Subject: IP DF problems (again)
To: Current Users <current-users@NetBSD.ORG>
From: Jukka Marin <>
List: current-users
Date: 02/01/1998 14:05:12
I have been whining about this before.. and not it is happening to me

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 > P 138:1598(1460) ack 373 win 8760 (DF)
13:44:04.878446 > icmp: 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!



                       1503 kHz @ 21:30 EET DST Mon-Fri

                     ---> <---