TCP Fast Open

[Michael Tuexen]

> On 5. Dec 2019, at 20:58, Jeremy Harris <jgh at wizmail.org> wrote:
> 
> On 05/12/2019 19:43, Michael Tuexen wrote:
>> Are you asking how to figure out whether TFO was used or not?
>> In that case you can use 
>> getsockopt(fd, IPPROTO_TCP, TCP_FASTOPEN, &on, &len);
>> If on == 0, TFO was not used, on != 0, TFO was used.
> 
> I'd found that, but it's so far unclear what choices it
> makes among
> - didn't try TFO
This means it is disabled in the cookie cache or you didn't enable the socket option.
I would expect on = 0.
> - tried TFO but the server didn't take it up
I would expect on = 0.
> - server accepted the TFO cookie, but not the data that was on the SYN
I don't know. I can test it and report...
> - server acked the data
I would expect on = 1.

Best regards
Michael
> -- 
> Cheers,
> Jeremy
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