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

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Message-Id: <1447858590.895715.443293345.0FE778BF@webmail.messagingengine.com>
Date:	Wed, 18 Nov 2015 15:56:30 +0100
From:	Hannes Frederic Sowa <hannes@...essinduktion.org>
To:	Lorenzo Colitti <lorenzo@...gle.com>
Cc:	Eric Dumazet <eric.dumazet@...il.com>,
	Stephen Hemminger <stephen@...workplumber.org>,
	netdev@...r.kernel.org, Eric Dumazet <edumazet@...gle.com>,
	Erik Kline <ek@...gle.com>,
	Maciej Żenczykowski <maze@...gle.com>,
	Dmitry Torokhov <dtor@...gle.com>
Subject: Re: Add a SOCK_DESTROY operation to close sockets from userspace

On Wed, Nov 18, 2015, at 15:45, Lorenzo Colitti wrote:
> On Wed, Nov 18, 2015 at 10:31 PM, Hannes Frederic Sowa
> <hannes@...essinduktion.org> wrote:
> > I was not saying using tcp_close literally, sorry for not making that
> > clear, but just model the state transitions after tcp_close. At least it
> > seems like a normal close to me.
> 
> But it shouldn't be a normal close. Consider calling SOCK_DESTROY on a
> socket that is streaming data to a peer. If SOCK_DESTROY results in
> the kernel sending a FIN, the remote side might think that the sender
> closed the connection gracefully, even though the local side aborted
> the connection.

Oh, yes, I understand. The connection wasn't closed by the application
but by the administrator forcefully. So we should never indicate a
successful TCP shutdown with FIN but with RST. A TIME_WAIT period
actuallty still seems useful to me, maybe with different semantics, only
RST incoming data?

Bye,
Hannes
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