DNS and UDP checksum

Quoting from Geert Jan de Groot's message:
> 
> 
> Hi,
> 
> Not all machines behave the way you describe - BSD/OS for instance,
> always checks the checksum if one is given and the kernel variable
> only controls UDP checksumming on transmitted packets.
> 
> I think it makes sense to make a list of operating systems and describe
> the behaviour:
> 
> Operating system, version:
> UDP checksum receive:  {ALWAYS, udp_cksum, NEVER} (default=XX)
> UDP checksum transmit: {ALWAYS, udp_cksum, NEVER} (default=XX)
> And for those that don't have checksumming on by default, a description
> how to change it as they are the only ones affected by an enforcement
> of UDP checksumming.
> 
> It is quite likely that only SunOS 4.x or deratives are seriously affected
> (well, there may be a BSD4.2 system or two in the world but I don't
> think there are many left).
> 
> 
> To start things off:
> 
> OS, version:	SunOS, version 4.1.x
> UDP checksum RX: udp_cksum (default=off)
> UDP checksum TX: udp_cksum (default=off)
> Default can be changed by:
> > Unix OSs have a kernel flag named usually "udpcksum"
> > settable by a binary editor, config tools (like sysctl,
> > ndd, no, ...) and defined in .../sys/netinet/in_proto.c
> > which is distributed in the source form in order to
> > allow the setting of various TCP/IP flags. [Francis Dupont at inria]

The following is the script we use on several SunOS machines

#!/bin/sh
#
# Turns ON UDP checksumming on SunOS
# to be launched from /etc/rc.local
# 
# Suggested by: cgull+l-udp at smoke.marlboro.vt.us (John Hood)
# Taken from "FAQ: Sun Computer Administration Frequently Asked Questions"
# (thanks to Rob_Montjoy at ece.uc.edu)
#
adb -w -k /vmunix /dev/mem << EOF
udp_cksum?W1
udp_cksum/W1
EOF

Enjoy!

Blasco
> 
> OS, version:	BSD/OS, version 2.1
> UDP checksum RX: ALWAYS
> UDP checksum TX: udp_cksum (default=on)
> 
> OS, version:	FreeBSD, version 2.1
> UDP checksum RX: ALWAYS
> UDP checksum TX: udp_cksum (default=on)
> 
> Once collected, this can go in some kind of document be it RFC or otherwise.
> 
> Can people who know about other OSes please speak up?
> 
> Geert Jan
> 
> 
> On Sun, 05 May 1996 19:53:49 +0200  Francis Dupont wrote:
> > Here is a technical note about UDP checksums
> > (which should be mandatory for DNS, perhaps we should
> > write a RFC about this ?)
> > 
> > Francis.Dupont at inria.fr
> 
> (rest of original message removed)
> 
> 


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