tests/sys/kern: skip unix_connectat fdescfs cases when fdescfs is missing

[nickbanks_netflix.com]

Summary

unix_connectat's fdescfs cases call mount_fdescfs(), which skipped on
ENODEV. nmount(2) never returns ENODEV: vfs_donmount() remaps the
ENODEV from a failed fdescfs module load to EINVAL with errmsg
"Invalid fstype", so the skip never fired and the cases failed on
kernels without fdescfs.

Use ATF_REQUIRE_KERNEL_MODULE("fdescfs") instead, and drop the dead
ENODEV branch. modfind(2) sees loaded and static modules, not
unloaded .ko files, so a host with fdescfs.ko on disk but not loaded
will now skip rather than having nmount(2) implicitly kldload it.
Upstream CI keeps fdescfs mounted via tests/ci/tools/ci.conf, so it
still runs them.

Sponsored by: Netflix

[ngie]

Please use require.kmods instead of the macro as I recommend in the differential.

tests/sys/kern/unix_connectat.c

182–183

I really need to get rid of that macro since the ATF metadata added by @des makes a ton more sense.

[ngie]

tests/sys/kern/unix_connectat.c

182–183

I really need to get rid of that macro since the ATF metadata added by @des makes a ton more sense.

It looks like it nerfed the trailing newline. Please add it to the suggested change.

[nickbanks_netflix.com]

Use require.kmods ATF metadata instead of ATF_REQUIRE_KERNEL_MODULE(), per review. Macro include and its -I${SRCTOP}/tests CFLAGS dropped; macro line continuations and trailing newline verified intact.

[ngie]

Please doublecheck that the new support also meets your needs before committing.

[nickbanks_netflix.com]

In D59227#1362798, @ngie wrote:

Please doublecheck that the new support also meets your needs before committing.

I confirmed that all our internal tests here at Netflix were passing still with the updated commit.

[ngie]

In D59227#1362854, @nickbanks_netflix.com wrote:

In D59227#1362798, @ngie wrote:

Please doublecheck that the new support also meets your needs before committing.

I confirmed that all our internal tests here at Netflix were passing still with the updated commit.

("Goat for it!")