Privsep requires operating system support for file descriptor passing.
Compression will be disabled on systems without a working mmap MAP_ANON.
-PAM-enabled OpenSSH is known to function with privsep on AIX, HP-UX
-(including Trusted Mode), Linux and Solaris.
+PAM-enabled OpenSSH is known to function with privsep on AIX, FreeBSD,
+HP-UX (including Trusted Mode), Linux, NetBSD and Solaris.
On Cygwin, Tru64 Unix, OpenServer, and Unicos only the pre-authentication
part of privsep is supported. Post-authentication privsep is disabled