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

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Date:	Wed, 18 Nov 2015 12:19:12 +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 11:47, Lorenzo Colitti wrote:
> On Wed, Nov 18, 2015 at 7:19 PM, Hannes Frederic Sowa
> <hannes@...essinduktion.org> wrote:
> > I bet there will soon be a timewaitd which handles the not configurable
> > (David has rejected all those patches so far) timeout of TIME_WAIT
> > sockets. And I bet it will be used. :/
> 
> No, SOCK_DESTROY has no effect on TCP_TIME_WAIT sockets or any other
> non-full socket.
> 
> When called on any socket where sk_fullsock(sk) is false, it returns
> EOPNOTSUPP because there is nothing to do. Its purpose is to interrupt
> blocked userspace socket calls, not to release resources.

Okay, thanks for clarification! Still I don't see how you enter
TIME_WAIT in case you kill an active socket. At least my start-up idea
timewaitd seems to be not implementable. ;)

I was wondering why you didn't use tcp_close function, because still we
could have the address and we would like to do a proper shutdown of the
connection. While this patchset wants to tear down sockets for addresses
no longer alive, it still can be used with full sockets.

Thanks,
Hannes
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