When writing the test, I assumed that (linux) domain sockets do not
support OOB data, and that sockatmark returns 0, because it can never
read it.
In fact, as of 2021, linux does support OOB on domain sockets, but this
feature can be turned off at build time (CONFIG_AF_UNIX_OOB). In this
case (or in the case of older kernels), the kernel returns an error (and
the test fails).
Armed with this knowledge, I modify the test to test both "1" (OOB
present) and "0" (no OOB data) cases by actually sending OOB data into
the socket. I use the send call to determine the presence of OOB
support, and have the test skip itself if it is absent. OOB data only
makes sense on stream sockets, so change the socketpair type to that.
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Co-authored-by: Jeff Bailey <jbailey@raspberryginger.com>
Pavel LabathandJeff Bailey
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