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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">Hi Matt,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">Thanks for pointing out that this change was done in more recent versions. Updating to a more recent version should be possible for us.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">Regards,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">David<o:p></o:p></span></p>
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<p class="MsoNormal"><b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif">From:</span></b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"> Matt Johnston [mailto:matt@ucc.asn.au]
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<b>Sent:</b> Tuesday, June 7, 2016 8:44 AM<br>
<b>To:</b> David Chapdelaine <dchapdelaine@GENETEC.COM><br>
<b>Cc:</b> dropbear@ucc.asn.au<br>
<b>Subject:</b> Re: Keepalive timeout with dropbear client<o:p></o:p></span></p>
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<p class="MsoNormal">Hi David,<o:p></o:p></p>
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<p class="MsoNormal">Dropbear since 2015.68 always sets the socket non-blocking [1], so I think that change should be safe on older versions. The only risk I can think of is if it gets in some state where it might spin with 100% CPU.<o:p></o:p></p>
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<p class="MsoNormal">Cheers,<o:p></o:p></p>
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<p class="MsoNormal">Matt<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">[1] <a href="https://secure.ucc.asn.au/hg/dropbear/annotate/10f198d4a308/common-session.c#l68">https://secure.ucc.asn.au/hg/dropbear/annotate/10f198d4a308/common-session.c#l68</a><o:p></o:p></p>
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<p class="MsoNormal">On Tue 7/6/2016, at 7:59 pm, David Chapdelaine <<a href="mailto:dchapdelaine@genetec.com">dchapdelaine@GENETEC.COM</a>> wrote:<o:p></o:p></p>
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<p class="MsoNormal"><span lang="FR-CA" style="font-size:11.0pt;font-family:"Calibri",sans-serif">Hi everyone,</span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"><o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="FR-CA" style="font-size:11.0pt;font-family:"Calibri",sans-serif"> </span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif">We have been using version 65 of Dropbear to maintain an ssh connection to a central server. It usually works fine, but when there is a network failure the Dropbear client
waits until there is a tcp timeout before declaring that there was a keepalive timeout. So in practice even though we set the keepalive timeout as 30 seconds, dbclient doesn’t exit before ~15 minutes which is when the tcp timeout is triggered.<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"> <o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif">By digging in dropbear’s code I noticed that when running in client mode, the connection to the server is blocking whereas that connection is non blocking when running in server
mode. I thus changed the connection to non blocking in client mode. To do this I changed<span class="apple-converted-space"> </span></span><span style="font-size:9.0pt;font-family:"Verdana",sans-serif;color:#484848">the call to connect_remote line 75-76 of
cli-main.c from</span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Verdana",sans-serif;color:#484848"> </span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"><o:p></o:p></span></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt;background:#FAFAFA"><span style="font-size:9.0pt;font-family:"Courier New";color:#484848">int sock = connect_remote(cli_opts.remotehost, cli_opts.remoteport, 0, &error);</span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"><o:p></o:p></span></p>
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<span style="background:white">to</span><br>
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<p class="MsoNormal" style="margin-bottom:12.0pt;background:#FAFAFA"><span style="font-size:9.0pt;font-family:"Courier New";color:#484848">int sock = connect_remote(cli_opts.remotehost, cli_opts.remoteport, 1, &error);</span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"> <o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif">Initial tests are good so far and it addresses our issue, but I wanted to run this through you to get your insights on potential problems with this change. As far as you know,
is there any side effect that we should be aware of? Was there a reason why the connection was blocking in client mode?<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"> <o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif">Thanks a lot for your inputs!<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"> <o:p></o:p></span></p>
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<p class="MsoNormal"><b><span lang="FR-CA" style="font-size:11.0pt;font-family:"Arial",sans-serif;color:#00749B">David Chapdelaine</span></b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"><o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="FR-CA" style="font-size:9.0pt;font-family:"Arial",sans-serif;color:#575958">Développeur logiciel | Software Developer</span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"><o:p></o:p></span></p>
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<p class="MsoNormal"><b><span style="font-size:9.0pt;font-family:"Arial",sans-serif;color:#575958">T|P</span></b><span style="font-size:9.0pt;font-family:"Arial",sans-serif;color:#575958">:<b> </b>+1-514-332-4000 p.6595 |<span class="apple-converted-space"> </span></span><span style="font-size:9.0pt;font-family:"Arial",sans-serif"><a href="mailto:dchapdelaine@genetec.com"><span style="color:#0563C1">dchapdelaine@genetec.com</span></a></span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif;color:#575958"> </span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"><o:p></o:p></span></p>
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<p class="MsoNormal"><b><span style="font-size:9.0pt;font-family:"Arial",sans-serif;color:#575958">Conçu pour évoluer</span></b><span class="apple-converted-space"><b><u><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#575958"> </span></u></b></span><b><span style="font-size:9.0pt;font-family:"Arial",sans-serif;color:#575958">|
Built to evolve</span></b><span class="apple-converted-space"><b><u><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#575958"> </span></u></b></span><b><span style="font-size:9.0pt;font-family:"Arial",sans-serif;color:#575958">|<span class="apple-converted-space"> </span></span></b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"><a href="http://www.genetec.com/dna"><b><span style="font-size:9.0pt;font-family:"Arial",sans-serif">www.genetec.com/dna</span></b></a><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"><a href="http://www.facebook.com/Genetec"><span style="font-size:9.0pt;font-family:"Arial",sans-serif;color:#575958;text-decoration:none"><image002.png></span></a><a href="http://www.linkedin.com/company/genetec/"><span style="font-size:9.0pt;font-family:"Arial",sans-serif;color:#575958;text-decoration:none"><image003.png></span></a></span><span lang="FR-CA" style="font-size:9.0pt;font-family:"Arial",sans-serif;color:#575958"> </span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"><a href="http://www.twitter.com/_Genetec_"><span style="font-size:9.0pt;font-family:"Arial",sans-serif;color:#575958;text-decoration:none"><image004.png></span></a></span><span lang="FR-CA" style="font-size:9.0pt;font-family:"Arial",sans-serif;color:#575958"> </span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"><a href="http://www.youtube.com/Genetec"><span style="font-size:9.0pt;font-family:"Arial",sans-serif;color:#575958;text-decoration:none"><image005.png></span></a><o:p></o:p></span></p>
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