Bug 242492 - [tcp] TCP fast open observability
Summary: [tcp] TCP fast open observability
Status: New
Alias: None
Product: Base System
Classification: Unclassified
Component: kern (show other bugs)
Version: 12.1-RELEASE
Hardware: Any Any
: --- Affects Only Me
Assignee: Michael Tuexen
Depends on:
Reported: 2019-12-06 22:31 UTC by j2465
Modified: 2020-10-23 15:21 UTC (History)
2 users (show)

See Also:


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Description j2465 2019-12-06 22:31:25 UTC
A TCP connection made by sendto() with TCP_FASTOPEN set always sets the
TCP_FASTOPEN readback getsockopt.  It would be (possibly more) useful to the
client application to know if a supposedly valid TFO cookie was sent on the SYN
(as opposed to the current possibilty of only having sent a TFO request) and/or
whether the server agreed that the cookie was acceptable.

TCP_INFO TCPOPT_FAST_OPEN appears to match getsockopt/TCP_FASTOPEN, for a client.

I'm not sure that we really want to go so far as knowing whether client
data-on-SYN was actually accepted with the SYN, but it's another item in the