Thanks to :-
Gary Richardson <Gary.Richardson@proteon.com>
Benjamin Cline <email@example.com>
Casper Dik <casper@holland.Sun.COM>
Hal Stern - Distinguished Systems Engineer <stern@sunrise.East.Sun.COM>
with the most detailed response from David Beard
On Thu, 28 Nov 1996, David Beard wrote:
> Hi Dave,
> [ I originally wrote ]
> > I've just compiled BIND 4.9.5 for a 4.1.4 system, and when I try to run
> > it, it complains about UDP checksums. Looking into the makefile, the
> > SunOS 4 options include a CHECKSUM definition, and the code itself is
> > pulling out an nlist from the kernel for _udp_cksum. When the code opens
> > the /vmunix to have a look inside, the value being read is zero, and I
> > think it doesn't really want that :)
> Yes, UDP checksums are a *good* thing if you are running a DNS. This is *off*
> by default on SunOS boxes, unfortunately.
> > Looking in the GENERIC kernel config file, I couldn't find anything that
> > references this. And searching through the man pages didn't help either.
> > Is this something that I can enable?
> Yes, have a look at the file /usr/kvm/sys/netinet/in_proto.c
> and change the line
> int udp_cksum = 0;
> int udp_cksum = 1;
> and then rebuild your kernel (install it and reboot).
> You can also change this on a `live' system using adb, e.g.
> adb -w -k /vmunix /dev/mem << EOF
> which will update the file /vmunix and the `live' copy in memory.
> There was some more detailed information about this in the newsgroup
> comp.protocols.tcp-ip.domains about 5 months ago.
> To quote Tom Fitzgerald:
> > Nameservers that have UDP checksums disabled can cause corrupted DNS
> > data to be accepted by other nameservers, and propagated around the
> > net indefinitely, to the suffering of everyone involved. A few times
> > a year this involves corrupted root domain data, which makes the
> > damage orders of magnitude worse.
> You therefore need to take this advise seriously.
> Hope this helps.
> Regards, David
> David Beard Phone: (+61 8) 830 35709
> Computer Systems Manager FAX: (+61 8) 830 33773
> Departments of Statistics, Pure & Applied Mathematics
> University of Adelaide
> South Australia, 5005 E-mail: firstname.lastname@example.org
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