netdev - Re: Add a SOCK_DESTROY operation to close sockets from userspace

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Message-Id: <1447841538.833901.443067761.28637F38@webmail.messagingengine.com>
Date:	Wed, 18 Nov 2015 11:12:18 +0100
From:	Hannes Frederic Sowa <hannes@...essinduktion.org>
To:	Lorenzo Colitti <lorenzo@...gle.com>, netdev@...r.kernel.org
Cc:	edumazet@...gle.com, ek@...gle.com, maze@...gle.com,
	dtor@...gle.com
Subject: Re: Add a SOCK_DESTROY operation to close sockets from userspace

Hello,

On Wed, Nov 18, 2015, at 02:43, Lorenzo Colitti wrote:
> This patch series adds the ability for a privileged process to
> destroy sockets belonging to other userspace processes via the
> sock_diag interface, and implements that for TCP sockets.
> 
> This functionality is needed on laptops and mobile hosts to
> ensure that network switches / disconnects do not result in
> applications being blocked for long periods of time (minutes) in
> read or connect calls on TCP sockets that will never succeed
> because the IP address they are bound to is gone. Closing the
> sockets in the protocol layer causes these calls to fail fast and
> allows applications to reconnect on another network.

I regularly do this with gdb, connecting to the process, looking up the
filedescriptors in /proc/pid/fd and closing the socket. Actually it will
also be removed from the poll tables and thus unlocks the system. I
think a user space approach would be preferred to do so, or some out of
band signalling (which we actually already have in terms of netlink
monitor).

Bye,
Hannes
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