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Date:      Wed, 2 Sep 2015 12:24:02 -0400
From:      Patrick Kelsey <pkelsey@freebsd.org>
To:        Rui Paulo <rpaulo@me.com>
Cc:        "net@freebsd.org" <net@freebsd.org>
Subject:   Re: TCP Fast Open (RFC7413) for FreeBSD
Message-ID:  <1D272A8E-C411-4FE1-A8C7-6E6FBDE23DC8@freebsd.org>
In-Reply-To: <1441210862.1183.14.camel@me.com>
References:  <CAD44qMVK82rB_MM_fsFt7LXV%2BuwCFj3%2B9BXXj=30teUQs0gzrg@mail.gmail.com> <1441169643.1183.12.camel@me.com> <AEE23E04-C0B7-40D3-B55C-502A41B0D5BE@freebsd.org> <1441210862.1183.14.camel@me.com>

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> On Sep 2, 2015, at 12:21 PM, Rui Paulo <rpaulo@me.com> wrote:
>=20
>> On Wed, 2015-09-02 at 01:30 -0400, Patrick Kelsey wrote:
>>=20
>>=20
>>=20
>>>> On Sep 2, 2015, at 12:54 AM, Rui Paulo <rpaulo@me.com> wrote:
>>>>=20
>>>> On Tue, 2015-09-01 at 21:19 -0400, Patrick Kelsey wrote:
>>>> Hi,
>>>>=20
>>>> About two weeks from now, I will be starting work on server-side=20
>>>> TCP=20
>>>> Fast
>>>> Open (TFO) support for FreeBSD head and stable/10, with the=20
>>>> intention=20
>>>> of
>>>> having patches up for review by November.  This message is an=20
>>>> attempt=20
>>>> to
>>>> uncover any existing work on TFO for FreeBSD, as the existence of=20
>>>> such work
>>>> may change my plans.
>>>>=20
>>>> Copying Sara Dickinson and Tom Jones due to this thread:
>>>> https://lists.freebsd.org/pipermail/freebsd-net/2015
>>>> -January/040910.html.
>>>=20
>>> Have you performed any measurements on the likelihood that stateful
>>> packet inspectors (firewalls, NATs, etc.) will allow a SYN or a=20
>>> SYN/ACK
>>> to pass with data in it?
>>=20
>> I have not performed any such measurements.  This issue is discussed=20
>> in section 7.1 of the RFC, which cites such studies and summarizes=20
>> the finding as being that 6% of the probed internet paths dropped SYN=20
>> packets with data or with unknown TCP options.
>>=20
>>=20
>>>=20
>>> How would this interact with our syncache?  Does it just need to=20
>>> store
>>> the cookie?
>>=20
>> The exact interaction with the syncache is still TBD, but I do not=20
>> expect to be storing TFO cookies in the syncache as the cookies are=20
>> per client-server IP pair and not per-connection.
>=20
> OK.  The only request I have is to be conservative and leave it
> disabled for a while.  The RFC is pretty much experimental for a good
> reason and we don't want to repeat the T/TCP mistake.
>=20

I agree completely.  This feature will be guarded with an #ifdef, default di=
sabled.

-Patrick=



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