Thanks. It is clear now.
.as
On 26 Jan 2012, at 12:00, Fernando Gont wrote:
> [Subject changed so that this doesn't "mix" with the poll]
>
> Hi, Arturo,
>
> On 01/26/2012 09:59 AM, Arturo Servin wrote:
>> When you say "Namely, they try to perform IPv6 reassembly with the
>> "atomic fragment" and any other fragments already queued with the
>> same set {IPv6 Source Address, IPv6 Destination Address, Fragment
>> Identification}." If there is just one packet what happen? Does the
>> host just hang in there waiting for the next fragment (that possibly
>> will never arrive) until it times out?
>
> I didn't test *this* one (will do this weekend, and let you know). But
> they *do* mix the atomic fragment with fragments present in the fragment
> queue. That is, the attacker (knowing that you're relying on atomic
> fragments) can send lots of forged fragments to the victim system, such
> that when your legitimate fragments arrive at the victim they get mixed
> up with the malicious fragments, and hence they get discarded.
>
>
>> Also, you quoted RFC2640 "In response to an IPv6 packet that is sent
>> to an IPv4 destination (i.e., a packet that undergoes translation
>> from IPv6 to IPv4) …" I wonder if there is any negative implication
>> for IPv4/IPv6 translators if atomic fragments are forbidden as
>> proposed.
>
> Dan Wing has noted that forbidding atomic fragments breaks RFC 6144. It
> would also break the DNS if atomic fragments are employed for it.
>
> That's why draft-gont-6man-ipv6-atomic-fragments does *not* forbid
> atomic fragments, but rather improves the their processing at the
> receiving node.
>
> Essentially, what this proposal says "If you receive an atomic fragment,
> don't 'merge it' with fragmented traffic, but just remove the
> Fragmentation Header and process the packet as if it was not fragmented".
>
> Thanks!
>
> Best regards,
> --
> Fernando Gont
> SI6 Networks
> e-mail: fg...@si6networks.com
> PGP Fingerprint: 6666 31C6 D484 63B2 8FB1 E3C4 AE25 0D55 1D4E 7492
>
>
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