From: Ken Brown <kbrown@cornell.edu>
To: cygwin-developers@cygwin.com
Subject: Re: Questions about select for sockets
Date: Tue, 6 Apr 2021 13:37:13 -0400 [thread overview]
Message-ID: <6306d8f3-cf05-07bb-e944-05aed69266f3@cornell.edu> (raw)
In-Reply-To: <YGyMPZOxpSnWaApt@calimero.vinschen.de>
On 4/6/2021 12:28 PM, Corinna Vinschen wrote:
> On Apr 6 11:44, Ken Brown wrote:
>> On 4/6/2021 10:33 AM, Corinna Vinschen wrote:
>>> On Apr 6 16:20, Corinna Vinschen wrote:
>>>> On Apr 3 14:16, Ken Brown via Cygwin-developers wrote:
>>>>> 4. Why do we set
>>>>>
>>>>> except_ready = saw_shutdown_write () || saw_shutdown_read () ?
>>>>>
>>>>> I can't find any documentation that says that a shutdown should be
>>>>> considered an exceptional condition. On the other hand, POSIX does say,
>>>>> "Other circumstances under which a socket may be considered to have an
>>>>> exceptional condition pending are protocol-specific and
>>>>> implementation-defined." So maybe there's some Cygwin-specific reason for
>>>>> doing this?
>>>>
>>>> Nope, this is old (and wrong) cruft. Neither Steven's book nor the
>>>> Linux man pages, nor testing on Linux imply that ready for exception
>>>> is used to indicate anything other than out-of-band data. This should
>>>> be fixed.
>>>
>>> We may also have to change the saw_shutdown_read/saw_shutdown_write
>>> handling. I checked this on Linux and what happens is:
>>>
>>> After shutdown (fd, SHUT_RD), the socket is ready for reading and writing
>>
>> This seems surprising to me. Is it really the shutdown that caused it to be
>> ready for writing in your test, or was it ready for writing anyway (e.g.,
>> because the relevant buffer was empty)?
>
> I guess so, too. How to make sure the socket isn't ready for writing
> without going to great lengths?
I guess you could have a subprocess write to the socket in a loop, so that its
buffer will quickly fill up and a further write will block.
Ken
next prev parent reply other threads:[~2021-04-06 17:37 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-03 18:16 Ken Brown
2021-04-06 14:20 ` Corinna Vinschen
2021-04-06 14:33 ` Corinna Vinschen
2021-04-06 15:44 ` Ken Brown
2021-04-06 16:28 ` Corinna Vinschen
2021-04-06 17:37 ` Ken Brown [this message]
2021-04-06 18:24 ` Corinna Vinschen
2021-04-06 19:36 ` Corinna Vinschen
2021-04-07 14:04 ` Ken Brown
2021-04-07 15:31 ` Corinna Vinschen
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