Merge branch 'selftest-packetdrill-import-tfo-server-tests'

Kuniyuki Iwashima says:

====================
selftest: packetdrill: Import TFO server tests.

The series imports 15 TFO server tests from google/packetdrill and
adds 2 more tests.

The repository has two versions of tests for most scenarios; one uses
the non-experimental option (34), and the other uses the experimental
option (255) with 0xF989.

Basically, we only import the non-experimental version of tests, and
for the experimental option, tcp_fastopen_server_experimental_option.pkt
is added.

The following tests are not (yet) imported:

  * icmp-baseline.pkt
  * simple1.pkt / simple2.pkt / simple3.pkt

The former is completely covered by icmp-before-accept.pkt.

The later's delta is the src/dst IP pair to generate a different
cookie, but supporting dualstack requires churn in ksft_runner.sh,
so defered to future series.  Also, sockopt-fastopen-key.pkt covers
the same function.

The following tests have the experimental version only, so converted
to the non-experimental option:

  * client-ack-dropped-then-recovery-ms-timestamps.pkt
  * sockopt-fastopen-key.pkt

For the imported tests, these common changes are applied.

  * Add SPDX header
  * Adjust path to default.sh
  * Adjust sysctl w/ set_sysctls.py
  * Use TFO_COOKIE instead of a raw hex value
  * Use SOCK_NONBLOCK for socket() not to block accept()
  * Add assertions for TCP state if commented
  * Remove unnecessary delay (e.g. +0.1 setsockopt(SO_REUSEADDR), etc)

With this series, except for simple{1,2,3}.pkt, we can remove TFO server
tests in google/packetdrill.
====================

Link: https://patch.msgid.link/20250927213022.1850048-1-kuniyu@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>