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Date:      Sun, 22 Apr 2007 02:29:37 +1000
From:      Alan Garfield <alan@fromorbit.com>
To:        Yar Tikhiy <yar@comp.chem.msu.su>
Cc:        freebsd-net@freebsd.org
Subject:   Re: rtentry and rtrequest
Message-ID:  <462A3BF1.5070202@fromorbit.com>
In-Reply-To: <20070420233619.GC52136@comp.chem.msu.su>
References:  <20070418120622.GF40826@comp.chem.msu.su>	<1176947814.4175.39.camel@hiro.auspc.com.au>	<20070419073525.GA60301@comp.chem.msu.su>	<1176972863.4177.7.camel@hiro.auspc.com.au>	<20070419093847.GC60301@comp.chem.msu.su>	<1176976273.4177.17.camel@hiro.auspc.com.au>	<20070419113842.GE60301@comp.chem.msu.su>	<1176990600.4177.26.camel@hiro.auspc.com.au>	<20070419175331.GA5999@comp.chem.msu.su>	<1177077805.4063.7.camel@hiro.auspc.com.au> <20070420233619.GC52136@comp.chem.msu.su>

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Yar Tikhiy wrote:
>> ----
>> Disconnecting: Corrupted MAC on input.
>> ----
> 
> That looks like data corruption happening when TCP segments and/or
> IP packets become relatively large, i.e., approach or reach the mtu
> limit.

Indeed that would appear to be the case.


>> I'm sure it's something to do with how I'm doing the output. Does this
>> look sane?
> 
> Well, there's certain space for improvement, 

Aww it's not _that_ bad is it. :) hehe

> but now I fail to find a
> bug that would result in corrupted data.

Phew /me wipes brow... so I'm not _totally_ useless then. :)

> Would you mind testing the link with ping using packets of size
> equal to, just below, and slightly above the mtu, and with different
> data patterns?  See -s and -p options to ping.  You can observe the
> patterns in echo replies with tcpdump -X.  The data patterns in
> echo requests and echo replies should be exactly the same.  If they
> aren't, the character of corruption can hint you at the bug.

I've done a pretty preliminary tcpdump'ing and the packets seem ok above 
and below the MTU via the bpf taps. I wonder if it's a bug in the SP 
side... then again I could be completely off base and it's all my dodgy 
codes fault. :)

I'll poke around with tcpdump and ping a bit more.

Many thanks again Yar,

Alan.



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