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<TITLE>sane-devel: Re: xsane requests username and password after sane</TITLE>
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<META NAME="Author" CONTENT="Nick Lamb (njl98r@ecs.soton.ac.uk)">
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<META NAME="Subject" CONTENT="Re: xsane requests username and password after saned has exited">
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<H1>Re: xsane requests username and password after saned has exited</H1>
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<!-- received="Mon Jun 4 11:42:33 2001" -->
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<STRONG>From:</STRONG> Nick Lamb (<A HREF="mailto:njl98r@ecs.soton.ac.uk?Subject=Re:%20xsane%20requests%20username%20and%20password%20after%20saned%20has%20exited&In-Reply-To=<20010604194422.A25439@ecs.soton.ac.uk>"><EM>njl98r@ecs.soton.ac.uk</EM></A>)<BR>
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<STRONG>Date:</STRONG> Mon Jun 04 2001 - 11:44:22 PDT
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<P>
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<LI><STRONG>Next message:</STRONG> <A HREF="0069.html">Henning Meier-Geinitz: "Semaphores (sys/sem.h) in sane-backends"</A>
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<UL>
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<LI><STRONG>Previous message:</STRONG> <A HREF="0067.html">Franz Bakan: "Re: Compiling on OS/2"</A>
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<LI><STRONG>In reply to:</STRONG> <A HREF="0058.html">Oliver Rauch: "Re: xsane requests username and password after saned has exited"</A>
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<LI><STRONG>Next in thread:</STRONG> <A HREF="0070.html">Chris Pinkham: "Re: xsane requests username and password after saned has exited"</A>
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<LI><STRONG>Next in thread:</STRONG> <A HREF="0060.html">Oliver Rauch: "Re: xsane requests username and password after saned has exited"</A>
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<LI><STRONG>Reply:</STRONG> <A HREF="0070.html">Chris Pinkham: "Re: xsane requests username and password after saned has exited"</A>
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<LI><STRONG>Reply:</STRONG> <A HREF="0072.html">Henning Meier-Geinitz: "Re: xsane requests username and password after saned has exited"</A>
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<LI><STRONG>Reply:</STRONG> <A HREF="0093.html">Oliver Rauch: "Re: xsane requests username and password after saned has exited"</A>
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<P>
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On Mon, Jun 04, 2001 at 02:51:10PM +0200, Oliver Rauch wrote:
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<BR>
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<EM>> Hi Nick,
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</EM><BR>
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<EM>>
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</EM><BR>
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<EM>> I think the reason is if the frontend dies and does not inform saned to exit
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</EM><BR>
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<EM>> then saned never will exit at all.
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</EM><BR>
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<P>Without trying it my understanding is that on anything vaguely modern
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<BR>
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(are people trying to use SANE from DOS? from Windows 3.1?) the TCP stack
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<BR>
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is an OS component and will perform a full TCP shutdown on behalf of the
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<BR>
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frontend. So this can ONLY happen when a user turns off their PC while
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<BR>
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using the frontend -- little wonder that things break if you do that!
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<BR>
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<P>Does anyone have evidence to contradict that? Once again I ask for the
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<BR>
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person who added this watchdog timer kludge to step forward.
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<BR>
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<P><EM>> The fork() in sane-net has the advantage that the network protocol works
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</EM><BR>
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<EM>> invisiblie for the fronten, no frontend has to care about.
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</EM><BR>
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<EM>>
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</EM><BR>
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<EM>> The advantage of the frontend initiated keep alive package is that we
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</EM><BR>
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<EM>> don<6F>t need to create a separate keep-alive process.
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</EM><BR>
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<EM>>
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</EM><BR>
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<EM>> May be we could define a well_known_option "create_keepalives" that can be
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</EM><BR>
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<EM>> set by GUI-frontends, so for command-line-frontends the fork() is not called.
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</EM><BR>
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<P>I think this problem (user turns off PC while using scanner remotely)
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<BR>
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is rare enough not to require extreme measures. Try this instead, one
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<BR>
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step at a time
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<BR>
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<P>0. Eliminate the watchdog timer
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<BR>
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This will make SANE behave properly for the _normal_ case
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<BR>
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<P>1. Turn on TCP keep alive socket option in saned where available
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<BR>
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This makes it recover (eventually) from PC crash
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<BR>
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<P>2. Permit null operation/ null result packets from the server
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<BR>
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and send these to elicit ACK vs RST indicator from client TCP stack
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<BR>
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<P>Note that the first two require NO CHANGE to the remote client, and
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<BR>
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the last one if it turns out to be necessary requires only some
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<BR>
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small changes, maybe a dozen lines.
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<BR>
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<P>Nick.
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<BR>
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<P><PRE>
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--
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Source code, list archive, and docs: <A HREF="http://www.mostang.com/sane/">http://www.mostang.com/sane/</A>
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To unsubscribe: echo unsubscribe sane-devel | mail <A HREF="mailto:majordomo@mostang.com?Subject=Re:%20xsane%20requests%20username%20and%20password%20after%20saned%20has%20exited&In-Reply-To=<20010604194422.A25439@ecs.soton.ac.uk>">majordomo@mostang.com</A>
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</PRE>
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<HR NOSHADE>
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<UL>
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<!-- next="start" -->
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<LI><STRONG>Next message:</STRONG> <A HREF="0069.html">Henning Meier-Geinitz: "Semaphores (sys/sem.h) in sane-backends"</A>
|
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<LI><STRONG>Previous message:</STRONG> <A HREF="0067.html">Franz Bakan: "Re: Compiling on OS/2"</A>
|
||
<LI><STRONG>In reply to:</STRONG> <A HREF="0058.html">Oliver Rauch: "Re: xsane requests username and password after saned has exited"</A>
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||
<!-- nextthread="start" -->
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<LI><STRONG>Next in thread:</STRONG> <A HREF="0070.html">Chris Pinkham: "Re: xsane requests username and password after saned has exited"</A>
|
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<LI><STRONG>Next in thread:</STRONG> <A HREF="0060.html">Oliver Rauch: "Re: xsane requests username and password after saned has exited"</A>
|
||
<LI><STRONG>Reply:</STRONG> <A HREF="0070.html">Chris Pinkham: "Re: xsane requests username and password after saned has exited"</A>
|
||
<LI><STRONG>Reply:</STRONG> <A HREF="0072.html">Henning Meier-Geinitz: "Re: xsane requests username and password after saned has exited"</A>
|
||
<LI><STRONG>Reply:</STRONG> <A HREF="0093.html">Oliver Rauch: "Re: xsane requests username and password after saned has exited"</A>
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