     hannes@...essinduktion.org
Cc:     netdev@...r.kernel.org, bjorn@...k.no, Valdis.Kletnieks@...edu,
        jonas@...puner.ca, aszlig@...moonstudios.org
Subject: Re: [PATCH net] tun: fix premature POLLOUT notification on tun
 devices

From: Hannes Frederic Sowa <hannes@...essinduktion.org>
Date: Mon, 13 Mar 2017 00:00:26 +0100

> aszlig observed failing ssh tunnels (-w) during initialization since
> commit cc9da6cc4f56e0 ("ipv6: addrconf: use stable address generator for
> ARPHRD_NONE"). We already had reports that the mentioned commit breaks
> Juniper VPN connections. I can't clearly say that the Juniper VPN client
> has the same problem, but it is worth a try to hint to this patch.
> 
> Because of the early generation of link local addresses, the kernel now
> can start asking for routers on the local subnet much earlier than usual.
> Those router solicitation packets arrive inside the ssh channels and
> should be transmitted to the tun fd before the configuration scripts
> might have upped the interface and made it ready for transmission.
> 
> ssh polls on the interface and receives back a POLL_OUT. It tries to send
> the earily router solicitation packet to the tun interface.  Unfortunately
> it hasn't been up'ed yet by config scripts, thus failing with -EIO. ssh
> doesn't retry again and considers the tun interface broken forever.
> 
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=121131
> Fixes: cc9da6cc4f56 ("ipv6: addrconf: use stable address generator for ARPHRD_NONE")
> Cc: Bjørn Mork <bjorn@...k.no>
> Reported-by: Valdis Kletnieks <Valdis.Kletnieks@...edu>
> Cc: Valdis Kletnieks <Valdis.Kletnieks@...edu>
> Reported-by: Jonas Lippuner <jonas@...puner.ca>
> Cc: Jonas Lippuner <jonas@...puner.ca>
> Reported-by: aszlig <aszlig@...moonstudios.org>
> Cc: aszlig <aszlig@...moonstudios.org>
> Signed-off-by: Hannes Frederic Sowa <hannes@...essinduktion.org>

Applied and queued up for -stable.