IPv6 fragment reassembly regression following FreeBSD-SA-18:10.ip

Andrey V. Elsukov bu7cher at yandex.ru
Mon Sep 24 20:26:35 UTC 2018

On 23.09.2018 16:43, John W. O'Brien wrote:
> I'd like to check my understanding and then ask a procedural question.
> FreeBSD-SA-18:10.ip [0], released on 08/14, was resolved by r337828 [1].
> That changeset, resulting in 11.1R-p13 and 11.2R-p2, included a patch to
> the way IPv6 fragment reassembly is handled [2] that was part of the
> merge to releng. In an ensuing thread [3] two weeks later, an
> implementation defect was identified, but not before that defect had
> shipped. The defect is now being tracked as a bug [4], as of 09/03 has
> been fixed in head and stable/11, and is registered as a blocker for 12.0.
> I believe this defect is the cause of a problem I detected recently
> where postfix would query BIND on ::1 for the DNSSEC-signed AAAA of an
> MX, and never receive a response. I'm a little puzzled that lo0 is
> affected in spite of having a 16k MTU, but the other signs are there:
> the symptoms appeared after upgrading from 11.2R-p1 to -p3, and I can
> perform that query successfully on UDPv4 or TCPv6.
> What I have been unable so far to determine is, will another 11.2R patch
> be forthcoming to resolve this regression, and if so, when? I can limp
> along without UDPv6 for a little while, but not until 11.3. The only
> clear alternative is to downgrade to -p1.
> [0] https://www.freebsd.org/security/advisories/FreeBSD-SA-18:10.ip.asc
> [1] https://svnweb.freebsd.org/changeset/base/337828
> [2] https://svnweb.freebsd.org/changeset/base/337776
> [3] https://lists.freebsd.org/pipermail/svn-src-head/2018-August/117514.html
> [4] https://bugs.freebsd.org/231045

Your analysis looks correct to me. r338406 was not merged to releng/11.2.

WBR, Andrey V. Elsukov

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