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Date:      Thu, 16 Jan 2020 20:35:53 +0100
From:      Michael Tuexen <tuexen@freebsd.org>
To:        Jeremy Harris <jgh@wizmail.org>
Cc:        freebsd-transport@freebsd.org
Subject:   Re: TCP Fast Open
Message-ID:  <984788AA-EEE0-4348-9F8C-B07E650B6E09@freebsd.org>
In-Reply-To: <75f12c4d-63fb-40d5-8569-f8780de63521@wizmail.org>
References:  <5276cc23-d37f-e55e-11c5-030314e9e32c@wizmail.org> <1206B1BE-3B7E-45D0-8C2B-6012A5CB6298@freebsd.org> <2752006b-cd6b-7b8b-d23b-ae2c794dc104@wizmail.org> <f59092f1-9f93-d5c3-e7a2-06ba88bd7385@wizmail.org> <F24D850E-C6B6-4600-9B28-2439D70447A0@freebsd.org> <f07bb11e-4f69-b714-ce8d-881e68a20c6b@wizmail.org> <46A739DC-CCF5-4EA1-802A-0D8E559AC187@freebsd.org> <70c1649f-b3b8-3c3b-ef80-22e851461e9f@wizmail.org> <75f12c4d-63fb-40d5-8569-f8780de63521@wizmail.org>

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> On 6. Dec 2019, at 15:23, Jeremy Harris <jgh@wizmail.org> wrote:
>=20
> On 05/12/2019 20:31, Jeremy Harris wrote:
>> On 05/12/2019 20:17, Michael Tuexen wrote:
>>>> - tried TFO but the server didn't take it up
>>> I would expect on =3D 0.
>>=20
>> Excellent; that's the most-useful one to know.
>=20
> Unfortunately, it seems not to be so; it appears
> to be recording the sending of a TFO option
> (of _either_ type; so a cookie-Request still
> gets it set).  This means I can't use it to log
> "TFO was actually doing something useful for
> this connection".
> The TCPOPT_FAST_OPEN bit in TCP_INFO says the same
> (either pre-ESTABLISHED or post-).
>=20
>=20
> Another problem, this time server-side.  I was hoping
> to get the initial server output piggybacked on
> the SYN,ACK, given the TFO design notes in
> https://people.freebsd.org/~pkelsey/TFO_Design_Details.pdf
>=20
> - but so far I'm not getting that.  Packet capture (on lo0):
>           SYN     ->               (TFO=3DC)
> 0.000224           <- SYN,ACK       (TFO=3DC  same value)
> 0.000078   SYN,ACK ->
> 0.001421           <- server_data
>=20
> The 224us response time for the SYN,ACK looks immediate, not
> a delack time as I'd expect.
A fix is under review:
https://reviews.freebsd.org/D23212

Best regards
Michael
> --=20
> Cheers,
>  Jeremy
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