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Re: Data sent through sockets are *sometimes* inverted ?!!!

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Jorgen Grahn <grahn+nntp@snipabacken.se> wrote:
> On Wed, 2012-02-22, Jerry Peters wrote:
>> Jorgen Grahn <grahn+nntp@snipabacken.se> wrote:
>>> On Mon, 2012-02-20, Jorgen Grahn wrote:
>>>> On Mon, 2012-02-20, Joe Pfeiffer wrote:
>>>>> Jorgen Grahn <grahn+nntp@snipabacken.se> writes:
>>>>>
>>>>>> On Fri, 2012-02-17, Joe Pfeiffer wrote:
>>> ...
>>>>>>> write() is also not guaranteed to send all the bytes out in a single
>>>>>>> try, so careful programming would require a similar loop for your
>>>>>>> write()s.  I've never actually seen a write() do anything but either
>>>>>>> send all the bytes or else fail, however.
>>>>>>
>>>>>> Have you looked? If you have a TCP socket with just N bytes of free Tx
>>>>>> buffer, and you write N+1 bytes to it, I'd expect a partial write to
>>>>>> happen.  I'd consider /not/ handling that case a serious bug.
>>>>>
>>>>> Yes, I have -- as part of debugging more instances than I want to admit
>>>>> to of discovering I wasn't doing a good enough job of what we discuss
>>>>> above.
>>>>>
>>>>> I've wound up dumping lots and lots of "tried to write %d, write
>>>>> returned %d" and I can't remember ever seeing an instance of something
>>>>> other than -1 or what I was trying to send.  It's an easy enough
>>>>> loop to write that I always do it (you're right, not handling the case
>>>>> would be a bug that might turn up now and might turn up in a decade),
>>>>> but so far I can't remember ever going around that loop twice.
>>>>
>>>> Interesting -- I must try it tonight. (On Linux, since I don't have
>>>> easy access to any other Unix outside work.)
>>> 
>>> So far I have failed to disprove what you wrote. Netcat to a
>>> SIGSTOPped server, until first the server's RX buffer got filled and
>>> then the client's TX buffer got filled. The client blocked instead of
>>> performing a partial write.
> 
>> What happens if you set the socket to non-blocking?
> 
> Something else, probably. But at this point I'd rather look at the
> linux/net/ sources -- when I have the time and energy.
> 
> Noone here has claimed that you don't need to check for partial writes,
> but it could be very useful to know (e.g. for debugging purposes) how
> Linux behaves in this case.
> 
> /Jorgen
> 
Why? The behavior could change at the next kernel upgrade.

But how do you know how it behaves in all circumstances? What about a
loaded server, where the problem is *NOT* the client has stopped
accepting packets, but the server is running low on transmit buffers?

	Jerry

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Thread

Data sent through sockets are *sometimes* inverted ?!!! mast4as <mast4as@yahoo.com> - 2012-02-17 00:38 -0800
  Re: Data sent through sockets are *sometimes* inverted ?!!! Chris Davies <chris-usenet@roaima.co.uk> - 2012-02-17 09:50 +0000
  Re: Data sent through sockets are *sometimes* inverted ?!!! Jorgen Grahn <grahn+nntp@snipabacken.se> - 2012-02-17 10:25 +0000
    Re: Data sent through sockets are *sometimes* inverted ?!!! Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2012-02-17 13:42 -0700
      Re: Data sent through sockets are *sometimes* inverted ?!!! Jorgen Grahn <grahn+nntp@snipabacken.se> - 2012-02-19 19:50 +0000
        Re: Data sent through sockets are *sometimes* inverted ?!!! Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2012-02-19 21:19 -0700
          Re: Data sent through sockets are *sometimes* inverted ?!!! Jorgen Grahn <grahn+nntp@snipabacken.se> - 2012-02-20 09:01 +0000
            Re: Data sent through sockets are *sometimes* inverted ?!!! Jorgen Grahn <grahn+nntp@snipabacken.se> - 2012-02-22 08:56 +0000
              Re: Data sent through sockets are *sometimes* inverted ?!!! Jerry Peters <jerry@example.invalid> - 2012-02-22 22:59 +0000
                Re: Data sent through sockets are *sometimes* inverted ?!!! Jorgen Grahn <grahn+nntp@snipabacken.se> - 2012-02-23 00:13 +0000
                Re: Data sent through sockets are *sometimes* inverted ?!!! Ralph Spitzner <rasp@spitzner.org> - 2012-02-23 06:00 +0100
                Re: Data sent through sockets are *sometimes* inverted ?!!! Jorgen Grahn <grahn+nntp@snipabacken.se> - 2012-02-23 07:34 +0000
                Re: Data sent through sockets are *sometimes* inverted ?!!! Chris Davies <chris-usenet@roaima.co.uk> - 2012-02-23 11:12 +0000
                Re: Data sent through sockets are *sometimes* inverted ?!!! Rick Jones <rick.jones2@hp.com> - 2012-02-24 19:25 +0000
                Re: Data sent through sockets are *sometimes* inverted ?!!! Chris Davies <chris-usenet@roaima.co.uk> - 2012-02-24 21:03 +0000
                Re: Data sent through sockets are *sometimes* inverted ?!!! Jorgen Grahn <grahn+nntp@snipabacken.se> - 2012-02-25 04:49 +0000
                Re: Data sent through sockets are *sometimes* inverted ?!!! Chris Davies <chris-usenet@roaima.co.uk> - 2012-02-26 12:18 +0000
                Re: Data sent through sockets are *sometimes* inverted ?!!! Pascal Hambourg <boite-a-spam@plouf.fr.eu.org> - 2012-02-26 14:10 +0100
                Re: Data sent through sockets are *sometimes* inverted ?!!! Jorgen Grahn <grahn+nntp@snipabacken.se> - 2012-02-26 14:02 +0000
                Re: Data sent through sockets are *sometimes* inverted ?!!! Ralph Spitzner <rasp@spitzner.org> - 2012-02-23 17:03 +0100
                Re: Data sent through sockets are *sometimes* inverted ?!!! Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2012-02-23 10:17 -0700
                Re: Data sent through sockets are *sometimes* inverted ?!!! Grant Edwards <invalid@invalid.invalid> - 2012-02-23 19:13 +0000
                Failing TCP checksums (was Re: Data sent through sockets are *sometimes* inverted ?!!!) Jorgen Grahn <grahn+nntp@snipabacken.se> - 2012-02-23 20:40 +0000
                Re: Data sent through sockets are *sometimes* inverted ?!!! Jerry Peters <jerry@example.invalid> - 2012-02-23 21:34 +0000
                Re: Data sent through sockets are *sometimes* inverted ?!!! Jorgen Grahn <grahn+nntp@snipabacken.se> - 2012-02-23 22:12 +0000
                Re: Data sent through sockets are *sometimes* inverted ?!!! Grant Edwards <invalid@invalid.invalid> - 2012-02-24 15:23 +0000
                Re: Data sent through sockets are *sometimes* inverted ?!!! Jorgen Grahn <grahn+nntp@snipabacken.se> - 2012-02-25 10:54 +0000
  Re: Data sent through sockets are *sometimes* inverted ?!!! Richard Kettlewell <rjk@greenend.org.uk> - 2012-02-17 10:07 +0000

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