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Date:      Thu, 2 Apr 2015 19:32:19 +0100
From:      "Robert N. M. Watson" <rwatson@FreeBSD.org>
To:        Hans Petter Selasky <hps@selasky.org>
Cc:        Mateusz Guzik <mjguzik@gmail.com>, Ian Lepore <ian@freebsd.org>, svn-src-all@freebsd.org, src-committers@freebsd.org, Gleb Smirnoff <glebius@FreeBSD.org>, svn-src-head@freebsd.org
Subject:   Re: svn commit: r280971 - in head: contrib/ipfilter/tools share/man/man4 sys/contrib/ipfilter/netinet sys/netinet sys/netipsec sys/netpfil/pf
Message-ID:  <8900318B-8155-4131-A0C3-3DE169782EFC@FreeBSD.org>
In-Reply-To: <551D8945.8050906@selasky.org>
References:  <201504012226.t31MQedN044443@svn.freebsd.org> <1427929676.82583.103.camel@freebsd.org> <20150402123522.GC64665@FreeBSD.org> <20150402133751.GA549@dft-labs.eu> <20150402134217.GG64665@FreeBSD.org> <20150402135157.GB549@dft-labs.eu> <1427983109.82583.115.camel@freebsd.org> <20150402142318.GC549@dft-labs.eu> <20150402143420.GI64665@FreeBSD.org> <20150402153805.GD549@dft-labs.eu> <alpine.BSF.2.11.1504021657440.27263@fledge.watson.org> <551D8143.4060509@selasky.org> <551D8945.8050906@selasky.org>

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On 2 Apr 2015, at 19:24, Hans Petter Selasky <hps@selasky.org> wrote:

> In my sketchup I assume that packets for the same destination will not =
be re-ordered. I see that the current ip_reass() code does not care =
about TCP or UDP port numbers at all. Maybe we should add code to check =
that the packet belongs to the same ports too?

Higher-level network headers will appear only in the first fragment, so =
can't be used in matching later fragments.

> Does somebody here know what happens in these two cases:
>=20
> If we are transmitting using TSO, will the network adapter increment =
the IP ID field somehow? What happens if an outgoing IP packet resulting =
from a TSO packet get fragmented by a router?

Quite possibly -- this is presumably specified by the NIC vendor, but it =
would be good to do a bit of a survey and see what happens in practice.

> In ip_fragment() when we create fragments we should increment the =
ip_id value for each fragment?


That you are asking this question while hacking on the IP ID code is =
deeply troubling. Please go read up on how IP fragmentation works before =
going any further with these changes!

Robert=



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