<div dir="ltr"><div><div><div><div><div>As for testing tools, scamper is the only one I've found when I last looked (in 2014?) it doesn't<br></div>support running on Linux out of the box. <a href="http://wand.net.nz/scamper/pmtud">http://wand.net.nz/scamper/pmtud</a><br>For example, you can do:<br><br>sudo scamper -F ipfw -I "tbit -M 1280 -t pmtud -S $sourceip -u $url" $targetip<br><br></div>Where $url has to be an HTTP URL that returns a large enough object and $targetip is what you want<br></div>to test. On Linux, $sourceip is a dedicated non-primary address where you have a firewall rule filter:<br><br> ip6tables -I INPUT -p tcp --sport 80 -d $sourceip -j DROP<br><br></div>The right way to do this on Linux would be to add a new backend to scamper<br></div><div>but for this to work you have to disable the existing check that BSD ipfw is working.<br></div><div>For example:<br><br></div><div>==== CUT HERE ====<br></div><div>--- scamper-cvs-20140530/scamper/tbit/scamper_tbit_do.c 2013-08-07 17:55:29.000000000 -0400<br>+++ scamper-cvs-mod/scamper/tbit/scamper_tbit_do.c 2014-10-21 14:07:33.053470510 -0400<br>@@ -2634,11 +2636,26 @@<br> sfw.sfw_5tuple_sport = tbit->dport;<br> sfw.sfw_5tuple_dport = tbit->sport;<br> <br>+ <br>+ <br>+ <br>+ <br>+ <br>+#if 1 /* Hack to run on Linux... */<br></div><div>+ run with: <br></div><div>+ scamper -F ipfw -I "tbit -M 1280 -t pmtud -S $sourceip -u $url" $targetip</div><div>+ after putting in a firewall rule first to drop inputs on a dedicated address: <br></div><div>+ ip6tables -I INPUT -p tcp --sport 80 -d $sourceip -j DROP<br>+ */<br>+ <br>+ state->fw = NULL;<br>+#else<br> if((state->fw = scamper_firewall_entry_get(&sfw)) == NULL)<br> {<br> scamper_debug(__func__, "could not get firewall entry");<br> goto err;<br> }<br>+#endif<br> <br> state->mode = MODE_SYN;<br> }<br>==== CUT HERE ====</div><br><br><div><div><br><br><br><div><br><br><br><br><div><br><br><br><br><br></div></div></div></div></div><div class="gmail_extra"><br><div class="gmail_quote">On Fri, Apr 29, 2016 at 2:30 AM, Mikael Abrahamsson <span dir="ltr"><<a href="mailto:swmike@swm.pp.se" target="_blank">swmike@swm.pp.se</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><br>
Hi,<br>
<br>
I've run into a scenario where a website doesn't seem to be listening to PTB. I can reach them just fine from an MTU1500 clean IPv6 connection, but if I reach from a MTU1500<->MTU1480<->MTU1500 connection, it doesn't work. I don't get the big packets after SYN handshake.<br>
<br>
I've been considering asking <a href="http://iis.se" rel="noreferrer" target="_blank">iis.se</a> (the .SE ccTLD registry) who are already running multiple testing tools for web sites and domain name owners) to include these kinds of testing, and perhaps develop more of them.<br>
<br>
So I'd like to gather some information and feedback here.<br>
<br>
1. Are there are already FOSS tools out there that could be used for this, or would be good to enhance to include capability for this kind of testing. I don't want to waste work, and if I can enhance FOSS tools already existing and also solve my problem, that's a double win.<br>
<br>
2. Test cases? From my testing, I've seen two different behavior just in the last two days:<br>
<br>
Site A as described in top paragraph, probably doesn't listen to PTB. Can be either because they drop PTBs, or traffic traverses a load balancer/IPv4v6proxy that doesn't correctly handle PTB.<br>
<br>
Site B which sends all data packets as fragments. This is most likely because they have some kind of AFTR where the IPv4 side has MTU1500 and the IPv6 side has MTU1320 or something like that.<br>
<br>
Neither of this is of course optimal, and I'd like to be able to test for these and tell the site owner that their solution either is broken or suboptimal (the fragment case isn't strictly broken, it's just not a good way to do things).<br>
<br>
Opinions? Thoughts?<span class="HOEnZb"><font color="#888888"><br>
<br>
-- <br>
Mikael Abrahamsson email: <a href="mailto:swmike@swm.pp.se" target="_blank">swmike@swm.pp.se</a><br>
</font></span></blockquote></div><br></div>