netdev - Re: Fw: [Bug 106241] New: shutdown(3)/close(3) behaviour is incorrect for sockets in accept(3)

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Message-ID: <56281192.20606@oracle.com>
Date:	Wed, 21 Oct 2015 23:28:34 +0100
From:	Alan Burlison <Alan.Burlison@...cle.com>
To:	Al Viro <viro@...IV.linux.org.uk>
CC:	Eric Dumazet <eric.dumazet@...il.com>,
	Stephen Hemminger <stephen@...workplumber.org>,
	netdev@...r.kernel.org, dholland-tech@...bsd.org,
	Casper Dik <casper.dik@...cle.com>
Subject: Re: Fw: [Bug 106241] New: shutdown(3)/close(3) behaviour is incorrect
 for sockets in accept(3)

On 21/10/2015 19:51, Al Viro wrote:

> BTW, is SCM_RIGHTS outside of scope?  They do mention it in one place
> only:
> | Ancillary data is also possible at the socket level. The <sys/socket.h>
> | header shall define the following symbolic constant for use as the cmsg_type
> | value when cmsg_level is SOL_SOCKET:
> |
> | SCM_RIGHTS
> |     Indicates that the data array contains the access rights to be sent or
> | received.

That's still exactly the same in Issue 7, Technical Corrigenda 2 which 
is in final review at the moment.

>>> In other words, is that destruction of
>>> 	* any descriptor refering to this socket [utterly insane for obvious
>>> reasons]
>>> 	* the last descriptor refering to this socket (modulo descriptor
>>> passing, etc.) [a bitch to implement, unless we treat a syscall in progress
>>> as keeping the opened file open], or
>>> 	* _the_ descriptor used to issue accept(2) [a bitch to implement,
>>> with a lot of fun races in an already race-prone area]?
>>
>>  From reading the POSIX close() page I believe the second option is
>> the correct one.
>
> Er...  So fd2 = dup(fd);accept(fd)/close(fd) should *not* trigger that
> behaviour, in your opinion?  Because fd is sure as hell not the last
> descriptor refering to that socket - fd2 remains alive and well.
>
> Behaviour you describe below matches the _third_ option.

Ah, I wasn't 100% sure what the intended difference between #2 and #3 
was TBH, it does sound like I meant #3, yes :-)

-- 
Alan Burlison
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