Subject: Re: TCP/IP problem in 1.2
To: None <>
From: Jukka Marin <>
List: tech-kern
Date: 07/17/1997 13:08:02
On Thu, Jul 17, 1997 at 11:49:03AM +0200, Stefan Grefen wrote:
> The TCP stack sets the DF flag (dont't fragment) so packets greater than
> MTU size will not be transmitted (netstat -p ip should show the as 
>  'datagrams that can't be fragmented').

> The bug is in windows and on the merita system. Sending to destinations outside
> of the local network with DF set, an MSS > 512 and no dynamic MTU discovery is 
> a call for trouble. (A lot of routers ignore the DF bit, thats the practical
> approach to ...)

Thanks for the detailed explanation.  Now I understand what is happening.
Even better, I can tell that the bug is NOT in NetBSD :-))))

> I would patch the kernel to ignore the DF bit. Maybe this should become
> an sysctl option or an interface option.

This sounds like a good idea to me.  Of course, the real bug should be fixed,
but there's only so much we can do to fix all the TCP/IP stacks in the world..



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