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Date:      Thu, 9 Apr 2009 11:02:06 +0200 (CEST)
From:      "Bjoern Koenig" <bkoenig@alpha-tierchen.de>
To:        pyunyh@gmail.com
Cc:        stable@freebsd.org
Subject:   Re: fxp: stalled transfers
Message-ID:  <c527997835b4ea46c1e492c3a3c9d030.squirrel@webmail.alpha-tierchen.de>
In-Reply-To: <20090409072309.GF37714@michelle.cdnetworks.co.kr>
References:  <70ba25e4f1a5e43ab8d99b361235dda2.squirrel@webmail.alpha-tierchen.de> <20090409000427.GD37714@michelle.cdnetworks.co.kr> <2f68678165f20f2e1dae10cb0e63761d.squirrel@webmail.alpha-tierchen.de> <20090409072309.GF37714@michelle.cdnetworks.co.kr>

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pyunyh@gmail.com wrote:

> If you can easily reproduce the issue, can you capture stalled TCP
> session with tcpdump on receiving host?(Make sure to disable Rx
> checksum offload prior to capturing the session.)

I transferred a 256 kiB file and these are the tcpdumps:

http://www.alpha-tierchen.de/~bkoenig/fxp0-with-tso.txt
http://www.alpha-tierchen.de/~bkoenig/fxp0-without-tso.txt

Actually the transfer doesn't stall although ftp and scp told me so. It
becomes incredibly slow. It seems like that the chunks are too large and a
smaller packet will be resent. I decreased the MTU from 1500 to 1492 and
it works fine with TSO enabled.

I also captured the traffic on my router:

http://www.alpha-tierchen.de/~bkoenig/fxp0-with-tso-router.txt
http://www.alpha-tierchen.de/~bkoenig/fxp0-without-tso-router.txt

It reveals a suspect information: "truncated-ip - 8 bytes missing!"

I almost suppose that this is a PPPoE-related configuration issue and the
fxp driver is not necessarily the problem since decreasing the MTU of the
LAN host solves it.

Björn




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