Date: Thu, 02 Apr 2015 20:37:32 +0200 From: Hans Petter Selasky <hps@selasky.org> To: "Robert N. M. Watson" <rwatson@FreeBSD.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: <551D8C6C.9060504@selasky.org> In-Reply-To: <8900318B-8155-4131-A0C3-3DE169782EFC@FreeBSD.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> <8900318B-8155-4131-A0C3-3DE169782EFC@FreeBSD.org>
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Hi Robert, On 04/02/15 20:32, Robert N. M. Watson wrote: > 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. Right. > >> Does somebody here know what happens in these two cases: >> >> 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? > I'm asking because the code in FreeBSD, since the beginning probably, just copies the IP header, and use the same IP ID for all the fragments ! This just hit my mind after some recent work in this area. > > 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! I see from ip_reass() how it works. --HPS
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