Implement TCP UTO

by Fang Wang for The FreeBSD Project

The objective of the project is to implement TCP UTO(User Timeout Option, defined by RFC 5482) in FreeBSD's TCP stack. The TCP user timeout controls how long transmitted data may remain unacknowledged before a connection is forcefully closed . RFC 5482 specifies a new TCP UTO option that allows one end of a TCP connection to advertise its current user timeout value and provides advice to the other end of the TCP connection to adapt its user timeout accordingly.