Date: Mon, 15 Oct 2012 23:17:42 +0200 From: Andreas Longwitz <longwitz@incore.de> To: Iain Hibbert <plunky@rya-online.net> Cc: freebsd-bluetooth@freebsd.org Subject: Re: btpand problem Message-ID: <507C7D76.4090303@incore.de> In-Reply-To: <alpine.NEB.2.00.1210150936490.753@galant.ukfsn.org> References: <507736A8.4050605@incore.de> <BDA3CA14-92C0-414E-9D55-E96EA7A73312@gmail.com> <5077490F.7010901@incore.de> <CAFPOs6pF51wy9PvKLn4-OnrOqo8hU1S=P5PzTFwgUppBjqAtuA@mail.gmail.com> <alpine.NEB.2.00.1210120949170.628@galant.ukfsn.org> <50782E05.5080005@incore.de> <alpine.NEB.2.00.1210122254010.965@galant.ukfsn.org> <CAFPOs6qWVAcSuPz6%2BB=3uq_KqCXa=YcXwx-PNncGVrbDE8AimQ@mail.gmail.com> <5079E8F7.5050903@incore.de> <alpine.NEB.2.00.1210140843330.548@galant.ukfsn.org> <alpine.NEB.2.00.1210140917360.673@galant.ukfsn.org> <507B0C57.7030506@incore.de> <alpine.NEB.2.00.1210150936490.753@galant.ukfsn.org>
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Hi, > as I said, I think 672 is a bit low, though I used 4096 for NetBSD (with a > sysctl for runtime adjustment if necessary) and that is still potentially > prone to error with larger packets (L2CAP MTU between 48-65535 bytes is > valid) so I guess that requiring the application to set the buffer size is > best practice.. I agree. >> Now I describe another problem with my ping test, I am not sure if this >> problem concerns btpand too. If the ICMP packet must be fragmented, then the >> first fragment ist lost on the tap interface (and can not be found by tcpdump >> running on this tap) if an ARP request is necessary. >> ping -c 1 -s 1400 panserver >> works all the time, >> ping -c 1 -s 1600 panserver >> only works if the ip address of panserver is in the arp cache. > > does the ARP request get sent out? Yes and the arp answer comes in. >> I did nothing special with the tap interface, it is included in my >> "cloned_interfaces" in rc.conf and opened by btpand. >> >> Any ideas ? > > No, I confess. My problem was a phantom ! It seems to be normal behavior in any network and has nothing to do with btpand or tap interface. This was a little bit suprising to me but I have checked this on several networks. An explanation for this was given on freebsd-net some years ago titled Lost fragment when send to ip that need arp resolve. Thanks again for help! Andreas Longwitz
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