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Date:      Thu, 14 Dec 2000 11:48:43 +0100
From:      Udo Erdelhoff <ue@nathan.ruhr.de>
To:        freebsd-net@freebsd.org
Subject:   Strange fragmentation needed message
Message-ID:  <20001214114843.A85041@nathan.ruhr.de>

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Hi,
I've been experiencing problems with TCP connections. The symptoms are: 

- I can't upload large (>5 KByte) files with ftp, the client reports
  "stalled" at file position 19456; the server receives only the first
  1024 Bytes of the file. Downloads work just fine.
- Sending mail (uucp-over-ip) takes a long time. uucico complains about a
  timeout, closes the connection, calls again and restarts after 1024 bytes
  (2048 for the third connection, etc).
- cvsup fails with
  Establishing multiplexed-mode data connection
  Running
  Detailer failed: Network read failure: Connection timed out
  Will retry at ...

Aborting and restarting cvsup will eventually result in a successfull run.

The box runs -current (PRE_SMPNG), the connection to the outside is an
ADSL line (768/128). I'm using ppp with the assorted netgraph modules
and ipfw&natd for NAT. Using ppp -nat instead doesn't help.

I've had to ignore the problems for some time due to RL. I've tried to
analyse the network traffic and found the following messages with
tcpdump -ni tun0

11:36:33.213801 212.185.239.152 > 212.185.239.152: icmp: 212.185.239.152 unreachable - need to frag (mtu 1480)

212.185.239.152 being *my* IP-address.

I don't understand what's going on. Traffic for my machine shouldn't
be routed into the tunnel (i.e. ppp should add a route to 127.0.0.1 for
$MYADDR). And I don't understand the reason for them, either.

What's going on? 

/s/Udo
-- 
>Every program evolves until it is capable of sending email.
Except Microsoft Exchange


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