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Date:      Thu, 5 Dec 2019 19:28:12 +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:  <1206B1BE-3B7E-45D0-8C2B-6012A5CB6298@freebsd.org>
In-Reply-To: <5276cc23-d37f-e55e-11c5-030314e9e32c@wizmail.org>
References:  <5276cc23-d37f-e55e-11c5-030314e9e32c@wizmail.org>

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> On 5. Dec 2019, at 16:25, Jeremy Harris <jgh@wizmail.org> wrote:
>=20
> Hi,
>=20
> 12.1 kernel with TCP_RFC7413
> net.inet.tcp.fastopen.server_enable: 1
> net.inet.tcp.fastopen.client_enable: 1
>=20
>=20
> Using code copied from
> https://people.freebsd.org/~pkelsey/tfo-tools/tfo-client.c
>=20
> I'm not seeing any TFO option on SYN.  This is on a loopback
> connection.
>=20
> Also, it appears to make no difference to the success of the
> sendto whether or not TCP_FASTOPEN was set on the socket, adding to
> the confusion.
>=20
> What might I be doing wrong?
The program works (on FreeBSD head, but I do not expect a difference to =
12.1).
However, you need a server having TCP FO enabled.

I would expect the TFO option being present on the first connection =
attempt.
If the server does not support TFO, the following attempts will not have =
the
option.

Can you provide the output of
sudo sysctl net.inet.tcp.fastopen.ccache_list
after at least one attempt.

On my system I see
> sudo sysctl net.inet.tcp.fastopen.ccache_list
net.inet.tcp.fastopen.ccache_list:=20
Local IP address     Remote IP address     Port   MSS Disabled Cookie
127.0.0.1            127.0.0.1               80 16344       No =
4c402b8365433ca7

Whether TFO is used or not has no impact on the return value of =
sendto().

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