btpand problem

[Maksim Yevmenkin]

On Mon, Oct 15, 2012 at 2:17 PM, Andreas Longwitz <longwitz at incore.de> wrote:
> 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!

just in case

Author: emax
Date: Thu Oct 18 16:34:00 2012
New Revision: 241699
URL: http://svn.freebsd.org/changeset/base/241699

Log:
  make sure that socket's send and receive buffers are properly sized

  Submitted by: Iain Hibbert plunky at rya-online dot net
  MFC after:    3 weeks

Modified:
  head/usr.sbin/bluetooth/btpand/client.c
  head/usr.sbin/bluetooth/btpand/server.c

thanks
max