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

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Date:	Wed, 18 Nov 2015 16:33:34 +0100
From:	Hannes Frederic Sowa <hannes@...essinduktion.org>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Lorenzo Colitti <lorenzo@...gle.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 16:32, Hannes Frederic Sowa wrote:
> On Wed, Nov 18, 2015, at 16:16, Eric Dumazet wrote:
> > On Wed, 2015-11-18 at 15:56 +0100, Hannes Frederic Sowa wrote:
> > > 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?
> > 
> > There is some confusion.
> > 
> > TIME_WAIT are used to be able to send ACK packets to incoming valid
> > packets.
> 
> I was only talking to prevent fast address/port reuse on the same socket
> and preventing delayed packets being accepted by a 

sorry...

accepted by a later connection reusing the same quadrupel.

Bye,
Hannes
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