Subject: IP DF problems (again)
To: Current Users <current-users@NetBSD.ORG>
From: Jukka Marin <jmarin@pyy.jmp.fi>
List: current-users
Date: 02/01/1998 14:05:12
I have been whining about this before.. and not it is happening to me
again.
Someone is trying to send mail to our machine from a m$ system, it seems.
The sender uses large IP packets with the DF flag set. My NetBSD 1.2
router can't transmit the packets over a PPP line due to MTU of 576 bytes,
so it responds to the sender like this:
13:44:04.878280 mailhost.orion.fi.34036 > kyyhky.jmp.fi.smtp: P 138:1598(1460) ack 373 win 8760 (DF)
13:44:04.878446 muikku.jmp.fi > mailhost.orion.fi: icmp: kyyhky.jmp.fi unreachable - need to frag (DF)
Of course, the sender doesn't care but tries to send the packet all over
again. Finally, it opens a new SMTP connection to our system and I end up
with several sendmail processes just hanging there, getting no data from
the sender.
Is there a way to tell the NetBSD 1.2 router to fragment the packets so
they would get through? I have mailed to the postmaster of the sender
system, but if every single m$ driven machine in the world has this problem,
I will spend the rest of my life trying to convince them to get their TCP/IP
fixed... :-(
It should be illegal to connect broken systems to the net!
-jm
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