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Date:      Sun, 28 Jun 2009 11:28:14 +0000 (UTC)
From:      Poul-Henning Kamp <phk@FreeBSD.org>
To:        cvs-src-old@freebsd.org
Subject:   cvs commit: src/sys/dev/ath/ath_hal/ar5416 ar5416_reset.c src/sys/kern sys_socket.c src/sys/sys filio.h
Message-ID:  <200906281128.n5SBSbG4002135@repoman.freebsd.org>

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phk         2009-06-28 11:28:14 UTC

  FreeBSD src repository

  Modified files:
    sys/dev/ath/ath_hal/ar5416 ar5416_reset.c 
    sys/kern             sys_socket.c 
    sys/sys              filio.h 
  Log:
  SVN rev 195134 on 2009-06-28 11:28:14Z by phk
  
  There are a number of ways an application can check if there are
  inbound data waiting on a filedescriptor, such as a pipe or a socket,
  for instance by using select(2), poll(2), kqueue(2), ioctl(FIONREAD)
  etc.
  
  But we have no way of finding out if written data have yet to be
  disposed of, for instance, transmitted (and ack'ed!) to some remote
  host, or read by the applicantion at the far end of the pipe.
  
  The closest we get, is calling shutdown(2) on a TCP socket in
  non-blocking mode, but this has the undesirable sideeffect of
  preventing future communication.
  
  Add a complement to FIONREAD, called FIONWRITE, which returns the
  number of bytes not yet properly disposed of.  Implement it for
  all sockets.
  
  Background:
  
  A HTTP server will want to time out connections, if no new request
  arrives within a certain period after the last transmitted response
  has actually been sent (and ack'ed).
  
  For a busy HTTP server, this timeout can be subsecond duration.
  
  In order to signal to a load-balancer that the connection is truly
  dead, TCP_RST will be the preferred method, as this avoids the need
  for a RTT delay for FIN handshaking, with a client which, surprisingly
  often, no longer at the remote IP number.
  
  If a slow, distant client is being served a response which is big
  enough to fill the window, but small enough to fit in the socket
  buffer, the write(2) call will return immediately.
  
  If the session timeout is armed at that time, all bytes in the
  response may not have been transmitted by the time it fires.
  
  FIONWRITE allows the timeout to check that no data is outstanding
  on the connection, before it TCP_RST's it.
  
  Input & Idea from: rwatson
  Approved by:    re (kib)
  
  Revision  Changes    Path
  1.9       +1 -1      src/sys/dev/ath/ath_hal/ar5416/ar5416_reset.c
  1.81      +5 -0      src/sys/kern/sys_socket.c
  1.11      +1 -0      src/sys/sys/filio.h



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