Support for message signing was merged into 3.19, along with
nocephx_require_signatures option. But, all that option does is allow
the kernel client to talk to clusters that don't support MSG_AUTH
feature bit. That's pretty useless, given that it's been supported
since bobtail.
Meanwhile, if one disables message signing on the server side with
"cephx sign messages = false", it becomes impossible to use the kernel
client since it expects messages to be signed if MSG_AUTH was
negotiated. Add nocephx_sign_messages option to support this use case.
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
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