http://www.blogjava.net/Even/archive/2006/08/31/66805.html
http://happyman-bruce.blogbus.com/logs/1729369.html

ldd `which sshd` | grep libwrap

# 确认sshd是否支持TCP Wrapper，输出类似:libwrap.so.0 => /lib/libwrap.so.0 (0x00bd1000)