Date: Sun, 24 Feb 2019 07:14:30 -0500 From: Randall Stewart <rrs@netflix.com> To: "Scheffenegger, Richard" <Richard.Scheffenegger@netapp.com> Cc: Michael Tuexen <tuexen@freebsd.org>, "freebsd-transport@freebsd.org" <freebsd-transport@freebsd.org> Subject: Re: DSACK Message-ID: <824585F6-342D-4F7F-BB2A-FA9CA661E5D2@netflix.com> In-Reply-To: <SN4PR0601MB3728B5FF0CBE3154773FA7BE86790@SN4PR0601MB3728.namprd06.prod.outlook.com> References: <SN4PR0601MB3728752D55B7231BC4CF22B586780@SN4PR0601MB3728.namprd06.prod.outlook.com> <5ACAD39A-2A77-43BB-BE93-994C1C6C93AB@freebsd.org> <SN4PR0601MB3728DDE5402768567DA9415F86780@SN4PR0601MB3728.namprd06.prod.outlook.com> <5AD822A0-06D7-44DB-AFB1-2453FD59A222@freebsd.org> <F75B74B6-752F-4F6A-886A-E00A484E051E@netflix.com> <58102EB5-6A5A-4BE1-ADEA-4EDCB56A39AE@freebsd.org> <328BFA58-EF05-473C-9DC0-05549E662213@netflix.com> <SN4PR0601MB3728B5FF0CBE3154773FA7BE86790@SN4PR0601MB3728.namprd06.prod.outlook.com>
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Richard: I agree it would be a nice to add thing.. I have thought about doing it for Rack and BBR, but there are so many other things that need = tending too :) As to =E2=80=9Csupport is claimed=E2=80=9D.. where is that, A simple = grep through the code for 2883 i.e. cd sys/netinet grep =E2=80=9C2883=E2=80=9D tcp* does not show anything.. is it in one of the man pages or something? Thanks R > On Feb 24, 2019, at 7:10 AM, Scheffenegger, Richard = <Richard.Scheffenegger@netapp.com> wrote: >=20 > Well, RFC2883 support is claimed, and it may have been working = somewhat in very old code (before 2005?) incidentally... >=20 > Even though FBSD doesn't make use of DSACK information, Linux does = (unwind of spurious RTOs for example). So having minimal DSACK (again?) = is certainly good to have. >=20 > Also, I wanted to see what tcp_update_sack_list does under certain = corner cases, where we've run into issues, when not adjusting the sack = block left edge (belt + suspenders). >=20 > -----Original Message----- > From: Randall Stewart <rrs@netflix.com>=20 > Sent: Sonntag, 24. Februar 2019 04:03 >=20 >=20 > I just don=E2=80=99t remember ever seeing code in the stack to do = DSACK. I know I have added some small bits to be aware of DSACK coming = in from other stacks in BBR and Rack, but it only does accounting and = does not use the information.. nor does it generate any.. >=20 > I have thought about doing it, but I have not placed a big priority on = it=E2=80=A6. >=20 > R >=20 >> On Feb 24, 2019, at 7:01 AM, Michael Tuexen <tuexen@freebsd.org> = wrote: >>=20 >>> On 24. Feb 2019, at 12:32, Randall Stewart <rrs@netflix.com> wrote: >>>=20 >>> I don=E2=80=99t think I have ever seen FreeBSD emit a DSACK. Now = admittedly I=20 >>> have only paid close attention in current. But that spans even back=20= >>> into 11 days I think. >>>=20 >>> Hmm wonder if I have a 10 machine I can go back and look at :) >> I tried to test on 10.4 yesterday, but packetdrill doesn't run that=20= >> well on 10.4 (missing pcap functions)... I'm not sure I want to = backport it. >>=20 >> Best regards >> Michael >>>=20 >>> R >>>=20 >>>> On Feb 23, 2019, at 5:30 AM, Michael Tuexen <tuexen@freebsd.org> = wrote: >>>>=20 >>>>> On 23. Feb 2019, at 11:28, Scheffenegger, Richard = <Richard.Scheffenegger@netapp.com> wrote: >>>>>=20 >>>>>=20 >>>>> Bin grad am flughafen und hab leider nur HEAD bei mir (und ein iso = von 10, wo ich grad versuch, das mit scapy zu checken). >>>>>=20 >>>>> Falls du schnell einen packetdrill gegen BSD11 ohne D18960 machen = kannst, und es da noch DSACKs raussendet, w=C3=A4re das toll! >>>>>=20 >>>>> Ich f=C3=BCrchte aber, das das schon l=C3=A4ngere Zeit kaputt ist = - da wir nun doch noch nicht D18960 drinnen haben, wie ich irrt=C3=BCmlich= dachte. >>>> OK. I'll take a look. >>>>=20 >>>> Have a save trip! >>>>=20 >>>> Best regards >>>> Michael >>>>>=20 >>>>>=20 >>>>>=20 >>>>> -----Original Message----- >>>>> From: Michael Tuexen <tuexen@freebsd.org> >>>>> Sent: Samstag, 23. Februar 2019 11:25 >>>>> To: Scheffenegger, Richard <Richard.Scheffenegger@netapp.com> >>>>> Cc: freebsd-transport@freebsd.org >>>>> Subject: Re: DSACK >>>>>=20 >>>>> NetApp Security WARNING: This is an external email. Do not click = links or open attachments unless you recognize the sender and know the = content is safe. >>>>>=20 >>>>>=20 >>>>>=20 >>>>>=20 >>>>>> On 23. Feb 2019, at 10:29, Scheffenegger, Richard = <Richard.Scheffenegger@netapp.com> wrote: >>>>>>=20 >>>>>> Hi, >>>>>>=20 >>>>>> A colleague pointed me to the stack (HEAD) no longer emitting = DSACK options a few days ago... >>>>>>=20 >>>>>> I was under the impression, that older versions of FreeBSD would = send out DSACKs for spurious duplicate packets. >>>>>>=20 >>>>>> But when I try this script against HEAD, regular cumulative ACKs = without DSACK blocks are showing up. >>>>>>=20 >>>>>> Currently bandwidth starved - but was that a conscious decision? = Or was me observing DSACKs never a thing? >>>>> I would say if it is working in stable/11, but not in stable/12 = and head, it is a regression. >>>>>=20 >>>>> Best regards >>>>> Michael >>>>>>=20 >>>>>> Thanks a lot, >>>>>> Richard >>>>>>=20 >>>>>=20 >>>>=20 >>>> _______________________________________________ >>>> freebsd-transport@freebsd.org mailing list=20 >>>> https://lists.freebsd.org/mailman/listinfo/freebsd-transport >>>> To unsubscribe, send any mail to = "freebsd-transport-unsubscribe@freebsd.org" >>>=20 >>> ------ >>> Randall Stewart >>> rrs@netflix.com >>>=20 >>>=20 >>>=20 >>=20 >=20 > ------ > Randall Stewart > rrs@netflix.com >=20 >=20 >=20 ------ Randall Stewart rrs@netflix.com
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