Le 5 août 09 à 08:29, Rémi Denis-Courmont a écrit :
On Wednesday 05 August 2009 00:09:13 ext Rémi Després wrote:
"No harm expected"? I find that generating scary-reading false
positive in my
system logs is harmful.
I don't get the point about "scary-reading false positive".
As already mentioned (several times?), some operating systems log
errors when
they receive packets with invalid checksums.
Right.
They do what RFC 2460 says they should: "IPv6 receivers must discard
UDP packets containing a zero checksum, and should log
the error".
(You don't need to repeat it once more ;-))
But if *received* UDP zero checksums are no longer considered as
errors in IPv6 (the proposal), I don't see in what it is relevant to
note that "some operating systems log errors when they receive
packets with invalid checksums" .
The rationale is that some piece
of hardware might be defective, or whatever.
For this, non-zero checksums are available.
(Translators don't change them to zero.)
IMHO also, hosts, at their next patch release, SHOULD silently
accept
zero-checksum IPv6 datagrams RATHER THAN silently dropping them. No
harm expected.
That will cause silent software failures when running on a "too
old" system.
*IPv4 compatible applications should have no problem with UDP zero-
checksums*, or I am mistaken?
It will break silently when an *IPv6* application is run on a
system that has
not been updated to accept zero-checksum. The system will drop the
packet, and
the application will mysteriously not receive anything.
My proposal is precisely to AVOID these mysterious blackholes (in
systems that are patched before translators get largely used).
But maybe you have another proposal to have the same result.
If yes, could you tell what it is?
Silent failures are the most harmful kind of failures to me.
And to me too, but I don't see any silent "failure" here.
Regards,
RD
--
Rémi Denis-Courmont
Nokia Devices R&D, Maemo Software, Helsinki
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