As documented, MACH_SEND_TRAILER would allow a sender to provide its own
message trailer instead of having the kernel append its own
kernel-generated trailer. This is a Mach feature that supports a network
of multiple Mach hosts, but even in that environment, the option is
restricted to use by privileged callers. In reality, MACH_SEND_TRAILER
has never been implemented in OS X.
The system’s mach_msg_server() family does consider the value of
MACH_SEND_TRAILER, but this is pointless. Any purported trailer set by a
server function would be ignored.
Maintaining this code gives the illusion that it’s functional, so it’s
being removed.
TEST=util_test MachMessageServer.*
R=rsesek@chromium.org
Review URL: https://codereview.chromium.org/736493007
306625dac4