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Date:      Sat, 16 May 2009 15:13:42 +0930
From:      "Daniel O'Connor" <doconnor@gsoft.com.au>
To:        Iain Hibbert <plunky@rya-online.net>
Cc:        freebsd-bluetooth@freebsd.org
Subject:   Re: btpand example
Message-ID:  <200905161513.43690.doconnor@gsoft.com.au>
In-Reply-To: <1242299035.690452.893.nullmailer@galant.ukfsn.org>
References:  <200905141438.17380.doconnor@gsoft.com.au> <200905141920.47717.doconnor@gsoft.com.au> <1242299035.690452.893.nullmailer@galant.ukfsn.org>

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On Thu, 14 May 2009, Iain Hibbert wrote:
> > I found that pinging worked and I could connect to an SSH port but
> > they SSH key exchange stalled so I guessed MTU and got lucky.
>
> Hm, I do manage to use ssh successfully over a btpand/winmobile
> link..
>
> > I later tried l2ping -s 1500 -a pda and it worked so I'm not sure
> > what's going on.
>
> probably better to try actual ping with larger packet sizes..?=20
> l2ping only tests the bluetooth link.

Sorry, I missed a step before, I did try ICMP pings when trying to work=20
it out.

600 was the largest I found (650 was too large)

> If you also added a log_debug() to the end of bnep_send() to display
> the nw and pkt->len values you might see if lossage was happening at
> any particular packet size. There is already a check that the packet
> doesn't exceed the MTU of the link though.

I can't reproduce the problem now.. Perhaps my phone was out of RAM or=20
something.

> > I have done the same operation on the same hardware in Linux and it
> > worked without MTU tweaks, however I haven't looked to see what MTU
> > it used or anything.
>
> I do get a weird problem sometimes where incoming ethernet packet
> payload is rejected by tap for being oversized. I've never tracked it
> down but I'm blaming windows mobile for that because the ethernet
> packet probably originates there rather than at the other end of the
> GPRS link (I could be wrong)
>
> eg
>
> May  2 11:06:36 galant btpand[820]: bnep_recv: received long packet
> (type=3D0x02, proto=3D0x0800, len=3D1568) May  2 11:06:36 galant /netbsd:
> tap0: discarding oversize frame (len=3D1582)

I haven't seen that [yet] but I've barely used it.

> I find this will cause a HTTP transfer to stall but I think ssh
> recovers from the lost packet ok.

OK.

=2D-=20
Daniel O'Connor software and network engineer
for Genesis Software - http://www.gsoft.com.au
"The nice thing about standards is that there
are so many of them to choose from."
  -- Andrew Tanenbaum
GPG Fingerprint - 5596 B766 97C0 0E94 4347 295E E593 DC20 7B3F CE8C

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