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Date:      Tue, 4 Feb 1997 12:16:19 +0100 (MET)
From:      Søren Schmidt <sos@ravenock.cybercity.dk>
To:        proff@suburbia.net
Cc:        hackers@freebsd.org
Subject:   Re: linux net killer or no idea? (fwd)
Message-ID:  <199702041116.MAA23479@ravenock.cybercity.dk>
In-Reply-To: <19970204101020.12479.qmail@suburbia.net> from "proff@suburbia.net" at "Feb 4, 97 09:10:20 pm"

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In reply to proff@suburbia.net who wrote:

I've tried this and it works just fine:

ftp> get xppp1B-x86-ELF.tar.gz
local: xppp1B-x86-ELF.tar.gz remote: xppp1B-x86-ELF.tar.gz
200 Connected to 194.16.57.32 port 40033
150 Opening data connection
226-File written successfully
226 67.196 seconds (measured here), 4.85 Kbytes per second
384604 bytes received in 71.53 seconds (5.25 Kbytes/s)
ftp> 

Seems Linux has a problem :) :)

> 
> This is the weirdest problem I've ever, ever seen.  Or so it feels
> like.
> 
> I've just seen machines running linux/2.0.27, linux/2.1.24 and
> freebsd/3.0-current freeze after downloading 144540 bytes of this
> file:
> 
> 	ftp://ftp.troll.no/contrib/xppp1B-x86-ELF.tar.gz
> 
> Many clients can download this file just fine, many others can not.
> Those who can't all freeze after exactly 144540 bytes.  A file of the
> same size but with different contents works.  The same file with a
> different name does not work.  The same file recompressed (zcat | gzip
> - -9) to be 600 bytes smaller can be downloaded by everyone as far as I
> can test.  The same file recompressed (-5) to be 2100 bytes larger
> too.
> 
> The FTP daemon is troll-ftpd 1.20 running on linux 2.0.26 and then on
> 2.0.28.  The same file _can_ be downloaded from the same version of
> troll-ftpd running on a different linux box, which runs 2.0.27.  There
> are no tcp-related changes between .27 and .28, as far as I can see.
> 
> A huge tcpdump packet trace showing first a successful transfer of a
> 384604-byte file, then the one which freezes is available at
> 
> 	ftp://ftp.troll.no/tmp/thud
> 
> The two transfers look much the same to me, except that there appears
> to be a single packet loss while the window is wide-open, and the
> connection never recovers if this crucial file is being transferred.
> 
> I don't know which of several netstat lines -t correspond to the
> packet trace.  The most likely one shows a send queue of 43880 bytes,
> the others are similar.
> 
> I don't know whether the file, the ftpd or the packet trace helps.
> Should anyone feel like tracing something so weird and need other
> data, or access to the box, do write.
> 
> (Please cc any replies to me - I don't read linux-net right now,
> and probably won't for another two weeks or so.)
> 
> - --Arnt
> 
> ------- End of Forwarded Message
> 
> 
> 
> 
> 


-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
Søren Schmidt               (sos@FreeBSD.org)               FreeBSD Core Team
                Even more code to hack -- will it ever end
..



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